JP5526066B2 - Gas diffusion layer and fuel cell, and method for manufacturing gas diffusion layer - Google Patents

Description

  Embodiments described herein relate generally to a gas diffusion layer, a fuel cell, and a method for manufacturing the gas diffusion layer.

  A fuel cell is a device that converts the chemical energy of a fuel gas into electrical energy by electrochemically reacting a fuel gas such as hydrogen and an oxidant gas such as air. This fuel cell includes a unit cell composed of a fuel electrode and an oxidant electrode arranged with an electrolyte layer having ionic conductivity interposed therebetween, and a separator that sandwiches the unit cell from above and below. The separator is provided with a gas supply groove for supplying a reactive gas (fuel gas, oxidant gas) to each electrode.

  Fuel cells are classified into alkaline fuel cells, phosphoric acid fuel cells, polymer electrolyte fuel cells, molten carbonate fuel cells, and solid oxide fuel cells, depending on the electrolyte layer used. Among these fuel cells, a polymer electrolyte fuel cell using a solid polymer membrane as an electrolyte layer can be operated at a relatively low temperature, has a short start-up time, and provides a large output density. It has attracted a great deal of attention as an in-vehicle power source and a portable power source.

  As the solid polymer electrolyte membrane used for the electrolyte layer of the polymer electrolyte fuel cell, a perfluorocarbon sulfonic acid membrane having a thickness of about 10 to 100 μm, such as a total fluoride ionomer, is used. This solid polymer electrolyte membrane is excellent in the reaction gas separation function for separating the fuel gas and the oxidant gas and the hydrogen ion conductivity for carrying the hydrogen ions generated in the fuel electrode to the oxidant electrode.

  The solid polymer electrolyte membrane exhibits good hydrogen ion conductivity when it contains moisture, but has an attribute of significantly reducing hydrogen ion conductivity when dried. Further, it is known that when the solid polymer electrolyte membrane is dried, the solid polymer electrolyte membrane deteriorates. Therefore, in order to prevent the solid polymer electrolyte membrane from being dried, it is necessary to give moisture to the fuel gas and the oxidant gas. Further, since water is generated at the oxidant electrode in the reaction of the fuel cell, the diffusibility of the reaction gas is lowered and the characteristics are remarkably lowered unless this water is removed. Therefore, it is necessary to prevent the solid polymer electrolyte membrane from being dried and to remove the generated water in order to prevent deterioration of the solid polymer electrolyte membrane and battery characteristics.

  In order to remove water generated by the electrode reaction, the fuel electrode and the oxidant electrode are generally composed of a gas diffusion layer for improving water discharge and a catalyst layer for causing an electrode reaction. An electrically conductive porous substrate is used for the gas diffusion layer. In order to improve water discharge, a water-repellent material is added to the porous substrate or it has a water-repellent function. An intermediate layer having micropores is provided. As a method of providing an intermediate layer on a porous substrate, a method of preparing an ink with a material constituting the intermediate layer, for example, carbon black and a water repellent material, and applying the ink to the porous substrate with a die coater, a bar coater or the like There is. There is also a method of forming a mixed powder of carbon black and a water repellent material on a porous substrate by dry coating. Among these, it is excellent in manufacturing cost to produce the intermediate layer by forming the mixed powder on the porous substrate by dry coating.

JP 2005-317240 A

  As described above, as a method for producing the gas diffusion layer, it is promising to apply a mixed powder of carbon powder and binder to the surface of the porous substrate. However, when the mixed powder constituting the intermediate layer is applied on the porous substrate, the porous substrate of the mixed powder is difficult to bite into the porous substrate, and the fixability of the mixed powder to the porous substrate is deteriorated. For this reason, when this was used for the fuel cell, there existed a problem which caused deterioration of a battery characteristic.

  Also, a method has been proposed in which the surface roughness Ra of the porous substrate is 15 μm or less. However, when forming an intermediate layer by dry coating, the powder for forming the intermediate layer is fixed, and the porous layer is porous. A structure that does not penetrate the substrate is required. If the surface roughness of the porous substrate is extremely small, the intermediate layer may not be fixed.

  The problem to be solved by the present invention is to provide a gas diffusion layer having an intermediate layer excellent in stability, which can improve the fixing of the porous layer and the intermediate layer having electrical conductivity and the intermediate layer. There is.

The gas diffusion layer of the embodiment is a gas diffusion in which an intermediate layer formed by pulverizing a mixed powder of carbon powder having electrical conductivity and a binder is formed on the surface of a porous substrate having electrical conductivity. It is a layer, The average particle diameter L of the pulverized mixed powder is smaller than the surface roughness Ra of the porous substrate.

  According to the present invention, it is possible to improve the fixation between the porous gas diffusion base material having electrical conductivity and the intermediate layer, and it is possible to realize a gas diffusion layer having excellent stability. Furthermore, when this gas diffusion layer is used in a fuel cell, it can contribute to improving the characteristics of the fuel cell.

Sectional drawing which shows schematic structure of the gas diffusion layer concerning 1st Embodiment. The conceptual diagram which shows the structure of the manufacturing apparatus for forming an intermediate | middle layer. FIG. 4 is a schematic diagram showing the relationship between the surface roughness Ra and the average particle diameter L in terms of fixability. Sectional drawing which shows schematic structure of the fuel cell concerning 2nd Embodiment.

  Hereinafter, details of the embodiment will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing a schematic configuration of a gas diffusion layer according to the first embodiment.

  The gas diffusion layer of the present embodiment has a configuration in which the intermediate layer 2 is provided on the surface of the porous substrate 1. The surface roughness Ra of the porous substrate 1 is 8 μm or more, and the average particle diameter of the mixed powder of the electrically conductive particles constituting the intermediate layer 2 and the binder is 5 μm or less. The average particle diameter means an arithmetic average value of particle size distribution obtained by a laser diffraction / scattering method.

  Below, the formation method of the gas diffusion layer in this embodiment is described. As the porous substrate 1, carbon paper having a thickness of 180 μm and a surface roughness Ra of 8 μm was used. Denka Black (registered trademark) manufactured by Denka Kogyo Co., Ltd. was used as the carbon powder of the intermediate layer 2, and polytetrafluoroethylene powder having an average particle diameter of 300 μm was used as the binder. The weight ratio of the carbon powder and the polytetrafluoroethylene powder was 60:40. The above powder was mixed with a cutter mixer for 1 minute to obtain an intermediate layer forming powder.

  A gas diffusion layer was formed using the produced porous substrate and the mixed powder for forming an intermediate layer using the apparatus shown in FIG.

  FIG. 2 shows a manufacturing apparatus for forming an intermediate layer, in which 20 is a substrate suction / suction stage, 21 is an intermediate layer forming chamber, 22 is a mixture supply unit, 23 is a gas supply unit, and 24 is a substrate 1. Carbon paper, 25 is a gas flow rate adjusting unit, 26 is an exhaust blower, and 27 is a pressure adjusting valve.

  After the carbon paper 24 is placed on the gas diffusion base material suction stage 20, the exhaust blower 26 is operated, the suction stage pressure is adjusted to -30 mm water column by the pressure adjustment valve 27, and the carbon paper 24 is sucked to the stage 20 side. did. Then, the intermediate layer forming chamber 21 was covered so as to cover the carbon paper 24 while sucking the carbon paper 24. Next, the mixed powder for forming an intermediate layer was charged from the mixture supply unit 22 while flowing nitrogen from the gas supply unit 23. The charged mixed powder for forming the intermediate layer is pulverized by nitrogen gas supplied from the gas supply unit 23 to have an average particle diameter L of 5 μm and laminated on the carbon paper 24 (base material 1) to form an intermediate layer ( 2) was obtained.

After the intermediate layer was laminated, the nitrogen gas was stopped, the chamber 21 was removed, the gas diffusion base material on which the intermediate layer was laminated was passed through a roller to fix the intermediate layer, and this was designated as gas diffusion layer A. The weight of the intermediate layer was 1 mg / cm ² and the thickness was 40 μm.

  As Comparative Example 1, a gas diffusion layer B was manufactured by providing an intermediate layer in the same manner as the gas diffusion layer A using a nonwoven fabric having a surface roughness Ra of 5 μm for the porous substrate.

  As Comparative Example 2, Denka black was used for the carbon powder of the intermediate layer, and polytetrafluoroethylene powder having an average particle diameter of 300 μm was used for the binder. The weight ratio of the carbon powder and the polytetrafluoroethylene powder was 60:40. As the porous substrate, similarly to the diffusion layer A, carbon paper (thickness: 180 μm) having a surface roughness Ra of 8 μm was used. The powder was mixed with a cutter mixer for 1 minute, and a gas diffusion layer C was formed in the same manner as the gas diffusion layer A. In the gas diffusion layer C, the nitrogen pressure and flow rate when the intermediate layer was formed were adjusted so that the mixed powder for forming the intermediate layer had an average particle diameter L of 8 μm.

  Gas diffusion layer B and gas diffusion layer C are those that cannot be used in the subsequent steps of catalyst layer coating, if the intermediate layer is fixed with a roller and then air is blown with an air brush, the intermediate layer is easily peeled off and the fixability is poor. Met. This is because the mixed powder constituting the intermediate layer is porous because the average particle diameter L of the mixed powder of carbon powder and polytetrafluoroethylene powder constituting the intermediate layer is equal to the surface roughness Ra of the porous substrate. This seems to be due to the poor fixability, which makes it difficult to bite into the base material.

  On the other hand, the gas diffusion layer A has a very good fixability of the intermediate layer to the porous substrate, and after fixing the intermediate layer with a roller in the same manner as described above, the intermediate layer can be blown with an air brush. Did not peel at all. In the gas diffusion layer A, the same effect was obtained even when the surface roughness Ra of the base material was increased to 9 μm and 10 μm. Further, in the gas diffusion layer A, the same effect was obtained even when the average particle diameter L of the mixed powder of the intermediate layer was reduced to 4 μm and 3 μm. On the other hand, when the surface roughness Ra of the base material of the gas diffusion layer A was reduced to 7 μm and 6 μm, although it was better than the gas diffusion layer B, peeling of the intermediate layer was likely to occur. Furthermore, in the gas diffusion layer A, when the average particle diameter L of the mixed powder of the intermediate layer was increased to 6 μm and 7 μm, although better than the gas diffusion layer C, peeling easily occurred.

  Further, in the gas diffusion layer B, even if the surface roughness Ra of the base material is reduced to 4 μm, the same result as that of the gas diffusion layer B can be obtained, and the average particle diameter L of the mixed powder of the intermediate layer is increased to 6 μm. The same result was obtained. Further, in the gas diffusion layer C, even if the surface roughness Ra of the substrate is reduced to 7 μm, the same result as that of the gas diffusion layer C is obtained, and the average particle diameter L of the mixed powder of the intermediate layer is increased to 9 μm. Similar results were obtained.

  When these results are summarized, as shown in FIG. 3, sufficiently good results are obtained in the region P where the surface roughness Ra ≧ 8 μm and the average particle diameter L ≦ 5 μm, and relatively good in the region Q where Ra> L. As a result, it was found that the region R of Ra ≦ L is not useful at all. That is, it was found that Ra> L is essential for the relationship between the surface roughness Ra and the average particle diameter L, and that Ra ≧ 8 μm and L ≦ 5 μm are more desirable.

  As described above, in this embodiment, by fixing the average particle diameter L of the mixed powder composed of the carbon powder having electric conductivity and the binder rather than the surface roughness Ra of the porous base material, the fixability is relatively high. A good gas diffusion layer can be obtained. Furthermore, the surface roughness of the porous substrate is set to 8 μm or more, and the average particle size of the mixed powder composed of the carbon powder having electric conductivity and the binder is set to 5 μm or less, so that the gas diffusion layer having extremely good fixability. Is obtained.

(Second Embodiment)
FIG. 4 is a cross-sectional view showing a schematic configuration of a fuel cell according to the second embodiment.

  In the present embodiment, the gas diffusion layer 10 of the first embodiment is used as an electrode of a fuel cell having a solid polymer electrolyte membrane.

  Reference numeral 40 in the figure denotes a solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte. A fuel electrode 50 is provided on one main surface of the electrolyte membrane 40, and the other main surface is provided with a fuel electrode 50. An oxidizer electrode 60 is provided.

  The fuel electrode 50 is obtained by forming a fuel electrode catalyst layer 53 on a diffusion layer (10) in which an intermediate layer 52 is formed on a porous substrate 51. The oxidant electrode 60 is obtained by forming an oxidant electrode catalyst layer 63 on a diffusion layer (10) in which an intermediate layer 62 is formed on a porous substrate 61. Here, the diffusion layer (10) of the fuel electrode 50 and the oxidant electrode 60 is formed in the first embodiment, and the surface roughness Ra ≧ 8 μm or more of the porous substrates 51, 61, the intermediate layer 52, The average particle diameter L of 62 is 5 ≦ m.

  A separator 55 having a fuel gas supply groove 56 is installed on the fuel electrode 50, and a separator 65 having an oxidant gas supply groove 66 is installed on the oxidant electrode 60. Here, the respective flow paths 56 and 66 are orthogonal to each other. Although not shown in the drawing, a plurality of the fuel cells shown in FIG. 4 are stacked to constitute a fuel cell stack.

  In the fuel cell main body having such a configuration, each reaction gas (fuel gas, fuel gas supply groove 56 and oxidant gas supply groove 66 is provided via a reaction gas supply manifold provided on a side surface of the fuel cell stack. When the oxidant gas is supplied, the electrochemical reaction shown below occurs at the pair of electrodes of the unit cell, and an electromotive force is generated between the electrodes.

Fuel electrode: 2H ₂ → 4H ⁺ + 4e ⁻ (1)
Oxidant electrode: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)
In the above equation, the fuel electrode 50 dissociates the supplied hydrogen into hydrogen ions and electrons as shown in Equation (1). At that time, hydrogen ions pass through the electrolyte layer and electrons move through the external circuit to the oxidant electrode 60.

  On the other hand, in the oxidant electrode 60, as shown in the formula (2), oxygen in the supplied oxidant gas reacts with the hydrogen ions and electrons to generate water. At this time, electrons that have passed through the external circuit become current and can be supplied with electric power.

  In addition, the water produced | generated by reaction of Formula (1), (2) passes through the reaction gas discharge manifold provided in the side surface of the fuel cell laminated body with the reaction gas (already-reacted gas) which was not consumed with the fuel cell main body. It is discharged outside the fuel cell body.

  Next, the fuel cell of the present embodiment will be described in more detail together with a comparative example.

A catalyst layer was formed on the gas diffusion layer (10) manufactured in the first embodiment, and a fuel cell was manufactured using the formed electrodes 50 and 60 and the solid polymer electrolyte membrane 40. The fuel electrode catalyst layer 53 was formed by a doctor blade. That is, an ink composed of a mixed solution of a Pt—Ru alloy catalyst and a solid polymer electrolyte solution was produced, and this ink was used to form the ink on the produced gas diffusion layer by the doctor blade method. The metal amount of the Pt—Ru alloy catalyst was 0.5 mg / cm ² . The weight ratio of the Pt—Ru alloy catalyst to the solid polymer electrolyte was 2: 1. Similarly, the oxidant electrode catalyst layer 63 was made of an ink composed of a mixed solution of a Pt catalyst and a solid polymer electrolyte solution, and formed on the gas diffusion layer produced by the doctor blade method. The metal amount of the Pt catalyst was 0.4 mg / cm ² . The weight ratio of the Pt catalyst to the solid polymer electrolyte was 2: 1.

The solid polymer electrolyte membrane 40 was sandwiched between the fuel electrode 50 and the oxidizer electrode 60, and an electrode-solid polymer electrolyte membrane assembly a was obtained by thermocompression bonding. As the solid polymer electrolyte membrane 40, a 25 μm thick perfluorinated ionomer (for example, Nafion NR111 (registered trademark)) membrane was used. Thermocompression bonding was performed using a hot press at a temperature of 135 ° C., a pressure of 20 kgf / cm ² , and a time of 2 minutes.

  Next, the same gas diffusion layer A as that of the electrode-solid polymer electrolyte membrane assembly a is used, and a catalyst layer is formed on the gas diffusion layer A using a mixed powder using the catalyst powder and the electrolyte membrane. An electrode 50 and an oxidizer electrode 60 were produced. A fuel cell was manufactured by sandwiching the solid polymer electrolyte membrane 40 between the electrodes 50 and 60.

  The catalyst layer was formed using the same apparatus as that shown in FIG. 2 for producing the intermediate layer. The fuel layer and oxidant electrode catalyst layer forming ink produced from the electrode-solid polymer electrolyte membrane assembly a was dried at 70 ° C. to obtain catalyst layer forming powder. This powder was applied to the gas diffusion layer A to produce a fuel electrode and an oxidant electrode. A solid polymer electrolyte membrane was sandwiched between the produced fuel electrode and oxidant electrode, and an electrode-solid polymer electrolyte membrane assembly b was obtained by thermocompression bonding. The solid polymer electrolyte membrane and bonding conditions were the same as those of the electrode-solid polymer electrolyte membrane assembly a.

A method for forming the fuel electrode and the oxidizer electrode in Comparative Example 1 will be described below. A nonwoven fabric with a surface roughness Ra = 5 μm was used as the porous base material of the gas diffusion layer. Denca black was used as the electrically conductive material of the intermediate layer, and polytetrafluoroethylene having an average particle size of 0.3 μm was used as the binder. An ink was prepared with a dispersion of Denka Black and polytetrafluoroethylene so that the weight ratio of solids was 60:40, and an intermediate layer was formed by applying with a doctor blade to obtain a gas diffusion layer. The average particle size of the dispersion medium in the ink was L = 2 μm. The basis weight of the intermediate layer was 1.0 mg / cm ² as in the gas diffusion layer A. The thickness was 20 μm.

  A fuel electrode 50 and an oxidant electrode 60 were produced by forming a catalyst layer on the intermediate layer of the gas diffusion layer by the same method as that for the electrode-solid polymer electrolyte membrane assembly a. Then, an electrode-solid polymer electrolyte membrane assembly c was manufactured using the fuel electrode 50, the oxidizer electrode 60, and the solid polymer electrolyte membrane 40.

  Next, a method for forming the fuel electrode and the oxidizer electrode in Comparative Example 2 will be described. By using the gas diffusion layer B manufactured in the first embodiment and forming a catalyst layer on the gas diffusion layer B by the same method as the electrode-solid polymer electrolyte membrane assembly a, a catalyst is formed on the gas diffusion layer A. A fuel electrode 50 and an oxidizer electrode 60 were manufactured by forming a catalyst layer using a mixed powder using a powder and an electrolyte membrane. Then, an electrode-solid polymer electrolyte membrane assembly d was manufactured using the solid polymer electrolyte membrane 40 with the electrodes 50 and 60. In addition, since the intermediate | middle layer was easy to peel, the gas diffusion layer B selected and used the thing from which the intermediate | middle layer is not peeled.

  Electrode-solid polymer electrolyte membrane assemblies a to d were incorporated in an oxidant gas supply separator and a fuel gas supply separator, and a power generation test was performed. A reforming simulation gas having a hydrogen concentration of 70% and a carbon monoxide concentration of 10 ppm is supplied to the fuel, air is supplied to the oxidizer electrode, the battery temperature is 80 ° C., the anode humidification is 80 ° C., and the cathode humidification is 70 ° C. Conducted power generation tests at 80% and 40%, respectively.

The following (Table 1) shows the alternating current resistance values measured at a voltage of 1 A / cm ² and a current density of 0.3 A / cm ² and 1 A / cm ² for each electrode-solid polymer electrolyte membrane assembly.

As shown in Table 1, there is no voltage difference between the electrode-solid polymer electrolyte membrane assemblies ad at a current density of 0.3 A / cm ² , but a comparative example electrode at a current density of 1.0 A / cm ^2. -The electrolyte membrane assembly c resulted in the lowest voltage. Compared with the electrode-electrolyte membrane assembly a using the same catalyst layer, the average particle size of the mixed particles comprising the carbon powder having electrical conductivity and the binder forming the intermediate layer of the gas diffusion layer is fine and the intermediate layer This is probably because the gas diffusion performance was lowered because the thickness was reduced. The reason why the voltage at the current density of 1.0 A / cm ² is higher in the electrode-electrolyte membrane assembly b than in the electrode-electrolyte membrane assembly a is that the gas diffusibility is improved because the catalyst layer is dry-coated. It is.

Further, in the joined body d using the gas diffusion layer B, the contact between the intermediate layer and the porous substrate in the gas diffusion layer is poor, so that the AC resistance value is high and the voltage at a current density of 1.0 A / cm ² is low. It seems to have been.

  As described above, an intermediate layer formed by applying a mixed powder composed of carbon powder having electrical conductivity and a binder having an average particle diameter L of 5 μm or less, and a porous material having a surface roughness Ra having electrical conductivity of 8 μm or more. By using a gas diffusion layer made of a porous substrate, a fuel cell with excellent gas diffusibility can be formed. In addition, the average particle diameter L made of carbon powder having electric conductivity and a binder is desirably 2 to 5 μm. Further, the surface roughness Ra of the porous substrate is desirably 8 μm or more, but if it is too large, the mixed powder cannot be fixed. Therefore, the surface roughness Ra of the porous substrate is desirably about 20 μm or less.

  As described above, according to the present embodiment, by using the gas diffusion layer as in the first embodiment as the fuel electrode and the oxidant electrode of the fuel cell, the manufacturing cost can be reduced and the characteristics can be improved. . In particular, by setting the surface roughness Ra of the porous substrate to 8 μm or more and the average particle diameter L of the mixed powder composed of the carbon powder having electric conductivity and the binder to 5 μm, the gas having extremely excellent fixability. By realizing a diffusion layer and dry-coating a catalyst layer on this gas diffusion layer, a fuel cell with better diffusibility can be obtained.

(Modification)
The gas diffusion layer is not necessarily used as an electrode of a fuel cell, but can be applied to a portion where gas diffusion is required and conductivity is required. Furthermore, the electrolyte is not necessarily limited to a solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte, and may be an alkaline electrolyte.

  Further, the upper limit of the surface roughness Ra of the porous substrate is not particularly defined, but if it is too large, the particles do not stay, so about 20 μm or less is desirable. Further, the lower limit of the average particle diameter L is not particularly limited, but it is difficult to make very small particles, and it is preferably about 2 μm or more. In the embodiment, Ra> L is defined for both the fuel electrode and the oxidant electrode in the fuel cell. However, it is not always necessary to satisfy Ra> L with both electrodes, and Ra> L is satisfied with only one electrode. You may be satisfied.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

1 ... Porous substrate
DESCRIPTION OF SYMBOLS 2 ... Intermediate | middle layer 10 ... Gas diffusion layer 20 ... Gas diffusion base material suction stage 21 ... Intermediate | middle layer formation chamber 22 ... Mixture supply part 23 ... Gas supply part 24 ... Carbon paper 25 ... Gas flow volume adjustment part 26 ... Exhaust blower 27 ... Pressure Adjustment valve 40 ... Solid polymer electrolyte membrane 50 ... Fuel electrode 51 ... Fuel electrode porous substrate 52 ... Fuel electrode intermediate layer 53 ... Fuel electrode catalyst layer 55 ... Fuel electrode side separator 56 ... Fuel gas supply groove 60 ... Oxidant electrode 61 ... oxidant electrode porous substrate 62 ... oxidant electrode intermediate layer 63 ... oxidant electrode catalyst layer 65 ... oxidant electrode side separator 66 ... oxidant gas supply groove

Claims (7)

A gas diffusion layer in which an intermediate layer formed by pulverizing a mixed powder of carbon powder having electrical conductivity and a binder is formed on the surface of a porous substrate having electrical conductivity,
The gas diffusion layer, wherein an average particle diameter L of the pulverized mixed powder is smaller than a surface roughness Ra of the porous substrate. 2. The gas diffusion layer according to claim 1, wherein the porous substrate has a surface roughness Ra of 8 μm to 20 μm and an average particle diameter L of the pulverized mixed powder of 2 μm to 5 μm. A fuel electrode diffusion layer and an oxidant electrode diffusion layer disposed opposite to each other with an electrolyte membrane interposed therebetween;
Catalyst layers respectively disposed on surfaces of the fuel electrode diffusion layer and the oxidant electrode diffusion layer facing the electrolyte membrane;
Comprising
At least one of the fuel electrode diffusion layer and the oxidant electrode diffusion layer comprises a porous base material having electrical conductivity, and a powder obtained by pulverizing a mixed powder of carbon powder and binder having electrical conductivity. And an intermediate layer deposited on the surface of the material, wherein the average particle diameter L of the pulverized mixed powder is smaller than the surface roughness Ra of the porous substrate. 4. The fuel cell according to claim 3, wherein the porous substrate has a surface roughness Ra of 8 μm to 20 μm and an average particle diameter L of the pulverized mixed powder of 2 μm to 5 μm. The fuel cell according to claim 3 or 4, wherein the catalyst layer is formed by applying a powder obtained by pulverizing a mixed powder composed of a catalyst powder and a binder to the intermediate layer. Preparing a porous substrate having electrical conductivity;
Preparing a mixed powder of electrically conductive carbon powder and binder;
Crushing the mixed powder in an inert gas so that the average particle size L of the mixed powder is smaller than the surface roughness Ra of the porous substrate;
Forming an intermediate layer by laminating the pulverized mixed powder on the surface of the porous substrate;
A method for producing a gas diffusion layer, comprising:   A carbon-based material having a surface roughness Ra of 8 μm to 20 μm is used as the porous substrate, and the average particle diameter L of the mixed powder is adjusted to 2 μm to 5 μm by pulverization in the inert gas. The manufacturing method of the gas diffusion layer of Claim 6.

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