JP2008186798A - Electrolyte membrane-electrode assembly - Google Patents

Abstract

The present invention provides a simple electrode catalyst layer structure for a fuel cell having further improved battery performance and high battery performance.
An electrolyte membrane, a cathode catalyst layer disposed on one side of the electrolyte membrane, an anode catalyst layer disposed on the other side of the electrolyte membrane, and a cathode catalyst layer An electrolyte membrane-electrode assembly having a cathode side gas diffusion layer and an anode side gas diffusion layer disposed on the anode catalyst layer, wherein at least one of the cathode catalyst layer and the anode catalyst layer is an electrolyte. Electrolyte membrane-electrode having a structure in which a plurality of catalyst layers having different pore structures are stacked such that the pore structure of the catalyst layer 12 on the membrane side is larger than the pore structure of the catalyst layer 50 on the gas diffusion layer side Joined body.
[Selection] Figure 3

Description

  The present invention relates to an electrolyte membrane-electrode assembly (MEA), and more particularly to an electrolyte membrane-electrode assembly for a fuel cell. In particular, the present invention relates to an electrolyte membrane-electrode assembly (MEA) excellent in power generation performance and durability.

  In recent years, in response to social demands and trends against the background of energy and environmental problems, fuel cells that can operate at room temperature and obtain high output density have attracted attention as power sources for electric vehicles and stationary power sources. A fuel cell is a clean power generation system in which the product of an electrode reaction is water in principle and has almost no adverse effect on the global environment. In particular, the polymer electrolyte fuel cell is expected as a power source for electric vehicles because it operates at a relatively low temperature. In general, the polymer electrolyte fuel cell has a structure in which an electrolyte membrane-electrode assembly is sandwiched between a gas diffusion layer and a separator. The electrolyte membrane-electrode assembly is obtained by sandwiching a polymer electrolyte membrane between a pair of electrode catalyst layers.

In a polymer electrolyte fuel cell having an MEA as described above, an electrode reaction represented by the following reaction formula is allowed to proceed in accordance with the polarity of both electrodes (cathode and anode) sandwiching the polymer electrolyte membrane. Are getting electrical energy. First, hydrogen contained in the fuel gas supplied to the anode (hydrogen electrode) side is oxidized by the catalyst component to become protons and electrons (2H ₂ → 4H ⁺ + 4e ⁻ : reaction 1). Next, the generated protons pass through the solid polymer electrolyte contained in the electrode catalyst layer and the solid polymer electrolyte membrane in contact with the electrode catalyst layer, and reach the cathode (oxygen electrode) side electrode catalyst layer. In addition, the electrons generated in the anode-side electrode catalyst layer include the conductive carrier constituting the electrode catalyst layer, the gas diffusion layer in contact with the side of the electrode catalyst layer different from the solid polymer electrolyte membrane, the separator, and the outside. The cathode side electrode catalyst layer is reached through the circuit. The protons and electrons that have reached the cathode-side electrode catalyst layer react with oxygen contained in the oxidant gas supplied to the cathode side to generate water (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O: Reaction 2). . In the fuel cell, electricity can be taken out through the above-described electrochemical reaction.

In the electrochemical reaction, hydrogen ions (H ⁺ ) (hereinafter also referred to as “protons”) generated by the reaction 1 on the anode side permeate the solid polymer electrolyte membrane in a hydrated state (H ₃ O ⁺ ). Protons that have diffused and permeated through the membrane are supplied to the reaction 2 together with oxygen and electrons that have permeated (diffused) through a gas diffusion layer (hereinafter also referred to as “GDL”) at the cathode. That is, the reaction at the anode and the cathode uses the electrode catalyst layer in close contact with the solid polymer electrolyte membrane as a reaction site, and the catalyst in the electrode catalyst layer and the solid polymer electrolyte (hereinafter also referred to as “polymer electrolyte”). Progress at the interface. Therefore, if the interface between the catalyst and the polymer electrolyte is increased and the formation of the interface is made uniform, the above reactions 1 and 2 are preferable because the reaction proceeds more smoothly and actively.

  In view of such a situation, it has been attempted to obtain an electrode excellent in battery performance by changing the composition of the electrode catalyst layer (for example, Patent Documents 1 to 5). Patent Document 1 proposes a technique in which an electrode catalyst layer is in a state in which catalyst-supported carbon is dispersed in a polymer electrolyte for the purpose of increasing and homogenizing the interface. The membrane catalyst layer described in Patent Document 1 uses an electrode catalyst layer forming paste in which catalyst-carrying carbon is dispersed in a polymer electrolyte solution in forming the catalyst layer. In other words, the electrode catalyst layer forming paste was directly applied to the solid polymer electrolyte membrane, or a sheet obtained by forming a film from the paste was pressed onto the solid polymer electrolyte membrane, thereby being adhered to the solid polymer electrolyte membrane. An electrode catalyst layer is formed. Thus, the interface of the catalyst in the electrode catalyst layer is formed not only with the solid polymer electrolyte membrane but also with the polymer electrolyte, so that the interface is increased and made uniform.

  Patent Document 2 describes that the aggregate of supported catalyst particles used in the catalyst layer has two particle size distribution peaks. However, only the addition of agglomerates of catalyst particles having different particle size peaks to one catalyst layer, it is described that the pore structure of the catalyst layer is defined by the regulation of the spatial distribution of the agglomerate particle size of the catalyst support particles. Not. Further, Patent Document 3 describes that the density of the catalyst metal has a maximum value at the interface with the electrolyte membrane. However, there is no description regarding the pore structure of the catalyst layer by the regulation of the spatial distribution of the aggregate particle diameter of the catalyst carrier particles supporting the catalyst (particularly, paragraph “0014” in Patent Document 3). Patent Document 4 describes that the first catalyst layer and the second catalyst layer are laminated so as to face each other. However, the same catalyst carrier particles are used for the first catalyst layer and the second catalyst layer, and there is no description regarding the pore structure of the catalyst layer by the regulation of the spatial distribution of the aggregate particle diameter of the catalyst carrier particles. . In Patent Document 5, a catalyst carrier of the catalyst layer is provided in which a plurality of catalyst layers including catalyst-carrying particles in which a catalyst is carried on catalyst carrier particles are provided on an electrode for a fuel cell and is in contact with a solid polymer electrolyte membrane. There is disclosed a fuel cell electrode in which the average particle size of particles is set smaller than the average particle size of the other catalyst support particles of the catalyst layer. Thus, the solid polymer electrolyte close to the membrane-electrode interface where the electrode reaction takes place due to the fact that the average particle diameter of the catalyst carrier particles of the catalyst layer in contact with the electrolyte membrane is smaller than that of the other catalyst layers. The ratio of the catalyst present on the surface of the catalyst carrier particles is increased in the catalyst layer in contact with the membrane, and high catalyst activity can be realized. In the other catalyst layers, the average particle size of the aggregates of the catalyst carrier particles is large. The gas and water diffusivity can be improved. As a result, gas and water diffusivity and high catalytic activity are achieved.

  As described above, starting with Patent Documents 1 to 5, the catalyst particle size (primary particle size) distribution of the catalyst carrier particles and the particle size (secondary particle size) distribution of the aggregates of the catalyst carrier particles are conventionally controlled. There was no detailed study on designing the spatial distribution of the aggregate particle size of the catalyst support particles in the layer, and no influence on the electrode activity or the like was reported.

On the other hand, it is also reported that the pore structure of the catalyst layer is defined by the spatial distribution of the aggregate particle diameter of the catalyst carrier particles (for example, Patent Documents 6 and 7). In Patent Document 6, an electrode catalyst layer is laminated so that a catalyst carrier having a small particle size is included on the solid polymer electrolyte membrane side (inside) and a catalyst carrier having a large particle size is included on the GDL side (outside). Is disclosed. Here, the gap between the catalyst carriers in the electrode catalyst layer is such that the amount of the polymer electrolyte (ionomer) covering the catalyst carrier is larger on the side of the catalyst carrier having a smaller particle size and smaller on the side of the catalyst carrier having a larger particle size. Thus, by changing along the stacking direction of the catalyst carrier, the pore structure of the electrode catalyst layer is made larger on the GDL side than on the solid polymer electrolyte membrane side. It is described that by adopting such a structure, the conductivity of hydrogen ions on the membrane side can be increased, and the diffusion permeability of the reaction gas can be increased on the GDL side (for example, paragraph “0020” in Patent Document 6). ). Similarly, in Patent Document 7, the amount of the polymer electrolyte (ionomer) is substantially constant from the solid polymer electrolyte membrane side to the GDL side (outside) with respect to the amount of the catalyst-supporting carbon, and the density An electrode catalyst is formed by laminating a catalyst layer having a large (low porosity) on the solid polymer electrolyte membrane side so that a catalyst layer having a low density (large porosity) is on the GDL side (outside). It is intended to make the pore structure of the layer larger on the GDL side than on the solid polymer electrolyte membrane side.
Japanese Patent Publication No. 5-507583 JP-A-8-227716 JP-A-9-265992 JP 2001-345110 A JP-A-2004-288388 Japanese Patent No. 3555196 JP 2005-56583 A

For smoothening and activating the above reactions 1 and 2 in the anode and cathode catalyst layers, in addition to increasing the interface between the catalyst and the polymer electrolyte in the electrode catalyst layer and making the interface uniform, the reaction gas in the electrode catalyst layer The diffusion and permeability of protons, the conductivity of protons, and the diffusion and removal of generated water are essential. However, in the fuel cells proposed in Patent Documents 1 to 7, the catalyst-supported carbon is averagely dispersed in the polymer electrolyte in the electrode catalyst layer, and an average pore structure is formed or the pore structure is Since the structure is larger on the GDL side than the electrolyte membrane, there are the following problems. That is, as shown in FIG. 1, the polymer electrolyte membrane side (“Membrane” side in the figure) of the cathode catalyst layer is a reaction between the cathode electrode and water that has diffused together with protons (H ⁺ ) from the anode electrode. Since the generated water is in a very wet state, when an average pore structure is formed, the degree of swelling of the polymer electrolyte is large and the diffusibility of the reaction gas is greatly reduced. On the other hand, although the humidified reaction gas (O ₂ gas) is supplied to the GDL film side of the cathode electrode catalyst layer, it is in a dry state as compared with the solid polymer electrolyte membrane side, so an average pore structure is formed. Then, the degree of swelling of the polymer electrolyte is small, and the proton conductivity decreases greatly.

  Also, in an electrode catalyst layer composed of a catalyst carrier (catalyst-carrying carbon) and a polymer electrolyte, the polymer electrolyte is interposed in the gap between adjacent catalyst carriers, and the catalyst carrier is bound by this polymer electrolyte. It exists in the state that was done. For this reason, if the polymer electrolysis mass of the electrode catalyst layer is increased, the polymer electrolysis mass interposed in the gap between the catalyst carriers increases. Therefore, as the polymer electrolysis mass increases, the gap between the catalyst carriers in the electrode catalyst layer decreases, and the diffusion permeability of the reaction gas decreases, but the proton conductivity in the electrode catalyst layer increases. On the other hand, if the polymer electrolysis mass is reduced, the gap between the catalyst supports increases and the diffusion / permeability of the reaction gas increases, but the proton conductivity decreases. That is, the diffusion permeability of the reaction gas and the proton conductivity are contradictory characteristics.

At the cathode, water (H ₂ O) is generated by the reaction 2 at the interface between the catalyst and the polymer electrolyte in the electrode catalyst layer. Part of this generated water diffuses in the polymer electrolyte cluster, reaches the interface between the electrode catalyst layer and the solid polymer electrolyte membrane, and moves as back diffusion water from the cathode side to the anode side of the solid polymer electrolyte membrane. . On the other hand, part of the generated water diffuses in the cluster of the polymer electrolyte, reaches the interface between the electrode catalyst layer and the GDL, and is discharged from the electrode catalyst layer side of the GDL to the separator side. At this time, if a large amount of generated water stays in the gaps between the catalyst-supporting carbons in the electrode catalyst layer, the diffusion / permeability of the reaction gas decreases (flooding), and the power generation performance decreases.

  Further, in an electrolyte membrane-electrode assembly having an electrode catalyst layer having an average pore structure or a pore structure larger on the GDL side than the electrolyte membrane, the cathode electrode reaction is caused from the GDL side (outside) of the electrode catalyst layer. Since it progresses remarkably on the solid polymer electrolyte membrane side (inside) (within the range surrounded by the dotted line in FIG. 1), on the inside, oxidative corrosion of carbon as a carrier and elution of platinum as a catalyst are likely to occur. It is a factor that power generation performance deteriorates over time after long-term use. In addition to the above, when the cathode electrode reaction proceeds significantly inside the electrode catalyst layer from the outside, as the reaction proceeds, the reaction gas runs short on the inside and the proton runs short on the outside. Cannot be fully expressed.

  That is, in the electrode catalyst layer of the conventional fuel cell described in Patent Documents 1 to 7, an average pore structure or a pore structure larger on the GDL side than the electrolyte membrane is formed. The permeability decreases from the outside to the inside of the electrocatalyst layer. In other words, the diffusion of the reaction gas uniformly from the inside to the outside of the layer causes the diffusion of the reaction gas to the solid polymer electrolyte membrane side (inside). Speed is limited. In addition, in the conventional electrode catalyst layers described in Patent Documents 1 to 7, an average pore structure or a pore structure larger on the GDL side than the electrolyte membrane is formed. The discharge characteristics decrease from the inside to the outside of the electrode catalyst layer. In other words, the proton conductivity and the generated water to the gas diffusion electrode (outside) are uniform due to the uniform proton conductivity and the generated water discharge characteristics from the inside to the outside of the layer. The diffusion rate is limited. Further, in the electrode catalyst layer, the catalyst-supported carbon is averagely dispersed in the polymer electrolyte, and the conventional fuel cell in which the average pore structure is formed, or the pore structure is larger on the GDL side than the electrolyte membrane. In the conventional fuel cell formed in the above, the diffusion / permeability of the reaction gas, the conductivity of the proton, and the discharge characteristic of the generated water change as described above due to the increase / decrease in the polymer electrolysis mass. For this reason, it is difficult to make all the diffusion / permeability of the reactive gas suitable for the electrode catalyst layer, the proton conductivity, and the discharge characteristic of the generated water compatible, and there is still room for improvement in battery performance.

  For this reason, the diffusion permeability of the reaction gas, the conductivity of protons, and the discharge characteristics of the generated water cannot be increased or decreased on the inside and outside of the electrode catalyst layer, and the efficiency of using the catalyst in the electrode catalyst layer is low. Further improvement in performance was hindered. This also leaves room for improvement in battery performance.

  Therefore, the present invention solves the above-described problems, further improves battery performance, and provides a simple electrode catalyst layer structure for a fuel cell having high battery performance, and an electrolyte membrane-electrode junction having the electrode catalyst layer. The purpose is to provide a body.

  Another object of the present invention is to provide an electrode catalyst layer structure that is excellent in durability in addition to power generation performance, and an electrolyte membrane-electrode assembly having the electrode catalyst layer.

As a result of intensive studies to achieve the above object, the present inventor has found that in order to improve the performance and durability of the MEA, the material transport characteristics (in particular, H ₂ O, H ⁺ , O in the electrode catalyst layer). design for diffusive and transfer characteristics of ₂₎ by noting is important. As a result, it was found that the material transport characteristics in these electrocatalyst layers depend on the pore structure such as the porosity, the pore distribution, and the amount of pores. For this reason, as a result of intensive studies on the pore structure of the electrode catalyst layer, the pore structure of the electrode catalyst layer is: (a) From the viewpoint of diffusion permeability of the reaction gas, the reaction gas is placed outside the electrode catalyst layer ( In order to quickly diffuse and permeate from the GDL side) to the inner side (solid polymer electrolyte membrane side), it is desirable that the inner side is higher than the outer side; In order to move (diffuse) quickly from the inside of the catalyst layer to the outside, it is desirable that it is high outside the inside; (c) The discharge characteristic of the produced water is higher than that inside the electrode catalyst layer. In order to permeate and quickly move (discharge) from the cathode side to the anode side, it is desirable that it is higher on the inner side than the outer side; (iv) Uniform proton conductivity limits the proton conduction rate to the GDL side (outer side) Is Therefore, it was found that it is preferably higher in the outer than the inner.

As a result of further intensive studies aimed at satisfying the above (a) to (d) in a well-balanced manner, the present inventors have found that a catalyst carrier (catalyst-carrying carbon) is attached to a polymer electrolyte membrane having proton permselectivity. A fuel cell having a solid polymer electrolyte membrane sandwiched between a pair of gas diffusion layers with the electrode catalyst layer interposed therebetween, wherein the electrode catalyst layer is formed by laminating the anode and cathode electrode catalyst layers. The layer is composed of at least two layers having different pore structures (pore diameter, pore volume, porosity) constituted by a catalyst-supported carbon bound with a polymer electrolyte, and a catalyst having a large pore structure. It was found that an electrolyte membrane-electrode assembly excellent in both power generation performance and durability can be obtained by laminating the layer on the polymer electrolyte membrane side and the catalyst layer having a small pore structure on the GDL side. That is, as shown in FIG. 2, the electrolyte membrane side of the electrode catalyst layer has a structure with a larger pore diameter or pore volume and a higher liquid water retention capacity than the GDL side, so that the electrolyte membrane interface The nearby generated water tends to move from the cathode surface of the electrolyte membrane to the anode surface by back diffusion due to the liquid phase. For this reason, the electrolyte membrane-electrode assembly having such a pore structure can improve the power generation performance, and at the same time, can suppress the corrosion deterioration of carbon and the like and the elution deterioration of catalyst metal such as platinum and the durability. It has been found that can also be improved. Further, in the pore structure of the electrode catalyst layer, assuming that the pore diameter and the amount of pores are in a desired range, on the electrolyte membrane side of the catalyst layer, the reaction gas (O ₂ ) transport characteristics (gas diffusibility), that is, It has also been found that the power generation performance can be improved by improving the O ₂ utilization efficiency.

  In addition, in order to form the pore structure of the electrode catalyst layer according to the present invention, an attempt was made to use an electrode catalyst layer forming paste in which catalyst-supported carbon is averagely dispersed in a polymer electrolyte solution. Here, the electrode catalyst layer forming paste is prepared by mixing a predetermined amount of catalyst-supporting carbon, a polymer electrolyte solution, an organic solvent and water (pure water) and dispersing them on average. In general, in these dispersion steps, mixing and pulverization are simultaneously performed using various pulverizers, and the particle size distribution of the catalyst-supported carbon is also adjusted. Further, in the catalyst support (catalyst-supported carbon particles), the primary particles of carbon form a dense aggregate, and therefore it is very difficult to pulverize the aggregate to the primary particles in the dispersion step. It is. Therefore, the particle size distribution of the catalyst-supporting carbon is determined by the particle size and particle size distribution of the carbon particle aggregates (secondary particles). The carbon particle aggregates (secondary particles) are formed by large and small aggregates. Since it is formed, the particle size distribution is wide, and it is very difficult to control to a single particle size. Since the carbon particle aggregate has a particle size distribution, the pore structure constituted by the catalyst-supported carbon bound with the polymer electrolyte has a small aggregate amount and a polymer electrolyte that occupy the space between the large aggregates. It varies depending on the amount. When the large particle size and small particle size of the catalyst-supported carbon particle aggregates are mixed, the larger the amount of small aggregates, the larger the amount of small aggregates that occupy the space between adjacent large aggregates. It has been found that if the amount of small aggregates is small, the amount of small aggregates occupying the gap is also small, and the voids between the catalyst-supporting carbon particles are large. That is, according to the method, the catalyst-carrying carbon particle aggregates can be changed by changing the particle size distribution of the conventional catalyst-carrying carbon particle aggregates without using a large particle size and a small particle size catalyst-carrying carbon particle aggregate separately. It is possible to control the voids between the carbon particles.

  On the other hand, the degree of contact between polymer electrolytes coated with catalyst-carrying carbon particles also varies depending on the polymer electrolysis mass that occupies the interval between adjacent catalyst-carrying carbon particles. For this reason, if the polymer electrolysis mass is large, the polymer electrolysis mass occupying the space between adjacent catalyst-carrying carbon particles also increases, the gap between the catalyst-carrying carbon particles is small, and if the polymer electrolysis mass is small, the gap is occupied. It has also been found that the polymer electrolysis mass is reduced and the gap between the catalyst-supporting carbon particles is increased. Furthermore, in addition to the change in the particle size distribution of the catalyst-carrying carbon particle aggregates, it has also been found that the voids between the catalyst-carrying carbon particles can be further controlled by increasing or decreasing the polymer electrolysis mass.

  Therefore, the electrolyte membrane-electrode assembly having the pore structure as described above is obtained by changing the particle size and particle size distribution of the catalyst-carrying carbon particle aggregate and the polymer electrolysis mass, so that the catalyst-carrying carbon particles in the electrode catalyst layer are changed. The gap between the catalyst supports (catalyst-supported carbon particles) in the electrode catalyst layer can be made larger on the polymer electrolyte membrane side than on the gas diffusion layer side, so that the reaction gas is diffused and permeated. It was found that the property can be improved on the polymer electrolyte membrane side. On the other hand, it was found that the proton conductivity can be increased on the gas diffusion layer side by increasing the polymer electrolysis mass on the gas diffusion layer side than on the polymer electrolyte membrane side.

  Based on the above findings, the present invention has been completed.

  That is, the object is to place the electrolyte membrane, the cathode catalyst layer disposed on one side of the electrolyte membrane, the anode catalyst layer disposed on the other side of the electrolyte membrane, and the cathode catalyst layer. In the electrolyte membrane-electrode assembly, comprising at least one of the cathode catalyst layer and the anode catalyst layer, the cathode-side gas diffusion layer and the anode-side gas diffusion layer disposed on the anode catalyst layer. An electrolyte membrane-electrode having a structure in which a plurality of catalyst layers having different pore structures are stacked such that the pore structure of the catalyst layer on the electrolyte membrane side is larger than the pore structure of the catalyst layer on the gas diffusion layer side Achieved by the joined body.

  The electrolyte membrane-electrode assembly of the present invention is excellent in power generation performance and durability.

  The first of the present invention is an electrolyte membrane, a cathode catalyst layer disposed on one side of the electrolyte membrane, an anode catalyst layer disposed on the other side of the electrolyte membrane, and the cathode catalyst layer. In an electrolyte membrane-electrode assembly, comprising: a cathode side gas diffusion layer disposed; and an anode side gas diffusion layer disposed in the anode catalyst layer, at least one of the cathode catalyst layer and the anode catalyst layer However, the electrolyte membrane has a structure in which a plurality of catalyst layers having different pore structures are stacked such that the pore structure of the catalyst layer on the electrolyte membrane side is larger than the pore structure of the catalyst layer on the gas diffusion layer side. The present invention relates to an electrode assembly. The generated water in the vicinity of the electrolyte membrane interface is likely to move from the cathode surface to the anode surface of the electrolyte membrane by back diffusion due to the liquid phase. Therefore, according to the present invention, by making the pore structure of the catalyst layer on the electrolyte membrane side larger than the pore structure of the catalyst layer on the gas diffusion layer side (for example, the pore diameter, the porosity, the amount of pores). The electrolyte membrane side of the electrode catalyst layer can have a structure having a high liquid water holding capacity, that is, a structure capable of holding a large amount of liquid water in the pore structure. For this reason, on the electrolyte membrane side of the electrode catalyst layer, protons generated on the anode side can move better deeply to the GDL side due to the presence of water held in the polymer electrolyte (ionomer) constituting the catalyst layer. . For this reason, the cathode reaction does not concentrate in the interface region between the electrolyte membrane and the cathode catalyst layer, and can occur uniformly in the entire thickness direction of the catalyst layer. On the other hand, the generated water near the GDL interface easily moves from the catalyst layer side to the GDL side due to diffusion by the gas phase. Therefore, as in the present invention, the water retention amount in the polymer electrolyte is reduced by making the pore structure of the catalyst layer on the GDL side smaller than the pore structure (porosity / amount) of the catalyst layer on the electrolyte membrane side. High structure, that is, a structure capable of holding liquid water in the ionomer cluster.

In particular, on the cathode catalyst layer side, the reaction gas (O ₂ ) has a gas diffusion resistance that increases from the GDL side toward the electrolyte membrane side. Therefore, by taking the pore structure of the electrolyte membrane side, such as described above and GDL side, while suppressing the flooding reduced, can improve gas diffusivity, hence the reaction even in the vicinity of ^{_{GDL (O 2 + 4H + +}} 4e - → 2H ₂ O) can proceed efficiently. In particular, by arranging the polymer electrolysis mass so that the GDL side becomes larger, the proton conductivity on the GDL side is improved, and the above effect can be achieved remarkably. On the other hand, proton (H ⁺ ) has a proton transfer resistance that increases from the electrolyte membrane side toward the GDL side. Therefore, by taking the pore structure of the electrolyte, such as the membrane side and GDL side, it can favorably ensure the proton mobility in GDL side, hence the reaction even in the vicinity of ^{_{GDL (O 2 + 4H + +}} 4e - → 2H 2 O) can proceed efficiently. In particular, the proton conductivity on the GDL side can be improved by arranging the polymer electrolysis mass or ion exchange capacity so as to increase on the GDL side, so that the above effect can be achieved more remarkably.

  In addition to the above advantages, according to the present invention, the pore structure of the electrode catalyst layer is a uniform structure, and the porosity / amount can be controlled, so that a non-uniform structure (distribution) due to cracks and the like can be suppressed. Network structure.

  Hereinafter, the present invention will be described in more detail.

In the present invention, at least one of the cathode catalyst layer and the anode catalyst layer (hereinafter also simply referred to as “electrode catalyst layer”) has a pore structure of the catalyst layer on the electrolyte membrane side of the catalyst layer on the gas diffusion layer side. It is an essential constituent requirement that it is larger than the pore structure. In the present invention, it is sufficient that at least one of the cathode catalyst layer and the anode catalyst layer has a layered structure with different pore structures as described above. However, the proton conductivity is improved, the reaction gas (especially O ₂ ) Considering the necessity of improving transport properties (gas diffusibility), at least the cathode catalyst layer is such that the pore structure of the catalyst layer on the electrolyte membrane side is larger than the pore structure of the catalyst layer on the gas diffusion layer side. It is preferable to have a structure in which a plurality of catalyst layers having different pore structures are stacked. Hereinafter, the embodiment of the present invention will be mainly described in detail for the effect / function when the cathode catalyst layer has a larger pore structure of the catalyst layer on the electrolyte membrane side than the pore structure of the catalyst layer on the gas diffusion layer side. As will be described, the present invention is not limited to the cathode catalyst layer, and the same definition applies to the anode catalyst layer.

The form of the pore structure according to the present invention is not particularly limited as long as the pore structure of the catalyst layer on the electrolyte membrane side can be made larger than the pore structure of the catalyst layer on the gas diffusion layer side. Specifically, (i) the pore diameter [D1 (nm)] of the catalyst layer on the electrolyte membrane side is larger than the pore diameter [D2 (nm)] of the catalyst layer on the gas diffusion layer side (D1> D2), and A structure in which the amount of pores [V1 (cm ³ / g)] of the catalyst layer on the electrolyte membrane side is larger than the amount of pores [V2 (cm ³ / g)] of the catalyst layer on the gas diffusion layer side (V1> V2) (Ii) The porosity [X1 (%)] of the catalyst layer on the electrolyte membrane side is larger than the porosity [X2 (%)] of the catalyst layer on the gas diffusion layer side (X1> X2). (Iii) The polymer electrolysis mass [B1 (g / cm ³ )] of the catalyst layer on the electrolyte membrane side is equal to or less than the polymer electrolysis mass [B2 (g / cm ³ )] of the catalyst layer on the gas diffusion layer side; A structure that satisfies (B1 ≦ B2) is preferable.

  In particular, the following advantages can be obtained by adopting the configurations (i) to (iii).

  The generated water in the vicinity of the electrolyte membrane interface is likely to move from the cathode surface to the anode surface of the electrolyte membrane by back diffusion due to the liquid phase. For this reason, by taking the structure of (i)-(iii) on the electrolyte membrane side of the electrode catalyst layer, as a structure having a high liquid water retention capability (a structure capable of holding a large amount of liquid water in the pore structure), Water generated in the vicinity of the electrolyte membrane interface can be smoothly transferred from the cathode surface to the anode surface of the electrolyte membrane by reverse diffusion due to the liquid phase. In addition, since the polymer electrolyte in the catalyst layer on the electrolyte membrane side has a large amount of liquid water, the degree of swelling is large. Therefore, by adopting the configurations (i) to (iii), the polymer electrolyte in the catalyst layer on the electrolyte membrane side When the molecular electrolyte mass is at least, the polymer electrolyte swells, and the three-phase interface between the polymer electrolyte, the active species (noble metal / noble metal alloy), and the reaction gas (oxygen or hydrogen) can be maintained. On the other hand, the generated water near the GDL interface easily moves from the catalyst layer side to the mill layer / GDL side due to diffusion by the gas phase. Therefore, by adopting the configurations (i) to (iii), the electrode catalyst layer on the electrolyte membrane side of the electrode catalyst layer has a structure with a high water retention amount in the polymer electrolyte (a structure in which liquid water can be retained in the ionomer cluster). ).

In addition, the reaction gas (O ₂ ) has a gas diffusion resistance that increases from the GDL side toward the electrolyte membrane side. For this reason, by adopting the configurations (i) to (iii), the gradient of the pore structure (for example, the pore diameter, the porosity, and the amount of the pores) increases conversely from the GDL side toward the electrolyte membrane side. Thus, the diffusibility of the reaction gas can be improved.

Furthermore, proton (H ⁺ ) has a proton transfer resistance that increases from the electrolyte membrane side toward the GDL side. For this reason, by adopting the configurations (i) to (iii), particularly (iii), the gradient of the polymer electrolysis mass increases from the GDL side toward the electrolyte membrane side, and the proton conductivity is significantly improved. Can do.

  In addition to the above advantages, the pore structure of the electrode catalyst layer can be a relatively uniform structure with little / no non-uniform structure (distribution) such as cracks.

In (i) above, by defining the pore size and the amount of pores on the electrolyte membrane side and the GDL side so that D1> D2 and V1> V2, the electrolyte membrane side of the electrode catalyst layer has a large pore size and void. Since it has the amount of pores, the transport property (gas diffusibility) of the reaction gas (especially O ₂ ) on the electrolyte membrane side can be improved. For this reason, the O ₂ utilization efficiency of the entire electrode catalyst layer can be significantly improved, and as a result, the reaction (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O) can proceed efficiently and the power generation performance can be improved. Furthermore, if the electrolyte membrane side of the electrode catalyst layer has a large pore diameter and amount of pores, even if the catalyst layer on the electrolyte membrane side has a large swelling of the polymer electrolyte due to excessive liquid water, Since clogging can be suppressed and the transport property (gas diffusibility) of the reaction gas (O ₂ ) can be improved, the O ₂ utilization efficiency over the entire catalyst layer can be significantly improved. As a result, the reaction (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O) can proceed efficiently and power generation performance can be improved. At this time, D1, D2, V1 and V2 are not particularly limited as long as they satisfy the above relationship, but the pore diameter [D1 (nm)] of the catalyst layer on the electrolyte membrane side is preferably 80 to 200 nm. More preferably, it is 80-180 nm, Most preferably, it is 80-150 nm. The pore size [D2 (nm)] of the catalyst layer on the gas diffusion layer side is preferably 30 to 80 nm, more preferably 30 nm or more and less than 80 nm, and even more preferably 50 nm or more and less than 80 nm. D1 and D2 are not particularly limited as long as D1 is greater than D2 (D1> D2), but preferably the ratio of D1 to D2 (D1 / D2) is 1 Is more than 3, more preferably more than 1, more than 2.5, and most preferably more than 1, more than 2. Furthermore, the average pore diameter [Dave (nm)] of the entire catalyst layer according to the present invention is not particularly limited as long as it satisfies the above relationship, but is preferably 60 to 100 nm. Further, vacancy of the catalyst layer of the electrolyte membrane side ^{[V1 (cm 3 / g)} ] is preferably from 0.5 to 1.0 cm ³ / g, more preferably 0.5~0.9cm ³ / g, and most preferably 0.5 to 0.8 cm ³ / g. Pores of the gas diffusion layer side of the catalyst layer ^{[V2 (cm 3 / g)} ] is preferably 0.3~0.5cm ³ / g, 0 more preferably 0.3 cm ³ / g or more. less than 5 cm ³ / g, even more preferably less than 0.5 cm ³ / g at 0.35 cm ³ / g or more.
Further, the average pore volume [Vave (cm ³ / g) of the entire catalyst layer according to the present invention is not particularly limited as long as it satisfies the above relationship, but preferably 0.4 to 0.8 cm ³ / g. It is. V1 and V2 are not particularly limited as long as V1 is greater than V2 (V1> V2), but preferably the ratio of V1 to V2 (V1 / V2) is 1 Exceeding 3 and more preferably 1 to 2.5, most preferably 1 to 2. If the pore diameter and the amount of pores are within the above ranges, it is possible to make the pore structure of the electrode catalyst layer a relatively uniform structure with little or no non-uniform structure (distribution) such as cracks. In addition, it is possible to maintain a high liquid water holding capacity on the electrolyte membrane side of the electrode catalyst layer, and to have a structure excellent in reaction gas transport characteristics.

In the present invention, the pore diameter and the amount of pores are measured using a mercury positometry method. The mercury positometry method is a method of theoretically calculating how much pressure is applied when mercury enters the pores. While increasing the applied pressure, the mercury solution This is a method of measuring the size and volume of pores on the sample surface by detecting changes in the surface of the surface (that is, the amount of mercury entering the pores). Specifically, the electrode catalyst layer according to the present invention is formed on both surfaces of the electrolyte membrane to produce a CCM (catalyst coated membrane). This CCM is put into a measurement cell, the measurement cell containing this sample is filled with mercury, the inside of the cell is pressurized, and the mercury intrusion volume (W1 (cm ³ )) in the process is measured by a capacitance detector. Detect. Separately, instead of CCM, the same operation is performed on the electrolyte membrane alone before forming the catalyst layer, and the mercury intrusion volume (W0 (cm ³ )) is detected. The difference (W1−W0) between the mercury penetration amount of the CCM and the mercury penetration amount of the electrolyte membrane is the pore volume of the electrode catalyst layer, and this pore volume is the mass (g) of the catalyst metal used in the catalyst layer. The value divided by is the amount of pores in the electrode catalyst layer. In addition, a calibration curve is separately prepared using a sample having a known pore diameter, and the pore diameter is obtained from the pore volume of the electrode catalyst body.

In (ii) above, by defining the porosity of the electrolyte membrane side and the GDL side so that X1> X2, the porosity of the electrode catalyst layer on the electrolyte membrane side is the same as in (i) above. Therefore, the transport property (gas diffusibility) of the reaction gas (especially O ₂ ) on the electrolyte membrane side can be improved. For this reason, the O ₂ utilization efficiency of the entire electrode catalyst layer can be significantly improved, and as a result, the reaction (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O) can proceed efficiently and the power generation performance can be improved. Furthermore, if the electrolyte membrane side of the electrode catalyst layer has a large porosity, even if the catalyst layer on the electrolyte membrane side has a large swelling of the polymer electrolyte due to excessive liquid water, the pore structure is blocked. In addition, since the transport property (gas diffusibility) of the reaction gas (O ₂ ) can be improved, the O ₂ utilization efficiency over the entire catalyst layer can be more significantly improved. As a result, the reaction (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O) progresses efficiently and power generation performance can be improved. In this case, X1 and X2 are not particularly limited as long as they satisfy the above relationship, but the porosity [X1 (%)] of the catalyst layer on the electrolyte membrane side is not particularly limited, and catalyst particles (carbon aggregates) ), The composition of the catalyst particles and the polymer electrolyte, the coating method, etc., but preferably 50% to 80%, more preferably 50 to 70%, most preferably 50 to 60%. . The porosity [X2 (%)] of the catalyst layer on the gas diffusion layer side is also not particularly limited, and depends on the size of the catalyst particles (carbon aggregates), the composition of the catalyst particles and the polymer electrolyte, the coating method, and the like. Depending on, but preferably 30% to 50%, more preferably 30% or more and less than 50%, even more preferably 35% or more and less than 50%, most preferably 40% or more and 50%. Is less than. X1 and X2 are not particularly limited as long as X1 is larger than X2 (X1> X2), but preferably the ratio of X1 to X2 (X1 / X2) exceeds 1. 3 or less, more preferably 1 to 2.5, and most preferably 1 to 2. By setting the porosity to the above range, the pore structure of the electrode catalyst layer can be a relatively uniform structure with little / non-uniform structure (distribution) such as cracks, and In addition, it is possible to maintain a high liquid water holding capacity on the electrolyte membrane side of the electrode catalyst layer and to have a structure excellent in reaction gas transport characteristics. Moreover, if the porosity is in the above range, the electrolyte membrane side of the electrode catalyst layer can exhibit excellent liquid water retention ability and excellent reaction gas transport characteristics.

  In the present invention, “porosity” is an index indicating the degree of formation of voids in the catalyst layer. The porosity is obtained by observing a cross section of the catalyst layer with a scanning electron microscope (SEM) and calculating the ratio of the voids by image processing. More specifically, the CCM is frozen and cleaved, and Adobe is used. Using software such as Photoshop or Jtrim, image processing of SEM photographs of the cross section of the catalyst layer and identifying the black and white in the cross section of the catalyst layer, by calculating the ratio as porosity Measured.

In (iii) above, by defining the polymer electrolysis mass in the electrode catalyst layer so as to satisfy B1 ≦ B2, proton conductivity (proton proton) on the GDL side of the electrode catalyst layer, which has been conventionally low in proton conductivity, is determined. (Moving characteristics) can be significantly improved, reaction efficiency is improved, and therefore power generation performance can be improved. Moreover, since the electrode catalyst layer on the GDL side has a small amount of liquid water, the swelling of the polymer electrolyte is small. For this reason, even if the polymer electrolysis mass on the GDL side of the electrode catalyst layer is increased, blockage (flooding) of the pore structure can be suppressed, and the power generation performance can be improved. At this time, B1 and B2 are not particularly limited as long as they satisfy the above relationship, but the polymer electrolysis mass [B1 (g / cm ³ )] of the catalyst layer on the electrolyte membrane side is the same as that of the catalyst layer on the electrolyte membrane side. The polymer electrolyte composition [B1 ′ (wt%)] is preferably 20 to 40 wt%, more preferably 25 to 40 wt%, and most preferably 30 to the total mass of the polymer electrolyte and the electrode catalyst. The amount is 40 wt%. The polymer electrolyte mass [B2 (g / cm ³ )] of the catalyst layer on the gas diffusion layer side is the polymer electrolyte composition [B2 ′ (wt%)] of the catalyst layer on the gas diffusion layer side. The amount is preferably 30 to 50 wt%, more preferably 35 to 50 wt%, and most preferably 40 to 50 wt% with respect to the total mass of the catalyst and the electrode catalyst. The total mass of the polymer electrolyte and the electrode catalyst is a preparation standard when preparing the catalyst ink described in detail below, and the polymer electrolyte and the electrode catalyst (= catalyst component +) added at the time of preparing the catalyst ink. The total mass of the conductive carrier). At this time, B1 ′ ≦ B2 ′. B1 and B2 are larger or smaller if B2 is greater than or equal to B1 (B1 ≦ B2), or B1 ′ and B2 ′ are greater than or equal to B2 ′ if greater than or equal to B1 ′ (B1 ≦ B2). Although not particularly limited, preferably, the ratio of B2 to B1 (B2 / B1) or the ratio of B2 ′ to B1 ′ (B2 ′ / B1 ′) is 1 or more and 3 or less, more preferably more than 1 and 3 or less. Even more preferably, it is 1-2.5, most preferably 1-2. By setting the polymer electrolysis mass in the electrode catalyst layer within the above range, the water generated in the vicinity of the GDL interface that easily moves from the catalyst layer side to the mill layer / GDL side by diffusion in the gas phase is the amount of water retained in the polymer electrolyte. High structure (structure that can hold liquid water in the ionomer cluster), and at the same time, blockage (flooding) of the pore structure can be suppressed, and power generation performance and durability can be improved.

  In the present invention, the electrode catalyst layer is not particularly limited as long as the electrode catalyst layer on the GDL side and the catalyst layer on the electrolyte membrane side are stacked. Specifically, the electrode catalyst layer may be laminated in two or more layers so that the pore diameter decreases stepwise or continuously from the electrolyte membrane side toward the gas diffusion layer side; Even if two or more layers are stacked so as to decrease stepwise or continuously from the gas diffusion layer side, the porosity decreases stepwise or continuously from the electrolyte membrane side to the gas diffusion layer side Two or more layers may be laminated so that the polymer electrolysis mass in the catalyst layer may be laminated step by step or continuously from the electrolyte membrane side to the gas diffusion layer side. Either is acceptable. The number of layers in the electrode catalyst layer on the GDL side and the catalyst layer on the electrolyte membrane side is not particularly limited as described above, but is preferably 2 to 5 layers, more preferably 2 to 3 layers, and most preferably 2 respectively. Is a layer. At this time, the number of layers in the electrode catalyst layer on the GDL side and the catalyst layer on the electrolyte membrane side may be the same or different. When the number of layers in the electrode catalyst layer on the GDL side and the catalyst layer on the electrolyte membrane side is three or more, the pore diameter, the amount of pores, and the voids of the catalyst layer arranged closest to the electrolyte membrane side and the GDL side It is preferable that at least one of the porosity, the polymer electrolyte mass, and the polymer electrolyte composition satisfies the relationship as described above. That is, the electrode catalyst layer preferably has a structure in which two layers of a GDL-side electrode catalyst layer and an electrolyte membrane-side catalyst layer are laminated. The thicknesses of the electrode catalyst layer on the GDL side and the catalyst layer on the electrolyte membrane side are not particularly limited as described above. The thickness of the electrode catalyst layer on the GDL side is preferably 1 to 10 μm, more preferably 1 to 8 μm, still more preferably 1 to 6 μm, and the thickness of the catalyst layer on the electrolyte membrane side is preferably 1 to 10 μm, more Preferably it is 1-8 micrometers, More preferably, it is 1-6 micrometers. Moreover, the thickness of the whole electrode catalyst layer becomes like this. Preferably it is 2-20 micrometers, More preferably, it is 2-15 micrometers. At this time, if the thickness of the electrode catalyst layer on the GDL side, the catalyst layer on the electrolyte membrane side, and the entire electrode catalyst layer is in the above range, good drainage can be secured. That is, the electrode catalyst layer particularly preferably has a structure in which two layers of a catalyst layer on the electrolyte membrane side having a thickness of 1 to 10 μm and a catalyst layer on the gas diffusion layer side having a thickness of 1 to 10 μm are laminated. At this time, the thickness of the GDL-side electrode catalyst layer and the electrolyte membrane-side catalyst layer may be the same or different.

In the present invention, the method for forming the pore structure of the catalyst layer on the GDL side and the electrolyte membrane side is not particularly limited, and the pore diameter, the amount of pores, and the porosity defined in the above (i) to (ii) are achieved. It is preferable that the method be able to. For example, as described above, a catalyst layer having a desired pore structure is formed by adjusting each polymer layer so that the polymer electrolysis mass is increased on the GDL side and decreased on the electrolyte membrane side. it can. In the conventional method for producing an electrode catalyst layer, as described in the background section above, the pore structure of the catalyst layer is formed by the degree of carbon particle re-aggregation after ink preparation and the composition / evaporation rate of the organic solvent. Therefore, the porosity, amount, and distribution could not be controlled intentionally. For example, when a desired amount is obtained by applying the catalyst ink several times by the printing method (direct printing method), if the overcoating (repeating the application) is performed again on the catalyst layer that has been applied once, It was thought that part of the pore structure was locally destroyed and the porosity and the amount of pores gradually decreased. Here, although the factor that changes the pore structure due to overcoating cannot be specified, the polymer electrolyte that coats the catalyst particles of the undercoat layer locally changes the coating state due to the organic solvent contained in the topcoat ink. Or the catalyst particle network (three-dimensional network structure) was assumed to change. In the case of the printing method (transfer method), the electrolyte membrane and the catalyst layer are joined (by applying pressure and temperature), so that the catalyst layer pore structure at the contact interface is partially crushed, and the mass transport properties ( It is presumed that the H ₂ O, H ⁺ , and O ₂ diffusivity and mobility characteristics are reduced.

  On the other hand, according to the present invention, it has been found that even if the composition of the catalyst ink is the same, a desired pore structure can be formed by changing the amount of the polymer electrolyte in the catalyst ink. That is, when the polymer electrolysis mass increases, the polymer electrolysis mass that fills the interval between adjacent catalyst carriers increases, the interval between the catalyst carriers (pore structure) decreases, and conversely, when the polymer electrolysis mass decreases, The polymer electrolysis mass that fills the space between adjacent catalyst carriers is reduced, and the space between the catalyst carriers (hole structure) is increased. More specifically, a desired pore structure is preferably formed by the polymer electrolyte / conductive carrier (Ionomer / Carbon ratio; I / C ratio) in the catalyst ink. As shown in FIGS. 6-1 to 6-3, the particle size distribution does not depend on the I / C ratio (see FIG. 6-1). On the other hand, as shown in FIGS. 6-2 and 6-3, the pore structure (the amount of pores) tends to become smaller in proportion to I / C. As described, the pore structure of catalyst layers made with catalyst inks having a high I / C ratio (ie, high polymer electrolysis mass) has a low I / C ratio (ie, high polymer electrolysis mass). This is smaller than the pore structure of the catalyst layer made of the catalyst ink. Therefore, according to the present invention, the desired pore structure can be intentionally and easily controlled by appropriately adjusting the polymer electrolysis mass in the catalyst layer.

  In the present invention, in the catalyst layer on the GDL side, the polymer electrolyte / conductive carrier (Ionomer / Carbon ratio; I / C ratio) in the catalyst ink is preferably 1.0 to 2.0, more preferably. Is 1.0 to 1.5. In the catalyst layer on the electrolyte membrane side, the polymer electrolyte / conductive carrier (Ionomer / Carbon ratio; I / C ratio) in the catalyst ink is preferably 0.7 to 1.5, more preferably 0.9-1.3. In such a range, a desired pore structure can be easily formed.

  Alternatively, in the pore structure according to the present invention, many catalyst carriers having a large particle diameter are arranged in the catalyst layer on the electrolyte membrane side, and many catalyst carriers having a small particle diameter are arranged in the catalyst layer on the gas diffusion layer side. It can be formed by arranging. Here, the catalyst carrier contained in the catalyst ink (paste) described in detail below has a particle distribution (large and small) mixed by pulverization, and if this mixture ratio changes, the change in the average particle diameter is small. , The size of the gap formed is changed. For example, when large particle size and small particle size of catalyst-supported carbon particle aggregates are mixed, the larger the amount of small aggregates, the smaller the amount of small aggregates that occupy the space between adjacent large aggregates. On the contrary, if the amount of small aggregates is small, the amount of small aggregates occupying the gap is also small, and the space between the catalyst-supporting carbon particles is large. Therefore, one type of catalyst carrier (catalyst-carrying carbon particle aggregate) can be used without separately using catalyst carriers (catalyst-carrying carbon particle aggregates) having different particle sizes (large particle size and small particle size). By changing the particle size distribution, it is possible to control the voids between the catalyst-carrying carbon particles.

  In the above embodiment, the particle diameter of the catalyst carrier disposed in the catalyst layer on the electrolyte membrane side or the catalyst layer on the gas diffusion layer side is not particularly limited, but the pore diameter defined in the above (i) to (ii) The particle size is preferably such that the amount of pores and the porosity can be achieved. Specifically, the particle size of the catalyst carrier disposed in the catalyst layer on the electrolyte membrane side is preferably 0.1 to 1.0 μm, more preferably 0.2 to 0.8 μm, and gas diffusion The particle size of the catalyst carrier disposed in the catalyst layer on the layer side is preferably 0.1 to 1.0 μm, more preferably 0.1 to 0.6 μm. If a catalyst carrier having such a particle size is used, the pore diameter, the amount of pores and the porosity defined in the above (i) to (ii) can be easily achieved. The “particle diameter of the catalyst carrier” in the present invention is the average value of the particle diameter of the catalyst component determined from the crystallite diameter or transmission electron microscope image obtained from the half width of the diffraction peak of the catalyst component in X-ray diffraction. Can be measured.

  In the above embodiment, “a large number of catalyst carriers having a small particle diameter are arranged in the catalyst layer on the gas diffusion layer side” means that the particle diameter is such that the pore structure according to the present invention can be formed. This means that a small catalyst carrier is disposed in the catalyst layer on the gas diffusion layer side. Specifically, a catalyst carrier having a small particle size (preferably having a particle size as described above) is a polymer electrolyte. It is contained in the catalyst layer on the gas diffusion layer side in an amount of preferably 20 to 40% by mass, more preferably 25 to 35% by mass with respect to the total mass of the catalyst support (electrode catalyst). Similarly, “a large number of catalyst carriers having a large particle size are arranged in the catalyst layer on the electrolyte membrane side” means that a catalyst particle having a large particle size that can form the pore structure according to the present invention. Means that the catalyst support having a large particle size (preferably having a particle size as described above) is used as the polymer electrolyte and the catalyst support. It is contained in the catalyst layer on the electrolyte membrane side in an amount of preferably 20 to 40% by mass, more preferably 25 to 35% by mass with respect to the total mass with (electrode catalyst).

  Further, in the above embodiment, the amount of the polymer electrolyte contained in the catalyst layer on the gas diffusion layer side where a large number of catalyst carriers having a small particle size are arranged is an electrolyte where a large number of catalyst carriers having a large particle size are arranged. More preferably, the amount is greater than the amount of polymer electrolyte contained in the catalyst layer on the membrane side. This is because the degree of contact between the polymer electrolytes coated with a catalyst carrier (for example, carbon particles) also varies depending on the polymer electrolyte mass that occupies the interval between adjacent catalyst carriers. For this reason, if the polymer electrolysis mass is large, the polymer electrolysis mass occupying the space between adjacent catalyst carriers also increases, and the gap between the catalyst carriers is reduced. Conversely, if the polymer electrolysis mass is small, the gap is increased. This is because the polymer electrolytic mass occupied also decreases, and the gap between the catalyst carriers increases. At this time, the amount of the polymer electrolyte contained in the catalyst layer on the gas diffusion layer side where many catalyst carriers having a small particle diameter are arranged, and the catalyst layer on the electrolyte membrane side where many catalyst carriers having a large particle diameter are arranged The ratio with respect to the amount of the polymer electrolyte contained in is not particularly limited, but is preferably a particle size that can achieve the pore diameter, the pore amount, and the porosity defined in the above (i) to (ii). Specifically, the mass of the polymer electrolyte contained in the catalyst layer on the gas diffusion layer side where a large number of catalyst carriers having a small particle diameter are arranged is on the side of the electrolyte membrane where a large number of catalyst carriers having a large particle diameter are arranged. When the mass of the polymer electrolyte contained in the catalyst layer is 1, the ratio is preferably 1 to 2, more preferably 1 to 1.5. Alternatively, the polymer electrolyte composition (B1 ′ or B2 ′) of the catalyst layer on the electrolyte membrane side and the GDL side as described above or the I / C ratio of the catalyst layer on the electrolyte membrane side and the GDL side as described above is preferably applied. The

  In the above description, the method for forming the pore structure according to the present invention has been described in detail. However, in the present invention, at least one of the cathode and anode catalyst layers is formed by gas diffusion of the catalyst layer on the electrolyte membrane side. It is only necessary to have a structure in which a plurality of catalyst layers having different pore structures are stacked so as to be larger than the pore structure of the catalyst layer on the layer side, and the catalyst layer on the side not having such a pore structure is It can be formed in the same manner as in the prior art by using the production method of the house as it is, with some modifications, or by appropriately combining them. For this reason, description is abbreviate | omitted about the formation method of the catalyst layer in case it does not have the void | hole structure based on this invention.

  In the present invention, the catalyst component used in the cathode catalyst layer is not particularly limited as long as it has a catalytic action for the oxygen reduction reaction, and known catalysts can be used in the same manner. Further, the catalyst component used in the anode catalyst layer is not particularly limited as long as it has a catalytic action for the oxidation reaction of hydrogen, and a known catalyst can be used in the same manner. Specifically, it is selected from platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum and the like, and alloys thereof. Is done. Among these, those containing at least platinum are preferably used in order to improve catalyst activity, poisoning resistance to carbon monoxide and the like, heat resistance, and the like. The composition of the alloy is preferably 30 to 90 atomic% for platinum and 10 to 70 atomic% for the metal to be alloyed, depending on the type of metal to be alloyed. The composition of the alloy when the alloy is used as a cathode catalyst varies depending on the type of metal to be alloyed and can be appropriately selected by those skilled in the art, but platinum is 30 to 90 atomic%, and other metals to be alloyed are 10 It is preferable to set it to -70 atomic%. In general, an alloy is a generic term for a metal element having one or more metal elements or non-metal elements added and having metallic properties. The alloy structure consists of a eutectic alloy, which is a mixture of the component elements as separate crystals, a component element completely melted into a solid solution, and a component element composed of an intermetallic compound or a compound of a metal and a nonmetal. There is what is formed, and any may be used in the present application. At this time, the catalyst component used for the cathode catalyst layer and the catalyst component used for the anode catalyst layer can be appropriately selected from the above. In the following description, unless otherwise specified, the description of the catalyst component for the cathode catalyst layer and the anode catalyst layer has the same definition for both, and is collectively referred to as “catalyst component”. However, the catalyst components for the cathode catalyst layer and the anode catalyst layer do not need to be the same, and are appropriately selected so as to exhibit the desired action as described above.

  The shape and size of the catalyst component are not particularly limited, and the same shape and size as known catalyst components can be used, but the catalyst component is preferably granular. At this time, the average particle diameter of the catalyst particles used in the catalyst ink is not particularly limited as long as it is a diameter capable of forming the pore structure according to the present invention. However, in the catalyst layer on the electrolyte membrane side, preferably 1 to 30 nm. The thickness is preferably 1.5 to 20 nm, particularly preferably 2 to 10 nm. In the catalyst layer on the GDL side, the thickness is preferably 1 to 25 nm, more preferably 1.5 to 15 nm, and particularly preferably 2 to 8 nm. In the catalyst layer having no pore structure according to the present invention, the smaller the average particle size of the catalyst particles used in the catalyst ink, the higher the effective electrode area where the electrochemical reaction proceeds, so the oxygen reduction activity increases. Although it is preferable, the average particle size of the catalyst particles contained in the catalyst ink is preferably 1 to 30 nm, more preferably in consideration of the fact that the phenomenon in which the oxygen reduction activity is actually reduced when the average particle size is too small is observed. It is preferably 1.5 to 20 nm, more preferably 2 to 10 nm, particularly preferably 2 to 5 nm. Here, the thickness is preferably 1 nm or more from the viewpoint of easy loading, and is preferably 30 nm or less from the viewpoint of catalyst utilization. The “average particle diameter of the catalyst particles” in the present invention is the average value of the particle diameter of the catalyst component determined from the crystallite diameter or transmission electron microscope image determined from the half width of the diffraction peak of the catalyst component in X-ray diffraction. Can be measured.

  In the present invention, the catalyst particles described above are included in the catalyst ink as an electrode catalyst supported on a conductive carrier.

  The conductive carrier may have any specific surface area for supporting the catalyst particles in a desired dispersed state and has sufficient electronic conductivity as a current collector. The main component is carbon. Preferably there is. Specific examples include carbon particles made of carbon black, activated carbon, coke, natural graphite, artificial graphite and the like. In the present invention, “the main component is carbon” refers to containing a carbon atom as a main component, and is a concept including both a carbon atom only and a substantially carbon atom. In some cases, elements other than carbon atoms may be included in order to improve the characteristics of the fuel cell. In addition, being substantially composed of carbon atoms means that mixing of impurities of about 2 to 3% by mass or less is allowed.

The BET specific surface area of the conductive carrier may be a specific surface area sufficient to carry the catalyst component in a highly dispersed state, but is preferably 20 to 1600 m ² / g, more preferably 80 to 1200 m ² / g. Is good. When the specific surface area is in the above range, the dispersibility of the catalyst component and the polymer electrolyte in the conductive support is good, sufficient power generation performance can be achieved, and sufficient catalyst component and polymer electrolyte are effective. Utilization rate can be achieved.

  The size of the conductive carrier is not particularly limited, and is appropriately selected depending on the particle size of the catalyst support on the electrolyte membrane side and the GDL side of the electrode catalyst layer as described above. For example, for the catalyst carrier on the electrolyte membrane side of the electrode catalyst layer, the average particle diameter of the conductive carrier is 100 to 900 nm, preferably about 200 to 700 nm. Further, for the catalyst carrier on the GDL side of the electrode catalyst layer, the average particle diameter of the conductive carrier is 50 to 700 nm, preferably about 100 to 600 nm. In the catalyst layer having no pore structure according to the present invention, the size of the conductive carrier is not particularly limited, but the ease of loading, the catalyst utilization rate, and the thickness of the electrode catalyst layer are controlled within an appropriate range. From such a viewpoint, it is preferable that the average particle diameter is 50 to 1000 nm, preferably about 100 to 900 nm.

  In the electrode catalyst in which the catalyst component is supported on the conductive support, the supported amount of the catalyst component is preferably 10 to 80% by mass, more preferably 30 to 70% by mass with respect to the total amount of the electrode catalyst. Good. If the loading is within the above range, it is preferable because a sufficient degree of dispersion of the catalyst components on the conductive support, improvement in power generation performance, economic advantages, and catalytic activity per unit mass can be achieved. The supported amount of the catalyst component may be the same or different on the electrolyte membrane side and the GDL side of the electrode catalyst layer. Further, the amount of the catalyst component supported can be examined by inductively coupled plasma emission spectroscopy (ICP).

  Alternatively, in the present invention, a commercially available electrode catalyst may be used. As such commercially available products, for example, electrode catalysts such as those manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., N.E. Chemcat, E-TEK, and Johnson Matthey can be used. Or, carbon support (Ketjen Black, Vulcan, Acetylene Black, Black Pearl, graphitized carbon support (for example, graphitized Ketjenbrak) pre-heated at high temperature, carbon nanotube, carbon nanohorn, carbon fiber, etc.) A material in which platinum or a platinum alloy is supported (supporting concentration of catalyst species, 30% to 70%) can also be used as an electrode catalyst.

  The electrode catalyst layer of the present invention contains a polymer electrolyte in addition to the electrode catalyst. The polymer electrolyte is not particularly limited, and a known one can be used, but any member having at least high proton conductivity may be used. The polymer electrolyte that can be used in this case is roughly classified into a fluorine-based electrolyte that contains fluorine atoms in the whole or a part of the polymer skeleton and a hydrocarbon-based electrolyte that does not contain fluorine atoms in the polymer skeleton.

  Specific examples of the fluorine electrolyte include perfluorocarbon sulfonic acids such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.). Polymer, polytrifluorostyrene sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene A preferred example is a fluoride-perfluorocarbon sulfonic acid-based polymer.

  Specific examples of the hydrocarbon electrolyte include polysulfone sulfonic acid, polyaryl ether ketone sulfonic acid, polybenzimidazole alkyl sulfonic acid, polybenzimidazole alkyl phosphonic acid, polystyrene sulfonic acid, polyether ether ketone sulfonic acid, polyphenyl. A suitable example is sulfonic acid.

  The polymer electrolyte preferably contains a fluorine atom because of its excellent heat resistance and chemical stability. Among them, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.) Fluorine electrolytes such as Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) are preferred. In particular, in the present invention, when a polymer electrolyte having a sulfonic acid group such as Nafion (registered trademark, manufactured by DuPont) is used, EW (Equivalent Weight; dry membrane weight per mole of sulfonic acid group) It is preferable to use a sulfonic acid group having a specific gravity of about 600 to 1100.

  The catalyst component can be supported on the conductive carrier by a known method. For example, known methods such as impregnation method, liquid phase reduction support method, evaporation to dryness method, colloid adsorption method, spray pyrolysis method, reverse micelle (microemulsion method) can be used. Alternatively, a commercially available electrode catalyst may be used.

  In the present invention, an electrode catalyst layer can be produced by a method such as a transfer method using a catalyst ink comprising the above-described electrode catalyst, polymer electrolyte and solvent. The production method of the electrode catalyst layer in such a case is not particularly limited, and a known transfer method can be used in the same manner or with appropriate modification. For example, the following method can be used. That is, the catalyst ink for forming the catalyst layer on the electrolyte membrane side and the catalyst ink for forming the catalyst layer on the gas diffusion layer side are prepared. First, a catalyst ink for forming a catalyst layer on the gas diffusion layer side is applied and dried on a transfer mount to form an electrode catalyst layer on the gas diffusion layer side. Next, the catalyst ink for forming the catalyst layer on the electrolyte membrane side is applied and dried on the electrode catalyst layer on the gas diffusion layer side thus formed, and the electrode catalyst layer on the electrolyte membrane side is gas diffused. It is formed on the electrode catalyst layer on the layer side. In this case, the solvent is not particularly limited, and a normal solvent used for forming the electrode catalyst layer can be used in the same manner. Specifically, water, lower alcohols such as cyclohexanol, ethanol and 2-propanol can be used. Also, the amount of solvent used is not particularly limited, and the same amount as known can be used. In the catalyst ink, the electrode catalyst has a desired action, that is, hydrogen oxidation reaction (anode side) and oxygen reduction reaction. Any amount may be used as long as it can sufficiently exert the action of catalyzing (cathode side). It is preferable that the electrode catalyst is present in the catalyst ink in an amount of 5 to 30% by mass, more preferably 9 to 20% by mass. The polymer electrolyte is preferably present in the above amount / ratio.

  The catalyst ink of the present invention may contain a thickener. The use of a thickener is effective when the catalyst ink cannot be successfully applied onto a transfer mount. The thickener that can be used in this case is not particularly limited, and a known thickener can be used. Examples thereof include glycerin, ethylene glycol (EG), polyvinyl alcohol (PVA), and propylene glycol (PG). Of these, propylene glycol (PG) is preferably used. The use of propylene glycol (PG) increases the boiling point of the catalyst ink and decreases the solvent evaporation rate. For this reason, for example, when an electrode catalyst layer is formed on an electrolyte membrane by a transfer method, the catalyst ink is first applied and dried on a transfer mount different from the membrane using a screen printer or the like. By adding PG therein, the solvent evaporation rate in the applied catalyst ink is suppressed, and it is possible to suppress / prevent the occurrence of cracks in the electrode catalyst layer after the drying process. Further, the amount of the thickener added when using the thickener is not particularly limited as long as it does not interfere with the above-described effects of the present invention, but is preferably 5 with respect to the total mass of the catalyst ink. ˜20 mass%.

  The catalyst ink of the present invention is not particularly limited in its preparation method as long as an electrode catalyst, a polymer electrolyte and a solvent, and if necessary, a water-repellent polymer and / or a thickener are appropriately mixed. For example, a catalyst ink can be prepared by adding an electrolyte to a polar solvent, heating and stirring the mixed solution to dissolve the electrolyte in the polar solvent, and then adding an electrode catalyst thereto. Alternatively, after the electrolyte is once dispersed / suspended in a solvent, the dispersion / suspension may be mixed with an electrode catalyst to prepare a catalyst ink. In addition, a commercially available electrolyte solution (for example, DuPont Nafion solution: Nafion dispersed / suspended at a concentration of 5 wt% in 1-propanol) in which the electrolyte is previously prepared in the above other solvent is used as it is. May be used in the method. At this time, the catalyst ink is obtained by dispersing the slurry mixed as described above with an ultrasonic homogenizer, or after pulverizing the mixed slurry with an apparatus such as a sand grinder, a circulating ball mill, or a circulating bead mill. It is preferably produced by applying a vacuum degassing operation. In order to obtain the pore structure according to the present invention, the catalyst ink more specifically has the pore diameter, the amount of pores, the porosity and the polymer as described in the above (i) to (iii). It adjusts suitably so that it may become an electrolytic mass.

  Further, as the transfer mount, a known sheet such as a polyester sheet such as a PTFE (polytetrafluoroethylene) sheet or a PET (polyethylene terephthalate) sheet can be used. The transfer mount is appropriately selected according to the type of catalyst ink to be used (particularly, a conductive carrier such as carbon in the ink). In the above process, the thickness of the electrode catalyst layer is not particularly limited as long as it can sufficiently exhibit the catalytic action of the hydrogen oxidation reaction (anode side) and the oxygen reduction reaction (cathode side). Thickness can be used. Specifically, the thickness of each electrode catalyst layer is preferably 1 to 10 μm as described above. The method for applying the catalyst ink onto the transfer mount is not particularly limited, and a known method such as a screen printing method, a deposition method, or a spray method can be similarly applied.

  In the above method, the drying conditions for the applied electrode catalyst layer and gas diffusion layer side electrode catalyst layer are not particularly limited as long as the polar solvent can be completely removed from the electrode catalyst layer. Specifically, the catalyst ink coating layer (electrode catalyst layer) is dried in a vacuum dryer at room temperature to 100 ° C., more preferably 50 to 80 ° C., for 30 to 60 minutes. At this time, if the thickness of the catalyst layer is not sufficient, the coating and drying process is repeated until a desired thickness is obtained. Next, after sandwiching the polymer electrolyte membrane between the electrode catalyst layers according to the present invention laminated in this manner, hot pressing is performed on the laminate. At this time, the hot press conditions are not particularly limited as long as the electrode catalyst layer and the polymer electrolyte membrane can be sufficiently closely bonded, but are 100 to 200 ° C., more preferably 110 to 170 ° C. It is preferable to carry out at a press pressure of 1 to 5 MPa. Thereby, the bondability between the polymer electrolyte membrane and the electrode catalyst layer can be enhanced. After performing the hot press, the MEA composed of the electrode catalyst layer and the polymer electrolyte membrane can be obtained by removing the transfer mount.

  In the above description, the method for producing the MEA by applying the catalyst ink by the transfer method has been described. However, the MEA of the present invention is a catalyst for forming a catalyst layer on the electrolyte membrane side on the surface of the polymer electrolyte membrane. After directly applying the ink to form the catalyst layer on the electrolyte membrane side, the catalyst ink for the electrode catalyst layer on the gas diffusion layer side is further applied and dried on the catalyst layer on the electrolyte membrane side, and the electrolyte membrane side A method of forming an electrode catalyst layer on the gas diffusion layer side on the electrode catalyst layer may be used. In this case, the conditions for forming the electrode catalyst layer on the polymer electrolyte membrane are not particularly limited, and can be used in the same manner as known methods or with appropriate modifications. For example, the catalyst ink is applied onto the polymer electrolyte membrane so that the thickness after drying is 5 to 20 μm, and is 25 to 150 ° C., more preferably 60 to 120 ° C. in a vacuum dryer or under reduced pressure. And drying for 5 to 30 minutes, more preferably for 10 to 20 minutes. In addition, in the said process, when the thickness of an electrode catalyst layer is not enough, the said application | coating and drying process is repeated until it becomes desired thickness.

  The polymer electrolyte membrane used in the MEA of the present invention is not particularly limited, and examples thereof include a membrane made of the same polymer electrolyte as that used for the electrode catalyst layer. In addition, various Nafion (registered trademark of DuPont) manufactured by DuPont and perfluorosulfonic acid membranes represented by Flemion, ion exchange resins manufactured by Dow Chemical, ethylene-tetrafluoroethylene copolymer resin membrane, trifluoro Fluoropolymer electrolytes such as resin membranes based on styrene, hydrocarbon resin membranes with sulfonic acid groups, and other commonly available solid polymer electrolyte membranes and polymer microporous membranes A membrane impregnated with a liquid electrolyte, a membrane in which a porous body is filled with a polymer electrolyte, or the like may be used. The polymer electrolyte used for the polymer electrolyte membrane and the polymer electrolyte used for each electrode catalyst layer may be the same or different, but the adhesion between each electrode catalyst layer and the polymer electrolyte membrane From the viewpoint of improving the properties, it is preferable to use the same one.

  The thickness of the polymer electrolyte membrane may be appropriately determined in consideration of the properties of the obtained MEA, but is preferably 5 to 300 μm, more preferably 10 to 200 μm, and particularly preferably 15 to 100 μm. From the viewpoint of strength during film formation and durability during MEA operation, it is preferably 5 μm or more, and from the viewpoint of output characteristics during MEA operation, it is preferably 300 μm or less.

  The polymer electrolyte membrane includes polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) in addition to the above-described fluorine-based polymer electrolyte and membranes made of hydrocarbon resins having sulfonic acid groups. For example, a porous thin film formed from a material impregnated with an electrolyte component such as phosphoric acid or ionic liquid may be used.

  The MEA according to the present invention further includes a gas diffusion layer as will be described in detail below. At this time, it is preferable that the gas diffusion layer is further bonded to each electrode catalyst layer in the above method by peeling off the transfer mount or sandwiching the bonded body prepared above with the gas diffusion layer. Alternatively, after an electrode catalyst layer is formed on the surface of the gas diffusion layer in advance to produce an electrode catalyst layer-gas diffusion layer assembly, the electrode catalyst layer-gas diffusion layer assembly is used in the same manner as described above. It is also preferable to sandwich and bond the molecular electrolyte membrane by hot pressing.

  At this time, the gas diffusion layer used in the MEA is not particularly limited, and a known one can be used in the same manner. For example, the conductive and porous properties such as carbon woven fabric, paper-like paper body, felt, and non-woven fabric are used. The thing which uses the sheet-like material which has as a base material etc. are mentioned. The thickness of the substrate may be appropriately determined in consideration of the characteristics of the obtained gas diffusion layer, but may be about 30 to 500 μm. If the thickness is less than 30 μm, sufficient mechanical strength or the like may not be obtained, and if it exceeds 500 μm, the distance through which gas or water permeates is undesirably increased.

  The method for forming the electrode catalyst layer on the surface of the gas diffusion layer is not particularly limited, and known methods such as a screen printing method, a deposition method, and a spray method can be similarly applied. In addition, the conditions for forming the electrode catalyst layer on the surface of the gas diffusion layer are not particularly limited, and the same conditions as before can be applied by the specific forming method as described above.

  The gas diffusion layer preferably contains a water repellent in the base material for the purpose of further improving water repellency and preventing a flooding phenomenon. Although it does not specifically limit as said water repellent, It is fluorine-type, such as a polytetrafluoroethylene (PTFE), a polyvinylidene fluoride (PVDF), a polyhexafluoropropylene, a tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Examples thereof include polymer materials, polypropylene, and polyethylene.

  Moreover, in order to improve water repellency more, the said gas diffusion layer may have a carbon particle layer which consists of an aggregate | assembly of the carbon particle containing a water repellent on the said base material.

  The carbon particles are not particularly limited, and may be conventional ones such as carbon black, graphite, and expanded graphite. Of these, carbon blacks such as oil furnace black, channel black, lamp black, thermal black, and acetylene black are preferred because of their excellent electron conductivity and large specific surface area. The particle size of the carbon particles is preferably about 10 to 100 nm. Thereby, while being able to obtain the high drainage property by capillary force, it becomes possible to improve contact property with a catalyst layer.

  Examples of the water repellent used for the carbon particle layer include the same water repellents as those described above used for the substrate. Of these, fluorine-based polymer materials are preferably used because of their excellent water repellency and corrosion resistance during electrode reaction.

  In the carbon particle layer, the mixing ratio of the carbon particles to the water repellent may be insufficient to obtain water repellency as expected when there are too many carbon particles. If there are too many water repellents, sufficient electron conductivity may be obtained. There is a risk that it will not be obtained. Considering these, the mixing ratio of the carbon particles and the water repellent in the carbon particle layer is preferably about 90:10 to 40:60 in terms of mass ratio.

  The thickness of the carbon particle layer may be appropriately determined in consideration of the water repellency of the obtained gas diffusion layer.

  When a water repellent is contained in the gas diffusion layer, a general water repellent treatment method may be used. For example, after immersing the base material used for a gas diffusion layer in the dispersion liquid of a water repellent agent, the method of heat-drying with oven etc. is mentioned.

  When forming a carbon particle layer on a substrate in a gas diffusion layer, the carbon particles, water repellent, etc. are in a solvent such as water, alcohol solvents such as perfluorobenzene, dichloropentafluoropropane, methanol, ethanol, etc. A slurry is prepared by dispersing in a slurry, and the slurry is applied on a substrate and dried, or the slurry is dried and pulverized to form a powder, and this is applied to the gas diffusion layer. Use it. Then, it is preferable to heat-process at about 250-400 degreeC using a muffle furnace or a baking furnace.

  In addition, the manufacturing method of the joined body including the electrode catalyst layer, the electrolyte membrane, and preferably the gas diffusion layer is not limited to the method described above. That is, after applying and drying the catalyst ink on the electrolyte membrane, hot pressing is performed, the electrode catalyst layer is joined to the solid polymer electrolyte membrane, and the obtained joined body is sandwiched between the gas diffusion layers to form an MEA. Method: A catalyst ink may be applied to the gas diffusion layer and dried to form an electrode catalyst layer, which may be joined to the electrolyte membrane by hot pressing, etc. Just do it.

  The electrolyte membrane-electrode assembly (MEA) of the present invention described above is an electrode catalyst layer formed by laminating a catalyst carrier (catalyst-carrying carbon particles) covered with a polymer electrolyte having proton selective permeability. Is composed of at least two layers having different pore structures (pore diameter, amount of pores, porosity), and the electrode catalyst layer having a large pore structure is arranged on the solid polymer electrolyte membrane side (inside). The small electrode catalyst layer is laminated so as to be on the gas electrode side (outside). Furthermore, in the electrode catalyst layer of the fuel cell described above, by increasing the polymer electrolysis mass from the solid polymer electrolyte membrane side (inner side) to the gas electrode side (outer side), the electrode catalyst layer having a large pore structure becomes solid high. The electrode catalyst layer having a small pore structure is laminated on the molecular electrolyte membrane side (inner side) so as to be on the gas electrode side (outer side). In such a hole structure of the electrode catalyst layer, (a) the diffusion permeability of the reaction gas is such that the reaction gas diffuses quickly from the outside (GDL side) to the inside (solid polymer electrolyte membrane side) of the electrode catalyst layer. Can be transmitted. Therefore, as the reaction proceeds, there is no shortage of reaction gas on the inside, the catalyst utilization efficiency can be maintained high, and the battery performance can be fully expressed; (b) proton conductivity means that protons are electrocatalysts. Because it can move (diffusion) quickly from the inside to the outside of the layer, as the reaction proceeds, there is no shortage of protons on the outside, the catalyst utilization efficiency can be maintained high, and battery performance is fully expressed. (C) Inside the electrocatalyst layer, the produced water permeates the solid polymer electrolyte membrane and can quickly move (discharge) from the cathode side to the anode side. It is suppressed, the utilization efficiency of the catalyst can be maintained high, and the battery performance can be sufficiently expressed; (d) a part of the generated water diffuses in the cluster of the polymer electrolyte and reaches the interface between the electrode catalyst layer and the GDL, Since the discharge of DL from the electrode catalyst layer side to the separator side is promoted, the decrease in diffusion permeability (flooding) of the reaction gas is suppressed, the utilization efficiency of the catalyst can be maintained high, and the battery performance can be fully expressed. There is.

  By using such an electrolyte membrane-electrode assembly, a highly reliable fuel cell excellent in power generation performance and durability can be provided. Therefore, the present invention also provides a fuel cell using the electrolyte membrane-electrode assembly of the present invention.

  The type of the fuel cell is not particularly limited. In the above description, the polymer electrolyte fuel cell has been described as an example. In addition, an alkaline fuel cell, a direct methanol fuel cell, a micro cell, and the like are described. Examples include a fuel cell. Among these, a polymer electrolyte fuel cell is preferred because it is small in size, high density and high output. The fuel cell is useful as a stationary power source in addition to a power source for a moving body such as a vehicle in which a mounting space is limited. However, the fuel cell is particularly useful for an automobile application in which system start / stop and output fluctuation frequently occur. It can be particularly preferably used.

  The polymer electrolyte fuel cell is useful not only as a stationary power source but also as a power source for a moving body such as an automobile having a limited mounting space. In particular, it is particularly preferable to be used as a power source for a mobile body such as an automobile in which corrosion of a carbon support or a catalytic metal (such as Pt) is likely to occur due to a high output voltage required after a relatively long shutdown.

  The configuration of the fuel cell is not particularly limited, and a conventionally known technique may be used as appropriate. Generally, the fuel cell has a structure in which an MEA is sandwiched between separators.

  The separator can be used without limitation as long as it is conventionally known, such as those made of carbon such as dense carbon graphite and a carbon plate, and those made of metal such as stainless steel. The separator has a function of separating air and fuel gas, and a channel groove for securing the channel may be formed. The thickness and size of the separator, the shape of the flow channel, and the like are not particularly limited, and may be appropriately determined in consideration of the output characteristics of the obtained fuel cell.

  Further, in order to prevent the gas supplied to each catalyst layer from leaking to the outside, a gas seal portion may be further provided at a portion where the catalyst layer is not formed on the gasket layer. Examples of the material constituting the gas seal portion include rubber materials such as fluoro rubber, silicon rubber, ethylene propylene rubber (EPDM), polyisobutylene rubber, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoro. Fluorine polymer materials such as propylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and thermoplastic resins such as polyolefin and polyester. The thickness of the gas seal portion may be 2 mm to 50 μm, preferably about 1 mm to 100 μm.

  Furthermore, a stack in which a plurality of MEAs are stacked via a separator and connected in series may be formed so that the fuel cell can obtain a desired voltage or the like. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these.

Example 1
1. Preparation of Electrocatalyst 4.0 g of carbon black (manufactured by Ketjen Black International, Ketjen Black EC, BET surface area = 800 m ^{2 /} g) was prepared as a conductive carbon material, and dinitrodiammine platinum aqueous solution (Pt concentration 1) 0.0%) was added and stirred for 1 hour. Furthermore, 50 g of methanol was mixed as a reducing agent and stirred for 1 hour. Thereafter, while bubbling 10% -CO (carbon monoxide), the mixture was heated to 80 ° C. in 30 minutes, stirred at 80 ° C. for 6 hours, and then cooled to room temperature in 1 hour. After filtering the precipitate, the obtained solid was dried under reduced pressure at 85 ° C. for 12 hours, pulverized with a mortar, and an anode electrode catalyst (average particle diameter of Pt particles 2.6 nm, Pt support concentration 50% by mass). Obtained.

  Unless otherwise specified, the electrode catalyst thus obtained was used for the production of an anode catalyst layer and a cathode catalyst layer in Examples 1 to 15 and Comparative Examples 1 to 3 below.

2. Production of anode-side electrode catalyst layer Five times the amount of purified water was added to the mass of the anode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the solid mass ratio of the anode electrode catalyst to the carbon mass was Ionomer / Carbon (I / C ratio) = 1.0 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. An amount of the catalyst slurry corresponding to the desired thickness was printed on one side of the polytetrafluoroethylene sheet by screen printing and dried at 60 ° C. for 24 hours. The size of the formed anode catalyst layer was 5 cm × 5 cm. The coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the anode catalyst layer was 6 μm). Thus, an anode catalyst layer coated sheet A1 was obtained.

3. Production of cathode-side electrode catalyst layer The cathode-side electrode catalyst layer shown in FIG. 3 was produced as follows.

3-1. Cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2029CS manufactured by DuPont (solution with a solid content of 10%, EW = 900) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.3 / 1.0. The particle size distribution of the catalyst-supported carbon used here is indicated by “d” in FIGS. 6-1 to 6-3.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions according to the desired thickness and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a coating sheet B1 was obtained.

3-2. Cathode catalyst layer on the polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 0.9 / 1.0. The particle size distribution of the catalyst-supported carbon used here is indicated by “b” in FIGS. 6-1 to 6-3.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on the coating sheet B1 in an amount corresponding to the desired thickness in two portions, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet C1 was obtained.

4). Preparation of Electrolyte Membrane-Electrode Assembly (MEA) Nafion NRE211 (film thickness: 25 μm) as a solid polymer electrolyte membrane and electrode catalyst layer (anode side A1, cathode side) formed on the previously prepared polytetrafluoroethylene sheet And C1). At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Then, it hot-pressed for 10 minutes at 130 degreeC and 2.0 MPa, peeled only the polytetrafluoroethylene sheet, and obtained MEA.

The cathode catalyst layer transferred onto the solid polymer electrolyte membrane had a thickness of about 12 μm, the amount of Pt supported was 0.4 mg per 1 cm ^{2 of the} apparent electrode area, and the electrode area was 25 cm ² . The anode catalyst layer had a thickness of about 6 μm, the amount of Pt supported was 0.2 mg per 1 cm ^{2 of the} apparent electrode area, and the electrode area was 25 cm ² . Thus, a membrane electrode assembly (MEA) M1 was obtained.

5. MEA Performance Evaluation The performance of the electrolyte membrane-electrode assembly (MEA) obtained in 4 above was evaluated as follows.

  Carbon paper (size: 6.0 cm × 5.5 cm, thickness: 320 μm) as a gas diffusion layer and a gas separator with a gas flow path were respectively disposed on both sides of the electrolyte membrane-electrode assembly M1 and further plated with gold. The unit cell for evaluation was sandwiched between stainless steel current collector plates.

In the evaluation unit cell, hydrogen was supplied as a fuel to the anode side, and air was supplied as an oxidant to the cathode side. The supply pressure of both gases was atmospheric pressure, hydrogen was set to 58.6 ° C. and relative humidity 60%, air was set to 54.8 ° C. and relative humidity 50%, and the cell temperature was set to 70 ° C. The hydrogen utilization rate was 67% and the air utilization rate was 40%. Under this condition, the cell voltage when power was generated at a current density of 1.0 A / cm ² was measured as the initial cell voltage.

6). MEA Durability Test Subsequently, power generation was stopped after 60 seconds of power generation. After stopping, the supply of hydrogen and air was stopped, the single cell was replaced with air, and the system was on standby for 50 seconds. Thereafter, hydrogen gas was supplied to the anode side for 10 seconds at 1/5 of the above utilization rate. Thereafter, hydrogen gas was supplied to the anode side and air was supplied to the cathode side under the same conditions as described above, and power was generated again at a current density of 1.0 A / cm ² for 60 seconds. Also, the load current at this time was increased from 0 A / cm ² to 1 A / cm ² in 30 seconds. This power generation / stop operation was performed, the cell voltage was measured, and the power generation performance was evaluated. The number of cycles when the cell voltage at a current density of 1.0 A / cm ² was 0.45 V was used as the durability evaluation value. Tables 1 and 2 show the preparation conditions of the anode and cathode catalyst layers of this example, and the results of the performance test and durability test. In Table 1 below, “Ionomer (wt%)” represents the polymer electrolyte composition of the cathode catalyst layer on the GDL side and the cathode catalyst layer on the polymer electrolyte membrane side in mass%.

Comparative Example 1
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. Preparation of cathode catalyst layer 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 0.9 / 1.0. The particle size distribution of the catalyst-supported carbon used here is indicated by “b” in FIGS. 6-1 to 6-3.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on the coating sheet C1 in an amount corresponding to the desired thickness in two portions, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. The coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.4 mg / cm ² (the average thickness of the cathode catalyst layer was 12 μm). Thus, a cathode catalyst layer coated sheet D1 was obtained.

3. Preparation of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness: 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer (anode side A1, cathode side) formed on the previously prepared polytetrafluoroethylene sheet D1). At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Then, it hot-pressed for 10 minutes at 130 degreeC and 2.0 MPa, peeled only the polytetrafluoroethylene sheet, and obtained MEA.

The cathode catalyst layer transferred onto the solid polymer electrolyte membrane had a thickness of about 12 μm, the amount of Pt supported was 0.4 mg per 1 cm ^{2 of the} apparent electrode area, and the electrode area was 25 cm ² . The anode catalyst layer had a thickness of about 6 μm, the amount of Pt supported was 0.2 mg per 1 cm ^{2 of the} apparent electrode area, and the electrode area was 25 cm ² . Thus, a membrane electrode assembly (MEA) N1 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Comparative Example 2
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 0.9 / 1.0. The particle size distribution of the catalyst-supported carbon used here is indicated by “b” in FIGS. 6-1 to 6-3.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions according to the desired thickness and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a coating sheet D2 was obtained.

2-2. Cathode catalyst layer on the side of the solid polymer electrolyte membrane Five times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2029CS manufactured by DuPont (solution with a solid content of 10%, EW = 900) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.3 / 1.0. The particle size distribution of the catalyst-supported carbon used here is indicated by “d” in FIGS. 6-1 to 6-3.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. The catalyst slurry having an amount corresponding to a desired thickness was printed in two portions on the coating sheet D2, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet E2 was obtained.

3. Production of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer (anode side A1 on the cathode side) formed on the previously produced polytetrafluoroethylene sheet E2). At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Then, it hot-pressed for 10 minutes at 130 degreeC and 2.0 MPa, peeled only the polytetrafluoroethylene sheet, and obtained MEA.

The cathode catalyst layer transferred onto the solid polymer electrolyte membrane had a thickness of about 12 μm, the amount of Pt supported was 0.4 mg per 1 cm ^{2 of the} apparent electrode area, and the electrode area was 25 cm ² . The anode catalyst layer had a thickness of about 6 μm, the amount of Pt supported was 0.2 mg per 1 cm ^{2 of the} apparent electrode area, and the electrode area was 25 cm ² . Thus, a membrane electrode assembly (MEA) N2 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Comparative Example 3
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. Preparation of cathode catalyst layer 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2029CS manufactured by DuPont (solution with a solid content of 10%, EW = 900) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.3 / 1.0. The particle size distribution of the catalyst-supported carbon used here is indicated by “d” in FIGS. 6-1 to 6-3.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in four portions in an amount corresponding to the desired thickness, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. The coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.4 mg / cm ² (the average thickness of the cathode catalyst layer was 12 μm). Thus, a cathode catalyst layer coated sheet D3 was obtained.

3. Production of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer (anode side A1 on the cathode side) formed on the previously produced polytetrafluoroethylene sheet D3). At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Then, it hot-pressed for 10 minutes at 130 degreeC and 2.0 MPa, peeled only the polytetrafluoroethylene sheet, and obtained MEA.

The cathode catalyst layer transferred onto the solid polymer electrolyte membrane had a thickness of about 12 μm, the amount of Pt supported was 0.4 mg per 1 cm ^{2 of the} apparent electrode area, and the electrode area was 25 cm ² . The anode catalyst layer had a thickness of about 6 μm, the amount of Pt supported was 0.2 mg per 1 cm ^{2 of the} apparent electrode area, and the electrode area was 25 cm ² . Thus, a membrane electrode assembly (MEA) N3 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 2
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. Production of Cathode Catalyst Layer The cathode-side electrode catalyst layer shown in FIG. 4 was produced as follows.

2-1. Preparation of cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and an ionomer solution (solid content 10%, EW = 700) in which an electrolyte of EW700 was dispersed was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.3 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions according to the desired thickness and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a coating sheet B2 was obtained.

2-2. Preparation of cathode catalyst layer on the polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 0.9 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. An amount of the catalyst slurry corresponding to the desired thickness was printed once on the coating sheet B2 and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet C2 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 3
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. Production of Cathode Catalyst Layer The cathode-side electrode catalyst layer shown in FIG. 5 was produced as follows.

2-1. Preparation of cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2029CS manufactured by DuPont (solution with a solid content of 10%, EW = 900) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.3 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions according to the desired thickness and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a coating sheet B1 was obtained.

2-2. Preparation of cathode catalyst layer on the polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this was added 0.5 times the amount of n-propyl alcohol, and an ionomer solution (20% solid content, EW = 1,100) in which an electrolyte of EW1,100 was dispersed was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 0.9 / 1.0. The particle size distribution of the catalyst-supported carbon used here is indicated by “b” in FIGS. 6-1 to 6-3.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on the coating sheet B1 in an amount corresponding to the desired thickness in two portions, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet C3 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 4
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and an ionomer solution (10% solid content, EW = 700) in which the electrolyte of EW700 was dispersed was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.3 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions according to the desired thickness and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a coating sheet B2 was obtained.

2-2. Preparation of cathode catalyst layer on the polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 0.9 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. An amount of the catalyst slurry corresponding to the desired thickness was printed once on the coating sheet B2 and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet C4 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 5
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2029CS manufactured by DuPont (solution with a solid content of 10%, EW = 900) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.1 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in three times according to the desired thickness, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a coating sheet B3 was obtained.

2-2. Preparation of cathode catalyst layer on the polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.0 / 1.0.
The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on the coating sheet B3 in an amount corresponding to the desired thickness in two portions, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet C5 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was produced in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability were performed on the MEA. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 6
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side Example 5 A catalyst slurry prepared according to 2-1 was applied to one side of a polytetrafluoroethylene sheet by screen printing, and an amount of catalyst slurry corresponding to the desired thickness was applied four times. Printing was performed separately to obtain a coating sheet B4.

2-2. Production of Cathode Catalyst Layer on Polymer Electrolyte Membrane Example 5 A catalyst slurry produced according to 2-2 was printed twice on the aforementioned application sheet B4 to obtain a cathode catalyst layer application sheet C6.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 7
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on GDL side Example 6 Catalyst slurry prepared according to 2-1 was screen-printed on one side of a polytetrafluoroethylene sheet, and an amount of catalyst slurry corresponding to the desired thickness was applied five times. Printing was performed separately to obtain a coating sheet B5.

2-2. Preparation of Cathode Catalyst Layer on Polymer Electrolyte Membrane Example 6 A catalyst slurry prepared according to 2-2 was printed twice on the aforementioned application sheet B5 to obtain a cathode catalyst layer application sheet C7.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 8
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side Example 6 Catalyst slurry prepared according to 2-1 was applied on one side of a polytetrafluoroethylene sheet by screen printing in an amount corresponding to the desired thickness six times. Printing was performed separately to obtain a coating sheet B6.

2-2. Preparation of Cathode Catalyst Layer on Polymer Electrolyte Membrane Example 6 A catalyst slurry prepared according to 2-2 was printed twice on the aforementioned application sheet B6 to obtain a cathode catalyst layer application sheet C8.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 9
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and an ionomer solution (10% solid content, EW = 700) in which the electrolyte of EW700 was dispersed was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.1 / 1.0.

  The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of the polytetrafluoroethylene sheet by screen printing in five times in an amount corresponding to the desired thickness to obtain a coated sheet B7.

2-2. Production Example 6 for Cathode Catalyst Layer on Polymer Electrolyte Membrane The catalyst slurry produced according to 2-2 was printed twice on the aforementioned application sheet B7 to obtain a cathode catalyst layer application sheet C9.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 10
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and an ionomer solution (10% solid content, EW = 700) in which the electrolyte of EW700 was dispersed was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.3 / 1.0.

  The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of the polytetrafluoroethylene sheet by screen printing in four times in an amount corresponding to the desired thickness to obtain a coated sheet B8.

2-2. Production Example 6 of Cathode Catalyst Layer on Polymer Electrolyte Membrane The catalyst slurry produced according to 2-2 was printed twice on the aforementioned application sheet B8 to obtain a cathode catalyst layer application sheet C10.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 11
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side Application sheet B2 was obtained according to Example 2 2-1.

2-2. Preparation of Cathode Catalyst Layer on Polymer Electrolyte Membrane Side The cathode layer catalyst slurry on the GDL side in Example 5 2-1 was printed in two portions on the coating sheet B2 to obtain a cathode catalyst layer coating sheet C11.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 12
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and an ionomer solution (10% solid content, EW = 700) in which the electrolyte of EW700 was dispersed was added. The polymer electrolyte content in the solution was such that the mass ratio of solid content to carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.5 / 1.0.

  The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions in an amount corresponding to the desired thickness to obtain a coated sheet B10.

2-2. Production of Cathode Catalyst Layer on Polymer Electrolyte Membrane Side The cathode layer catalyst slurry on the GDL side in Example 5 2-1 was printed in two portions on coating sheet B10 to obtain cathode catalyst layer coated sheet C12.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 13
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side Application sheet B2 was obtained according to Example 2 2-1.

2-2. Preparation of cathode catalyst layer on the polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and further a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 10%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 0.7 / 1.0.

  The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one surface of the polytetrafluoroethylene sheet by screen printing in an amount corresponding to the desired thickness in two portions on the coating sheet B2 to obtain a coating sheet C13.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 14
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side According to Example 12 2-1, a coated sheet B10 was obtained.

2-2. Preparation of Cathode Catalyst Layer on Polymer Electrolyte Membrane Example 13 According to 2-2, an amount of catalyst slurry corresponding to the desired thickness was printed in two portions on application sheet B10, and application sheet C14 was obtained. Obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 15
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side According to Example 12 2-1, a coated sheet B10 was obtained.

2-2. Preparation of cathode catalyst layer on the polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and further a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 10%, EW = 1,000) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.1 / 1.0.

  The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one surface of the polytetrafluoroethylene sheet by screen printing in an amount corresponding to the desired thickness in two portions on the coating sheet B10 to obtain a coating sheet C15.

3. Preparation of Electrolyte Membrane Electrode Assembly (MEA) Nafion ™ NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane, A1 on the anode side formed on the previously prepared polytetrafluoroethylene sheet, C2 on the cathode side C15 was superimposed. Thus, membrane electrode assemblies (MEA) N4 to 17 were obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 16
1. Preparation of Electrode Catalyst Using carbon black (acetylene black OSAB manufactured by Electrochemical Co., Ltd., BET surface area = 850 m ² / g) as the conductive carbon material, the electrode catalyst (average particle diameter of Pt particles: 3.2 nm) was applied in accordance with Example 1. , Pt carrying concentration 50% by mass).

  The electrode catalyst thus obtained was used for the production of a cathode catalyst layer in Examples 16 to 20 below.

2. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

3. 3. Production of cathode catalyst layer 3-1. Cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2029CS manufactured by DuPont (solution with a solid content of 10%, EW = 900) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.3 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions according to the desired thickness and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a coating sheet B11 was obtained.

3-2. Cathode catalyst layer on the polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.1 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on the coating sheet B11 in an amount corresponding to the desired thickness in two portions and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet C16 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 17
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst of Example 16, and vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2029CS manufactured by DuPont (solution with a solid content of 10%, EW = 900) was added. The polymer electrolyte content in the solution was such that the mass ratio of solid content to carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.5 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions according to the desired thickness and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a coating sheet B12 was obtained.

2-2. Preparation of cathode catalyst layer on the polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon = 1.3 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on the coating sheet B12 in an amount corresponding to the desired thickness in two portions, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet C17 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was produced in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability were performed on the MEA. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 18
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst of Example 16, and vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and an ionomer solution (10% solid content, EW = 700) in which the electrolyte of EW700 was dispersed was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.3 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions according to the desired thickness and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a coating sheet B13 was obtained.

2-2. Preparation of cathode catalyst layer on the polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2029CS manufactured by DuPont (solution with a solid content of 10%, EW = 900) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.1 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on the coating sheet B13 in an amount corresponding to the desired thickness in two portions, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet C18 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 19
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side Application sheet B1 was obtained according to Example 1 2-1.

2-2. Preparation of cathode catalyst layer on polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst of Example 16, and vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.1 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on the coating sheet B1 in an amount corresponding to the desired thickness in two portions, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet C19 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

Example 20
1. Preparation of Anode Catalyst Layer According to Example 11 1, an anode catalyst layer coated sheet A1 was obtained.

2. 2. Production of cathode catalyst layer 2-1. Preparation of cathode catalyst layer on the GDL side In accordance with Example 16 2-1, a coated sheet B11 was obtained.

2-2. Preparation of cathode catalyst layer on polymer electrolyte membrane side 5 times the amount of purified water was added to the mass of the cathode electrode catalyst of Example 1, and vacuum degassing operation was added for 5 minutes. To this, 0.5 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The polymer electrolyte content in the solution was such that the mass ratio of the solid content to the carbon mass of the cathode electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.1 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on the coating sheet B11 in an amount corresponding to the desired thickness in two portions and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.2 mg / cm ² (the average thickness of the cathode catalyst layer was 6 μm). Thus, a cathode catalyst layer coated sheet C20 was obtained.

  An electrolyte membrane-electrode assembly (MEA) was prepared in the same manner as in Example 1 except that the anode catalyst layer and the cathode catalyst layer obtained above were used. Further, the MEA performance evaluation and MEA durability of the MEA were performed. Table 1 and Table 2 show the conditions for preparing the anode and cathode catalyst layers and the results of the performance test and durability test.

  The electrolyte membrane-electrode assembly (MEA) of the present invention can be applied to a fuel cell having excellent durability and good fuel efficiency.

It is explanatory drawing which shows reaction of the conventional cathode catalyst layer. It is explanatory drawing which shows reaction of the cathode catalyst layer of this invention. FIG. 3 is a schematic diagram of the presence state of catalyst-supporting carbon and polymer electrolyte (ionomer) in the cathode-side electrode catalyst layer produced in Example 1. 4 is a schematic diagram showing the presence state of catalyst-supporting carbon and polymer electrolyte (ionomer) in the cathode-side electrode catalyst layer produced in Example 2. FIG. FIG. 4 is a schematic diagram of the presence state of catalyst-supporting carbon and polymer electrolyte (ionomer) in the cathode-side electrode catalyst layer produced in Example 3. 3 is a graph showing the particle size distribution of catalyst-supporting carbon in the catalyst ink used for producing the cathode-side electrode catalyst layer in Example 1. FIG. 4 is a graph showing the control of the amount of pores in the electrode catalyst layer based on the I / C ratio of the catalyst-supporting carbon in the catalyst ink. 6 is a graph showing the control of the pore diameter of the electrode catalyst layer by the I / C ratio of the catalyst-supported carbon in the catalyst ink.

Explanation of symbols

10 solid polymer electrolyte membrane,
12 Electrocatalyst layer on the electrolyte membrane side,
50 Electrocatalyst layer on the gas diffusion layer (GDL) side.

Claims (12)

An electrolyte membrane;
A cathode catalyst layer disposed on one side of the electrolyte membrane;
An anode catalyst layer disposed on the other side of the electrolyte membrane;
A cathode-side gas diffusion layer disposed in the cathode catalyst layer;
An anode-side gas diffusion layer disposed in the anode catalyst layer;
In an electrolyte membrane-electrode assembly having
At least one of the cathode catalyst layer and the anode catalyst layer has a different pore structure such that the pore structure of the catalyst layer on the electrolyte membrane side is larger than the pore structure of the catalyst layer on the gas diffusion layer side. An electrolyte membrane-electrode assembly having a structure in which a plurality of catalyst layers are laminated. The pore size [D1 (nm)] of the catalyst layer on the electrolyte membrane side is larger than the pore size [D2 (nm)] of the catalyst layer on the gas diffusion layer side (D1> D2), and the catalyst on the electrolyte membrane side The amount of pores [V1 (cm ³ / g)] of the layer is larger than the amount of pores [V2 (cm ³ / g)] of the catalyst layer on the gas diffusion layer side (V1> V2). Electrolyte membrane-electrode assembly. The pore diameter [D1 (nm)] of the catalyst layer on the electrolyte membrane side is 80 to 200 nm,
The pore diameter [D2 (nm)] of the catalyst layer on the gas diffusion layer side is 30 to 80 nm,
The average pore diameter [Dave (nm)] of the entire catalyst layer is 60 to 100 nm,
The pores of the electrolyte membrane side of the catalyst layer ^{[V1 (cm 3 / g)} ] is a 0.5 to 1.0 cm ³ / g,
Vacancy of the gas diffusion layer side of the catalyst layer ^{[V2 (cm 3 / g)} ] is a 0.3~0.5cm ³ / g,
The average pore volume of the whole catalyst layer [Vave ^(cm 3 / g) is an 0.4~0.8cm ³ / g, the electrolyte membrane according to claim 2 - electrode assembly.   The porosity [X1 (%)] of the catalyst layer on the electrolyte membrane side is larger than the porosity [X2 (%)] of the catalyst layer on the gas diffusion layer side (X1> X2), The electrolyte membrane-electrode assembly according to any one of the above. The porosity [X1 (%)] of the catalyst layer on the electrolyte membrane side is 50% to 80%,
The electrolyte membrane-electrode assembly according to claim 4, wherein a porosity [X2 (%)] of the catalyst layer on the gas diffusion layer side is 30% to 50%. The polymer electrolysis mass [B1 (g / cm ³ )] of the catalyst layer on the electrolyte membrane side is equal to or less than the polymer electrolysis mass [B2 (g / cm ³ )] of the catalyst layer on the gas diffusion layer side (B1 The electrolyte membrane-electrode assembly according to claim 1, wherein ≦ B2). The polymer electrolyte composition [B1 ′ (wt%)] of the catalyst layer on the electrolyte membrane side is 20 to 40 wt% with respect to the total mass of the polymer electrolyte and the electrode catalyst,
The polymer electrolyte composition [B2 ′ (wt%)] of the catalyst layer on the gas diffusion layer side is 30 to 50 wt% with respect to the total mass of the polymer electrolyte and the electrode catalyst, and B1 ′ ≦ B2 ′. The electrolyte membrane-electrode assembly according to claim 6, wherein   8. The catalyst layer according to claim 1, wherein the catalyst layer has a structure in which two layers of a catalyst layer on the electrolyte membrane side having a thickness of 1 to 10 μm and a catalyst layer on the gas diffusion layer side having a thickness of 1 to 10 μm are stacked. The electrolyte membrane-electrode assembly according to Item.   The catalyst layer on the electrolyte membrane side has a large number of catalyst carriers having a large particle diameter, and the catalyst layer on the gas diffusion layer side has a large number of catalyst carriers having a small particle diameter. The electrolyte membrane-electrode assembly according to any one of the above.   The electrolyte membrane according to claim 9, wherein the amount of the polymer electrolyte contained in the catalyst layer on the gas diffusion layer side is equal to or more than the amount of the polymer electrolyte contained in the catalyst layer on the electrolyte membrane side. Electrode assembly.   The cathode catalyst layer has a structure in which a plurality of catalyst layers having different pore structures are laminated such that at least the pore structure of the catalyst layer on the electrolyte membrane side is larger than the pore structure of the catalyst layer on the gas diffusion layer side. The electrolyte membrane-electrode assembly according to any one of claims 1 to 10.   A fuel cell comprising the electrolyte membrane-electrode assembly according to any one of claims 1 to 11.

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