Membrane Electrode Assembly and Fuel Cell

Abstract

A membrane electrode assembly for fuel cells, said membrane electrode assembly comprising an electrolyte membrane, and a first electrode and a second electrode, between which the electrolyte membrane is sandwiched. With respect to this membrane electrode assembly for fuel cells, the first electrode sequentially comprises, from the electrolyte membrane side, a first catalyst layer and a first gas diffusion layer; the first gas diffusion layer comprises a first fibrous conductive member and a first resin material; the first catalyst layer contains a second fibrous conductive member, catalyst particles and a second resin material; and when viewed from the stacking direction of the membrane electrode assembly, a first angle between the first fibrous conductive member and a main flow path for a gas to be supplied to the membrane electrode assembly is arbitrary, while a second angle between the second fibrous conductive member and the main flow path is 45° or less.

Description

Technical Field

[0001] The present invention relates to a membrane electrode assembly for a fuel cell and a fuel cell.

Background Art

[0002] A fuel cell includes a membrane electrode assembly having an electrolyte membrane and a pair of electrodes sandwiching the electrolyte membrane. The pair of electrodes each include a catalyst layer and a gas diffusion layer in order from the electrolyte membrane side.

[0003] In Patent Document 1, it is proposed to configure a gas diffusion layer composed of three or more layers with three or more layers and change the direction in which the conductive carbon fibers contained in each layer are oriented. Thereby, a gas diffusion layer excellent in gas diffusibility can be provided at low cost.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with the method of Patent Document 1, the gas diffusibility is not sufficiently improved.

Means for Solving the Problems

[0006] One aspect of the present invention is a membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, wherein the first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, the first gas diffusion layer includes a first fibrous conductive member and a first resin material, the first catalyst layer includes a second fibrous conductive member, catalyst particles and a second resin material, and when viewed from the stacking direction of the membrane electrode assembly, the first angle formed by the first fibrous conductive member and the main flow path of the gas supplied to the membrane electrode assembly is arbitrary, and the second angle formed by the second fibrous conductive member and the main flow path is 45° or less.

[0007] Another aspect of the present invention relates to a fuel cell comprising the above-described membrane electrode assembly, a first separator and a second separator sandwiching the membrane electrode assembly.

Advantages of the Invention

[0008] According to the present invention, the gas diffusibility in the membrane electrode assembly is improved. Further, a fuel cell having excellent output characteristics can be provided.

Brief Description of the Drawings

[0009]

Figure 1A

Figure 1B

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Figure 12

Figure 13

Mode for Carrying Out the Invention

[0010] (First Embodiment) Fuel gas or oxidizing gas (hereinafter, simply referred to as gas in general) flows from the gas diffusion layer toward the electrolyte membrane. The gas is supplied to the gas diffusion layer, for example, through a separator arranged outside the gas diffusion layer or a flow path formed in the gas diffusion layer. Therefore, in order to enhance gas diffusibility, it is necessary to consider the extending direction of the gas flow path.

[0011] The gas diffusion layer and the catalyst layer according to this embodiment both contain fibrous conductive members. In this embodiment, the fibrous conductive members of the gas diffusion layer and the catalyst layer are oriented along the main gas flow path. As a result, the gas smoothly enters the gas diffusion layer and the catalyst layer without being blocked by the fibrous conductive members and is diffused in the plane direction. That is, the pressure loss is suppressed and the gas diffusibility in the electrode is improved. The membrane electrode assembly according to this embodiment is particularly useful for fuel cells having a plurality of gas flow paths with relatively small intervals.

[0012] [Membrane Electrode Assembly] The membrane electrode assembly (hereinafter sometimes referred to as MEA) according to this embodiment includes an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane. The first electrode includes a first catalyst layer and a first gas diffusion layer in order from the electrolyte membrane side. The first gas diffusion layer includes a first fibrous conductive member and a first resin material. The first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material. One of the first electrode and the second electrode is an anode, and the other is a cathode.

[0013] When viewed from the stacking direction of the MEA, the first angle formed by the first fibrous conductive member (hereinafter referred to as the first conductive fiber) and the main gas flow path supplied to the MEA is 45° or less. The first angle is the smaller of the angles formed by the first conductive fiber and the main gas flow path. The first angle is 0° or more.

[0014] Similarly, when viewed from the stacking direction of the MEA, the second angle formed by the second fibrous conductive member (hereinafter referred to as the second conductive fiber) and the main flow path is 45° or less. The second angle is the smaller of the angles formed by the second conductive fiber and the main gas flow path. The second angle is 0° or more.

[0015] The first angle is preferably 30° or less, and more preferably 15° or less. Thereby, the gas diffusibility is further improved.

[0016] The second angle is preferably 30° or less, more preferably 15° or less. Also in this case, the gas diffusibility is further improved.

[0017] When looking at the cross-section along the main gas flow path of the MEA, the first conductive fibers are preferably oriented along the interface between the first gas diffusion layer and the first catalyst layer (hereinafter referred to as the first interface). Specifically, the first conductive fibers are parallel to the interface between the first gas diffusion layer and the first catalyst layer, or inclined from the upstream of the main flow path toward the first interface, and the third A angle formed with the first interface is preferably 70° or less. Thereby, the gas can enter the gas diffusion layer more smoothly without being hindered by the first conductive fibers. The third A angle is the smaller angle formed by the first conductive fibers parallel to the first interface or inclined from the upstream of the main flow path toward the first interface and the first interface. The third A angle is 0° or more.

[0018] The third A angle formed by the first conductive fibers and the first interface is more preferably 60° or less, and particularly preferably 45° or less.

[0019] On the other hand, when looking at the cross-section along the main gas flow path of the MEA, the second conductive fibers are preferably not along the first interface. Specifically, the fourth A angle formed by the second conductive fibers and the first interface is preferably 25° or more. Thereby, the gas that has entered the first catalyst layer is likely to diffuse in the thickness direction and can efficiently contact the electrolyte membrane. On the other hand, the fourth A angle is preferably 80° or less. Thereby, the bending of the second conductive fibers due to the application of an external force in the thickness direction is suppressed, and the gas diffusibility is more likely to be further improved. Furthermore, since the piercing of the second conductive fibers into the electrolyte membrane is suppressed, damage to the electrolyte membrane is also prevented. The fourth A angle is the smaller angle formed by the second conductive fibers and the first interface.

[0020] The fourth A angle is, for example, 25° or more and 80° or less, more preferably 25° or more and 70° or less, and particularly preferably 25° or more and 65° or less.

[0021] When looking at a cross-section along the main gas flow path of the MEA, it is particularly preferable that the second conductive fibers are inclined, especially, from the upstream of the main gas flow path toward the first interface. Also, the fourth A angle formed by the second conductive fibers and the first interface in this case is preferably 25° or more and 80° or less, more preferably 25° or more and 70° or less, and particularly preferably 25° or more and 65° or less.

[0022] Among these, it is preferable that both the first conductive fibers and the second conductive fibers are inclined from the upstream of the main gas flow path toward the first interface. In other words, it is preferable that the conductive fibers in each layer face each other with the first interface as a boundary.

[0023] In a fuel cell using a proton-conductive polymer electrolyte membrane as the electrolyte membrane, it is usually carried out to add water vapor to the fuel gas or the oxidizing gas, humidify it in advance, and then supply it to the gas diffusion layer. This is to moisten the electrolyte membrane and enhance proton conductivity.

[0024] On the other hand, on the cathode side of the electrolyte membrane, water is generated by an electrochemical reaction. The generated water (product water) may block the gas diffusion path. Therefore, consideration is being given to quickly discharging the product water.

[0025] As in this embodiment, by orienting the conductive fibers in the first gas diffusion layer and the first catalyst layer so as to face each other across the first interface, the gas can be humidified using the generated water. The generated water crawls up to the first interface along the second conductive fibers of the first catalyst layer. However, since the orientation of the conductive fibers in the first gas diffusion layer is opposite to that in the first catalyst layer, the generated water tends to stay in the vicinity of the first interface. On the other hand, gas flows into the gas diffusion layer along the first conductive fibers. The inflowing gas contacts the water staying in the vicinity of the first interface and is humidified, and then flows into the electrolyte membrane through the first catalyst layer. That is, the humidified gas is supplied to the electrolyte membrane. Therefore, it is possible to supply the gas directly to the MEA without humidifying it by an external device, that is, without passing through a humidifier. As a result, the cost and size of the fuel cell can be reduced, and the fuel cell can be started stably more easily. The fuel cell according to this embodiment is particularly suitable for in-vehicle use.

[0026] It is preferable that the sum of the third A angle formed by the first conductive fiber parallel to the first interface or inclined from the upstream of the main flow path toward the first interface and the first interface, and the fourth A angle formed by the second conductive fiber inclined from the upstream of the main flow path toward the first interface and the first interface is 25° or more and 110° or less. Thereby, the generated water tends to stay in the vicinity of the first interface, and the gas is humidified more efficiently. It is more preferable that the sum of the third A angle and the fourth A angle is 25° or more and 90° or less, and particularly preferably 25° or more and 60° or less.

[0027] When looking at the cross-section intersecting the main gas flow path of the MEA, it is preferable that the first conductive fiber is not along the first interface. Specifically, the fifth A angle formed by the first conductive fiber and the first interface is preferably 45° or more. Thereby, the gas that has entered the first gas diffusion layer is likely to diffuse in the thickness direction. The fifth A angle is the smaller angle formed by the first conductive fiber and the first interface. However, the fifth A angle may be 90°.

[0028] The fifth A angle is more preferably 55° or more, and particularly preferably 60° or more.

[0029] When looking at the cross-section intersecting the main gas flow path of the MEA, it is also preferable that the second conductive fiber is not along the first interface. Specifically, the 6A angle formed by the second conductive fiber and the first interface is preferably 45° or more. Thereby, the gas entering the catalyst layer easily diffuses in the thickness direction. The 6A angle is the smaller angle formed by the second conductive fiber and the first interface. However, the 6A angle may be 90°.

[0030] The 6A angle is more preferably 48° or more, and particularly preferably 50° or more.

[0031] "Viewed from the stacking direction of the MEA" is synonymous with viewing from the normal direction of the main surface of the MEA. The same applies to the following other embodiments.

[0032] The "main gas flow path" is the flow path in the direction in which the most gas flows. The direction of the gas flowing through the entire flow path is understood from the positional relationship between the gas inlet and the outlet. When viewed from the stacking direction of the MEA, the gas flow path is divided according to the direction in which the gas flows. When the gas flows in the same direction through one gas flow path, division of the gas flow path is not necessary. Even when the direction of the gas flow changes at an angle less than 90°, the gas flow can be regarded as the same, so division of the gas flow path is not necessary. When there are a plurality of regions where the gas flow is the same, the flow areas of these are added together. The direction in which the most gas flows is the direction of the gas flow in which the flow area is the largest. The region with the largest area is the main gas flow path. The direction of the gas flow can be regarded as the extension direction of the center line of the gas flow path, taking into account the positional relationship between the gas inlet and the outlet. The center line is a line that bisects the gas flow path along the direction in which the gas flows. The same applies to the following other embodiments.

[0033] Generally, the gas flow path is provided to extend generally in the direction from the gas inlet to the outlet. The gas flow path is formed, for example, in a parallel type or a serpentine type. The parallel type gas flow path is a plurality of grooves extending from the side (the first side) near the gas supply port of the separator or the gas diffusion layer to the opposite side (the second side) thereof. The serpentine type gas flow path is one or a plurality of grooves extending while meandering from the first side to the second side of the separator or the gas diffusion layer. The grooves can be straight or wavy.

[0034] Hereinafter, the main gas flow path will be described with reference to the drawings. However, the shape and arrangement of the gas flow path are not limited thereto.

[0035] FIG. 1A is a plan view schematically showing a parallel type gas flow path formed in a separator. In FIG. 1A, the separator is viewed from the stacking direction of the MEA. For convenience, the gas flow path is hatched.

[0036] A plurality of linear grooves (gas flow paths 260) are formed in the separator 240 from the first side 240a to the second side 240b. The gas flow paths 260 are substantially parallel to each other. In the plurality of gas flow paths 260, the direction of gas flow is the same. That is, all the supplied gases flow in the same direction A. In this case, the main gas flow path is all the gas flow paths 260. The gas flows from the first side 240a to the second side 240b. The upstream of the main flow path is the first side 240a side.

[0037] FIG. 1B is a plan view schematically showing a serpentine type gas flow path formed in a separator. In FIG. 1B, the separator is viewed from the stacking direction of the MEA. For convenience, the gas flow path is hatched.

[0038] The separator 240 is formed with one groove (gas flow path 260) that extends in a meandering manner from the first side 240a to the second side 240b. In the gas flow path 260, the gas flows in three directions. The three directions are: direction A from the first side 240a towards the second side 240b, direction B from the second side 240b towards the first side 240a, and direction C that intersects with both direction A and direction B. The gas flow path 260 is divided into regions (region A, region B, region C) corresponding to these three directions. However, at the bend angles of the flow path, two regions (for example, region A and region C) overlap. Each region is formed in one or more numbers. The area of each region (or the total area if there are more than one) is determined, and the region with the largest area is the main flow path. In FIG. 1B, the main flow path is region A. In the main flow path, the gas flows in direction A. The upstream of the main flow path is the first side 240a. In addition, if there are multiple regions with the largest area, any one of them can be used as the main flow path.

[0039] The "first angle" formed by the first conductive fiber and the main gas flow path is obtained as follows. First, prepare an MEA, and photograph the region on the main surface of the gas diffusion layer that faces the main gas flow path using a scanning electron microscope (SEM). From the obtained SEM image, arbitrarily determine three regions RP1 (for example, 50 μm × 50 μm) where 20 or more conductive fibers can be confirmed. The three regions RP1 should not overlap with each other. Arbitrarily select 10 conductive fibers that can be confirmed within each region RP1. For each of the 10 conductive fibers, draw a tangent LP1 at the midpoint PP1 of the observable length.

[0040] FIG. 2 is an explanatory diagram for explaining how to draw the tangent of the conductive fiber using the main surface of the first gas diffusion layer. FIG. 2 shows one region RP1. Also, FIG. 2 shows only three first conductive fibers that can be confirmed. For the plurality of first conductive fibers 131, tangents LP1 are drawn at the midpoint PP1 of the observable length respectively.

[0041] On one hand, a line that bisects the main flow path determined as described above along the gas flow direction is defined as the center line CL of the main flow path. When the main flow path includes a plurality of regions as described above, the center line of any one of the regions is defined as the center line CL of the main flow path (see Fig. 1A).

[0042] The average value of the angles formed by the plurality of (in the above case, 30) tangent lines LP1 obtained as described above and the center line CL of the main flow path is determined. After calculating this average value, data that differs from the obtained average value by 20% or more is excluded, and the average value is calculated again. This corrected average value is defined as the "first angle". The number of the first conductive fibers to be selected is 30 or more.

[0043] The "second angle" formed by the second conductive fiber and the main flow path of the gas is also determined in the same manner as the first angle. First, the gas diffusion layer is removed from the MEA to expose the catalyst layer, and the region of the main surface of the catalyst layer facing the main flow path of the gas is photographed by SEM. From the obtained SEM image, three regions RP2 (for example, 50 μm × 50 μm) where 20 or more conductive fibers can be confirmed are arbitrarily determined. The three regions RP2 should not overlap with each other. Arbitrarily select 10 conductive fibers that can be confirmed within each region RP2. For each of the 10 conductive fibers, draw a tangent line LP2 at the midpoint PP2 of the observable length.

[0044] The average value of the angles formed by the plurality of (in the above case, 30) tangent lines LP2 obtained as described above and the center line CL of the main flow path is determined. After calculating this average value, data that differs from the obtained average value by 20% or more is excluded, and the average value is calculated again. This corrected average value is defined as the "second angle". The number of the second conductive fibers to be selected is 30 or more.

[0045] The "third A angle" formed by the first conductive fiber and the first interface is determined as follows. First, prepare an MEA, and photograph three cross-sections along the main flow path and including the gas diffusion layer and the catalyst layer using SEM. The "cross-section along the main flow path" is synonymous with the cross-section obtained by cutting the MEA in the thickness direction with a straight line having an angle of 0° with the center line CL of the main flow path determined as described above.

[0046] From the obtained SEM images, arbitrarily determine one region RS1 (for example, 50 μm × 50 μm) where 20 or more first conductive fibers and first interfaces can be confirmed. Separately, determine one region RS1 for each of two different cross-sections in the same manner. Arbitrarily select 10 first conductive fibers that can be confirmed within each region RS1. For each of the 10 first conductive fibers, draw a tangent line LS1 at the midpoint PS1 of the observable length.

[0047] On the other hand, draw a straight line connecting the ends of the interfaces between the gas diffusion layer and the catalyst layer in the region RS1. This straight line is defined as the first interface.

[0048] Obtain the average value of the angles formed by the plurality (30 in the above case) of tangent lines LS1 obtained as described above and the first interface. After calculating this average value, exclude the data that differs from the obtained average value by 20% or more, and calculate the average value again. This corrected average value is defined as the "third A angle". The number of first conductive fibers to be selected is 30 or more.

[0049] The "fourth A angle" formed by the second conductive fibers and the first interface is also obtained in the same manner as the third A angle. Determine one region RS2 from each of the three cross-sections where 10 or more second conductive fibers and the first interface can be confirmed. Select 5 second conductive fibers from each of the three regions RS2 and draw a tangent line LS2. Obtain the average value of the angles formed by the plurality (15 in the above case) of tangent lines LS2 and the first interface. After calculating this average value, exclude the data that differs from the obtained average value by 20% or more, and calculate the average value again. This corrected average value is defined as the "fourth A angle". The number of second conductive fibers to be selected is 15 or more.

[0050] The "5A angle" formed by the first conductive fiber and the first interface is obtained in the same manner as the 3A angle, except that a cross-section intersecting the main flow path is photographed by SEM.

[0051] The "6A angle" formed by the second conductive fiber and the first interface is obtained in the same manner as the 4A angle, except that a cross-section intersecting the main flow path is photographed by SEM.

[0052] The "cross-section intersecting the main flow path" is synonymous with the cross-section obtained by cutting the MEA in the thickness direction by a straight line that forms a 90° angle with the center line CL of the main flow path determined as described above.

[0053] The fact that the first conductive fiber is inclined from the upstream of the main flow path toward the first interface is synonymous with the fact that the end of the first conductive fiber on the downstream side of the main flow path is closer to the first interface than the end on the upstream side thereof.

[0054] The fact that the second conductive fiber is inclined from the upstream of the main flow path toward the first interface is synonymous with the fact that the end of the second conductive fiber on the downstream side of the main flow path is closer to the first interface than the end on the upstream side thereof.

[0055] The 3A angle formed by the first conductive fiber that is parallel to the first interface or inclined from the upstream of the main flow path toward the first interface and the first interface is calculated in the same manner as above by selecting 10 first conductive fibers that are parallel to the first interface or inclined from the upstream of the main flow path toward the first interface from the three regions RS1 determined as described above.

[0056] Similarly, the 4A angle formed by the second conductive fiber that is inclined from the upstream of the main flow path toward the first interface and the first interface is calculated using the second conductive fibers that are inclined from the upstream of the main flow path toward the first interface selected from the three regions RS2.

[0057] The first conductive fiber and the second conductive fiber are preferably arranged in each layer while ensuring their linearity. Ensuring linearity means that the conductive fiber is not significantly bent, and it refers to the linearity rate R obtained by the method described below being 0.6 or more. From the perspective of gas diffusibility, the linearity rate R is preferably 0.7 or more.

[0058] The linearity rate R1 of the first conductive fiber is obtained as follows from the three regions RS1 determined as described above. Arbitrarily select 10 distinguishable first conductive fibers within each region RS1. For the 10 first conductive fibers, connect one end and the other end of the observable length portion with a straight line, and obtain the length Ls of the straight line. Also, for the same 10 first conductive fibers, obtain the actual length Lr of the observable length portion. For this plurality (in the above case, 30) of first conductive fibers, obtain the average value of the ratio of Ls to Lr: Ls / Lr. After calculating this average value, exclude the data that differs from the obtained average value by 20% or more, and calculate the average value again. This corrected average value is defined as the linearity rate R1. The number of first conductive fibers to be selected shall be 30 or more. The linearity rate R2 of the second conductive fiber is also obtained in the same manner from the three regions RS2. The number of second conductive fibers to be selected shall be 15 or more.

[0059] Next, the first gas diffusion layer and the first catalyst layer according to this embodiment will be specifically described with reference to the drawings. However, the first gas diffusion layer and the first catalyst layer according to this embodiment are not limited thereto.

[0060] FIG. 3 is a schematic plan view of the first gas diffusion layer as viewed from the stacking direction of the MEA. In FIG. 3, the first angle is illustrated for convenience, but the first angle is calculated by the above-described calculation method. The first gas diffusion layer 130A includes first conductive fibers 131 that are oriented along direction A. The first angle θ1 formed by the first conductive fibers 131 and the main gas flow path (direction A) is 45° or less.

[0061] FIG. 4 is a schematic plan view of the first catalyst layer as viewed in the stacking direction of the MEA. In FIG. 4, the second angle is illustrated for convenience, and the second angle is calculated by the above-described calculation method. The first catalyst layer 120A includes second conductive fibers 121 oriented along direction A. The second angle θ2 formed by the second conductive fibers 121 and the main gas flow path (direction A) is 45° or less.

[0062] FIG. 5 is a schematic cross-sectional view taken along the main flow path of the MEA. This cross-sectional view corresponds to the view obtained by cutting the MEA along the X-X line in FIG. 7, but for convenience, only the first gas diffusion layer and the first catalyst layer are shown. Also, in FIG. 5, the third A angle and the fourth A angle are illustrated for convenience, and these are calculated by the above-described calculation method.

[0063] The first conductive fibers 131 are also generally oriented along direction A in a cross-section along the main flow path. The first conductive fibers 131 gently incline from the upstream of the main flow path toward the first interface S. The third A angle θ3 formed by the first conductive fibers 131 and the first interface S is, for example, 70° or less.

[0064] On the other hand, the second conductive fibers 121 are generally oriented along the thickness direction Z in a cross-section along the main flow path. The second conductive fibers 121 incline from the upstream of the main flow path toward the first interface S. The fourth A angle θ4 formed by the second conductive fibers 121 and the first interface S is, for example, 25° or more.

[0065] Both the first conductive fibers 131 and the second conductive fibers 121 incline from the upstream of the main flow path toward the first interface S. At this time, the sum of the third A angle θ3 and the fourth A angle θ4 is, for example, 25° or more and 110° or less.

[0066] FIG. 6 is a schematic cross-sectional view taken along a direction intersecting the main flow path of the MEA. This cross-sectional view corresponds to the view obtained by cutting the MEA along the Y-Y line in FIG. 7, but for convenience, only the first gas diffusion layer and the first catalyst layer are shown. Also, in FIG. 6, the fifth A angle and the sixth A angle are illustrated for convenience, and these are calculated by the above-described calculation method.

[0067] The first conductive fiber 131 is oriented generally along the thickness direction Z in a cross section intersecting the main flow path. The fifth A angle θ5 formed by the first conductive fiber 131 and the first interface S is, for example, 45° or more.

[0068] The second conductive fiber 121 is also oriented generally along the thickness direction Z in a cross section intersecting the main flow path. The sixth A angle θ6 formed by the second conductive fiber 121 and the first interface S is, for example, 45° or more.

[0069] a. The first gas diffusion layer The first gas diffusion layer includes the first conductive fiber and the first resin material. Thereby, a microporous layer having conductivity is formed.

[0070] The first gas diffusion layer constitutes at least one of the cathode gas diffusion layer and the anode gas diffusion layer of the fuel cell. The MEA may include the gas diffusion layer according to the present embodiment for the cathode and the anode.

[0071] The first gas diffusion layer may further have a base material layer. The first gas diffusion layer having the base material layer has, for example, the base material layer and the microporous layer provided on the catalyst layer side thereof. A conductive porous sheet such as carbon cloth or carbon paper is used for the base material layer.

[0072] Considering miniaturization of the fuel cell, it is desirable that the thickness of the first gas diffusion layer is thin. On the other hand, from the viewpoint of strength, it is preferable that the first gas diffusion layer is not excessively thin. The thickness of the first gas diffusion layer is, for example, 30 μm or more and 1000 μm or less, and preferably 50 μm or more and 500 μm or less.

[0073] The thickness of the first gas diffusion layer is the average thickness, and is obtained by averaging the distances when straight lines are drawn along the thickness direction of the first gas diffusion layer from one main surface to the other main surface for any 10 locations in the cross section of the first gas diffusion layer.

[0074] (The first conductive fiber) The first conductive fiber has an aspect ratio of 2 or more and is conductive. The aspect ratio of the first conductive fiber may be 3 or more, and may be 5 or more. Also, the aspect ratio of the first conductive fiber may be 1000 or less, may be 500 or less, and may be 100 or less. The aspect ratio of the first conductive fiber is, for example, 3 or more and 1000 or less. The aspect ratio of the first conductive fiber is the ratio of the average diameter R1 to the average length L1 of the first conductive fiber.

[0075] Examples of the first conductive fiber include fibrous carbon materials such as vapor-grown carbon fiber (VGCF (registered trademark)), single-layer or multi-layer carbon nanotubes (CNT), and carbon nanofibers. The first conductive fiber may have a hollow space (hollow part) inside. Both ends in the length direction of the first conductive fiber may be open.

[0076] As the first conductive fiber, two or more types of conductive fibers having different materials, average diameters, and / or average lengths may be mixed and used. For example, the first conductive fiber may include single-layer carbon nanotubes (diameter 0.3 to 3 nm, fiber length 10 μm or less), and multi-layer carbon nanotubes (diameter 5 to 200 nm, fiber length 20 μm or less).

[0077] The average diameter R1 of the first conductive fiber is not particularly limited. The average diameter R1 may be 0.3 nm or more, may be 3 nm or more, and may be 20 nm or more. The average diameter R1 may be 300 nm or less, may be 250 nm or less, and may be 200 nm or less. When the average diameter R1 is within this range, the volume ratio of the first conductive fiber in the first gas diffusion layer becomes small, and it becomes easy to secure a sufficient gas path.

[0078] The average diameter R1 of the first conductive fiber is obtained by arbitrarily taking out 10 first conductive fibers from the first gas diffusion layer and averaging their diameters. The diameter is the length in a direction perpendicular to the length direction of the first conductive fiber. The average diameter R2 of the second conductive fiber is also obtained in the same manner.

[0079] The average length L1 of the first conductive fiber is not particularly limited. The average length L1 of the first conductive fiber may be, for example, 0.2 μm or more, and may be 0.5 μm or more. The average length L1 of the first conductive fiber may be, for example, 20 μm or less, and may be 10 μm or less. When the average length L1 is within this range, it becomes easier to orient the first conductive fiber in a desired direction, and the gas diffusibility is more likely to be improved.

[0080] The average length L1 of the first conductive fiber is obtained by arbitrarily taking out 10 first conductive fibers from the first gas diffusion layer and averaging the fiber lengths of these first conductive fibers. The above-mentioned fiber length is the length when one end and the other end of the taken-out conductive fiber are pulled so as to be straight. The average length L2 of the second conductive fiber is also obtained in the same manner.

[0081] The mass ratio of the first conductive fiber in the first gas diffusion layer is not particularly limited. In terms of easily ensuring sufficient gas diffusibility, it is desirable that the mass ratio of the first conductive fiber is higher. On the other hand, if the mass ratio of the first conductive fiber is excessively high, the film thickness of the first gas diffusion layer becomes excessively thick, and the electron transfer resistance is likely to increase. Considering the above, the mass ratio of the first conductive fiber in the first gas diffusion layer may be 10% by mass or more and 90% by mass or less, and may be 20% by mass or more and 75% by mass or less.

[0082] (First resin material) The first resin material has a function as a binder for binding the first conductive fibers to each other. The mass ratio of the first resin material in the first gas diffusion layer may be 5% by mass or more and 50% by mass or less, and may be 10% by mass or more and 40% by mass or less.

[0083] From the viewpoint of suppressing the retention of water in the first gas diffusion layer, it is preferable that 50% by mass or more, and further 90% by mass or more, of the first resin material is a water-repellent resin. The first resin material may further contain a proton-conductive resin (polymer electrolyte).

[0084] Examples of the water-repellent resin include fluororesin. Examples of the fluororesin include PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene - hexafluoropropylene copolymer), PVdF (polyvinylidene fluoride), ETFE (tetrafluoroethylene - ethylene copolymer), PCTFE (polychlorotrifluoroethylene), PFA (tetrafluoroethylene - perfluoroalkyl vinyl ether copolymer), etc. Among them, from the viewpoints of heat resistance, water repellency, and chemical resistance, the fluororesin is preferably PTFE.

[0085] The proton conductive resin is not particularly limited. Examples of the proton conductive resin include perfluorocarbon sulfonic acid - based polymers and hydrocarbon - based polymers. Among them, perfluorocarbon sulfonic acid - based polymers, etc. are preferable in terms of excellent heat resistance and chemical stability. Examples of the perfluorocarbon sulfonic acid - based polymer include Nafion (registered trademark).

[0086] (Others) The first gas diffusion layer may contain particulate conductive members, plate - like conductive members, etc. as the conductive material. Specific examples of the plate - like conductive member include flaky graphite, pulverized graphite - treated polyimide film, graphene, etc. Among them, pulverized graphite - treated polyimide film and graphene are likely to be oriented in the plane direction, which is advantageous for forming the first gas diffusion layer thinly and is suitable for enhancing gas diffusivity in the plane direction.

[0087] The mass ratio of the plate - like conductive member in the first gas diffusion layer is not particularly limited. Among them, from the viewpoint of gas diffusivity, the mass ratio of the plate - like conductive member in the first gas diffusion layer may be 20% by mass or less, and may be 10% by mass or less.

[0088] The particulate conductive member has an aspect ratio of less than 2 and is conductive. The particulate conductive member is not particularly limited, and examples thereof include carbon black, spherical graphite, activated carbon, etc. Among these, carbon black is preferable in terms of high conductivity and large pore volume. Examples of carbon black include acetylene black, ketjen black, thermal black, furnace black, channel black, etc. Its particle size (or the length of the structure composed of a plurality of connected primary particles) is not particularly limited, and those conventionally used for the first gas diffusion layer of a fuel cell can be used.

[0089] The mass ratio of the particulate conductive member in the first gas diffusion layer is not particularly limited. Among these, from the viewpoint of gas diffusibility, the mass ratio of the particulate conductive member in the first gas diffusion layer may be 20% by mass or less, and may be 10% by mass or less.

[0090] (Manufacturing method of the first gas diffusion layer) The first gas diffusion layer can be obtained, for example, by molding a mixture containing a conductive member such as the first conductive fiber, a first resin material, and a dispersion medium into a sheet shape and then baking it.

[0091] As the dispersion medium, for example, water, ethanol, propanol, etc. are used. For molding, for example, rolling by a roll press or the like is used. The orientation of the first conductive fiber can be adjusted by changing, in addition to its length, for example, the rolling speed and pressure, the viscosity of the mixture, etc.

[0092] The formed sheet may be baked. After baking, the sheet may be further rolled. For rolling after baking, a mold having ribs arranged in a predetermined gas flow path pattern may be used. Thereby, a gas flow path can be formed in the first gas diffusion layer. The gas flow path may be formed by cutting the main surface of the sheet after baking.

[0093] (Gas flow path) A gas flow path may be formed in the first gas diffusion layer. The gas flow path may be formed in the separator.

[0094] The fibrous conductive members of the gas diffusion layer and the catalyst layer according to this embodiment are oriented along the main gas flow path. Therefore, according to this embodiment, when the distance between a plurality of gas flow paths is relatively small, the gas diffusibility can be further improved. The distance between the gas flow paths is not particularly limited, but for example, it may be 0.5 times or more and 2 times or less the width of the gas flow path. The width of the gas flow path is the length of the gas flow path in the direction perpendicular to the gas flow. Specifically, the distance between the gas flow paths may be 0.3 mm or more and 5 mm or less.

[0095] b. First catalyst layer The first catalyst layer includes second conductive fibers, catalyst particles, and a second resin material.

[0096] The first catalyst layer constitutes at least one of the cathode catalyst layer and the anode catalyst layer of the fuel cell. During power generation of the fuel cell, water is generated at the cathode. According to this embodiment, since the gas diffusibility is improved, the first catalyst layer is particularly suitable as the cathode catalyst layer. Also, the first catalyst layer is suitable as the cathode catalyst layer in terms of being able to humidify the gas using the generated water. The MEA may include the catalyst layer according to this embodiment not only at the cathode but also at the anode.

[0097] Considering the miniaturization of the fuel cell, it is desirable for the thickness of the first catalyst layer to be thin, while from the perspective of strength, it is preferably not overly thin. The thickness of the catalyst layer is, for example, 1 μm or more and 50 μm or less, and preferably 2 μm or more and 20 μm or less.

[0098] The thickness of the first catalyst layer is the average thickness, and is obtained by averaging the distances when straight lines are drawn in the thickness direction of the first catalyst layer from one main surface to the other main surface for any 10 locations in the cross-section of the first catalyst layer.

[0099] (Second conductive fibers) The second conductive fibers have two or more aspect ratios and are conductive. Examples of the second conductive fibers include the same materials as the first conductive fibers.

[0100] The average diameter R2 of the second conductive fiber is not particularly limited. The average diameter R2 may be 0.3 nm or more, may be 3 nm or more, and may be 20 nm or more. The average diameter R2 may be 300 nm or less, may be 250 nm or less, and may be 200 nm or less. When the average diameter R2 is within this range, the volume ratio of the second conductive fiber in the first catalyst layer becomes small, and it becomes easy to secure a sufficient gas path.

[0101] The average length L2 of the second conductive fiber is not particularly limited. The average length L2 of the second conductive fiber may be, for example, 0.2 μm or more and may be 0.5 μm or more. The average length L2 of the second conductive fiber may be, for example, 20 μm or less and may be 10 μm or less. When the average length L2 is within this range, it becomes easy to orient the second conductive fiber in a desired direction, and the gas diffusibility is more likely to be improved. Furthermore, it is possible to suppress both ends of the second conductive fiber from contacting the electrolyte membrane and the first gas diffusion layer, respectively, and damage is prevented.

[0102] The content of the second conductive fiber in the first catalyst layer is preferably 1% by mass or more and 85% by mass or less, and more preferably 5% by mass or more and 75% by mass or less. This is because it becomes easy to arrange the second conductive fiber in a desired state, and the gas diffusibility and the efficiency of the electrochemical reaction are likely to increase.

[0103] (Catalyst particles) A part of the catalyst particles may be supported on the second conductive fiber. This is because the catalyst particles are more likely to contact the gas, and the efficiency of the oxidation reaction or reduction reaction of the gas is increased.

[0104] The catalyst particles are not particularly limited, and examples thereof include catalyst metals such as alloys and simple substances selected from Sc, Y, Ti, Zr, V, Nb, Fe, Co, Ni, Ru, Rh, Pd, Pt, Os, Ir, lanthanoid series elements, and actinoid series elements. For example, as the catalyst particles used for the anode, a Pt-Ru alloy or the like can be mentioned. As the catalyst metals used for the cathode, Pt, a Pt-Co alloy, or the like can be mentioned.

[0105] (Second Resin Material) The second resin material has a function as a binder for binding the second conductive fibers together. From the viewpoint of improving reactivity, the second resin material preferably contains the above proton-conductive resin. In this case, the proton-conductive resin coats at least a part of the second conductive fibers and the catalyst particles.

[0106] The proton-conductive resin is preferably contained in an amount of 50 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the conductive members (the total of the second conductive fibers and particulate conductive members, etc.) contained in the first catalyst layer carrying the catalyst particles.

[0107] (Method for Manufacturing the First Catalyst Layer) The first catalyst layer can be formed, for example, by applying a catalyst ink containing conductive members such as second conductive fibers, catalyst particles, a second resin material, and the above dispersion medium onto the surface of the electrolyte membrane and drying it. Alternatively, the catalyst ink may be applied to a transfer base sheet, dried, and the first catalyst layer may be formed. The formed first catalyst layer is transferred to the electrolyte membrane.

[0108] As the base sheet, it is preferable to use a sheet having a smooth surface such as polyethylene terephthalate (PET) or polypropylene.

[0109] As the coating method, a screen printing method and coating methods using various coaters such as a blade coater, a knife coater, and a gravure coater are preferable. The orientation of the second conductive fibers can be adjusted, for example, by changing the coating amount, coating speed, viscosity, etc. of the catalyst ink in addition to its length.

[0110] [Fuel Cell] The fuel cell according to this embodiment includes the above MEA, a first separator and a second separator sandwiching the MEA. Since the above MEA has excellent gas diffusibility, the fuel cell including this MEA has excellent output characteristics.

[0111] The first separator may have a gas flow path. The gas is supplied from the gas flow path to the MEA. The fuel cell may further include a frame-shaped seal member that surrounds the peripheral portion of the MEA in a loop shape.

[0112] c. Separator The first separator and the second separator only need to have airtightness, electronic conductivity, and electrochemical stability, and the material thereof is not particularly limited. As such a material, a carbon material, a metal material, etc. are preferable. The metal material may be coated with carbon. For example, by punching a metal plate into a predetermined shape and performing a surface treatment, the first separator and the second separator can be obtained.

[0113] d. Seal member The seal member is a material having elasticity and prevents gas from leaking to the outside of the fuel cell. The seal member has, for example, a frame shape that surrounds the peripheral portions of a pair of catalyst layers in a loop shape. As the seal member, known materials and known configurations can be adopted.

[0114] Next, the fuel cell according to the present embodiment will be specifically described with reference to the drawings. However, the fuel cell according to the present embodiment is not limited thereto.

[0115] FIG. 7 is a perspective view showing the components of a single cell arranged in the fuel cell according to the present embodiment in an unfolded manner. Usually, a plurality of single cells are stacked and arranged in the fuel cell as a cell stack. In FIG. 7, for convenience, one single cell is shown.

[0116] The fuel cell (single cell) 200 includes an MEA 100, a first separator 240A and a second separator 240B sandwiching the MEA 100. The MEA 100 includes an electrolyte membrane 110, a first catalyst layer 120A and a second catalyst layer 120B arranged so as to sandwich the electrolyte membrane 110, and a first gas diffusion layer 130A and a second gas diffusion layer 130B arranged so as to sandwich the electrolyte membrane 110 via the first catalyst layer 120A and the second catalyst layer 120B, respectively.

[0117] The first separator 240A and the second separator 240B are each formed with parallel gas flow paths 260A and 260B. The gas flow paths 260A and 260B each include three grooves. The gas flows in direction A inside the gas flow paths 260A and 260B. The shape, arrangement, etc. of the gas flow paths are not limited to this. When the separator does not have a gas flow path, a gas flow path may be formed on the surface of the corresponding gas diffusion layer facing the separator.

[0118] In the first catalyst layer 120A, second conductive fibers 121 oriented along direction A are arranged. In the first gas diffusion layer 130A as well, first conductive fibers 131 oriented along direction A are arranged. In the second catalyst layer 120B and the second gas diffusion layer 130B as well, conductive fibers oriented along direction A are respectively arranged, but are not limited to this. The second catalyst layer 120B and the second gas diffusion layer 130B may be of known materials and known configurations.

[0119] (Second Embodiment) Both the gas diffusion layer and the catalyst layer according to this embodiment include fibrous conductive members. In this embodiment, the fibrous conductive members of the gas diffusion layer are oriented so as to intersect the main gas flow path. Thereby, the gas is diffused in a direction intersecting the main flow path along the fibrous conductive members. On the other hand, in the catalyst layer, the fibrous conductive members are oriented in a direction different from that of the gas diffusion layer, that is, along the main flow path. Therefore, the gas that has diffused in a direction intersecting the main flow path diffuses in a direction along the main flow path in the catalyst layer. As a result, the gas diffusibility in the electrode is improved. The membrane electrode assembly according to this embodiment is particularly useful for fuel cells having a plurality of gas flow paths with a relatively large interval.

[0120] [Membrane Electrode Assembly] The membrane electrode assembly (MEA) according to this embodiment includes an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane. The first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side. The first gas diffusion layer includes a first fibrous conductive member and a first resin material. The first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material. One of the first electrode and the second electrode is an anode, and the other is a cathode.

[0121] When viewed from the stacking direction of the MEA, the first angle formed by the first fibrous conductive member (first conductive fiber) and the main gas flow path supplied to the MEA is greater than 45°. The first angle is the smaller angle formed by the first conductive fiber and the main gas flow path. However, the first angle may be 90°.

[0122] On the other hand, when viewed from the stacking direction of the MEA, the second angle formed by the second fibrous conductive member (second conductive fiber) and the main flow path is 45° or less. The second angle is the smaller angle formed by the second conductive fiber and the main gas flow path. The second angle is 0° or more.

[0123] The first angle is preferably greater than 60°, and more preferably greater than 75°. Thereby, the gas diffusibility is further improved.

[0124] The second angle is preferably 30° or less, and more preferably 15° or less. Also in this case, the gas diffusibility is further improved.

[0125] When looking at the cross-section intersecting the main gas flow path of the MEA, the first conductive fiber is preferably oriented in the direction along the interface between the first gas diffusion layer and the first catalyst layer (hereinafter referred to as the first interface). Specifically, the third B angle formed by the first conductive fiber and the first interface is preferably less than 45°. Thereby, the gas that has entered the first gas diffusion layer is more likely to further diffuse in the direction intersecting the main gas flow path. As a result, the gas diffusibility in the electrode is further improved. The third B angle is the smaller angle formed by the first conductive fiber and the first interface. The third B angle is 0° or more.

[0126] The third B angle is more preferably less than 30°, and particularly preferably less than 15°.

[0127] On the other hand, when looking at the cross-section intersecting the main gas flow path of the MEA, it is preferable that the second conductive fiber is not along the first interface. Specifically, the fourth B angle formed by the second conductive fiber and the first interface is preferably 45° or more. Thereby, the gas entering the catalyst layer is likely to diffuse in the thickness direction. The fourth B angle is the smaller one of the angles formed by the second conductive fiber and the first interface. However, the fourth B angle may be 90°.

[0128] The fourth B angle is more preferably 60° or more, and particularly preferably 75° or more.

[0129] When looking at the cross-section along the main gas flow path of the MEA, it is preferable that the first conductive fiber is not along the first interface. Specifically, the fifth B angle formed by the first conductive fiber and the first interface is preferably 45° or more. Thereby, the gas is likely to diffuse in the thickness direction of the gas diffusion layer. The fifth B angle is the smaller one of the angles formed by the first conductive fiber and the first interface. However, the fifth B angle may be 90°.

[0130] The fifth B angle formed by the first conductive fiber and the first interface is more preferably 60° or more, and particularly preferably 75° or more.

[0131] When looking at a cross-section along the main gas flow path of the MEA, it is preferable that the second conductive fiber is not along the first interface either. Specifically, the 6B angle formed by the second conductive fiber and the first interface is preferably 25° or more. Thereby, the gas that has entered the first catalyst layer is likely to diffuse in the thickness direction and can efficiently contact the electrolyte membrane. On the other hand, the 6B angle is preferably 80° or less. Thereby, the bending of the second conductive fiber due to the application of an external force in the thickness direction is suppressed, and the gas diffusibility is more likely to be improved. Furthermore, since the piercing of the second conductive fiber into the electrolyte membrane is suppressed, damage to the electrolyte membrane is also prevented. The 6B angle is the smaller one of the angles formed by the second conductive fiber and the first interface.

[0132] The 6B angle is, for example, 25° or more and 80° or less, more preferably 25° or more and 70° or less, and particularly preferably 25° or more and 65° or less.

[0133] Regarding the main gas flow path, it is as described in the first embodiment, but the shape and arrangement of the gas flow path are not limited thereto.

[0134] The "first angle" formed by the first conductive fiber and the main gas flow path is obtained as follows, similar to the first embodiment. First, prepare an MEA and photograph the region of the main surface of the gas diffusion layer facing the main gas flow path with a scanning electron microscope (SEM). From the obtained SEM image, arbitrarily determine three regions RP1 (for example, 50 μm × 50 μm) where 20 or more conductive fibers can be confirmed. The three regions RP1 should not overlap each other. Arbitrarily select 10 conductive fibers that can be confirmed within each region RP1. For each of the 10 conductive fibers, draw a tangent LP1 at the midpoint PP1 of the observable length.

[0135] FIG. 8 is an explanatory diagram for explaining how to draw a tangent line of a conductive fiber using the main surface of the first gas diffusion layer. In FIG. 8, one region RP1 is shown. Also, in FIG. 8, only three first conductive fibers that can be confirmed are shown. For a plurality of first conductive fibers 131, tangent lines LP1 are respectively drawn at the intermediate point PP1 of the observable length.

[0136] On the other hand, a line that bisects the main flow path determined as described above along the direction of gas flow is defined as the center line CL of the main flow path. When the main flow path includes a plurality of regions as described above, the center line of any one of the regions is defined as the center line CL of the main flow path (see FIG. 1A).

[0137] The average value of the angles formed by the plurality (in the above case, 30) of tangent lines LP1 obtained as described above and the center line CL of the main flow path is obtained. After calculating this average value, data that differs from the obtained average value by 20% or more is excluded, and the average value is calculated again. This corrected average value is defined as the "first angle". The number of first conductive fibers to be selected is 30 or more.

[0138] The "second angle" formed by the second conductive fiber and the main flow path of the gas is also obtained in the same manner as the first angle. First, the gas diffusion layer is removed from the MEA to expose the catalyst layer, and the region of the main surface of the catalyst layer facing the main flow path of the gas is photographed by SEM. From the obtained SEM image, for example, three regions RP2 (for example, 50 μm × 50 μm) where 20 or more conductive fibers can be confirmed are arbitrarily determined. The three regions RP2 should not overlap each other. Arbitrarily select 10 conductive fibers that can be confirmed within each region RP2. For the 10 conductive fibers, tangent lines LP2 are respectively drawn at the intermediate point PP2 of the observable length.

[0139] The average value of the angles formed by the plurality (in the above case, 30) of tangent lines LP2 obtained as described above and the center line CL of the main flow path is obtained. After calculating this average value, data that differs from the obtained average value by 20% or more is excluded, and the average value is calculated again. This corrected average value is defined as the "second angle". The number of second conductive fibers to be selected is 30 or more.

[0140] The "third B angle" formed by the first conductive fiber and the first interface is obtained as follows. First, prepare an MEA, and photograph three cross-sections that intersect the main flow path and include the gas diffusion layer and the catalyst layer using SEM. The "cross-section intersecting the main flow path" is synonymous with the cross-section obtained by cutting the MEA in the thickness direction with a straight line that forms a 90° angle with the center line CL of the main flow path determined as described above.

[0141] From the obtained SEM images, arbitrarily determine one region RS1 (for example, 50 μm × 50 μm) where 20 or more first conductive fibers and the first interface can be confirmed. Separately, determine one region RS1 for each of two different cross-sections in the same manner. Arbitrarily select 10 first conductive fibers that can be confirmed within each region RS1. For each of the 10 first conductive fibers, draw a tangent line LS1 at the midpoint PS1 of the observable length.

[0142] On the other hand, draw a straight line connecting the ends of the interface between the gas diffusion layer and the catalyst layer in the region RS1. This straight line is defined as the first interface.

[0143] Obtain the average value of the angles formed by the plurality (30 in the above case) of tangent lines LS1 and the first interface obtained as described above. After calculating this average value, exclude data that differs from the obtained average value by 20% or more, and calculate the average value again. This corrected average value is defined as the "third B angle". The number of first conductive fibers to be selected is 30 or more.

[0144] The "fourth B angle" formed by the second conductive fiber and the first interface is also obtained in the same manner as the third B angle. Determine one region RS2 from each of three cross-sections where 10 or more second conductive fibers and the first interface can be confirmed. Select 5 second conductive fibers from each of the three regions RS2 and draw a tangent line LS2. Obtain the average value of the angles formed by the plurality (15 in the above case) of tangent lines LS2 and the first interface. After calculating this average value, exclude data that differs from the obtained average value by 20% or more, and calculate the average value again. This corrected average value is defined as the "fourth B angle". The number of second conductive fibers to be selected is 15 or more.

[0145] The "fifth B angle" formed by the first conductive fiber and the first interface is determined in the same manner as the third B angle, except that a cross-section along the main flow path is photographed by SEM.

[0146] The "sixth B angle" formed by the second conductive fiber and the first interface is determined in the same manner as the fourth B angle, except that a cross-section along the main flow path is photographed by SEM.

[0147] The "cross-section along the main flow path" is synonymous with the cross-section obtained by cutting the MEA in the thickness direction by a straight line that forms an angle of 0° with the center line CL of the main flow path determined as described above.

[0148] The fact that the second conductive fiber is inclined from the upstream of the main flow path toward the first interface is synonymous with the fact that the end portion of the second conductive fiber on the downstream side of the main flow path is closer to the first interface than the end portion on the upstream side thereof.

[0149] The first conductive fiber and the second conductive fiber are preferably arranged in each layer while ensuring their linearity. Ensuring linearity means that the conductive fiber is not greatly bent, and refers to the linearity rate R obtained by the method described below being 0.6 or more. From the perspective of gas diffusibility, the linearity rate R is preferably 0.7 or more.

[0150] The linearity rate R1 of the first conductive fiber is determined from the three regions RS1 determined as described above in the same manner as in the first embodiment.

[0151] Next, the first gas diffusion layer and the first catalyst layer according to the present embodiment will be specifically described with reference to the drawings. However, the first gas diffusion layer and the first catalyst layer according to the present embodiment are not limited thereto.

[0152] FIG. 9 is a schematic plan view of the first gas diffusion layer as viewed from the stacking direction of the MEA. In FIG. 9, the first angle is illustrated for convenience, but the first angle is calculated by the above-described calculation method. The first gas diffusion layer 130A includes first conductive fibers 131 oriented so as to intersect the direction A. The first angle θ1 formed by the first conductive fibers 131 and the main gas flow path (direction A) is greater than 45°.

[0153] FIG. 10 is a schematic plan view of the first catalyst layer as viewed from the stacking direction of the MEA. In FIG. 10, the second angle is illustrated for convenience, but the second angle is calculated by the above-described calculation method. The first catalyst layer 120A includes second conductive fibers 121 oriented along the direction A. The second angle θ2 formed by the second conductive fibers 121 and the main gas flow path (direction A) is 45° or less.

[0154] FIG. 11 is a schematic cross-sectional view taken along a direction intersecting the main flow path of the MEA. This cross-sectional view corresponds to the view obtained by cutting the MEA along the Y-Y line in FIG. 13, but for convenience, only the first gas diffusion layer and the first catalyst layer are shown. Also, in FIG. 11, the third B angle and the fourth B angle are illustrated for convenience, but these are calculated by the above-described calculation method.

[0155] The first conductive fibers 131 are generally oriented along the direction A in a cross-section intersecting the main flow path. The third B angle θ3 formed by the first conductive fibers 131 and the first interface S is, for example, less than 45°.

[0156] On the other hand, the second conductive fibers 121 are generally oriented along the thickness direction Z in a cross-section intersecting the main flow path. The fourth B angle θ4 formed by the second conductive fibers 121 and the first interface S is, for example, 45° or more.

[0157] FIG. 12 is a schematic cross-sectional view taken along the main flow path of the MEA. This cross-sectional view corresponds to the view obtained by cutting the MEA along the X-X line in FIG. 13, but for convenience, only the first gas diffusion layer and the first catalyst layer are shown. Also, in FIG. 12, the fifth B angle and the sixth B angle are illustrated for convenience, but these are calculated by the above-described calculation method.

[0158] The first conductive fiber 131 is oriented generally along the thickness direction Z in a cross-section along the main flow path. The fifth B angle θ5 formed by the first conductive fiber 131 and the first interface S is, for example, 45° or more.

[0159] The second conductive fiber 121 is also oriented generally along the thickness direction Z in a cross-section along the main flow path. The sixth B angle θ6 formed by the second conductive fiber 121 and the first interface S is, for example, 25° or more.

[0160] a. The first gas diffusion layer The first gas diffusion layer is the same as the first embodiment except that the first angle formed by the first conductive fiber and the main gas flow path is greater than 45°. A gas flow path may be formed in the first gas diffusion layer. The gas flow path may be formed in the separator.

[0161] The fibrous conductive member of the gas diffusion layer according to the present embodiment is oriented so as to intersect the main gas flow path. Therefore, according to the present embodiment, the gas diffusibility in the case where the intervals between a plurality of gas flow paths are relatively large can be further improved. The intervals between the gas flow paths are not particularly limited, but may be, for example, 0.5 times or more and 3 times or less the width of the gas flow path. The width of the gas flow path is the length of the gas flow path in a direction perpendicular to the gas flow. Specifically, the intervals between the gas flow paths may be 0.3 mm or more and 7.5 mm or less.

[0162] b. The first catalyst layer The first catalyst layer is the same as the first embodiment and can be manufactured in the same manner.

[0163] [Fuel cell] The fuel cell according to the present embodiment is the same as the first embodiment except for the following points. Since the above MEA has excellent gas diffusibility, the fuel cell including this MEA has excellent output characteristics.

[0164] FIG. 13 is a perspective view showing the components of a single cell arranged in the fuel cell according to this embodiment. Usually, a plurality of single cells are stacked and arranged in the fuel cell as a cell stack. In FIG. 13, for convenience, one single cell is shown.

[0165] In the first catalyst layer 120A, second conductive fibers 121 oriented along direction A are arranged. In the first gas diffusion layer 130A, first conductive fibers 131 oriented so as to intersect direction A are arranged. Although conductive fibers oriented along direction A are also arranged in the second catalyst layer 120B, and conductive fibers oriented so as to intersect direction A are also arranged in the second gas diffusion layer, the present invention is not limited thereto. The second catalyst layer 120B and the second gas diffusion layer 130B may be of known materials and known configurations.

[0166] Hereinafter, the present invention will be described in detail based on examples. However, the present invention is not limited to the following examples.

[0167] (Example of the First Embodiment) [Example 1] (1) Fabrication of MEA (1-1) Fabrication of Gas Diffusion Layer After mixing the first conductive fibers and an appropriate amount of ethanol with a mixer, PTFE was further added and mixed to obtain a mixture. CNT (average diameter 150 nm, average length 6 μm) was used as the first conductive fibers. The obtained mixture was formed into a sheet using a roll press. Thereafter, firing was performed to obtain a fired sheet from which ethanol was removed. The fired sheet was further rolled to adjust the thickness to 200 μm. The obtained sheet was cut into a desired shape to obtain a gas diffusion layer for the cathode. The mass ratio of the first conductive fibers in the first gas diffusion layer was 60% by mass.

[0168] Separately, one sheet of carbon paper was prepared as the gas diffusion layer for the anode.

[0169] (1-2) Preparation of Catalyst Ink After adding an appropriate amount of water to the second conductive fiber and the particulate conductive member (carbon black) supporting catalyst particles (Pt-Co alloy) and stirring to disperse them, CNT (average diameter: 150 nm, average length: 6 μm) was used for the second conductive fiber. After adding an appropriate amount of ethanol while stirring the obtained dispersion liquid, 80 parts by mass of a proton conductive resin (Nafion (registered trademark)) was added to 100 parts by mass of the particulate conductive member supporting 30 parts by mass of catalyst particles, and catalyst ink for the cathode side catalyst layer was prepared.

[0170] In the same manner as the catalyst ink for the cathode side catalyst layer, catalyst ink for the anode side catalyst layer was prepared.

[0171] (1-3) Lamination of each layer Using a blade coater, the catalyst ink for the cathode side catalyst layer was uniformly coated on polyethylene terephthalate (PET) and dried to form a cathode side catalyst layer (thickness: 6 μm). At this time, the catalyst ink was applied in one direction from one side to the other side of the opposite sides in the rectangular PET. The coating amount of the catalyst ink was adjusted so that the thickness of the formed catalyst layer became 6 μm. The mass ratio of the second conductive fiber in the cathode side catalyst layer was 25% by mass.

[0172] In the same manner, an anode catalyst layer (thickness: 6 μm) was formed on another PET sheet.

[0173] As an electrolyte membrane, a Nafion membrane (registered trademark) was prepared, and the cathode catalyst layer and the anode catalyst layer were thermocompression bonded and transferred to each surface of the electrolyte membrane. Next, a frame-shaped seal member was arranged so as to surround the anode side catalyst layer and the cathode side catalyst layer.

[0174] Carbon paper was brought into contact with the anode side catalyst layer. The gas diffusion layer for the cathode was brought into contact with the cathode side catalyst layer. At this time, on the cathode side, the electrolyte membrane and the gas diffusion layer were arranged so that the direction in which the catalyst ink was applied on the electrolyte membrane and the rolling direction when forming the gas diffusion layer were the same. In this way, an MEA was fabricated.

[0175] (2) Fabrication of Single Cell A bridge plate for guiding fuel or oxidant to each gas diffusion layer was placed near the manifold pre-formed in the electrolyte membrane, and the whole was sandwiched between a pair of flat carbon plates (separators) to complete the test single cell A1.

[0176] Parallel-shaped gas flow paths were arranged in the separators. The parallel-shaped gas flow paths had a plurality of grooves (main flow paths) arranged in parallel from one side to the other side of the opposite sides of the separator. Gas flowed in parallel from one side to the other side of the opposite sides of the separator. The distance between the gas flow paths was 1 times the width of the gas flow path (1 mm).

[0177] On the cathode side, the separator and the MEA were arranged so that the longitudinal direction of the gas flow path formed in the separator, the direction in which the catalyst ink was applied on the electrolyte membrane, and the rolling direction of the gas diffusion layer were aligned.

[0178] (3) Evaluation of the Orientation of Conductive Fibers The main surface of the gas diffusion layer in the MEA obtained above was photographed by SEM. Using the SEM image, the first angle was obtained by the method described above. The first angle was 13°.

[0179] Also, the cathode-side gas diffusion layer of the MEA was removed, and the main surface on the gas diffusion layer side of the cathode-side catalyst layer was photographed by SEM. Using the SEM image, the second angle was obtained by the method described above. The second angle was 14°.

[0180] The MEA was cut in the direction along the main flow path, and its cross section was photographed by SEM. Using the SEM image, the 3A angle and the 4A angle were obtained by the method described above. The 3A angle was 34°. The 4A angle was 60°. The first conductive fiber was inclined from the upstream of the main flow path toward the first interface. Similarly, the second conductive fiber was also inclined from the upstream of the main flow path toward the first interface. The sum of the 3A angle and the 4A angle was 94°.

[0181] The MEA was cut in a direction intersecting the main flow path at 90°, and the cross-section was photographed by SEM. Using the SEM image, the 5A angle and the 6A angle were obtained by the method described above. The 5A angle was 60°. The 6A angle was 53°.

[0182] (4) Evaluation of output characteristics The power generation performance of single cell A1 was evaluated. Specifically, fuel gas was supplied to the anode so that the utilization rate was 70%. The dew point of the fuel gas was about 80°C. Also, oxidant gas was supplied to the cathode so that the utilization rate was 50%. The dew point of the oxidant gas (air) was about 80°C. Then, the load control device was controlled so that a constant current flowed, and the current density with respect to the electrode areas of the anode and the cathode was changed. The maximum output density of single cell A1 at this time was measured. The evaluation results are shown in Table 1. Note that the maximum output density is expressed as an index with the maximum output density of single cell B1 in Comparative Example 1 set to 100.

[0183] [Comparative Example 1] In the lamination of each layer (1-3), on the cathode side, an MEA was produced in the same manner as in Example 1, except that the electrolyte membrane and the gas diffusion layer were arranged so that the direction in which the catalyst ink was applied on the electrolyte membrane and the rolling direction when forming the gas diffusion layer intersected.

[0184] Furthermore, in the production of the single cell (2), on the cathode side, a single cell B1 was produced in the same manner as in Example 1, except that the separator and the MEA were arranged so that the longitudinal direction of the gas flow path formed in the separator and the rolling direction of the gas diffusion layer were aligned.

[0185] Regarding the obtained MEA, the evaluation of the orientation of the conductive fibers was performed in the same manner as in Example 1. The 1st angle was 14°. The 2nd angle was 70°. The 3A angle was 35°. The 4A angle was 58°. The 5A angle was 30°. The 6A angle was 60°.

[0186] Regarding the obtained single cell B1, the evaluation of the output characteristics was performed in the same manner as in Example 1. The results are shown in Table 1.

[0187]

Table 1

[0188] In single cell A1 of Example 1, a higher maximum output density was obtained compared to single cell B1 of Comparative Example 1.

[0189] (Example of the Second Embodiment) [Example 2] In the lamination (1-3) of each layer, on the cathode side, the electrolyte membrane and the gas diffusion layer were arranged such that the direction in which the catalyst ink was applied on the electrolyte membrane and the rolling direction when forming the gas diffusion layer intersected. In this way, an MEA was fabricated, and single cell A2 was fabricated in the same manner as in Example 1. Also, in the fabrication of the single cell (2), on the cathode side, the separator and the MEA were arranged such that the longitudinal direction of the gas flow path formed in the separator and the rolling direction of the gas diffusion layer intersected.

[0190] The main surface of the gas diffusion layer in the MEA obtained above was photographed by SEM. Using the SEM image, the first angle was obtained by the method described above. The first angle was 76°.

[0191] Also, the cathode-side gas diffusion layer of the MEA was removed, and the main surface of the cathode-side catalyst layer on the gas diffusion layer side was photographed by SEM. Using the SEM image, the second angle was obtained by the method described above. The second angle was 13°.

[0192] The MEA was cut in a direction intersecting the main flow path at 90°, and its cross-section was photographed by SEM. Using the SEM image, the 3B angle and the 4B angle were obtained by the method described above. The 3B angle was 34°. The 4B angle was 63°.

[0193] The MEA was cut in the direction along the main flow path, and the cross-section was photographed by SEM. Using the SEM image, the 5B angle and the 6B angle were obtained by the method described above. The 5B angle was 60°. The 6B angle was 55°. The second conductive fiber was inclined from the upstream of the main flow path toward the first interface.

[0194] The power generation performance of single cell A2 was evaluated in the same manner as in Example 1.

[0195] [Comparative Example 2] In the production of the single cell (2), on the cathode side, the separator and the MEA were arranged such that the longitudinal direction of the gas flow path formed in the separator intersected with the catalyst ink coating direction of the catalyst layer, and a single cell B2 was produced in the same manner as in Example 2 except for this.

[0196] Regarding the obtained MEA, the orientation of the conductive fiber was evaluated in the same manner as in Example 2. The first angle was 14°. The second angle was 70°. The 3B angle was 30°. The 4B angle was 60°. The 5B angle was 35°. The 6B angle was 58°.

[0197] Regarding the obtained single cell B2, the output characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0198]

Table 2

[0199] In the single cell A2 of Example 2, a higher maximum output density was obtained compared to the single cell B2 of Comparative Example 2.

Industrial Applicability

[0200] The fuel cell according to the present invention can be suitably used as a power source for a stationary domestic cogeneration system or a vehicle power source. The present invention is suitable for application to a polymer electrolyte fuel cell, but is not limited thereto, and can be generally applied to fuel cells.

Description of Symbols

[0201] 100: MEA 110: Electrolyte Membrane 120: Catalyst Layer 120A: First Catalyst Layer 120B: Second Catalyst Layer 121: Second Conductive Fiber 130A: First Gas Diffusion Layer 130B: Second Gas Diffusion Layer 131: First Conductive Fiber 200: Fuel Cell (Single Cell) 240A: First Separator 240B: Second Separator 260A, 260B: Gas Flow Path

Claims

1. A membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, wherein the first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, the first gas diffusion layer includes a first fibrous conductive member and a first resin material, the first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material, when viewed in the stacking direction of the membrane electrode assembly, a first angle formed by the first fibrous conductive member and a main flow path of gas supplied to the membrane electrode assembly is 45° or less, the main flow path of the gas is a linear or wavy flow path disposed outside the first gas diffusion layer or formed in the first gas diffusion layer and in the direction in which the gas flows most, a second angle formed by the second fibrous conductive member and the main flow path is 45° or less, when viewing a cross-section of the membrane electrode assembly along the main flow path, the first fibrous conductive member is parallel to the interface between the first gas diffusion layer and the first catalyst layer or is inclined from the upstream of the main flow path toward the interface, a third A angle formed by the first fibrous conductive member and the interface is 70° or less. The membrane electrode assembly.

2. A membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, wherein the first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, the first gas diffusion layer includes a first fibrous conductive member and a first resin material, the first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material, when viewed in the stacking direction of the membrane electrode assembly, a first angle formed by the first fibrous conductive member and a main flow path of gas supplied to the membrane electrode assembly is 45° or less, the main flow path of the gas is a linear or wavy flow path disposed outside the first gas diffusion layer or formed in the first gas diffusion layer and in the direction in which the gas flows most, a second angle formed by the second fibrous conductive member and the main flow path is 45° or less, when viewing a cross-section of the membrane electrode assembly along the main flow path, a fourth A angle formed by the second fibrous conductive member and the interface between the first gas diffusion layer and the first catalyst layer is 25° or more and 80° or less. The membrane electrode assembly.

3. A membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, A membrane electrode assembly, wherein the first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, the first gas diffusion layer includes a first fibrous conductive member and a first resin material, the first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material, when viewed from the stacking direction of the membrane electrode assembly, a first angle formed by the first fibrous conductive member and the main flow path of the gas supplied to the membrane electrode assembly is 45° or less, the main flow path of the gas is a linear or wavy flow path that is formed in a separator disposed outside the first gas diffusion layer or in the first gas diffusion layer and is in the direction in which the gas flows most, a second angle formed by the second fibrous conductive member and the main flow path is 45° or less, the second fibrous conductive member is inclined from the upstream of the main flow path toward the interface between the first gas diffusion layer and the first catalyst layer. The membrane electrode assembly.

4. A membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, wherein the first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, the first gas diffusion layer includes a first fibrous conductive member and a first resin material, the first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material, when viewed from the stacking direction of the membrane electrode assembly, a first angle formed by the first fibrous conductive member and the main flow path of the gas supplied to the membrane electrode assembly is 45° or less, the main flow path of the gas is a linear or wavy flow path that is formed in a separator disposed outside the first gas diffusion layer or in the first gas diffusion layer and is in the direction in which the gas flows most, a second angle formed by the second fibrous conductive member and the main flow path is 45° or less, when viewing a cross-section of the membrane electrode assembly along the main flow path, the first fibrous conductive member is parallel to the interface between the first gas diffusion layer and the first catalyst layer or is inclined from the upstream of the main flow path toward the interface, a third A angle formed by the first fibrous conductive member and the interface is 70° or less, a fourth A angle formed by the second fibrous conductive member and the interface between the first gas diffusion layer and the first catalyst layer is 25° or more and 80° or less, a sum of the third A angle and the fourth A angle is 25° or more and 110° or less. The membrane electrode assembly.

5. A membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, The first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, The first gas diffusion layer includes a first fibrous conductive member and a first resin material, The first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material, When viewed from the stacking direction of the membrane electrode assembly, A first angle formed by the first fibrous conductive member and the main flow path of the gas supplied to the membrane electrode assembly is 45° or less, The main flow path of the gas is a linear or corrugated flow path formed in a separator disposed outside the first gas diffusion layer or in the first gas diffusion layer and in the direction in which the gas flows most, A second angle formed by the second fibrous conductive member and the main flow path is 45° or less, When viewing a cross section of the membrane electrode assembly intersecting the main flow path, A membrane electrode assembly in which a fifth A angle formed by the first fibrous conductive member and the interface between the first gas diffusion layer and the first catalyst layer is 45° or more.

6. A membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, The first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, The first gas diffusion layer includes a first fibrous conductive member and a first resin material, The first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material, When viewed from the stacking direction of the membrane electrode assembly, A first angle formed by the first fibrous conductive member and the main flow path of the gas supplied to the membrane electrode assembly is 45° or less, The main flow path of the gas is a linear or corrugated flow path formed in a separator disposed outside the first gas diffusion layer or in the first gas diffusion layer and in the direction in which the gas flows most, A second angle formed by the second fibrous conductive member and the main flow path is 45° or less, When viewing a cross section of the membrane electrode assembly intersecting the main flow path, A membrane electrode assembly in which a sixth A angle formed by the second fibrous conductive member and the interface between the first gas diffusion layer and the first catalyst layer is 45° or more.

7. A membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, The first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, The first gas diffusion layer includes a first fibrous conductive member and a first resin material. The first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material. When viewed in the stacking direction of the membrane electrode assembly, a first angle formed by the first fibrous conductive member and the main gas flow path supplied to the membrane electrode assembly is greater than 45°. The main gas flow path is a linear or wavy flow path formed in a separator disposed outside the first gas diffusion layer or in the first gas diffusion layer and in the direction in which the most gas flows. When viewing a cross section intersecting the main flow path of the membrane electrode assembly, a membrane electrode assembly, wherein a third B angle formed by the first fibrous conductive member and the interface between the first gas diffusion layer and the first catalyst layer is less than 45°.

8. A membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, wherein the first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, the first gas diffusion layer includes a first fibrous conductive member and a first resin material, the first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material, when viewed in the stacking direction of the membrane electrode assembly, a first angle formed by the first fibrous conductive member and the main gas flow path supplied to the membrane electrode assembly is greater than 45°, the main gas flow path is a linear or wavy flow path formed in a separator disposed outside the first gas diffusion layer or in the first gas diffusion layer and in the direction in which the most gas flows, when viewing a cross section intersecting the main flow path of the membrane electrode assembly, a membrane electrode assembly, wherein a fourth B angle formed by the second fibrous conductive member and the interface between the first gas diffusion layer and the first catalyst layer is 45° or more.

9. A membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, wherein the first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, the first gas diffusion layer includes a first fibrous conductive member and a first resin material, the first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material, when viewed in the stacking direction of the membrane electrode assembly, a first angle formed by the first fibrous conductive member and the main gas flow path supplied to the membrane electrode assembly is greater than 45°. The main flow path of the gas is a linear or corrugated flow path that is formed in a separator disposed outside the first gas diffusion layer or in the first gas diffusion layer and is in the direction in which the most gas flows. When looking at a cross-section of the membrane electrode assembly along the main flow path. A membrane electrode assembly, wherein a fifth B angle formed by the first fibrous conductive member and an interface between the first gas diffusion layer and the first catalyst layer is 45° or more.

10. A membrane electrode assembly for a fuel cell, comprising an electrolyte membrane, a first electrode and a second electrode sandwiching the electrolyte membrane, wherein the first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, the first gas diffusion layer includes a first fibrous conductive member and a first resin material, the first catalyst layer includes a second fibrous conductive member, catalyst particles, and a second resin material, when viewed from the stacking direction of the membrane electrode assembly, a first angle formed by the first fibrous conductive member and the main flow path of the gas supplied to the membrane electrode assembly is greater than 45°, the main flow path of the gas is a linear or corrugated flow path that is formed in a separator disposed outside the first gas diffusion layer or in the first gas diffusion layer and is in the direction in which the most gas flows, when looking at a cross-section of the membrane electrode assembly along the main flow path. A membrane electrode assembly, wherein a sixth B angle formed by the second fibrous conductive member and an interface between the first gas diffusion layer and the first catalyst layer is 25° or more and 80° or less.

11. A fuel cell comprising the membrane electrode assembly according to any one of claims 1 to 10, and a first separator and a second separator sandwiching the membrane electrode assembly.

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