JP2016035877A - Diffusion layer of fuel battery and fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a diffusion layer of a fuel battery having both of dry-up resistance and flooding resistance; and a fuel battery including such a diffusion layer.SOLUTION: A diffusion layer 1 of a fuel battery according to the present invention comprises: a base material 2; and MPL 3 formed on a surface of the base material 2 and including hydrophilic carbon nanotube 4. The MPL 3 has first micropores 6A; and second micropores 6B. The carbon nanotube 4 is exposed in internal spaces of the first micropores 6A. The hydrophilic carbon nanotube 4 reduces a contact angle of water, and decreases the seepage pressure of the first micropores 6A, which allows water to easily enter the first micropores 6A and therefore, water can be adequately discharged through the first micropores 6A, and paths for supplying a fuel gas and an oxidant gas can be ensured. In internal spaces of the second micropores 6B, hydrophobic particles 7 are exposed. With the aid of the second micropores 6B with the hydrophobic particles 7 exposed, the following are made possible: to further ensure paths for supplying the fuel gas and the oxidant gas; to increase the flooding resistance; to supply water held around the carbon nanotube 4 to an electrolytic film; and to increase the dry-up resistance.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a diffusion layer of a fuel cell and a fuel cell.

  The polymer electrolyte fuel cell includes a battery cell in which a separator, a diffusion layer, a catalyst layer, an electrolyte membrane, a catalyst layer, a diffusion layer, and a separator are stacked in this order. The diffusion layer has a function of uniformly supplying gas to the catalyst layer. During power generation, hydrogen gas as fuel gas is supplied from the separator to the catalyst layer on the anode side through the diffusion layer, and oxygen gas or air as oxidant gas from the separator to the catalyst layer on the cathode side through the diffusion layer. Is supplied. In the catalyst layer on the anode side, hydrogen chemically reacts by the action of the catalyst, and hydrogen ions and electrons are released. The electrons move to the diffusion layer and the separator, and reach the catalyst layer on the cathode side through the external circuit from the separator. Hydrogen ions reach the cathode catalyst layer through the electrolyte membrane. In the catalyst layer on the cathode side, hydrogen ions, electrons and oxygen chemically react to generate water.

  When a high load is applied to the fuel cell to generate a large amount of electricity, in the fuel cell, a large amount of water is generated on the cathode side, and the water clogs the pores of the diffusion layer and the catalyst layer. There is a problem (flooding) that the supply of gas is insufficient and the power generation capacity is reduced. In addition, since the fuel cell becomes high temperature due to the heat generated by the chemical reaction, the moisture in the electrolyte membrane evaporates, the water for the movement of hydrogen ions becomes insufficient, and the ionic conductivity decreases. Therefore, in the fuel cell, there is a problem (dry up) that the ohmic overvoltage increases and the output of the fuel cell decreases. In order to solve such problems, various fuel cells have been researched and developed.

  For example, Patent Document 1 discloses a fuel cell having a structure in which a solid polymer electrolyte layer is sandwiched between a fuel electrode having a reaction layer and a diffusion layer and an oxygen electrode. The diffusion layer of the fuel cell of Patent Document 1 includes a diffusion layer substrate formed of carbon fibers and a porous microporous layer containing carbon powder and a water-repellent resin, and the microporous layer provided on the reaction layer side includes , Have pores with a size that allows gas to pass but not liquid. In the diffusion layer of the fuel cell of Patent Document 1, since water generated in the reaction layer cannot pass through the microporous layer, water is held in the reaction layer as a liquid. Therefore, the diffusion layer of the fuel cell of Patent Document 1 can prevent the solid polymer electrolyte layer from drying up.

JP 2008-293937 A

  However, in the diffusion layer of the fuel cell disclosed in Patent Document 1, liquid water cannot pass through the microporous layer, and water accumulates at the interface between the reaction layer and the diffusion layer, which may cause flooding. There is.

  In addition, in a diffusion layer having a conventional microporous layer, water can easily pass through the microporous layer by appropriately increasing the pore diameter of the microporous layer, and the flooding resistance of the diffusion layer is improved. However, since water is discharged outside through the pores of the microporous layer, the dry-up resistance of the diffusion layer is reduced.

  Thus, it has been difficult to achieve both dry-up resistance and flooding resistance of the diffusion layer of the fuel cell.

  Therefore, an object of the present invention is to provide a diffusion layer for a fuel cell that can achieve both dry-up resistance and flooding resistance, and a fuel cell including the diffusion layer.

  The diffusion layer of the fuel cell of the present invention comprises a substrate and a microporous layer formed on the surface of the substrate and containing hydrophilic carbon nanotubes, and the microporous layer has a plurality of first pores. The carbon nanotubes are exposed in the internal spaces of the plurality of first pores.

  The fuel cell of the present invention includes the diffusion layer of the fuel cell of the present invention.

  The diffusion layer of the fuel cell of the present invention comprises a substrate and a microporous layer formed on the surface of the substrate and containing hydrophilic carbon nanotubes, and the microporous layer has a plurality of first pores, Since the carbon nanotubes are exposed in the internal spaces of the plurality of first pores, the hydrophilic carbon nanotubes exposed in the internal spaces of the first pores reduce the contact angle of water and reduce the hydraulic pressure. Since water can easily enter one pore, water can be sufficiently discharged through the first pore, and water can be retained around the carbon nanotube. Therefore, when the diffusion layer of the present invention is used in a fuel cell, a supply path for fuel gas and oxidant gas is secured, and the flooding resistance can be improved, and water retained around the carbon nanotube is supplied to the electrolyte membrane. Therefore, the dry-up resistance can be improved.

  Since the fuel cell of the present invention includes the diffusion layer of the fuel cell of the present invention, it is possible to achieve both dry-up resistance and flooding resistance.

FIG. 1A is a schematic view showing a diffusion layer of a fuel cell according to an embodiment of the present invention, FIG. 1A is an end view schematically showing a cross section of the diffusion layer, and FIG. 1B is an enlarged schematic view of a part of the microporous layer. FIG. It is a SEM photograph which shows the 1st pore of the diffusion layer of the fuel cell of an Example. It is a SEM photograph which shows the 2nd pore of the diffusion layer of the fuel cell of an Example. It is a SEM photograph which expands and shows the 2nd pore shown in FIG. It is a figure which shows the current-voltage characteristic on the dry-up conditions of the fuel cell using the diffused layer of an Example and a comparative example. It is a figure which shows the current voltage characteristic on the flooding conditions of the fuel cell using the diffused layer of an Example and a comparative example.

  Hereinafter, embodiments of the present invention will be described in detail.

1. Configuration of Fuel Cell A fuel cell (not shown) is generally a fuel cell in which a separator, a diffusion layer, a catalyst layer, an electrolyte membrane, a catalyst layer, a diffusion layer, and a separator are stacked in this order from the anode side to the cathode side. Composed. The fuel cell has power generation capability even with one fuel cell, but a plurality of the fuel cells may be combined according to the target output. In the fuel cell, one end of the external circuit is connected to the anode side separator, and the other end of the external circuit is connected to the cathode side separator, and electricity is taken out.

  The separator is formed of a conductive member, and a gas flow path for supplying gas to the diffusion layer is provided on the surface. For example, a plate-like member made of metal or carbon is used as the separator, with a gas flow path provided on the surface.

  The catalyst layer is formed of a conductive member having a large surface area, and supports the catalyst. The catalyst layer is, for example, a network member formed of carbon fibers, and a catalyst is supported on the network. It may be a plate-like member formed by supporting a catalyst on carbon black and binding with ionomer and polytetrafluoroethylene (PTFE) having the same components as the electrolyte membrane. As the catalyst for the catalyst layer, platinum, platinum alloy, palladium, rhodium, gold, silver or the like is used.

  As the electrolyte membrane, a fluororesin ion exchange membrane is used. For example, Nafion (registered trademark), Flemion (registered trademark), Selemion (registered trademark), Aciplex (registered trademark), or the like is used as the electrolyte membrane.

  The diffusion layer is formed of a conductive member and has a large number of pores. For example, the diffusion layer is a non-woven fabric formed of carbon fibers. In this embodiment, the diffusion layer has a microporous layer (hereinafter referred to as MPL). The diffusion layer is arranged so that the MPL is in contact with the catalyst layer. Hereinafter, the diffusion layer of the fuel cell of this embodiment will be described.

2. Configuration of Diffusion Layer of Fuel Cell As shown in FIG. 1A, the diffusion layer 1 of the fuel cell of the present invention includes a base material 2 and an MPL 3. The base material 2 is a member having conductivity, is formed to a thickness of 200 to 300 μm, and has a large number of pores having a diameter of several tens to 100 μm. The substrate 2 is not particularly limited as long as it has conductivity and can diffuse fuel gas and oxidant gas. The substrate 2 is a plate-like member such as a woven fabric (carbon cloth), a nonwoven fabric (carbon paper), or a porous body (porous metal) formed of conductive fibers.

  The MPL 3 is formed in a plate shape on the surface of the substrate 2 by a mixture containing carbon nanotubes 4, carbon particles, and hydrophobic particles. In the present embodiment, the MPL 3 is formed to have a thickness of 90 to 240 μm. Part of the MPL 3 may enter the pores of the substrate 2. Since FIG. 1A is a diagram schematically showing the diffusion layer 1, the carbon nanotubes 4 are drawn in a straight line and form uniform stitches, but are actually entangled with each other in the MPL 3 to form a three-dimensional shape. A skeleton 5 having a network structure is formed. The carbon nanotube 4 is not particularly limited as long as it has hydrophilicity, but the contact angle with water measured using a contact angle meter is desirably 30 degrees or less. In addition, the length and diameter of the tube are not particularly limited, and the carbon nanotube 4 may be a single-walled carbon nanotube or a multi-walled carbon nanotube.

  As the carbon particles, for example, carbon black such as furnace black and acetylene black, graphite, and the like are used. The hydrophobic particles are made of, for example, a fluororesin such as polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), or tetrafluoroethylene hexafluoropropylene copolymer (FEP). It is formed as a raw material. The content of the hydrophobic particles is not particularly limited, but MPL3 preferably contains hydrophobic particles at a rate of 10 to 40 wt%. When the content of hydrophobic particles in MPL3 is less than 10 wt%, a mixture containing carbon nanotubes 4, carbon particles, and hydrophobic particles is not sufficiently bound. On the other hand, when the content of hydrophobic particles in MPL3 is more than 40 wt%, the conductivity is lowered.

  As shown in FIG. 1B, the MPL 3 has a plurality of first pores 6A and second pores 6B formed in the skeleton 5. Since FIG. 1B is a diagram schematically showing a part of the MPL 3 in an enlarged manner, the first pore 6A and the second pore 6B are represented as a planar mesh, but in reality, a three-dimensional mesh structure. It is a space formed in the skeleton 5 having The skeleton 5 has a portion where the hydrophobic particles 7 and the carbon particles 9 are sparse and a dense portion. In the portion where the hydrophobic particles 7 and the carbon particles 9 are dense, the hydrophobic particles 7 and the carbon particles 9 are mixed and aggregated.

  The first pore 6 </ b> A is formed in a region surrounded by the carbon nanotubes 4 where the hydrophobic particles 7 of the skeleton 5 are in a sparse part. Only the carbon nanotubes 4 entangled in a mesh shape are exposed in the internal space of the first pore 6A, and the hydrophobic particles 7 and the carbon particles 9 are not exposed.

  The second pores 6B are formed in a region surrounded by the carbon nanotubes 4 where the hydrophobic particles 7 of the skeleton 5 are in a dense portion and the hydrophobic particles 7 and the carbon particles 9 are attached. Hydrophobic particles 7 and carbon particles 9 are exposed in most of the internal space of the second pore 6B, and carbon nanotubes 4 are exposed in a part. Further, the aggregated hydrophobic particles 7 and carbon particles 9 are exposed between the carbon nanotubes 4.

  The first pore 6A and the second pore 6B are connected to each other by the first pore 6A, the second pore 6B, and the first pore 6A and the first pore 6B. Water and gas can circulate in the direction.

3. Method for Producing Diffusion Layer of Fuel Cell A method for producing the diffusion layer 1 will be described. First, the carbon nanotubes 4, the carbon particles 9, and the raw material of the hydrophobic particles 7 are weighed so as to have a predetermined ratio. A surfactant is added to the measured carbon nanotubes 4 and the like, and stirred for a predetermined time at a speed of several thousand revolutions per minute using a stirrer to prepare an MPL slurry. Subsequently, MPL slurry is apply | coated to the surface of the base material 2 to predetermined thickness using the coating machine with a micrometer. Finally, the base material 2 to which the MPL slurry is applied is put in a muffle furnace, a calciner or the like, and calcined at a predetermined temperature for a predetermined time. At this time, a skeleton 5 is formed by the carbon nanotubes 4. Since the raw material of the hydrophobic particles 7 contained in the MPL slurry is agglomerated in the course of drying, a portion where the hydrophobic particles 7 are sparse and a dense portion are formed inside the skeleton 5. The first pores 6A are formed in portions where the hydrophobic particles 7 are sparse, and the second pores 6B are formed in portions where the hydrophobic particles 7 are dense. The diffusion layer 1 is manufactured through the above steps.

4). Action and Effect The action of the fuel cell of the present invention during power generation will be described. First, the operation on the anode side of the fuel cell will be described. On the anode side, hydrogen gas, which is a fuel gas, is supplied to the diffusion layer 1 through a flow path provided in the separator. The hydrogen gas supplied to the diffusion layer 1 passes through the pores formed in the base material 2 and reaches the MPL 3. The hydrogen gas further passes through the first pore 6A and the second pore 6B of the MPL 3 and reaches the catalyst layer. The hydrogen gas diffuses through the base material 2 of the diffusion layer 1 and the pores of the MPL 3 and is uniformly supplied to the catalyst layer.

  In the catalyst layer, hydrogen gas acts on the catalyst to cause a chemical reaction to generate hydrogen ions and electrons. Hydrogen ions are supplied to the electrolyte membrane and move to the cathode side through the electrolyte membrane. Electrons are collected in the catalyst layer, conducted to the separator, and supplied from the separator to the external circuit.

  Next, the operation on the cathode side of the fuel cell will be described. On the cathode side, air as an oxidant gas is supplied to the diffusion layer 1 through a flow path provided in the separator. As the oxidant gas, oxygen gas may be supplied instead of air. The air supplied to the diffusion layer 1 passes through the pores formed in the base material 2 and reaches the MPL 3. The air further passes through the first pore 6A and the second pore 6B of the MPL 3, and reaches the catalyst layer. Air diffuses by passing through the base material 2 of the diffusion layer 1 and the pores of the MPL 3 and is uniformly supplied to the catalyst layer.

  In the catalyst layer, oxygen contained in the air, hydrogen ions supplied from the electrolyte membrane, and electrons supplied from an external circuit act on the catalyst and chemically react to generate water.

  Since water has a high surface tension and a large contact angle, it tends to form water droplets, and it is difficult for water to penetrate into fine pores. Further, the water-repellent pores have a high water permeation pressure. And as the pore is smaller, the water permeability is higher and the water is less likely to enter.

  Since the hydrophilic carbon nanotube 4 is exposed to the internal space in the first pore 6A, the contact angle of water is small in that portion. Therefore, water easily enters the first pore 6A from that portion, and as a result, the water permeability pressure of the first pore 6A decreases. Therefore, the first pore 6A has a lower water permeation pressure than the pores of the same size, and water easily enters the inside. Accordingly, water generated by power generation enters the first pore 6A and is discharged to the outside through the first pore 6A. Moreover, since the carbon nanotube 4 has hydrophilicity, water is easily held in the portion where the carbon nanotube 4 is exposed. Therefore, when there is little water produced | generated and the pressure of water is smaller than the hydraulic pressure of the 1st pore 6A, water is hold | maintained around the carbon nanotube 4 of the 1st pore 6A.

  On the other hand, in the second pores 6B, the hydrophobic particles 7 are exposed in the internal space, and the hydrophobic particles 7 have a large contact angle, so the water permeation pressure is high and water does not easily enter the interior. The second pores 6B are highly drainable because the water is easily separated from the exposed portions of the hydrophobic particles 7 and the water easily moves in the internal space. For this reason, even when water enters the second pore 6B, the water is immediately discharged. Further, since the carbon nanotube 4 is exposed in a part of the internal space of the second pore 6B, water is held in that part. However, since the carbon nanotubes 4 are exposed only in a part of the internal space of the second pores 6B, the second pores 6B are not blocked by the water retained around the carbon nanotubes 4. Therefore, the second pore 6B can function as a supply path for a gas such as hydrogen gas or air.

  In such a fuel cell, even when a large amount of water is generated from the catalyst layer on the cathode side, water can be sufficiently discharged through the first pores 6A, so that the flooding resistance is high. Further, in the fuel cell, it is difficult for water to enter the second pores 6B, and even when water enters, the second pores 6B are discharged immediately, so an air supply path can be secured. Therefore, in the fuel cell, air is sufficiently supplied to the catalyst layer on the cathode side, so that the performance of the fuel cell is hardly deteriorated and the flooding resistance is high.

  In the fuel cell, since the hydrophilic carbon nanotubes 4 are exposed in a part of the internal space of the first pore 6A and the internal space of the second pore 6B, water is easily held in that portion. Therefore, even when the temperature of the fuel cell becomes high, the water retained around the carbon nanotube 4 is sufficiently supplied to the electrolyte membrane, so that the performance of the fuel cell is unlikely to deteriorate. Therefore, the fuel cell has high dry-up resistance.

  In the above configuration, the diffusion layer 1 of the fuel cell of the present invention includes the base material 2 and the MPL (microporous layer) 3 formed on the surface of the base material 2 and including the hydrophilic carbon nanotubes 4. However, it comprised so that it might have the some 1st pore 6A, and the carbon nanotube 4 might be exposed to the internal space of the some 1st pore 6A.

  Therefore, in the diffusion layer 1 of the fuel cell of the present invention, the contact angle of water is reduced by the hydrophilic carbon nanotubes 4, the water permeability of the first pore 6A is reduced, and water easily enters the first pore 6A. Therefore, water can be sufficiently discharged through the first pore 6A. As a result, when the diffusion layer 1 is used in a fuel cell, a supply path for an oxidant gas is secured, and flooding resistance can be improved.

  Further, in the diffusion layer 1, the first pores 6 </ b> A can hold water around the carbon nanotubes 4. Therefore, when the diffusion layer 1 is used in a fuel cell, the water retained around the carbon nanotube 4 can be supplied to the electrolyte membrane, so that the dry-up resistance can be improved.

  Therefore, the diffusion layer 1 of the fuel cell can achieve both dry-up resistance and flooding resistance.

  Moreover, the diffusion layer 1 of the fuel cell of the present invention can further prevent water from entering the second pores 6B by further including the second pores in which the hydrophobic particles 7 are exposed in the internal space. Furthermore, drainage can be enhanced, and water can be discharged immediately even when water enters the second pores 6B. Therefore, when the diffusion layer 1 is used in a fuel cell, a supply path for fuel gas and oxidant gas can be secured, and flooding resistance can be further improved.

  The diffusion layer 1 also retains water around the carbon nanotubes 4 in the second pores 6B by exposing the hydrophilic carbon nanotubes 4 to a part of the internal space of the second pores 6B. it can. As a result, when the diffusion layer 1 is used in a fuel cell, water retained around the carbon nanotubes 4 exposed in the internal space of the second pore 6B can be supplied to the electrolyte membrane. It can be improved.

(1) Production of Diffusion Layer As an example, a diffusion layer comprising MPL containing carbon nanotubes at a rate of 4 wt% was produced.

  First, 4 wt% of carbon nanotubes, 76 wt% of carbon black (manufactured by Denki Kogyo Co., Ltd.) as carbon particles, and 20 wt% of PTFE (manufactured by Daikin Industries, Ltd.) as a raw material for hydrophobic particles, a surfactant (Triton X ( (Registered trademark)) and an impeller blade stirring type stirrer for 1 hour to prepare an MPL slurry. Next, using a coating machine with a micrometer, MPL slurry was applied to the surface of carbon paper (product name: 24BA, manufactured by SGL Carbon Co.) as a base material so that the finished film thickness of the diffusion layer was 250 to 300 μm. . Finally, the carbon paper coated with the MPL slurry was baked at 350 ° C. for 30 minutes in a muffle furnace to produce a diffusion layer of the example.

  As a comparative example, a diffusion layer having an MPL different from that of the example only in that carbon nanotubes were not included was prepared.

(2) Fabrication of fuel cell A fuel cell having the diffusion layers of Examples and Comparative Examples fabricated above was fabricated. In the fuel cell of Example, first, a membrane electrode assembly (manufactured by Gore Japan, product name: PRIMEA (registered trademark) series 5580) is used as a catalyst layer and an electrolyte membrane, and the membrane electrode assembly and MPL are in contact Thus, the membrane electrode assembly was sandwiched between the diffusion layers of the examples. Next, in the fuel cell of the example, a diffusion layer was sandwiched between separators made of graphite and provided with gas flow paths, and the separators were fixed with bolts to produce fuel cells. Moreover, the fuel cell which has a diffusion layer of a comparative example was produced by the same method. The characteristics of the produced fuel cell were evaluated, and the fuel cell was evaluated.

(3) Evaluation of MPL pores In order to evaluate the MPL pores, the surface of the MPL of the diffusion layer of the example was observed with a scanning electron microscope (hereinafter referred to as SEM).

  FIG. 2 is an example of an SEM photograph of the first pore 6A. The first pore 6A shown in FIG. 2 has a pore diameter of about 1 μm. The first pores 6A have carbon nanotubes 4 intertwined in an internal space and exposed. In addition, the carbon nanotubes 4 are intertwined in a network shape in portions other than the internal space of the first pore 6A.

  FIG. 3 is an example of an SEM photograph of the second pore 6B. The second pore 6B shown in FIG. 3 has a pore diameter of about 3 μm. Even in portions other than the second pores 6B, the carbon nanotubes 4 are intertwined in a network shape, and the carbon nanotubes 4 form a three-dimensional network structure.

  FIG. 4 is an SEM photograph showing the portion 8 in FIG. 3 in an enlarged manner. In the second pores 6B, the hydrophobic particles 7 are exposed in the internal space, and the carbon nanotubes 4 are intertwined in a mesh shape and exposed in part. In the second pore 6B, the hydrophobic particles 7 adhere to the carbon nanotubes 4, and the hydrophobic particles 7 aggregate to form a part of the inner wall of the second pore 6B.

(4) Performance Evaluation of Fuel Cell In order to evaluate the performance of the fuel cell, the current-voltage characteristics of the manufactured fuel cell were measured. Measurement of the current-voltage characteristics of the fuel cell is made by measuring the output voltage and current density of the fuel cell when a DC electronic load is connected to the fuel cell and the value of the DC electronic load is changed. I went there. The fuel cell was measured by supplying hydrogen gas as fuel gas to the anode and air as oxidant gas to the cathode.

  The measurement was performed under two conditions: a case where the relative humidity of hydrogen gas and air was 100%, and a case where the relative humidity of hydrogen gas was 60% and the relative humidity of air was 0%. The former is a condition in which a fuel cell without MPL causes flooding (hereinafter referred to as flooding condition), and the latter is a condition in which a fuel cell without MPL causes dry-up (hereinafter referred to as dry-up condition). is there.

  FIG. 5 shows dry-up conditions for the fuel cell having the diffusion layer of the example (black circle shown in the drawing) and the fuel cell having the diffusion layer of the comparative example (open circle shown in the drawing). The current-voltage characteristics are shown. In FIG. 5, the horizontal axis indicates the current density, and the vertical axis indicates the output voltage. The fuel cell of the example has a gradual decrease in output voltage with respect to the increase in current density compared to the fuel cell of the comparative example, and the performance of the fuel cell even in a situation where dry-up occurs in the fuel cell of the comparative example It can be seen that there is little decrease in the. Therefore, it turns out that the fuel cell of an Example has high dry-up resistance.

  FIG. 6 shows the flooding conditions for the fuel cell having the diffusion layer of the example (black circle shown in the drawing) and the fuel cell having the diffusion layer of the comparative example (open circle shown in the drawing). The current-voltage characteristics are shown as in FIG. In the fuel cell of the example, the output voltage decreases more slowly with respect to the increase in current density than the fuel cell of the comparative example, and the performance of the fuel cell is improved even in a situation where flooding occurs in the fuel cell of the comparative example. It turns out that there is little decline. Therefore, it turns out that the fuel cell of an Example has high flooding resistance.

  From the above, it has been confirmed that the fuel cell using the diffusion layer of the present invention can achieve both flooding resistance and dry-up resistance.

DESCRIPTION OF SYMBOLS 1 Diffusion layer 2 Base material 3 MPL (microporous layer)
4 Carbon nanotube 5 Skeleton 6A First pore 6B Second pore 7 Hydrophobic particle 9 Carbon particle

Claims (5)

A substrate and a microporous layer formed on the surface of the substrate and including hydrophilic carbon nanotubes;
The microporous layer has a plurality of first pores;
The diffusion layer of a fuel cell, wherein the carbon nanotube is exposed in an internal space of the plurality of first pores.   2. The fuel cell diffusion layer according to claim 1, further comprising second pores in which hydrophobic particles are exposed in the internal space.   2. The microporous layer includes a skeleton having a three-dimensional network structure formed by the carbon nanotubes, and the carbon nanotubes exposed to the internal space are part of the skeleton. 3. A diffusion layer of the fuel cell according to 2.   The diffusion layer of a fuel cell according to any one of claims 1 to 3, wherein the carbon nanotube has a contact angle of 30 degrees or less.   A fuel cell comprising the fuel cell diffusion layer according to claim 1.

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