JP5040424B2 - Membrane electrode assembly used in fuel cell and method for producing the same - Google Patents

Description

  The present invention relates to a membrane electrode assembly used in a fuel cell and a method for producing the same.

  A fuel cell that generates electricity by an electrochemical reaction between hydrogen and oxygen has attracted attention as an energy source. This fuel cell is configured by sandwiching a membrane electrode assembly formed by joining gas diffusion electrodes (anode and cathode) on both sides of an electrolyte membrane having proton conductivity, with a separator. Each of the anode and the cathode includes a catalyst layer for promoting the electrochemical reaction. The anode and the cathode may further include a gas diffusion layer for supplying the catalyst layer while diffusing the reaction gas (fuel gas and oxidant gas) supplied from the outside of the fuel cell. is there. In such a fuel cell, for example, the generated water generated by the electrochemical reaction may cause flooding, which may inhibit the diffusion of the reaction gas used for power generation in the gas diffusion electrode.

  Therefore, various techniques have been proposed for such membrane electrode assemblies. For example, in Patent Document 1 below, in a polymer electrolyte fuel cell, the catalyst layer is configured to include a catalyst powder and an electrolyte, and the electrolytic mass in the catalyst layer is set in the thickness direction and the surface direction of the catalyst layer. A technique for improving the diffusibility of the reaction gas in the catalyst layer is described. In this technique, a plurality of types of pastes (so-called catalyst pastes) with different electrolyte blending ratios are prepared, and these are deposited on a gas diffusion layer made of carbon paper or carbon cloth so that the electrolytic mass in the catalyst layer is equal to that of the catalyst layer. A membrane / electrode assembly is manufactured by applying the catalyst layer so as to change along the thickness direction and / or the surface direction, and bonding the catalyst layer to both surfaces of the electrolyte membrane. In addition, such a membrane electrode assembly can also be manufactured by applying a plurality of types of catalyst paste to the electrolyte membrane instead of the gas diffusion layer.

JP 2001-319663 A

  However, when a plurality of types of catalyst pastes are applied to the surface of the gas diffusion layer or electrolyte membrane to form a plurality of types of catalyst layers along the surface direction, it is difficult to form these without gaps. It was. In addition, a gap is naturally generated at the boundary between the plurality of types of catalyst layers, and power generation is not performed in the gap region, so that the power generation efficiency of the fuel cell is reduced or the electrolyte membrane is deteriorated. There was a case.

  The present invention has been made to solve the above-described problems, and is a membrane used for a fuel cell, in which a plurality of types of catalyst layers having different characteristics are formed side by side on at least one surface of an electrolyte membrane. An object of the electrode assembly is to suppress a decrease in power generation efficiency of a fuel cell and a deterioration of an electrolyte membrane.

  The present invention can be realized as the following forms or application examples in order to solve at least a part of the above-described problems.

Application Example 1 A membrane electrode assembly used in a fuel cell and having a catalyst layer formed on both surfaces of an electrolyte membrane, comprising a carrier carrying a catalyst and an electrolyte, and at least one of the electrolyte membranes a first catalyst layer formed on the surface, the carrier carrying the catalyst, and an electrolyte, in a second catalyst layer formed on the surface opposite to the electrolyte membrane of the first catalyst layer The mass ratio of the electrolyte to the carrier carrying the catalyst, the type of the catalyst carried on the carrier, the specific surface area of the catalyst in the carrier carrying the catalyst, the mass percent of the catalyst in the carrier carrying the catalyst, At least one of which includes a second catalyst layer different from the first catalyst layer , the first catalyst layer comprising a plurality of types of catalyst layers having different characteristics, and the plurality of types of catalysts. Layer is said electrolysis The second catalyst layer is formed side by side along the surface of the membrane, and the second catalyst layer is formed so as to fill a gap generated at a boundary between the plurality of types of catalyst layers formed side by side. The gist.

  In this way, in a membrane electrode assembly that is used in a fuel cell and in which a plurality of types of catalyst layers having different characteristics are formed side by side on at least one surface of the electrolyte membrane, the power generation efficiency of the fuel cell is reduced. And deterioration of an electrolyte membrane can be controlled.

Application Example 2 Application Example 1 the membrane electrode assembly, the second catalytic layer may be made of a catalyst layer having a same characteristic over the entire surface of the second catalyst layer .

Application Example 3 In the membrane electrode assembly according to Application Example 1 or 2, the first catalyst layer includes a carrier supporting a catalyst and an electrolyte, and the plurality of types of catalysts in the first catalyst layer. layer, as a parameter for defining the properties, the weight ratio of the electrolyte to the carrier, the type of the catalyst, the specific surface area of the catalyst in the carrier, at least one of the mass percent of the catalyst in the carrier different from each other You may do it. By changing these parameter values, a plurality of types of catalyst layers (the first catalyst layer) having different characteristics can be formed.

  [Application Example 4] In the membrane electrode assembly according to any one of Application Examples 1 to 3, the plurality of types of catalyst layers in the first catalyst layer include the membrane electrode assembly when the membrane electrode assembly is applied to a fuel cell. It is preferable that the gas is arranged in a plurality of regions set on the electrolyte membrane based on the distance from at least one of the inlet and the outlet of the reaction gas used for power generation by the fuel cell. .

  In general, in a fuel cell to which a membrane electrode assembly having a homogeneous catalyst layer (having the same characteristics over the entire surface) is applied on both sides of an electrolyte membrane, the reaction gas is consumed by power generation from the reaction gas inlet to the outlet. In addition, since the concentration of the reaction gas decreases, the power generation amount tends to decrease from the reaction gas inlet to the outlet. In this application example, a plurality of types of catalyst layers are provided in a plurality of regions set on the electrolyte membrane based on the distance from at least one of the inlet and the outlet of the reaction gas, that is, from the inlet to the outlet. Since they are arranged side by side, the power generation distribution in at least the membrane electrode assembly can be made uniform by appropriately setting the parameter values that define the characteristics of the plurality of types of catalyst layers.

Application Example 5 In the membrane electrode assembly according to Application Example 4, the plurality of types of catalyst layers in the first catalyst layer have at least different mass ratios of the electrolyte to the carrier as parameters defining the characteristics. The catalyst layer is composed of a catalyst layer, and the mass ratio of the electrolyte to the carrier in the catalyst layer arranged on the reaction gas outlet side of the plurality of types of catalyst layers is the catalyst layer arranged on the reaction gas inlet side. It is preferable that the ratio is set lower than the mass ratio of the electrolyte to the carrier.

In general, in a fuel cell, the generated water generated during power generation moves from the upstream side to the downstream side in the flow direction of the reaction gas by the flow of the reaction gas, so in a region near the reaction gas inlet in the membrane electrode assembly. Drying up (excessive drying) tends to occur, and flooding (excessive water) tends to occur in a region near the outlet of the reaction gas in the membrane electrode assembly. In the catalyst layer, if the mass ratio of the electrolyte to the carrier is set low, the gap between the carriers is widened, so that the cross-sectional area of the drainage path of generated water and the diffusion path of the reaction gas is widened. On the other hand, in the catalyst layer, if the mass ratio of the electrolyte to the carrier is set high, the gap between the carriers is narrowed, so that the sectional area of the drainage path of the generated water and the diffusion path of the reaction gas is narrowed.

In this application example, in the plurality of types of catalyst layers in the first catalyst layer, the mass ratio of the electrolyte with respect to the support in the catalyst layer disposed on the reaction gas outlet side is the catalyst disposed on the reaction gas inlet side. It is set lower than the mass ratio of the electrolyte to the carrier in the layer. Therefore, in the plurality of types of catalyst layers in the first catalyst layer, the gap between the carriers in the catalyst layer disposed in the region close to the reaction gas outlet is defined in the catalyst layer disposed in the region close to the reaction gas inlet. It can be made wider than the gap between the carriers, and the cross-sectional area of the drainage path of the generated water and the diffusion path of the reaction gas can be increased. As a result, flooding in the membrane electrode assembly described above can be suppressed.

On the other hand, in this application example, in the plurality of types of catalyst layers in the first catalyst layer, the mass ratio of the electrolyte to the carrier in the catalyst layer arranged on the reaction gas inlet side is arranged on the reaction gas outlet side. The mass ratio of the electrolyte to the carrier in the catalyst layer is set higher. Therefore, in the plurality of types of catalyst layers in the first catalyst layer, the gap between the carriers in the catalyst layer disposed in the region close to the reaction gas inlet is defined in the catalyst layer disposed in the region close to the reaction gas outlet. The gap between the carriers can be made narrower, and the cross-sectional area of the generated water drainage path can be made narrower. As a result, the dry-up in the membrane electrode assembly described above can be suppressed.

[Application Example 6] In the membrane electrode assembly according to Application Example 5, the mass ratio of the electrolyte to the carrier in the second catalyst layer may be selected from the plurality of types of catalyst layers in the first catalyst layer. In any catalyst layer, it is preferable that the mass ratio of the electrolyte to the carrier is set to be lower. By doing so, the cross-sectional area of the generated water drainage path and the reaction gas diffusion path in the second catalyst layer is determined from the cross-sectional area of the generated water drainage path and the reaction gas diffusion path in the first catalyst layer. And flooding due to water remaining in the first catalyst layer can be suppressed.

  The present invention can be configured as an invention of a method for manufacturing a membrane electrode assembly, a fuel cell using the membrane electrode assembly, and a method for manufacturing a fuel cell, in addition to the configuration as the membrane electrode assembly described above. . In addition, in each aspect, it is possible to apply the various additional elements shown above.

Hereinafter, embodiments of the present invention will be described based on examples.
A. Configuration of membrane electrode assembly:
FIG. 1 is an explanatory view showing a schematic configuration of a membrane electrode assembly 100 as one embodiment of the present invention. FIG. 1A shows a cross-sectional view of the membrane electrode assembly 100. FIG. 1B shows an enlarged view of the region R indicated by a broken line in FIG. The membrane electrode assembly 100 includes a proton conductive solid polymer membrane (for example, Nafion (registered trademark)) as the electrolyte membrane 110, and is used in a solid polymer fuel cell. As the electrolyte membrane 110, another material different from the solid polymer may be used. In FIG. 1A, the flow direction of hydrogen as fuel gas supplied to the anode of the fuel cell (membrane electrode assembly 100) and the anode off-gas discharged from the anode, and the fuel cell (membrane electrode assembly). 100), air as the oxidant gas supplied to the cathode, and the flow direction of the cathode off-gas discharged from the cathode are indicated by arrows.

  As shown in the figure, the membrane / electrode assembly 100 includes an anode-side catalyst layer 120 a on one surface of an electrolyte membrane 110. The membrane electrode assembly 100 includes a cathode side catalyst layer 120 c on the other surface of the electrolyte membrane 110.

  In the present embodiment, the cathode side catalyst layer 120c has a two-layer structure, and two types of catalyst layers having different characteristics as the first cathode side catalyst layer formed on the surface of the electrolyte membrane 110, That is, the catalyst layer 120c1 and the catalyst layer 120c2 are provided. The catalyst layer 120c1 and the catalyst layer 120c2 are formed side by side along the surface of the electrolyte membrane 110. In the first cathode side catalyst layer, the catalyst layer 120c1 is formed on the upstream side (inlet side) in the air flow direction, and the catalyst layer 120c2 is on the downstream side (outlet side). Are formed side by side. The cathode side catalyst layer 120c includes a catalyst layer 120c3 as a second cathode side catalyst layer formed on the surface of the first cathode side catalyst layer opposite to the electrolyte membrane 110. The boundary between the catalyst layer 120c1 and the catalyst layer 120c2 can be arbitrarily set based on the humidity distribution of the membrane electrode assembly 100, as will be described later. The difference in characteristics between the catalyst layer 120c1 and the catalyst layer 120c2 in the cathode side catalyst layer 120c will be described later.

  The catalyst layer 120c1 and the catalyst layer 120c2 are each formed by applying a catalyst ink on the electrolyte membrane 110, as will be described later. And as shown in FIG.1 (b), the clearance gap naturally arises between the catalyst layer 120c1 and the catalyst layer 120c2. The catalyst layer 120c3 is formed to fill this gap. These manufacturing methods will be described in detail later.

B. Cathode side catalyst layer:
In the cathode side catalyst layer 120c, the catalyst layer 120c1, the catalyst layer 120c2, and the catalyst layer 120c3 include a carrier carrying a catalyst and an electrolyte. In this example, platinum (Pt) was used as the catalyst. Further, carbon black was used as the carrier for supporting the catalyst. Further, Nafion (registered trademark) was used as the electrolyte.

By the way, regarding the catalyst layer, there are various parameters that define its characteristics. The parameters include, for example, the mass ratio of the electrolyte to the carrier carrying the catalyst, the type of catalyst carried on the carrier, the specific surface area of the catalyst on the carrier carrying the catalyst, and the proportion of the catalyst on the carrier carrying the catalyst. ( Mass percent) and the like. In the present embodiment, the catalyst layer 120c1, the catalyst layer 120c2, and the catalyst layer 120c3 include the mass ratio of the electrolyte to the carrier carrying the catalyst, or the carrier carrying the catalyst among the various parameters described above. The proportion of catalyst was different. Hereinafter, the ratio of the electrolyte (N: Nafion) to the carrier carrying the catalyst (C: carbon black) is referred to as “N / C ratio”. The ratio of the catalyst in the carrier carrying the catalyst is simply referred to as “catalyst ratio”.

  FIG. 2 is an explanatory diagram showing the N / C ratio of the catalyst layer 120c1, the catalyst layer 120c2, and the catalyst layer 120c3, and the ratio of the catalyst in this example. As shown in the drawing, the N / C ratio of the catalyst layer 120c1 was 1.0, and the ratio of the catalyst was 70 (wt%). The N / C ratio of the catalyst layer 120c2 was 0.85, and the catalyst ratio was 70 (wt%). The N / C ratio of the catalyst layer 120c3 was 0.75, and the catalyst ratio was 60 (wt%). Hereinafter, the reason why the N / C ratio of the catalyst layer 120c1 and the catalyst layer 120c2 and the ratio of the catalyst are set to the above-described values will be described.

  In FIG. 3, the cathode electrode catalyst layer of the membrane electrode assembly has a two-layer structure, and the membrane electrode assembly using the catalyst layer 120c1 as the first catalyst layer and the catalyst layer 120c3 as the second catalyst layer is applied. Power generation characteristics of a fuel cell (hereinafter referred to as fuel cell A), and a fuel cell to which a membrane electrode assembly using a catalyst layer 120c2 as a first catalyst layer and a catalyst layer 120c3 as a second catalyst layer is applied ( Hereinafter, the power generation characteristics of the fuel cell B) will be described. A graph in which the horizontal axis represents the amount of cathode humidified water and the vertical axis represents the cell voltage is shown. In this figure, the curve indicated by the solid line indicates the power generation characteristics of the fuel cell A. A curve indicated by a broken line indicates the power generation characteristics of the fuel cell B.

  As can be seen from the figure, in the fuel cell A and the fuel cell B, the cell voltage is reversed on the condition that the cathode humidified water amount is H1. That is, the cell voltage of the fuel cell A is higher than the cell voltage of the fuel cell B under conditions where the amount of cathode humidified water is less than H1. And under conditions where the amount of cathode humidified water is greater than H1, the cell voltage of the fuel cell B is higher than the cell voltage of the fuel cell A. That is, under conditions where the amount of cathode humidified water is less than H1, the power generation performance of fuel cell A is higher than the power generation performance of fuel cell B, and under conditions where the amount of cathode humidified water is greater than H1, The power generation performance is higher than the power generation performance of the fuel cell A.

  The reason why the power generation performance of the fuel cell A is higher than the power generation performance of the fuel cell B under the condition that the amount of cathode humidified water is less than H1 is that the N / C ratio of the catalyst layer 120c1 in the fuel cell A is This is because the gap between the carriers in the catalyst layer 120c1 is narrower than the gap between the carriers in the catalyst layer 120c2, because the N / C ratio of the catalyst layer 120c2 is higher, and the dry-up is suppressed in the fuel cell A. . On the other hand, the reason why the power generation performance of the fuel cell B is higher than the power generation performance of the fuel cell A under the condition where the amount of cathode humidified water is greater than H1 is that the N / C ratio of the catalyst layer 120c2 in the fuel cell B is the fuel cell. Since the N / C ratio of the catalyst layer 120c1 in A is lower, the gap between the carriers in the catalyst layer 120c2 is wider than the gap between the carriers in the catalyst layer 120c1, and flooding is suppressed in the fuel cell B. is there.

  In general, in a fuel cell, generated water generated during power generation moves from the upstream side to the downstream side in the flow direction of the reaction gas by the flow of the reaction gas. For this reason, dry-up tends to occur in the region near the reaction gas inlet in the membrane electrode assembly, and flooding tends to occur in the region near the reaction gas outlet in the membrane electrode assembly. In the membrane electrode assembly 100 of this embodiment, the catalyst layer 120c1 having an effect of suppressing dry-up is disposed on the air inlet side where dry-up is likely to occur, and the cathode off-gas outlet side where flooding is likely to occur. In addition, a catalyst layer 120c2 having an effect of suppressing flooding is disposed. Therefore, the power generation performance of the membrane electrode assembly 100 as a whole can be improved. Further, in the membrane electrode assembly 100 of this example, the catalyst layer 120c3 having a value lower than the N / C ratio of the catalyst layer 120c1 and the catalyst layer 120c2 is formed as the second cathode side catalyst layer. Therefore, the gap between the carriers in the catalyst layer 120c3 is wider than the gap between the carriers in the catalyst layer 120c1 and the catalyst layer 120c2. Therefore, flooding due to retention of generated water in the catalyst layer 120c1 and the catalyst layer 120c2 can be suppressed.

C. Manufacturing process of membrane electrode assembly:
FIG. 4 is an explanatory view showing a manufacturing process of the membrane electrode assembly 100. First, the anode-side catalyst layer 120a is formed on one surface of the electrolyte membrane 110 (step S100), and the catalyst layer 120c1 described above as the first cathode-side catalyst layer on the other surface of the electrolyte membrane 110, Then, the catalyst layer 120c2 is formed side by side along the surface of the electrolyte membrane 110 (step S110). The anode-side catalyst layer 120a and the cathode-side catalyst layers 120c1 and 120c2 are coated with the catalyst inks prepared for the anode-side catalyst layer 120a, the catalyst layer 120c1, and the catalyst layer 120c2 on both surfaces of the electrolyte membrane 110. Then, each is formed by drying. In this embodiment, the catalyst ink is a solution containing carbon black carrying platinum (Pt) as a catalyst metal, an electrolyte (Nafion), and a solvent. These mixing ratios and the like can be arbitrarily set according to the characteristics required for each catalyst layer.

  Next, a catalyst layer 120c3 is formed as a second cathode side catalyst layer on the first cathode side catalyst layer (catalyst layers 120c1 and 120c2) (step S120). In this embodiment, the catalyst layer 120c3 is formed by spraying the catalyst ink prepared for the catalyst layer 120c3 on the catalyst layers 120c1 and 120c2 and drying the catalyst ink. By doing so, it is possible to easily fill a gap that naturally occurs between the catalyst layer 120c1 and the catalyst layer 120c2.

  The membrane electrode assembly 100 can be manufactured by the above manufacturing process. Further, a fuel cell can be manufactured by forming gas diffusion layers on both surfaces of the membrane electrode assembly 100 and sandwiching the gas diffusion layers with separators.

  According to the manufacturing process of the membrane electrode assembly 100 of the present embodiment described above, when two types of catalyst layers 120c1 and 120c2 having different characteristics are formed side by side on the cathode side surface of the electrolyte membrane 110, A gap that naturally occurs at the boundary between the catalyst layers 120c1 and 120c2 can be filled with the catalyst layer 120c3 as the second catalyst layer. Accordingly, it is possible to suppress a decrease in power generation efficiency of the fuel cell and deterioration of the electrolyte membrane 110.

D. Variations:
Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and can be implemented in various modes without departing from the scope of the present invention. For example, the following modifications are possible.

D1. Modification 1:
In the above embodiment, two types of catalyst layers (catalyst layer 120c1 and catalyst layer 120c2) are provided as the first cathode side catalyst layer in the cathode side catalyst layer 120c. However, the present invention is not limited to this. . The first cathode side catalyst layer in the cathode side catalyst layer 120c may be composed of three or more types of catalyst layers. Further, in the above embodiment, the cathode side catalyst layer 120c has a two-layer structure, but the present invention is not limited to this and may have a three-layer structure or more.

D2. Modification 2:
In the above embodiment, for each of the catalyst layers 120c1, 120c2, and 120c3 constituting the cathode side catalyst layer 120c, the mass ratio of the electrolyte to the carrier carrying the catalyst, and the catalyst were carried as parameters defining the characteristics of the catalyst layer. Although the ratio ( mass percent) of the catalyst in the support is applied, the present invention is not limited to this. What is necessary is to apply at least one of the mass ratio of the electrolyte with respect to the support | carrier which carry | supported the catalyst, the kind of catalyst, the specific surface area of the catalyst in the support | carrier which carry | supported the catalyst, and the ratio of the catalyst in the support | carrier which supported the catalyst.

D3. Modification 3:
In the above embodiment, the N / C ratio and the catalyst ratio are set to the values described above for the catalyst layer 120c1, the catalyst layer 120c2, and the catalyst layer 120c3 in the cathode side catalyst layer 120c. The invention is not limited to this. Each value of various parameters defining the characteristics of each catalyst layer can be arbitrarily set based on characteristics required for each catalyst layer, for example, gas diffusibility, drainage, catalyst performance, etc. .

D4. Modification 4:
Although the case where the present invention is applied to the cathode side catalyst layer 120c has been described in the above embodiment, the present invention may be applied to the anode side catalyst layer 120a.

D5. Modification 5:
In the above embodiment, the catalyst layer 120c3 is composed of a catalyst layer having substantially the same characteristics over almost the entire surface of the catalyst layer 120c3, but the present invention is not limited to this. The catalyst layer 120c3 may be configured by a plurality of types of catalyst layers.

It is explanatory drawing which shows schematic structure of the membrane electrode assembly 100 as one Example of this invention. It is explanatory drawing which shows the N / C ratio of the catalyst layer 120c1, the catalyst layer 120c2, and the catalyst layer 120c3 in the present Example, and the ratio of a catalyst. Fuel cell power generation using a cathode electrode catalyst layer of a membrane electrode assembly having a two-layer structure, a catalyst layer 120c1 as a first catalyst layer, and a membrane electrode assembly using a catalyst layer 120c3 as a second catalyst layer It is explanatory drawing which shows a characteristic and the electric power generation characteristic of the fuel cell to which the membrane electrode assembly using the catalyst layer 120c3 as a 2nd catalyst layer is applied, using the catalyst layer 120c2 as a 1st catalyst layer. FIG. 10 is an explanatory view showing a manufacturing process of the membrane / electrode assembly 100.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Membrane electrode assembly 110 ... Electrolyte membrane 120a ... Anode side catalyst layer 120c ... Cathode side catalyst layer 120c1, 120c2 ... 1st cathode side catalyst layer 120c3 ... 2nd cathode side catalyst layer

Claims (7)

A membrane electrode assembly used in a fuel cell and having a catalyst layer formed on both sides of an electrolyte membrane,
A first catalyst layer comprising a carrier carrying a catalyst and an electrolyte, and formed on at least one surface of the electrolyte membrane;
A second catalyst layer formed on a surface of the first catalyst layer on the opposite side of the electrolyte membrane, the electrolyte for the carrier supporting the catalyst; At least one of the following: the mass ratio of the catalyst, the type of the catalyst supported on the support, the specific surface area of the catalyst on the support supporting the catalyst, and the mass percentage of the catalyst on the support supporting the catalyst. A second catalyst layer different from the catalyst layer of
The first catalyst layer comprises a plurality of types of catalyst layers having different characteristics from each other,
The plurality of types of catalyst layers are formed side by side along the surface of the electrolyte membrane,
The second catalyst layer is formed so as to fill a gap generated at a boundary between the plurality of types of catalyst layers formed side by side.
Membrane electrode assembly. The membrane electrode assembly according to claim 1,
The second catalyst layer comprises a catalyst layer having a same characteristic over the entire surface of the second catalyst layer, a membrane electrode assembly. The membrane electrode assembly according to claim 1 or 2 ,
Before SL plural types of catalyst layer in the first catalyst layer, as a parameter for defining the properties, the weight ratio of the electrolyte to the carrier, the type of the catalyst, the specific surface area of the catalyst in the carrier, in the carrier A membrane electrode assembly, wherein at least one of the catalyst mass percentages is different from each other. A membrane electrode assembly according to any one of claims 1 to 3,
The plurality of types of catalyst layers in the first catalyst layer are formed from at least one of an inlet and an outlet of a reaction gas used for power generation by the fuel cell when the membrane electrode assembly is applied to a fuel cell. The membrane electrode assembly is disposed in each of a plurality of regions set on the electrolyte membrane based on the distance. The membrane electrode assembly according to claim 4, wherein
The plurality of types of catalyst layers in the first catalyst layer are composed of catalyst layers having at least different mass ratios of the electrolyte to the carrier as parameters defining the characteristics,
The mass ratio of the electrolyte to the carrier in the catalyst layer disposed on the reaction gas outlet side of the plurality of types of catalyst layers is the mass ratio of the electrolyte to the carrier in the catalyst layer disposed on the reaction gas inlet side. A membrane electrode assembly, which is set lower than the mass ratio of the electrolyte. The membrane electrode assembly according to claim 5, wherein
Furthermore, the mass ratio of the electrolyte to the carrier in the second catalyst layer is greater than the mass ratio of the electrolyte to the carrier in any catalyst layer of the plurality of types of catalyst layers in the first catalyst layer. The membrane electrode assembly is also set low. A method for producing a membrane electrode assembly used in a fuel cell, wherein a catalyst layer is formed on each side of an electrolyte membrane,
A first catalyst layer forming step of forming a first catalyst layer having a carrier carrying a catalyst and an electrolyte on at least one surface of the electrolyte membrane;
A second catalyst layer having a catalyst-supporting carrier and an electrolyte on a surface of the first catalyst layer opposite to the electrolyte membrane, the mass ratio of the electrolyte to the catalyst-supporting carrier; At least one of the type of the catalyst supported on the support, the specific surface area of the catalyst on the support supporting the catalyst, and the mass percentage of the catalyst on the support supporting the catalyst is the first catalyst layer A second catalyst layer forming step of forming a different second catalyst layer,
The first catalyst layer forming step includes a step of forming a plurality of types of catalyst layers having different characteristics from each other along the surface of the electrolyte membrane,
The second catalyst layer forming step includes a step of forming the second catalyst layer so as to fill a gap generated at a boundary between the plurality of types of catalyst layers formed side by side.
Production method.

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