JP7615561B2 - Membrane electrode assembly for fuel cells and polymer electrolyte fuel cells - Google Patents

Description

The present invention relates to a membrane electrode assembly for a fuel cell and a polymer electrolyte fuel cell.

A fuel cell is a power generation system that uses a fuel gas containing hydrogen and an oxidant gas containing oxygen to generate electricity as well as heat by inducing a reverse reaction in the electrolysis of water at electrodes containing a catalyst. Compared to conventional power generation methods, this power generation system has features such as high efficiency, low environmental impact, and low noise, and is attracting attention as a clean energy source of the future. There are several types of fuel cells depending on the type of ion conductor used, and fuel cells that use a proton-conducting polymer membrane are called solid polymer fuel cells.

Among fuel cells, solid polymer fuel cells can be used at around room temperature, and are therefore seen as promising for use as vehicle power sources and stationary home power sources, and in recent years, various research and development efforts have been conducted on them. Solid polymer fuel cells are cells in which a membrane electrode assembly (hereinafter sometimes referred to as MEA), in which electrode catalyst layers are arranged on each side of a polymer electrolyte membrane, is sandwiched between a pair of separators.

One separator has a gas flow path formed therein for supplying a fuel gas containing hydrogen to one of the electrodes, and the other separator has a gas flow path formed therein for supplying an oxidizer gas containing oxygen to the other of the electrodes.

Here, the above-mentioned one electrode to which the fuel gas is supplied is referred to as the fuel electrode, and the above-mentioned other electrode to which the oxidant gas is supplied is referred to as the air electrode. These electrodes are provided with an electrode catalyst layer having a polymer electrolyte, carbon particles (catalyst-supported particles) supporting a catalyst such as a platinum-based precious metal, and a gas diffusion layer that has both gas permeability and electronic conductivity. The gas diffusion layer that constitutes these electrodes is disposed so as to face the separator, i.e., between the electrode catalyst layer and the separator.

In order to improve the output density of fuel cells, efforts have been made to increase the gas diffusion properties of the electrode catalyst layer. One of these efforts concerns the pores in the electrode catalyst layer. The pores in the electrode catalyst layer are located beyond the separator through the gas diffusion layer, and act as passages to transport multiple substances. At the fuel electrode, the pores not only smoothly supply fuel gas to the three-phase interface, which is the site of the oxidation-reduction reaction, but also supply water to smoothly conduct the generated protons within the polymer electrolyte membrane. At the air electrode, the pores not only supply oxidant gas, but also smoothly remove water generated in the electrode reaction.

Current polymer electrolyte fuel cells use expensive platinum as an electrode catalyst, and there is a strong demand for the development of alternative materials in order to make them widely available. In particular, since more platinum is used in the air electrode than in the fuel electrode, there is active development of platinum alternative materials (non-platinum catalysts) that exhibit high oxygen reduction catalytic activity in the air electrode.

As an example of a non-platinum catalyst in the air electrode, for example, Patent Document 1 describes a mixture of a nitride of iron, which is a transition metal, and a precious metal. Also, Patent Document 2 describes a nitride of molybdenum, which is a transition metal. However, the catalytic materials described in Patent Documents 1 and 2 have insufficient oxygen reduction ability in an acidic electrolyte, and the catalytic materials may dissolve.

JP 2005-44659 A JP 2005-63677 A

The present invention aims to provide a membrane electrode assembly for a fuel cell having an electrode catalyst layer that exhibits high power generation characteristics when used in a polymer electrolyte fuel cell.

The membrane electrode assembly for a fuel cell to solve the above problem includes a polymer electrolyte membrane and a pair of electrode catalyst layers sandwiching the polymer electrolyte membrane. At least one of the pair of electrode catalyst layers includes particles carrying a catalyst made of a precious metal component, a polymer electrolyte, a fibrous material having an average fiber length in the range of 1 μm to 15 μm, and an oxide-based catalyst material. The oxide-based catalyst material includes at least one transition metal element selected from the group consisting of Ta, Nb, Ti, and Zr.

According to the present invention, it is possible to provide an electrode catalyst layer that exhibits high power generation characteristics when used in a polymer electrolyte fuel cell.

FIG. 2 is an exploded perspective view showing a schematic structure of a membrane electrode assembly having a fuel cell electrode catalyst layer according to one embodiment of the present invention; FIG. 2 is an exploded perspective view showing a schematic structure of a polymer electrolyte fuel cell including the membrane electrode assembly of FIG. 1 .

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.
Here, the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc. are different from the actual ones. In addition, the embodiments shown below are examples of configurations for embodying the technical idea of the present disclosure, and the technical idea of the present disclosure is not limited to the materials, shapes, structures, etc. of the components described below. The technical idea of the present disclosure can be modified in various ways within the technical scope defined by the claims described in the claims.

[Membrane Electrode Assembly]
As shown in FIG. 1, a membrane electrode assembly 11 of this embodiment includes a polymer electrolyte membrane 1 and a pair of electrode catalyst layers 2 and 3 that sandwich the polymer electrolyte membrane 1 from above and below.

Each electrode catalyst layer 2, 3 comprises particles carrying a catalyst made of at least a precious metal component and a polymer electrolyte. At least one of the pair of electrode catalyst layers 2, 3 (hereinafter also referred to as the first electrode catalyst layer) has an oxide-based catalyst material and a fibrous material.

The oxide-based catalytic material contained in the first electrode catalyst layer contains at least one transition metal element selected from the group consisting of Ta, Nb, Ti, and Zr. The oxide-based catalytic material is preferably a partially oxidized nitride having P introduced as a substituting atom, and more preferably the transition metal element is Ti. In other words, the oxide-based catalytic material is made of a material in which a part of a nitride of a transition metal element containing P as a substituting atom is oxidized.

In the first electrode catalyst layer, the ratio (MB/MA) of the mass (MB) of the oxide-based catalyst material to the mass (MA) of the carrier in the catalyst-loaded particles is preferably within the range of 0.1 to 10, and more preferably within the range of 0.8 to 4.

In the first electrode catalyst layer, the ratio (MC/MA) of the mass of the polymer electrolyte (MC) to the mass of the carrier (MA) in the catalyst-loaded particles is preferably within the range of 0.2 to 2.8 times, and more preferably within the range of 0.6 to 1.2 times.

In the first electrode catalyst layer, the ratio (MD/MA) of the mass (MD) of the fibrous material to the mass (MA) of the carrier in the catalyst-loaded particles is preferably within the range of 0.05 to 1.0, and more preferably within the range of 0.1 to 0.4.

It is preferable that the particles carrying the catalyst made of the precious metal component contained in the first electrode catalyst layer are covered with a hydrophobic coating.

The inventors of the present application have confirmed that the first electrode catalyst layer having the following configuration has drainage properties. The detailed mechanism by which the first electrode catalyst layer has drainage properties is presumed to be as follows. The present invention is not limited to the mechanism described below.

In the first electrode catalyst layer, the fibrous material is entangled, which makes it possible to suppress the occurrence of cracks in the electrode catalyst layer that reduce the durability of the first electrode catalyst layer. This results in a first electrode catalyst layer with high durability and mechanical properties. In addition, pores are formed in the electrode catalyst layer due to the entanglement of the particles carrying a catalyst made of a precious metal component, the oxide-based catalyst material, and the fibrous material. When a polymer electrolyte fuel cell equipped with the first electrode catalyst layer is driven in a high current range, it is presumed that the pores can discharge water generated in the electrode reaction, and the diffusibility of the reaction gas can be improved. On the other hand, when the first electrode catalyst layer does not contain a fibrous material, entanglement does not occur between the particles carrying a catalyst made of a precious metal component and the oxide-based catalyst material, so that pores are unlikely to be formed in the electrode catalyst layer. Therefore, it is difficult to discharge the water generated in the electrode reaction, and as a result, it is presumed that when a polymer electrolyte fuel cell equipped with an electrode catalyst layer is driven in a high current range, the diffusibility of the reaction gas cannot be improved.

If the average fiber length of the fibrous material is less than 1 μm, it is believed that the mechanical properties of the electrode catalyst layer may be reduced. Also, if the average fiber length exceeds 15 μm, it is believed that the material may not be able to be dispersed as ink. In other words, by making the average fiber length of the fibrous material 1 μm or more, the deterioration of the mechanical properties of the electrode catalyst layer is suppressed. Also, by making the average fiber length of the fibrous material 15 μm or less, the fibrous material is more easily dispersed in the ink for forming the electrode catalyst layer.

If the mass of the oxide-based catalytic material is less than 0.1 times the mass of the carrier in the catalyst-supported particle, it is estimated that it may be difficult to draw a sufficient current due to the low catalytic activity of the oxide-based catalytic material. In other words, by making the ratio of the mass of the oxide-based catalytic material to the mass of the carrier in the catalyst-supported particle 0.1 or more, the catalytic activity of the oxide-based catalytic material is prevented from decreasing, making it possible to generate a sufficient current.

In addition, if it exceeds 10 times, it is estimated that the current may decrease due to the thickening of the electrode catalyst layer. In other words, by keeping the ratio of the mass of the oxide catalyst material to the mass of the carrier in the catalyst-supported particles at 10 times or less, the electrode catalyst layer is prevented from becoming excessively thick, which makes it possible to suppress the decrease in current.

If the mass of the polymer electrolyte is less than 0.2 times the mass of the carrier in the catalyst-supported particle, it is believed that it may be difficult to draw a sufficient current due to the effect of reduced proton conductivity in the electrode catalyst layer. In other words, by making the mass of the polymer electrolyte 0.2 times or more the mass of the carrier in the catalyst-supported particle, the reduction in proton conductivity in the electrode catalyst layer is suppressed, and it is possible to generate a sufficient current.

In addition, if it exceeds 2.8 times, it is estimated that the diffusibility of the reactant gas may not be improved due to the effect of reducing the number of pores formed in the electrode catalyst layer. In other words, by making the mass of the polymer electrolyte 2.8 times or less compared to the mass of the carrier in the catalyst-supported particles, it is possible to suppress the reduction in the number of pores in the electrode catalyst layer, thereby improving the diffusibility of the reactant gas.

If the mass of the fibrous material is less than 0.05 times the mass of the carrier in the catalyst-supported particle, it is estimated that the mechanical properties of the electrode catalyst layer may decrease. In other words, by making the ratio of the mass of the fibrous material to the mass of the carrier in the catalyst-supported particle 0.05 times or more, the decrease in the mechanical properties of the electrode catalyst layer is suppressed. Also, if it exceeds 1.0 times, it is estimated that the current may decrease due to the thickening of the electrode catalyst layer. In other words, by making the ratio of the mass of the fibrous material to the mass of the carrier in the catalyst-supported particle 1.0 times or less, it is possible to prevent the electrode catalyst layer from becoming excessively thick, thereby suppressing the decrease in current.

Unlike conventional methods of improving drainage by changing the configuration of the electrode catalyst layer, the membrane electrode assembly 11 of this embodiment does not result in a decrease in power generation characteristics due to an increase in interface resistance. As a result, a polymer electrolyte fuel cell equipped with the membrane electrode assembly 11 has higher power generation characteristics in the high current range where a large amount of water is generated, compared to a polymer electrolyte fuel cell equipped with a conventional membrane electrode assembly.

[Polymer electrolyte fuel cell]
Next, a polymer electrolyte fuel cell including a membrane electrode assembly 11 according to the embodiment will be described with reference to FIG.

The polymer electrolyte fuel cell 12 shown in FIG. 2 includes a pair of gas diffusion layers 4 and 5. The gas diffusion layer 4 is disposed so as to face the electrode catalyst layer 2 of the membrane electrode assembly 11. The gas diffusion layer 5 is disposed so as to face the electrode catalyst layer 3. The electrode catalyst layer 2 and the gas diffusion layer 4 form an air electrode (cathode, positive electrode) 6. The electrode catalyst layer 3 and the gas diffusion layer 5 form a fuel electrode (anode, negative electrode) 7.

A pair of separators 10a, 10b are disposed on the outside of the gas diffusion layers 4, 5, respectively. That is, the membrane electrode assembly 11 is sandwiched between the pair of separators 10a, 10b in the thickness direction of the membrane electrode assembly 11. The separators 10a, 10b have gas flow paths 8a, 8b for gas flow and cooling water flow paths 9a, 9b for cooling water flow. The separators 10a, 10b are formed from a material that is conductive and impermeable.

The gas flow passage 8b of the separator 10b facing the fuel electrode 7 is supplied with a fuel gas, such as hydrogen gas. On the other hand, the gas flow passage 8a of the separator 10a facing the air electrode 6 is supplied with an oxidizer gas, such as oxygen gas. An electromotive force can be generated between the fuel electrode 7 and the air electrode 6 by causing an electrode reaction between the hydrogen fuel gas and the oxygen oxidizer gas in the presence of a catalyst.

In the solid polymer fuel cell 12, a pair of separators 10a, 10b sandwich a polymer electrolyte membrane 1, a pair of electrode catalyst layers 2, 3, and a pair of gas diffusion layers 4, 5. The solid polymer fuel cell 12 shown in FIG. 2 is an example of a fuel cell having a single cell structure, but the solid polymer fuel cell may have a structure in which multiple cells are stacked with separator 10a or separator 10b interposed therebetween.

[Method for producing electrode catalyst layer]
Next, an example of a method for producing the first electrode catalyst layer will be described.
The first electrode catalyst layer is manufactured by a method including the following first and second steps. The first step is a step of manufacturing a catalyst ink containing catalyst-supporting particles, an oxide-based catalyst material, a fibrous material, a polymer electrolyte, and a solvent. The second step is a step of forming a first electrode catalyst layer by applying the catalyst ink obtained in the first step onto a substrate and drying the solvent. Note that a second electrode catalyst layer that is not the first electrode catalyst layer may also be manufactured by a similar step. However, the second electrode catalyst layer does not contain the oxide-based catalyst material contained in the first electrode catalyst layer. Then, a pair of the manufactured electrode catalyst layers 2, 3 are attached to each of the opposing surfaces of the polymer electrolyte membrane 1 to obtain a membrane electrode assembly 11.

〔detail〕
The membrane electrode assembly 11 and the polymer electrolyte fuel cell 12 will be described in more detail below.
The polymer electrolyte membrane 1 may be any membrane having proton conductivity, such as a fluorine-based polymer electrolyte membrane or a hydrocarbon-based polymer electrolyte membrane. Examples of the fluorine-based polymer electrolyte membrane include Nafion (registered trademark) manufactured by DuPont, Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd., Aciplex (registered trademark) manufactured by Asahi Kasei Corporation, and Gore Select (registered trademark) manufactured by Gore.

Examples of the hydrocarbon-based polymer electrolyte membrane include sulfonated polyether ketone,
An electrolyte membrane made of sulfonated polyethersulfone, sulfonated polyetherethersulfone, sulfonated polysulfide, sulfonated polyphenylene, etc. is usable. In particular, it is preferable to use a Nafion (registered trademark)-based material manufactured by DuPont as the polymer electrolyte membrane 1.

The electrode catalyst layers 2 and 3 are formed on both sides of the polymer electrolyte membrane 1 using a catalyst ink. The catalyst ink for the electrode catalyst layers 2 and 3 contains catalyst-supported particles, a polymer electrolyte, and a solvent. The catalyst ink for the improved electrode catalyst layer contains catalyst-supported particles, an oxide-based catalyst material, a polymer electrolyte, and a solvent.

The polymer electrolyte contained in the catalyst ink may be any material that has proton conductivity. The polymer electrolyte may be made of the same material as the polymer electrolyte membrane 1. The polymer electrolyte may be, for example, a fluorine-based polymer electrolyte or a hydrocarbon-based polymer electrolyte. The fluorine-based polymer electrolyte may be, for example, a Nafion (registered trademark)-based material manufactured by DuPont. The hydrocarbon-based polymer electrolyte may be, for example, a sulfonated polyether ketone, a sulfonated polyether sulfone, a sulfonated polyether ether sulfone, a sulfonated polysulfide, or a sulfonated polyphenylene. In particular, it is preferable to use a Nafion (registered trademark)-based material manufactured by DuPont as the fluorine-based polymer electrolyte.

The catalyst made of a precious metal component used in this embodiment may be, for example, a metal or alloy, a metal oxide, or a metal double oxide. Examples of the metal include one or more metals selected from the group consisting of platinum, palladium, ruthenium, iridium, and rhodium. Note that a double oxide here refers to an oxide made of two types of metals.

The average particle diameter of the above-mentioned catalyst is preferably within the range of 0.5 nm to 20 nm, and more preferably within the range of 1 nm to 5 nm. Here, the average particle diameter is the average particle diameter obtained by X-ray diffraction in the case of particles carrying a catalyst including a carrier such as carbon particles and a catalyst supported on the carrier. In the case of a catalyst not supported on a carrier, it is the arithmetic average particle diameter obtained by particle size measurement. When the average particle diameter of the catalyst particles is within the range of 0.5 nm to 20 nm, the activity and stability of the catalyst are improved, which is preferable.

Carbon particles are generally used as the electron-conductive powder that supports the above-mentioned catalyst, i.e., the carrier. There are no limitations on the type of carbon particles, so long as they are fine particles, conductive, and not affected by the catalyst. Examples of carbon particles that can be used include carbon black, graphite, activated carbon, carbon fiber, carbon nanotubes, and fullerenes.

The average particle diameter of the carbon particles is preferably within the range of 10 nm to 1000 nm, and more preferably within the range of 10 nm to 100 nm. Here, the average particle diameter is the average particle diameter determined from an SEM image. When the average particle diameter of the carbon particles is within the range of 10 nm to 1000 nm, the activity and stability of the catalyst are improved, which is preferable. In addition, when the average particle diameter of the carbon particles is within the range of 10 nm to 1000 nm, an electron conduction path is easily formed, and the gas diffusion properties and catalyst utilization rate of the two electrode catalyst layers 2 and 3 are improved, which is preferable.

The above-mentioned catalyst-supported particles may be provided with a hydrophobic coating. In other words, the catalyst-supported particles may be covered with a hydrophobic coating. In this case, it is preferable that the hydrophobic coating has a thickness that allows sufficient permeation of the reaction gas. Specifically, the thickness of the hydrophobic coating is preferably 40 nm or less. If it is thicker than this, the supply of the reaction gas to the active points may be hindered. On the other hand, if the hydrophobic coating is 40 nm or less, the reaction gas can sufficiently permeate the hydrophobic coating, and hydrophobicity can be imparted to the catalyst-supported particles.

The thickness of the hydrophobic coating covering the catalyst-supported particles is preferably such that it sufficiently repels the generated water. Specifically, the thickness of the hydrophobic coating is preferably 2 nm or more. If the hydrophobic coating is thinner than this, the generated water may accumulate, which may hinder the supply of the reaction gas to the active points. In other words, by having a hydrophobic coating with a thickness of 2 nm or more, the accumulation of the generated water is suppressed, and thus the supply of the reaction gas to the active points is prevented from being hindered.

The hydrophobic coating covering the catalyst-supported particles is formed, for example, from a fluorine-based compound having at least one polar group. Examples of polar groups include hydroxyl groups, alkoxy groups, carboxyl groups, ester groups, ether groups, carbonate groups, and amide groups. The presence of the polar group allows the fluorine-based compound to be fixed to the outermost surface of the electrode catalyst layer. The portion of the fluorine-based compound other than the polar group is preferably a structure consisting of fluorine and carbon because of its high hydrophobicity and chemical stability. However, the hydrophobic coating is not limited to such a structure as long as it has sufficient hydrophobicity and chemical stability.

In the present disclosure, the oxide-based catalytic material may be a material containing at least one selected from the group consisting of Ta, Nb, Ti, and Zr. The oxide-based catalytic material is preferably used as a substitute for platinum in the electrode catalyst layer of the air electrode, i.e., the positive electrode.

More preferably, a material can be used that is obtained by introducing P as a substituting atom into the nitride of these transition metal elements and partially oxidizing it in an atmosphere containing oxygen. That is, the oxide-based catalyst material is a material in which a part of a fiber metal nitride containing phosphorus (P) is oxidized. In other words, the oxide-based material contains a transition metal atom, a nitrogen atom, a phosphorus atom, and an oxygen atom. That is, in the transition metal nitride, a part of the transition metal atom is substituted with a phosphorus atom.

Specifically, it is a material (TiONP) that is produced by partially oxidizing a titanium nitride (TiNP) with P introduced as a substituting atom in an atmosphere containing oxygen. In this case, some of the titanium atoms in the titanium nitride (TiN) are replaced with phosphorus atoms. Also, some of the titanium nitride is oxidized.

As the fibrous material, for example, electron conductive fibers and proton conductive fibers can be used. Examples of electron conductive fibers include carbon fibers, carbon nanotubes, carbon nanohorns, and conductive polymer nanofibers. From the viewpoints of conductivity and dispersibility, it is preferable to use carbon nanofibers as the fibrous material.

The proton conductive fiber may be a fiber formed by processing a polymer electrolyte having proton conductivity into a fiber shape. That is, the proton conductive fiber is a fiber formed by a polymer electrolyte having proton conductivity. Materials for forming the proton conductive fiber may include fluorine-based polymer electrolytes and hydrocarbon-based polymer electrolytes. Examples of the fluorine-based polymer electrolyte include Nafion (registered trademark) manufactured by DuPont, Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd., Aciplex (registered trademark) manufactured by Asahi Kasei Corporation, and Gore Select (registered trademark) manufactured by Gore. Examples of the hydrocarbon-based polymer electrolyte include electrolytes such as sulfonated polyether ketone, sulfonated polyether sulfone, sulfonated polyether ether sulfone, sulfonated polysulfide, and sulfonated polyphenylene. Among these, it is preferable to use Nafion (registered trademark) manufactured by DuPont as the polymer electrolyte.

The fibrous material may be one of the above-mentioned fibers, or two or more of them. The fibrous material may be a combination of an electron conductive fiber and a proton conductive fiber. Of the above-mentioned fibrous materials, the fibrous material preferably includes at least one selected from the group consisting of carbon nanofibers, carbon nanotubes, and electrolyte fibers.

The solvent used as the dispersion medium of the catalyst ink is not particularly limited as long as it does not corrode the catalyst-supported particles, the oxide-based catalyst material, the fibrous material, and the polymer electrolyte, and can dissolve the polymer electrolyte in a highly fluid state or disperse it as a fine gel. However, it is preferable that the solvent contains at least a volatile organic solvent. The solvent used as the dispersion medium of the catalyst ink may be an alcohol, a ketone-based solvent, an ether-based solvent, a polar solvent, etc. The alcohol may be methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, pentanol, etc. The ketone-based solvent may be acetone, methyl ethyl ketone, pentanone, methyl isobutyl ketone, heptanone, cyclohexanone, methyl cyclohexanone, acetonyl acetone, diisobutyl ketone, etc. The ether-based solvent may be tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, dibutyl ether, etc. The polar solvent may be dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, diethylene glycol, diacetone alcohol, 1-methoxy-2-propanol, etc. The solvent may also be a mixed solvent of two or more of the above-mentioned materials.

In addition, since a dispersion medium using a lower alcohol has a high risk of ignition, when using a lower alcohol as the dispersion medium, it is preferable to use a mixed solvent of a lower alcohol and water. Furthermore, the dispersion medium may contain water that is compatible with the polymer electrolyte, i.e., water that has a high affinity for the polymer electrolyte. There is no particular restriction on the amount of water added to the dispersion medium, so long as the amount is such that the polymer electrolyte does not separate and become cloudy or gel.

The catalyst ink may contain a dispersant to disperse the catalyst-supported particles in the catalyst ink. Examples of dispersants include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants.

Examples of anionic surfactants include alkyl ether carboxylates, ether carboxylates, alkanoyl sarcosines, alkanoyl glutamates, acyl glutamates, oleic acid/N-methyl taurine, potassium oleate/diethanolamine salt, alkyl ether sulfate/triethanolamine salt, polyoxyethylene alkyl ether sulfate/triethanolamine salt, amine salts of special modified polyether ester acids, amine salts of higher fatty acid derivatives, amine salts of special modified polyester acids, amine salts of high molecular weight polyether ester acids, amine salts of special modified phosphate esters, high molecular weight polyester acid amide amine salts, special fatty acid derivatives Amidoamine salts of fatty acids, alkylamine salts of higher fatty acids, amidoamine salts of high molecular weight polycarboxylic acids, carboxylic acid surfactants such as sodium laurate, sodium stearate, and sodium oleate, dialkyl sulfosuccinates, dialkyl sulfosuccinates, 1,2-bis(alkoxycarbonyl)-1-ethanesulfonates, alkyl sulfonates, paraffin sulfonates, α-olefin sulfonates, linear alkylbenzene sulfonates, alkylbenzene sulfonates, polynaphthylmethanesulfonates, naphthalenesulfonate-formaldehyde condensates, alkylnaphthalenesulfonates, alkanoylmethyl taurides, lauryl sulfur Sulfonic acid surfactants such as sodium acid ester salts, cetyl sulfate sodium salts, stearyl sulfate sodium salts, oleyl sulfate sodium salts, lauryl ether sulfate salts, sodium alkylbenzenesulfonate, oil-soluble alkylbenzenesulfonates, and α-olefinsulfonates; sulfate ester surfactants such as alkyl sulfate salts, alkyl sulfate salts, alkyl ether sulfates, polyoxyethylene alkyl ether sulfates, alkyl polyethoxy sulfates, polyglycol ether sulfates, alkyl polyoxyethylene sulfates, sulfated oils, and highly sulfated oils; phosphoric acid (monophosphate) Examples of phosphate ester surfactants include (mono- or di-) alkyl salts, (mono- or di-) alkyl phosphates, (mono- or di-) alkyl phosphate ester salts, alkyl polyoxyethylene phosphate salts, alkyl ether phosphates, alkyl polyethoxy phosphates, polyoxyethylene alkyl ethers, alkyl phenyl polyoxyethylene phosphate salts, alkyl phenyl ether phosphates, alkyl phenyl polyethoxy phosphates, polyoxyethylene alkyl phenyl ether phosphates, higher alcohol phosphate monoester disodium salts, higher alcohol phosphate diester disodium salts, and zinc dialkyl dithiophosphates.

Examples of cationic surfactants include benzyldimethyl{2-[2-(P-1,1,3,3-tetramethylbutylphenoxy)ethoxy]ethyl}ammonium chloride, octadecylamine acetate, tetradecylamine acetate, octadecyltrimethylammonium chloride, beef tallow trimethylammonium chloride, dodecyltrimethylammonium chloride, coconut trimethylammonium chloride, hexadecyltrimethylammonium chloride, behenyltrimethylammonium chloride, coconut dimethylbenzyl ammonium chloride, tetradecyldimethylbenzyl Examples include ammonium chloride, octadecyldimethylbenzylammonium chloride, dioleyldimethylammonium chloride, 1-hydroxyethyl-2-beef tallow imidazoline quaternary salt, 2-heptadecenyl-hydroxyethyl imidazoline, stearamidoethyl diethylamine acetate, stearamidoethyl diethylamine hydrochloride, triethanolamine monostearate formate, alkylpyridinium salt, higher alkylamine ethylene oxide adduct, polyacrylamide amine salt, modified polyacrylamide amine salt, perfluoroalkyl quaternary ammonium iodide, etc.

Examples of amphoteric surfactants include dimethyl coconut betaine, dimethyl lauryl betaine, sodium lauryl aminoethyl glycine, sodium lauryl aminopropionate, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, amido betaine, imidazolinium betaine, lecithin, 3-[ω-fluoroalkanoyl-N-ethylamino]
-1-sodium propanesulfonate, N-[3-(perfluorooctanesulfonamido)propyl]-N,N-dimethyl-N-carboxymethylene ammonium betaine, and the like.

Examples of nonionic surfactants include coconut fatty acid diethanolamide (1:2 type), coconut fatty acid diethanolamide (1:1 type), cow fatty acid diethanolamide (1:2 type), cow fatty acid diethanolamide (1:1 type), oleic acid diethanolamide (1:1 type), hydroxyethyl laurylamine, polyethylene glycol laurylamine, polyethylene glycol coconut amine, polyethylene glycol stearylamine, polyethylene glycol tallow amine, polyethylene glycol tallow propylene diamine, polyethylene glycol dioleylamine, dimethyl laurylamine oxide, dimethyl stearylamine oxide, dihydroxyethyl laurylamine oxide, perfluoroalkylamine oxide, polyvinylpyrrolidone, higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, polypropylene glycol ethylene oxide adducts, fatty acid esters of glycerin, fatty acid esters of pentaerythritol, fatty acid esters of sorbitol, fatty acid esters of sorbitan, fatty acid esters of sugar, etc.

Among the surfactants mentioned above, sulfonic acid type surfactants such as alkylbenzene sulfonic acid, oil-soluble alkylbenzene sulfonic acid, α-olefin sulfonic acid, sodium alkylbenzene sulfonate, oil-soluble alkylbenzene sulfonate, and α-olefin sulfonate are suitable as dispersants from the viewpoints of the carbon dispersion effect and the change in catalyst performance due to residual dispersant.

Increasing the amount of polymer electrolyte in the catalyst ink generally reduces the pore volume. On the other hand, increasing the amount of carbon particles in the catalyst ink increases the pore volume. Also, the use of a dispersant reduces the pore volume.

The catalyst ink may be subjected to a dispersion process as necessary. The viscosity of the catalyst ink and the size of the particles contained in the catalyst ink can be controlled by the conditions of the dispersion process of the catalyst ink. The dispersion process can be performed using various devices. In particular, the method of the dispersion process is not limited. For example, the dispersion process may be performed using a ball mill or a roll mill, a shear mill, a wet mill, or an ultrasonic dispersion process. A homogenizer that stirs by centrifugal force may also be used for the dispersion process. As the dispersion time for the catalyst ink to be subjected to the dispersion process increases, the aggregates of the catalyst-supported particles are destroyed, and the pore volume becomes smaller in the electrode catalyst layer formed using the catalyst ink.

If the solid content in the catalyst ink is too high, the viscosity of the catalyst ink will be high, and cracks will easily occur on the surfaces of the electrode catalyst layers 2 and 3. On the other hand, if the solid content in the catalyst ink is too low, the film formation rate will be very slow, and productivity will decrease. Therefore, it is preferable that the solid content in the catalyst ink is 1% by mass (wt%) or more and 50% by mass or less. In other words, by having a solid content in the catalyst ink of 1% by mass or more, it is possible to prevent the film formation rate from becoming excessively low, and thereby to prevent a decrease in productivity. By having a solid content in the catalyst ink of 50% by mass or less, it is possible to prevent the viscosity of the catalyst ink from becoming excessively high, and thereby to prevent cracks from occurring on the surfaces of the electrode catalyst layers 2 and 3.

The solid content in the catalyst ink consists of catalyst-supported particles, oxide-based catalyst material, fibrous material, and polymer electrolyte. If the content of the catalyst-supported particles, oxide-based catalyst material, and fibrous material in the solid content is increased, the viscosity will be higher than when the content of the polymer electrolyte is greater, even if the solid content is the same. On the other hand, if the content of the catalyst-supported particles, oxide-based catalyst material, and fibrous material in the solid content is decreased, the viscosity will be lower than when the content of the polymer electrolyte is greater, even if the solid content is the same. Therefore, it is preferable that the proportion of the catalyst-supported particles, oxide-based catalyst material, and fibrous material in the solid content is within the range of 10% by mass to 80% by mass. In addition, the viscosity of the catalyst ink is preferably about 0.1 cP to 500 cP (0.0001 Pa.s to 0.5 Pa.s), and more preferably 5 cP to 100 cP (0.005 Pa.s to 0.1 Pa.s). The viscosity of the catalyst ink can also be controlled by adding a dispersant when dispersing the catalyst ink.

The catalyst ink may also contain a pore-forming agent. The pore-forming agent can be used to form pores in the electrode catalyst layer by removing the pore-forming agent after the electrode catalyst layer is formed. Examples of pore-forming agents include substances that dissolve in acids, alkalis, and water, substances that sublimate such as camphor, and substances that decompose thermally. For example, if the pore-forming agent is a substance that dissolves in hot water, the pore-forming agent may be removed from the electrode catalyst layer by the water that is generated during power generation in a polymer electrolyte fuel cell equipped with the electrode catalyst layer.

Examples of pore-forming agents that are soluble in acid, alkali, or water include acid-soluble inorganic salts, inorganic salts soluble in an aqueous alkali solution, metals soluble in acid or alkali, water-soluble inorganic salts, water-soluble organic compounds, etc. Examples of acid-soluble inorganic salts include calcium carbonate, barium carbonate,
Examples of inorganic salts soluble in alkaline aqueous solutions include magnesium carbonate, magnesium sulfate, and magnesium oxide. Examples of inorganic salts soluble in alkaline aqueous solutions include alumina, silica gel, and silica sol. Examples of metals soluble in acid or alkali include aluminum, zinc, tin, nickel, and iron. Examples of water-soluble inorganic salts include sodium chloride, potassium chloride, ammonium chloride, sodium carbonate, sodium sulfate, and monosodium phosphate. Examples of water-soluble organic compounds include polyvinyl alcohol and polyethylene glycol.

The above-mentioned pore-forming agents may be used alone or in combination of two or more, but it is preferable to use two or more in combination.

Methods for applying the catalyst ink onto the substrate include, for example, doctor blade method, dipping method, screen printing method, roll coating method, etc.

The substrate used in the manufacture of the electrode catalyst layers 2 and 3 may be a transfer sheet. The transfer sheet used as the substrate may be formed from a material having good transferability. A fluororesin may be used as the material for forming the transfer sheet. The fluororesin may be, for example, ethylene tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroperfluoroalkylvinylether copolymer (PFA), polytetrafluoroethylene (PTFE), or the like. The substrate may be a polymer sheet or a polymer film. The material for forming the polymer sheet or the polymer film may be, for example, polyimide, polyethylene terephthalate, polyamide (nylon (registered trademark)), polysulfone, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyetherimide, polyarylate, polyethylene naphthalate, or the like. In addition, when a transfer sheet is used as the substrate, an electrode catalyst layer, which is a coating film from which the solvent has been removed, is bonded to both sides of the polymer electrolyte membrane 1, and then the transfer sheet is peeled off from the electrode catalyst layer to form a membrane electrode assembly 11 having electrode catalyst layers 2 and 3 on both sides of the polymer electrolyte membrane 1.

The gas diffusion layers 4 and 5 can be made of a material that has gas diffusivity and electrical conductivity. For example, the gas diffusion layers 4 and 5 can be made of a porous carbon material. The porous carbon material can be, for example, carbon cloth, carbon paper, nonwoven fabric, etc.

The separators 10a and 10b may be carbon or metal type separators. The gas diffusion layers 4 and 5 and the separators 10a and 10b may each be integrally formed. That is, the gas diffusion layer 4 and the separator 10a may be integrally formed, and the gas diffusion layer 5 and the separator 10b may be integrally formed. In addition, when the separators 10a and 10b or the electrode catalyst layers 2 and 3 function as the gas diffusion layers 4 and 5, the gas diffusion layers 4 and 5 may be omitted. The solid polymer fuel cell 12 is manufactured by assembling associated devices such as a gas supply device and a cooling device (not shown).

<Actions and other details>
As described above, this embodiment describes a membrane electrode assembly 11 that exhibits high power generation characteristics under highly humidified conditions, a manufacturing method for the membrane electrode assembly 11, and a polymer electrolyte fuel cell 12 including the membrane electrode assembly 11. In the electrode catalyst layers 2 and 3 of the membrane electrode assembly 11 of this embodiment, entanglement of fibrous materials suppresses the occurrence of cracks in the electrode catalyst layers that cause a decrease in durability, thereby achieving high durability and mechanical characteristics.

In addition, pores are formed in the electrode catalyst layer due to the entanglement of the catalyst-supporting particles, the oxide-based catalyst material, and the fibrous material. The pores in the electrode catalyst layer enable the discharge of water produced in the electrode reaction in the high current region during operation of the polymer electrolyte fuel cell, and increase the diffusibility of the reaction gas.
The membrane electrode assembly manufactured by the manufacturing method of the electrode catalyst layer according to this embodiment has improved drainage properties in a high current region where a large amount of water is generated, without inhibiting water retention under low humidification conditions, and also exhibits high power generation performance and durability even under high humidification conditions. Furthermore, the manufacturing method of the electrode catalyst layer according to this embodiment can efficiently and economically easily, i.e., inexpensively manufacture the above-mentioned membrane electrode assembly.

In other words, the above-mentioned membrane electrode assembly can be manufactured by forming an electrode catalyst layer using a catalyst ink in which a platinum-supported carbon catalyst (catalyst-supported particles), i.e., carbon particles supporting a platinum catalyst, an oxide-based catalyst material, a fibrous material, and a polymer electrolyte are dispersed in a solvent.

Therefore, the electrode catalyst layer can be manufactured without complicated manufacturing steps, and the electrode catalyst layer manufactured by the above-mentioned procedure can improve both water retention and diffusibility of the reactant gas. Therefore, the electrode catalyst layer can be manufactured without providing a special means such as a humidifier, and as a result, costs can be reduced.

In addition, only one of the electrode catalyst layers 2, 3 formed on both sides of the polymer electrolyte membrane 1 may be the first electrode catalyst layer. In that case, as described above, it is preferable that the first electrode catalyst layer is an electrode catalyst layer that forms the air electrode (cathode) where water is generated by an electrode reaction, that is, the positive electrode.

Although the embodiments of the present disclosure have been described in detail above, in reality, the present disclosure is not limited to the above embodiments, and even if there are modifications that do not deviate from the gist of the present disclosure, they are included in the present disclosure.

The manufacturing method of the first electrode catalyst layer and the membrane electrode assembly for the polymer electrolyte fuel cell in this embodiment will be described below with specific examples and comparative examples. However, this embodiment is not limited to the following examples and comparative examples.

In the following examples and comparative examples, a pair of electrode catalyst layers are both first electrode catalyst layers. As described above, only one of the pair of electrode catalyst layers may be the first electrode catalyst layer.

Example 1
[Preparation of catalyst ink]
A platinum-supported carbon catalyst (catalyst-supported particles) with a support density of 50% by mass, an oxide-based catalyst material (TiONP), carbon fibers with an average fiber diameter of 150 nm and an average fiber length of 6 μm, and a 25% by mass polymer electrolyte solution were mixed in a solvent, and a dispersion process was performed in the solvent using a planetary ball mill. At this time, the dispersion time was set to 30 minutes, and a catalyst ink was prepared. The composition ratio of the starting materials in the prepared catalyst ink was set as follows. That is, the mass ratio of carbon support: oxide-based catalyst material: carbon fibers: polymer electrolyte was set to 1:1.4:0.2:0.8. A solvent in which ultrapure water and 1-propanol were mixed was used as the solvent for the catalyst ink. In the solvent, the volume ratio of ultrapure water to 1-propanol was set to 1:1. In addition, the catalyst ink was adjusted so that the solid content in the catalyst ink was 12% by mass.

[Substrate]
A polytetrafluoroethylene (PTFE) sheet was used as the base material constituting the transfer sheet.

[Method of forming an electrode catalyst layer on a substrate]
The catalyst ink prepared above was applied onto a substrate by a doctor blade method and dried in an air atmosphere at 80° C. The amount of catalyst ink applied was adjusted so that the amount of platinum supported in the electrode catalyst layer forming the fuel electrode (anode) was 0.05 mg/ ^cm2 , and the amount of platinum supported in the electrode catalyst layer forming the air electrode (cathode) was 0.1 mg/ ^cm2 .

[Preparation of Membrane Electrode Assembly]
The substrate on which the anode electrode catalyst layer was formed and the substrate on which the cathode electrode catalyst layer was formed were each punched out into a 5 cm x 5 cm square shape and transferred onto both sides of a polymer electrolyte membrane. That is, for a pair of opposing surfaces of the polymer electrolyte membrane, the anode electrode catalyst layer was transferred onto the first surface, and the cathode electrode catalyst layer was transferred onto the second surface. At this time, the transfer temperature was set to 130°C, and the transfer pressure was set to 5.0 x ¹⁰⁶ Pa. In this way, the membrane electrode assembly of Example 1 was produced.

<Comparative Example 1>
[Preparation of catalyst ink]
A platinum-supported carbon catalyst (catalyst-supported particles) with a support density of 50% by mass, carbon fibers with an average fiber diameter of 150 nm and an average fiber length of 6 μm, and a 25% by mass polymer electrolyte solution were mixed in a solvent, and a dispersion process was performed in the solvent using a planetary ball mill. At this time, the dispersion time was set to 30 minutes, and a catalyst ink was prepared. The composition ratio of the starting materials in the prepared catalyst ink was set as follows. That is, the mass ratio of carbon support:carbon fiber:polymer electrolyte was set to 1:0.2:0.8. A solvent in which ultrapure water and 1-propanol were mixed was used as the solvent for the catalyst ink. The volume ratio in the solvent was set to 1:1. The catalyst ink was also prepared so that the solid content in the catalyst ink was 12% by mass.

[Substrate]
A polytetrafluoroethylene (PTFE) sheet was used as the base material constituting the transfer sheet.

[Method of forming an electrode catalyst layer on a substrate]
The catalyst ink prepared above was applied onto a substrate by a doctor blade method and dried in an air atmosphere at 80° C. The amount of catalyst ink applied was adjusted so that the amount of platinum supported in the electrode catalyst layer forming the fuel electrode (anode) was 0.05 mg/ ^cm2 , and the amount of platinum supported in the electrode catalyst layer forming the air electrode (cathode) was 0.1 mg/ ^cm2 .

[Preparation of Membrane Electrode Assembly]
The substrate on which the anode electrode catalyst layer was formed and the substrate on which the cathode electrode catalyst layer was formed were each punched out into a 5 cm x 5 cm square shape and transferred onto both sides of a polymer electrolyte membrane. That is, for a pair of opposing surfaces of the polymer electrolyte membrane, the anode electrode catalyst layer was transferred onto the first surface, and the cathode electrode catalyst layer was transferred onto the second surface. At this time, the transfer temperature was set to 130°C, and the transfer pressure was set to 5.0 x ¹⁰⁶ Pa. In this way, a membrane electrode assembly of Comparative Example 1 was produced.

<Comparative Example 2>
[Preparation of catalyst ink]
A platinum-supported carbon catalyst (catalyst-supported particles) with a support density of 50% by mass, an oxide-based catalyst material (TiONP), and a 25% by mass polymer electrolyte solution were mixed in a solvent, and a dispersion process was performed in the solvent using a planetary ball mill. At this time, the dispersion time was set to 30 minutes, and a catalyst ink was prepared. The composition ratio of the starting materials in the prepared catalyst ink was set as follows. That is, the mass ratio of carbon support: oxide-based catalyst material: polymer electrolyte was set to 1:1.4:0.8. A solvent in which ultrapure water and 1-propanol were mixed was used as the solvent for the catalyst ink. In the solvent, the volume ratio of ultrapure water to 1-propanol was set to 1:1. In addition, the catalyst ink was prepared so that the solid content in the catalyst ink was 12% by mass.

[Substrate]
A polytetrafluoroethylene (PTFE) sheet was used as the base material constituting the transfer sheet.

[Method of forming an electrode catalyst layer on a substrate]
The catalyst ink prepared above was applied onto a substrate by a doctor blade method and dried in an air atmosphere at 80° C. The amount of catalyst ink applied was adjusted so that the amount of platinum supported in the electrode catalyst layer forming the fuel electrode (anode) was 0.05 mg/ ^cm2 , and the amount of platinum supported in the electrode catalyst layer forming the air electrode (cathode) was 0.1 mg/ ^cm2 .

[Preparation of Membrane Electrode Assembly]
The substrate on which the anode electrode catalyst layer was formed and the substrate on which the cathode electrode catalyst layer was formed were each punched out into a 5 cm x 5 cm square shape and transferred onto both sides of a polymer electrolyte membrane. That is, for a pair of opposing surfaces of the polymer electrolyte membrane, the anode electrode catalyst layer was transferred onto the first surface, and the cathode electrode catalyst layer was transferred onto the second surface. At this time, the transfer temperature was set to 130°C, and the transfer pressure was set to 5.0 x ¹⁰⁶ Pa. In this way, a membrane electrode assembly of Comparative Example 2 was produced.

<Evaluation>
[Power generation characteristics]
Carbon paper, which is a gas diffusion layer, was attached so as to sandwich each of the membrane electrode assemblies of Example 1 and Comparative Examples 1 and 2 to prepare samples. Each sample was then placed in a power generation evaluation cell, and current and voltage measurements were performed using a fuel cell measurement device. The cell temperature during measurement was set to 65° C., and the operating conditions were set to high humidification and low humidification as shown below. Hydrogen was used as the fuel gas, and air was used as the oxidizing gas. At this time, the flow rate of hydrogen was set to a flow rate at which the hydrogen utilization rate was 90%, and the flow rate of air was set to a flow rate at which the oxygen utilization rate was 40%. The back pressure was set to 50 kPa.

[Operating conditions]
Condition 1 (high humidity): Relative humidity Anode: 90% RH, Cathode: 80% RH
Condition 2 (low humidity): Relative humidity Anode: 90% RH, Cathode: 30% RH

[Measurement results]
The polymer electrolyte fuel cell including the membrane electrode assembly of Example 1 exhibited superior power generation performance under highly humidified operating conditions than the polymer electrolyte fuel cells including the membrane electrode assemblies of Comparative Examples 1 and 2. It was also confirmed that the membrane electrode assembly of Example 1 had the same power generation performance under highly humidified operating conditions as under low humidified operating conditions. In particular, the membrane electrode assembly of Example 1 improved the power generation performance at a current density of about 1.5 A/ ^cm2 .

Under highly humidified operating conditions, in the polymer electrolyte fuel cell including the membrane electrode assembly of Example 1, the cell voltage at a current density of 1.5 A/ ^cm2 was found to be 0.26 V higher than the cell voltage at a current density of 1.5 A/ ^cm2 in the polymer electrolyte fuel cell including the membrane electrode assembly of Comparative Example 1. Under highly humidified operating conditions, in the polymer electrolyte fuel cell including the membrane electrode assembly of Example 1, the cell voltage at a current density of 1.5 A/ ^cm2 was found to be 0.22 V higher than the cell voltage at a current density of 1.5 A/ ^cm2 in the polymer electrolyte fuel cell including the membrane electrode assembly of Comparative Example 2.

From the measurement results of the power generation performance of a polymer electrolyte fuel cell equipped with the membrane electrode assembly of Example 1 and the power generation characteristics of a polymer electrolyte fuel cell equipped with the membrane electrode assemblies of Comparative Examples 1 and 2, it was confirmed that the membrane electrode assembly of Example 1 improves drainage, and as a result, the power generation characteristics under high humidification operating conditions are equivalent to those under low humidification operating conditions.

Moreover, under low humidification operating conditions, in the polymer electrolyte fuel cell including the membrane electrode assembly of Example 1, the cell voltage at a current density of 1.5 A/cm ² was found to be 0.28 V higher than the cell voltage at a current density of 1.5 A/cm ² in the solid polymer electrolyte fuel cell including the membrane electrode assembly of Comparative Example 1. Moreover, under low humidification operating conditions, in the solid polymer electrolyte fuel cell including the membrane electrode assembly of Example 1, the cell voltage at a current density of 1.5 A/cm ² was found to be 0.24 V higher than the cell voltage at a current density of 1.5 A/cm ² in the solid polymer electrolyte fuel cell including the membrane electrode assembly of Comparative Example 2.

From the measurement results of the power generation performance of a polymer electrolyte fuel cell equipped with the membrane electrode assembly of Example 1 and the power generation characteristics of a polymer electrolyte fuel cell equipped with the membrane electrode assemblies of Comparative Examples 1 and 2, it was confirmed that the membrane electrode assembly of Example 1 has high drainage properties for water generated in the electrode reaction and does not inhibit water retention under low humidification conditions.

REFERENCE SIGNS LIST 1: Polymer electrolyte membrane 2: Electrode catalyst layer 3: Electrode catalyst layer 4: Gas diffusion layer 5: Gas diffusion layer 6: Air electrode (cathode)
7...Fuel electrode (anode)
8a, 8b... Gas flow passages 9a, 9b... Cooling water flow passages 10a, 10b... Separators 11... Membrane electrode assembly 12... Solid polymer fuel cell

Claims (8)

A polymer electrolyte membrane and a pair of electrode catalyst layers sandwiching the polymer electrolyte membrane,
At least one of the pair of electrode catalyst layers includes particles carrying a catalyst made of a precious metal component, a polymer electrolyte, a fibrous material having an average fiber length falling within a range of 1 μm or more and 15 μm or less, and an oxide-based catalyst material,
The oxide-based catalytic material contains a transition metal element ,
The transition metal element is Ti.
Membrane electrode assembly for fuel cells. 2. The membrane electrode assembly for a fuel cell according to claim 1, wherein the electrode catalyst layer containing the particles, the polymer electrolyte, the fibrous material, and the oxide-based catalyst material comprises an electrode catalyst layer for a positive electrode in a polymer electrolyte fuel cell. 3. The membrane electrode assembly for a fuel cell according to claim 1, wherein the oxide-based catalytic material contains P as a substitution atom for the nitride of the transition metal element, and the nitride is a partially oxidized material. 4. The membrane electrode assembly for a fuel cell according to claim 1, wherein a ratio (MB/MA) of a mass (MB) of the oxide-based catalytic material to a mass (MA) of a support in a particle carrying a catalyst made of a precious metal component is within a range of 0.1 to 10 times. 5. The membrane electrode assembly for a fuel cell according to claim 1, wherein a ratio (MC/MA) of a mass (MC) of the polymer electrolyte to a mass of a carrier ( MA ) in the particles supporting a catalyst made of a precious metal component is within a range of 0.2 times or more and 2.8 times or less. 6. The membrane electrode assembly for a fuel cell according to claim 1, wherein a ratio (MD/MA) of a mass (MD) of the fibrous material to a mass (MA) of a support in a particle supporting a catalyst made of a precious metal component is within a range of 0.05 times or more and 1.0 times or less. 7. The membrane electrode assembly for a fuel cell according to claim 1, wherein the particles carrying the catalyst made of a precious metal component are covered with a hydrophobic coating. The fuel cell membrane electrode assembly according to any one of claims 1 to 7 ,
a pair of gas diffusion layers sandwiching the fuel cell membrane electrode assembly;
a pair of separators sandwiching the pair of gas diffusion layers.