Method for manufacturing a gas diffusion layer for fuel cells and gas diffusion layer for fuel cells

Abstract

To easily manufacture a gas diffusion layer having a microporous layer.SOLUTION: A method for manufacturing a gas diffusion layer for a fuel cell includes a stirring step of stirring a solution containing copper methylacetylide as precursors to form the precursors into a wire-like shape and entangle the precursors with each other in the solution, an adding step of adding the precursor to a surface layer of a porous substrate sheet so as to fill pores in the surface layer, and a firing step of baking the substrate sheet and the precursor at 1000°C or more and 1200°C or less to grow a graphene multilayer film from the precursor and thermally remove copper, thereby forming porous carbon that is composed of the graphene multilayer films, has mesoporosity, and has a hollow wire-like crystal structure.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a gas diffusion layer for a fuel cell and a gas diffusion layer for a fuel cell.

Background Art

[0002] A solid polymer fuel cell includes a fuel cell stack composed of a plurality of single cells stacked together. A single cell includes a membrane electrode assembly composed of a solid polymer electrolyte membrane (hereinafter referred to as an electrolyte membrane) and a pair of catalyst layers sandwiching the electrolyte membrane, a pair of gas diffusion layers sandwiching the membrane electrode assembly, and an anode-side separator and a cathode-side separator sandwiching the pair of gas diffusion layers.

[0003] Examples of such a gas diffusion layer include the gas diffusion electrode disclosed in Patent Document 1. The gas diffusion electrode disclosed in Patent Document 1 includes a sheet-like porous base material and a microporous layer disposed in contact with one surface of the porous base material. The porous base material is carbon paper, carbon cloth, carbon non-woven fabric, or the like. The microporous layer is formed by applying a paste-like coating liquid in which conductive fine particles, a binder, a solvent, a thickener, and the like are mixed and dispersed on one surface of the porous base material. The conductive particles are carbon black such as acetylene black having an average particle diameter of 20 to 150 nm. The binder is, for example, polytetrafluoroethylene (PTFE).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] These fuel cell gas diffusion layers are required to be manufactured using simple methods. Furthermore, further improvements are needed in the control of conductivity, gas diffusivity, and water retention capacity of fuel cell gas diffusion layers. [Means for solving the problem]

[0006] A method for manufacturing a gas diffusion layer for a fuel cell to solve the above problems comprises: a stirring step of stirring a solution containing copper methyl acetylide as a precursor to form the precursor into a wire and to intertwine the precursors in the solution; an addition step of adding the precursor to the surface layer of a porous substrate sheet or substrate sheet precursor to fill the pores in the surface layer; and a firing step of firing the substrate sheet or substrate sheet precursor and the precursor at a temperature of 1000°C or higher and 1200°C or lower to grow a multilayer graphene film on the precursor and thermally remove the copper, thereby forming a porous carbon composed of a multilayer graphene film, having mesoporous properties and a hollow wire-shaped crystalline structure.

[0007] According to this method, a wire-like precursor is formed by stirring a solution containing copper methyl acetylide during the stirring step. At this time, in the subsequent heating step, the copper becomes spherical or elliptical due to the difference in specific gravity between copper and carbon, while the carbon coats the copper, forming a wire-like structure. Furthermore, the wire-like precursors become entangled with each other in the solution.

[0008] Next, in the addition step, the precursor is added to the surface layer of the porous base sheet or base sheet precursor in such a way that it fills the pores in the surface layer. Next, in the firing process, the precursor is fired together with the base sheet or base sheet precursor at a temperature of 1000°C or higher and 1200°C or lower, causing the copper to sublimate and be removed. The portion of the carbon in the precursor that is in contact with copper comes into contact with molten copper at a temperature of 1000°C or higher. At this time, the surface tension generated in the carbon creates an ideal two-dimensional carbon surface, and the carbon grows into a multilayer graphene film. As a result, porous carbon is formed, which is composed of a multilayer graphene film and has a structure in which hollow wire-like crystals with mesoporous properties are intertwined with each other. In addition, when a base sheet precursor is used, the base sheet is formed by firing the base sheet precursor. For this reason, the base sheet can be formed by firing the base sheet precursor at the same time as firing the precursor.

[0009] By calcining the copper methyl acetylide precursor in this way, the precursor is carbonized while maintaining its wire-like structure. Furthermore, since the firing temperature is between 1000°C and 1200°C according to the above method, the firing temperature can be lowered compared to conventional manufacturing methods, such as firing silver methyl acetylide at 2000°C. This makes it possible to miniaturize the firing furnace and reduce the energy required for firing.

[0010] Furthermore, copper is preferable to silver when growing thick graphene multilayer films to enhance conductivity. Thus, according to the above method, a gas diffusion layer in which the pores of the surface layer of the substrate sheet are filled with the porous carbon can be obtained through a simple process. The porous carbon functions as a microporous layer. Therefore, a gas diffusion layer having a microporous layer can be manufactured by a simple method.

[0011] Furthermore, a method for manufacturing a gas diffusion layer for a fuel cell to solve the above problems comprises: a stirring step of stirring a solution containing copper methyl acetylide as a precursor to form the precursor into a wire and to intertwine the precursors in the solution; a first firing step of firing the precursor at 1000°C or higher and 1200°C or lower to grow it into a graphene multilayer film and thermally remove the copper to form porous carbon composed of a graphene multilayer film, having mesoporosity and a hollow wire-shaped crystalline structure; a grinding step of grinding the porous carbon while maintaining the crystalline structure; an addition step of applying or spraying a solution containing the ground porous carbon onto the surface layer of a porous substrate sheet to add the porous carbon so as to fill the pores in the surface layer; and a second firing step of firing the substrate sheet and the porous carbon to integrate the porous carbon with the substrate sheet.

[0012] According to this method, a wire-like precursor is formed by stirring a solution containing copper methyl acetylide during the stirring step. At this time, in the subsequent heating step, the copper becomes spherical or elliptical due to the difference in specific gravity between copper and carbon, while the carbon coats the copper, forming a wire-like structure. Furthermore, the wire-like precursors become entangled with each other in the solution.

[0013] Next, in the first firing process, the precursor is fired at a temperature of 1000°C or higher and 1200°C or lower, causing the copper to sublimate and be removed. The portion of the carbon in the precursor that is in contact with copper comes into contact with molten copper at a temperature of 1000°C or higher. At this time, the surface tension generated in the carbon creates an ideal two-dimensional surface of carbon, and the carbon grows into a multilayer graphene film. As a result, porous carbon is formed, which is composed of a multilayer graphene film and has a structure in which hollow wire-like crystals with mesoporous properties are intertwined with each other.

[0014] By calcining the copper methyl acetylide precursor in this way, the precursor is carbonized while maintaining its wire-like structure. Next, in the grinding process, the porous carbon is ground while maintaining its crystalline structure.

[0015] Next, in the addition step, a solution containing pulverized porous carbon is applied or sprayed onto the surface layer of a porous substrate sheet, thereby adding porous carbon to fill the pores in the surface layer.

[0016] Next, in the second firing process, the base sheet and the porous carbon are fired, causing the porous carbon to bond to the base sheet and become integrated. According to the above method, the firing temperature in the first firing step is between 1000°C and 1200°C. Therefore, compared to conventional manufacturing methods in which silver methyl acetylide is fired at 2000°C, for example, the firing temperature can be lowered. This makes it possible to miniaturize the firing furnace and reduce the energy required for firing.

[0017] Furthermore, copper is preferable to silver when growing thick graphene multilayer films to enhance conductivity. Thus, a gas diffusion layer in which the pores of the surface layer of the substrate sheet are filled with the porous carbon can be obtained through a simple process. The porous carbon functions as a microporous layer. Therefore, a gas diffusion layer having a microporous layer can be manufactured by a simple method.

[0018] Furthermore, the fuel cell gas diffusion layer for solving the above problems comprises a porous substrate sheet. The fuel cell gas diffusion layer has porous carbon integrally formed on the substrate sheet so as to fill the pores in the surface layer of the substrate sheet. The porous carbon is composed of a multilayer film of graphene and has a structure in which hollow wire-shaped crystals having mesoporous properties are intertwined with each other. The wire diameter of the crystals is 100 nm or more and 500 nm or less, and the pore diameter of the holes formed by the intertwined crystals is 10 nm or more and 200 nm or less.

[0019] According to the same structure, although the porous carbon itself is brittle, since it is formed integrally with the base material sheet, the rigidity of the porous carbon can be increased. In addition, since the porous carbon is composed of a multi-layer film of graphene, it has high conductivity. Further, the crystal wire diameter is 100 nm or more and 500 nm or less, and the pore diameter of the pores formed by the crystals intertwined with each other is 10 nm or more and 200 nm or less. Therefore, the porous carbon has high gas permeability, that is, gas diffusibility. In addition, since water can be stored in the mesopores present in large numbers in the crystal or discharged from the mesopores, the porous carbon is excellent in adjusting the water retention amount. For this reason, the porous carbon functions as a microporous layer. In a fuel cell, when protons move from the anode to the cathode, water functions as a carrier for transporting protons. As described above, since the porous carbon of the gas diffusion layer is adjacent to the catalyst layer, the humidity of the catalyst layer is adjusted by the porous carbon. Thereby, the amount of moisture in the catalyst layer can be increased, which contributes to an improvement in the output of the fuel cell.

Effects of the Invention

[0020] According to the method for manufacturing a gas diffusion layer for a fuel cell according to the present invention, a gas diffusion layer having a microporous layer can be easily manufactured. Further, according to the gas diffusion layer for a fuel cell according to the present invention, it has high conductivity and high gas diffusibility, and is excellent in adjusting the water retention amount.

Brief Description of the Drawings

[0021] [Figure 1] FIG. 1 is a cross-sectional view of a single cell of a fuel cell. [Figure 2] FIG. 2 is a cross-sectional view schematically showing the gas diffusion layer of the first embodiment. [Figure 3] FIG. 3 is a SEM image of the surface layer portion of the gas diffusion layer of the first embodiment. [Figure 4] FIG. 4 is a SEM image of the surface layer portion of the gas diffusion layer of the first embodiment. [Figure 5]Figure 5 is an SEM image of the porous carbon constituting the first gas diffusion layer in the first embodiment. [Figure 6] Figure 6 shows an SEM image of the porous carbon constituting the gas diffusion layer in the first embodiment. [Figure 7] Figure 7 shows an SEM image of the porous carbon that constitutes the gas diffusion layer in the first embodiment. [Figure 8] Figure 8 shows an SEM image of the porous carbon constituting the gas diffusion layer in the first embodiment. [Figure 9] Figure 9 is a TEM image of the porous carbon constituting the gas diffusion layer in the first embodiment. [Figure 10] Figure 10 shows a TEM image of the precursor during the drying process of the first embodiment. [Figure 11] Figure 11 is a flowchart showing the manufacturing procedure for the gas diffusion layer of the first embodiment. [Figure 12] Figure 12 is a schematic diagram showing a substrate sheet coated with a solution containing a precursor. [Figure 13] Figure 13 is a flowchart showing the manufacturing procedure for the gas diffusion layer of the second embodiment. [Figure 14] Figure 14 is a schematic diagram showing how a sheet-like precursor is layered onto a base sheet. [Figure 15] Figure 15 is a flowchart showing the manufacturing procedure for the gas diffusion layer of the third embodiment. [Figure 16] Figure 16 is a schematic diagram showing a substrate sheet coated with a solution containing pulverized porous carbon. [Figure 17] Figure 17 shows an SEM image of a comparative example of porous carbon. [Figure 18] Figure 18 shows an SEM image of a comparative example of porous carbon. [Modes for carrying out the invention]

[0022] <First Embodiment> A first embodiment of a gas diffusion layer for a fuel cell and a method for manufacturing the same will be described below with reference to Figures 1 to 12, 17, and 18.

[0023] A polymer electrolyte fuel cell comprises a fuel cell stack composed of multiple single cells 10 stacked on top of each other. As shown in Figure 1, the single cell 10 includes a membrane electrode assembly 13, a pair of gas diffusion layers 20 sandwiching the membrane electrode assembly 13, and an anode-side separator and a cathode-side separator (neither of which are shown) sandwiching the pair of gas diffusion layers 20. The membrane electrode assembly 13 includes a solid polymer electrolyte membrane (hereinafter referred to as the electrolyte membrane 11) and a pair of catalyst layers 12 sandwiching the electrolyte membrane 11.

[0024] As shown in Figures 1 and 2, the gas diffusion layer 20 comprises a porous base sheet 21 and porous carbon 22 integrally formed on the base sheet 21 so as to fill the pores in the surface layer 21a of the base sheet 21.

[0025] The base sheet 21 of this embodiment is a carbon cloth having a fiber diameter of about 7 μm and pores of about 1 to 2 μm. As shown in Figures 3 to 8, the porous carbon 22 is composed of a multilayer film of graphene and has a structure in which hollow wire-like crystals with mesoporous properties are intertwined with each other.

[0026] As shown in Figure 3, the pores formed between the carbon fibers that make up the base sheet 21, i.e., between the thicker fibers, are filled with porous carbon 22. As shown in Figure 9, the porous carbon 22 has a void structure separated by a multilayer film of graphene.

[0027] The wire diameter of the crystals is between 100 nm and 500 nm. The pore diameter of the pores formed by the intertwined crystals is between 10 nm and 200 nm. Next, with reference to Figure 11, the manufacturing procedure for the gas diffusion layer 20 of this embodiment will be described.

[0028] As shown in Figure 11, the method for manufacturing the gas diffusion layer 20 of this embodiment comprises a precursor synthesis step, a stirring step, an addition step, a drying step, and a calcination step. The precursor synthesis step involves synthesizing copper methyl acetylide as a precursor using a well-known method.

[0029] The stirring step involves stirring a solution containing copper methyl acetylide as a precursor to form the precursor into a wire-like structure and to cause the precursors to intertwine within the solution. The solvent used is water. Adding a small amount of ethanol to the solvent can make the precursor easier to stretch.

[0030] During the stirring process, a wire-like precursor is formed by stirring the solution containing copper methyl acetylide. In the subsequent heating process, the copper becomes spherical or elliptical due to the difference in specific gravity between copper and carbon, while the carbon coats the copper, resulting in a wire-like structure. Furthermore, the wire-like precursors become intertwined with each other in the solution.

[0031] As shown in Figure 12, the addition step is to add the precursor 22A to the surface layer 21a of the porous substrate sheet 21 so as to fill the pores in the surface layer 21a. In the addition step, the precursor 22A is added to the surface layer 21a by applying or spraying a solution containing the precursor 22A onto the surface layer 21a. In this embodiment, the phenol resin solution containing the precursor 22A is applied to the surface layer 21a of the base sheet 21, allowing the solution to penetrate into the pores of the surface layer 21a of the base sheet 21.

[0032] The drying process involves heating the precursor 22A, which has been added to the surface layer 21a of the substrate sheet 21, to approximately 170°C to 300°C in a vacuum to dry it. This process causes phase separation between copper and carbon, but helps maintain the shape of the precursor 22A.

[0033] Figure 10 shows how copper and methylacetylene polymers separate during the drying process when precursor 22A is heated to 60-200°C. More specifically, it shows how the copper becomes spherical and the methyl groups are released from the system as methane and ethylene gas.

[0034] The firing process involves firing the base sheet 21 and the precursor 22A at a temperature of 1000°C or higher and 1200°C or lower to grow a multilayer graphene film and thermally remove copper, thereby forming porous carbon 22.

[0035] The firing process is preferably carried out under reduced pressure lower than atmospheric pressure. In the firing process, the precursor 22A is fired together with the base sheet 21 at a temperature of 1000°C or higher and 1200°C or lower, causing the copper to sublimate and be removed. The portion of the carbon in the precursor 22A that is in contact with copper comes into contact with the molten copper at a temperature of 1000°C or higher. At this time, the surface tension generated in the carbon creates an ideal two-dimensional surface of carbon, and the carbon grows into a multilayer graphene film. As a result, porous carbon 22 is formed, which is composed of a multilayer graphene film and has a structure in which hollow wire-like crystals with mesoporous properties are intertwined with each other.

[0036] Although the melting point of copper is 1085°C, in the case of particles smaller than 50 nm, melting point depression occurs, causing copper to liquefy below 1000°C. Figures 17 and 18 show SEM images of the porous carbon of the comparative example. The porous carbon of the comparative example was formed by vacuum calcination while dropping the precursor of this embodiment into a furnace.

[0037] Next, the effects and advantages of this embodiment will be described. (1-1) The method for manufacturing the gas diffusion layer 20 comprises a stirring step, an addition step, and a firing step.

[0038] This method allows for firing temperatures between 1000°C and 1200°C, which is lower than conventional methods that fire silver methyl acetylide at 2000°C. This enables the miniaturization of the firing furnace and reduces the energy required for firing.

[0039] Furthermore, copper is preferable to silver when growing thick graphene multilayer films to enhance conductivity. Thus, according to the above method, a gas diffusion layer 20 can be obtained in which the pores of the surface layer 21a of the base sheet 21 are filled with porous carbon 22 through a simple process. The porous carbon 22 functions as a microporous layer 23. Therefore, a gas diffusion layer 20 having a microporous layer 23 can be manufactured by a simple method.

[0040] (1-2) In the addition step, the precursor 22A is added to the surface layer 21a by applying or spraying a solution containing the precursor 22A onto the surface layer 21a. According to this method, in the addition step, the precursor 22A is added to the surface layer 21a by applying or spraying a solution containing the precursor 22A onto the surface layer 21a. Therefore, it is easy to add the precursor 22A to the surface layer 21a of the porous substrate sheet 21 in a way that fills the pores of the surface layer 21a.

[0041] (1-3) The gas diffusion layer 20 comprises a porous substrate sheet 21 and porous carbon 22 integrally formed on the substrate sheet 21 so as to fill the pores in the surface layer 21a of the substrate sheet 21. The porous carbon 22 is composed of a multilayer film of graphene and has a structure in which hollow wire-shaped crystals with mesoporous properties are intertwined with each other. The wire diameter of the crystals is 100 nm or more and 500 nm or less, and the pore diameter of the pores formed by the intertwined crystals is 10 nm or more and 200 nm or less.

[0042] With this configuration, although the porous carbon 22 itself is brittle, its rigidity can be increased because it is formed integrally with the base sheet 21. Furthermore, since the porous carbon 22 is composed of a multilayer graphene film, it has high conductivity. In addition, because the crystal wire diameter is between 100 nm and 500 nm, and the pore diameter formed by the intertwined crystals is between 10 nm and 200 nm, the porous carbon 22 has high gas permeability, i.e., gas diffusion. Moreover, because water can be stored in the mesopores that are abundant in the crystal and water can be discharged from the mesopores, the porous carbon 22 is excellent at adjusting the amount of water it can retain. For this reason, the porous carbon 22 functions as a microporous layer 23. Furthermore, in a fuel cell, when protons move from the anode to the cathode, water functions as a carrier that transports protons. As described above, since the porous carbon 22 of the gas diffusion layer 20 is adjacent to the catalyst layer 12, the porous carbon 22 regulates the humidity of the catalyst layer 12. This increases the moisture content in the catalyst layer 12, which contributes to improving the output of the fuel cell.

[0043] <Second Embodiment> The second embodiment will be described below, focusing on the differences from the first embodiment, with reference to Figures 13 and 14.

[0044] As shown in Figure 13, the method for manufacturing the gas diffusion layer 20 in this embodiment differs from the first embodiment in that it includes a sheeting step and a drying step between the stirring step and the addition step. The sheet process is a process of forming the precursor 22A into a sheet.

[0045] In the sheet-forming process, the intertwined, wire-like precursors 22A are formed into a sheet. Methods for forming the wire-like precursors 22A into a sheet include, for example, filtering a solution containing the precursors 22A using filter paper to form a sheet on the filter paper, coating it onto a flat jig, or spraying it onto a flat jig.

[0046] The drying process involves heating the sheet-formed precursor to approximately 170°C to 300°C in a vacuum to dry it. This process causes phase separation between copper and carbon, but helps maintain the shape of the precursor.

[0047] As shown in Figure 14, in the addition step, the sheet-like precursor 22A is pressed against the surface layer 21a with the sheet-like precursor 22A placed on top of it. In this embodiment, a roller (not shown) is used to press the sheet-like precursor 22A against the surface layer 21a.

[0048] After the additional steps are performed, the firing process is carried out in the same manner as in the first embodiment. Next, the effects and advantages of this embodiment will be described. (2-1) The method for manufacturing the gas diffusion layer 20 includes a sheeting step in which the precursor 22A is made into a sheet. In the addition step, the sheet-shaped precursor 22A is pressed onto the surface layer 21a with the sheet-shaped precursor 22A on top of it.

[0049] This method makes it easy to add a precursor 22A of uniform thickness to the surface layer 21a of the porous substrate sheet 21 so as to fill the pores in the surface layer 21a. (2-2) Since the porous carbon 22 has a structure in which hollow wire-like crystals are intertwined with each other, the microporous layer 23 can be easily thinned. Furthermore, thinning the microporous layer 23 can reduce the resistive overpotential of the microporous layer 23.

[0050] <Third Embodiment> The third embodiment will be described below with reference to Figures 15 and 16. As shown in Figure 15, the method for manufacturing the gas diffusion layer 20 of this embodiment comprises a precursor synthesis step, a stirring step, a first calcination step, a grinding step, an addition step, and a second calcination step.

[0051] The precursor synthesis step and the stirring step are the same as in the first and second embodiments. The first calcination step involves calcining the precursor at a temperature of 1000°C or higher and 1200°C or lower to grow a graphene multilayer film and thermally remove copper to form porous carbon 22.

[0052] The first firing process is preferably carried out under reduced pressure lower than atmospheric pressure. Here, in the first firing step, the precursor 22A is fired at a temperature of 1000°C or higher and 1200°C or lower, and the copper is removed by sublimation, which is the same as in the firing step of the first embodiment.

[0053] The grinding process is a process of grinding the porous carbon 22 while maintaining the above-mentioned crystalline structure. As shown in Figure 16, the addition step is a step of adding porous carbon 22 to the surface layer 21a of a porous base sheet 21 by applying or spraying a solution containing pulverized porous carbon 22 onto the surface layer 21a of the porous base sheet 21 to fill the pores of the surface layer 21a. In this embodiment, the phenol resin solution containing pulverized porous carbon 22 is applied to the surface layer 21a of the base sheet 21, thereby allowing the solution to penetrate the pores of the surface layer 21a of the base sheet 21.

[0054] The second firing process involves firing the base sheet 21 and the porous carbon 22 to integrate the porous carbon 22 into the base sheet 21. Next, the effects and advantages of this embodiment will be described.

[0055] (3-1) The method for manufacturing the gas diffusion layer 20 comprises a stirring step, a first calcination step, a grinding step, an addition step, and a second calcination step. According to the above method, the firing temperature in the first firing step is between 1000°C and 1200°C. Therefore, compared to conventional manufacturing methods in which silver methyl acetylide is fired at 2000°C, for example, the firing temperature can be lowered. This makes it possible to miniaturize the firing furnace and reduce the energy required for firing.

[0056] Furthermore, copper is preferable to silver when growing thick graphene multilayer films to enhance conductivity. Thus, according to the above method, a gas diffusion layer 20 can be obtained in which the pores of the surface layer 21a of the base sheet 21 are filled with porous carbon 22 through a simple process. The porous carbon 22 functions as a microporous layer 23. Therefore, a gas diffusion layer 20 having a microporous layer 23 can be manufactured by a simple method.

[0057] <Variation> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0058] The fiber diameter of the carbon fibers constituting the base sheet 21 and the size of the pores in the base sheet 21 can be changed as appropriate. The base sheet 21 is not limited to carbon cloth, but may also be carbon paper or carbon nonwoven fabric.

[0059] In the first and second embodiments described above, in the addition step, copper methyl acetylide as a precursor is added to the surface layer 21a of the base sheet 21, and then in the firing step, the base sheet 21 and the precursor are fired at a temperature of 1000°C or higher and 1200°C or lower. Alternatively, in the addition step, copper methyl acetylide as a precursor is added to the surface layer of the base sheet precursor, and then in the firing step, the base sheet precursor and the precursor are fired at a temperature of 1000°C or higher and 1200°C or lower. The base sheet precursor can be any material that becomes a base sheet when fired, and for example, nonwoven fabrics or papers made of polyacrylonitrile are preferred. Nonwoven fabrics or papers made of cellulose may also be used. In this case, the base sheet is formed when the base sheet precursor is fired. Therefore, when firing the precursor, carbon paper or carbon nonwoven fabric can be formed as a base sheet by firing the base sheet precursor at the same time. [Explanation of symbols]

[0060] 10... Single cell 11...Electrolyte membrane 12...Catalyst layer 13...Membrane electrode assembly 20...Gas diffusion layer 21…Base sheet 21a...surface layer 22…Porous carbon 23... Microporous layer

Claims

1. A method for manufacturing a gas diffusion layer for fuel cells, A stirring step involves stirring a solution containing copper methyl acetylide as a precursor to form the precursor into a wire and to intertwine the precursors in the solution, An addition step of adding the precursor to the surface layer of a porous substrate sheet or substrate sheet precursor so as to fill the pores in the surface layer, The invention comprises a firing step in which the substrate sheet or substrate sheet precursor and the precursor are fired at a temperature of 1000°C or higher and 1200°C or lower to grow a multilayer film of graphene on the precursor and thermally remove copper, thereby forming a porous carbon composed of a multilayer film of graphene, having mesoporous properties and a hollow wire-like crystalline structure. A method for manufacturing a gas diffusion layer for fuel cells.

2. In the addition step, the precursor is added to the surface layer by applying or spraying a solution containing the precursor to the surface layer. A method for manufacturing a gas diffusion layer for a fuel cell according to claim 1.

3. The process includes a sheeting step to form the precursor into a sheet, In the above-mentioned additional step, the sheet-like precursor is pressed onto the surface layer with the sheet-like precursor on top. A method for manufacturing a gas diffusion layer for a fuel cell according to claim 1.

4. A method for manufacturing a gas diffusion layer for fuel cells, A stirring step involves stirring a solution containing copper methyl acetylide as a precursor to form the precursor into a wire and to intertwine the precursors in the solution, A first calcination step involves calcining the precursor at a temperature of 1000°C or higher and 1200°C or lower to grow a graphene multilayer film and thermally remove copper, thereby forming a porous carbon composed of a graphene multilayer film, having mesoporous properties and a hollow wire-like crystalline structure. A grinding step for grinding the porous carbon while maintaining the aforementioned crystalline structure, An addition step is to apply or spray a solution containing the pulverized porous carbon onto the surface layer of a porous substrate sheet to add the porous carbon so as to fill the pores in the surface layer, The invention comprises a second firing step, in which the porous carbon is integrated into the base sheet by firing the base sheet and the porous carbon. A method for manufacturing a gas diffusion layer for fuel cells.

5. A gas diffusion layer for a fuel cell comprising a porous substrate sheet, The substrate sheet has porous carbon integrally formed on it so as to fill the pores in the surface layer of the substrate sheet, The porous carbon is composed of a multilayer film of graphene and has a structure in which hollow wire-like crystals with mesoporous properties are intertwined with each other. The wire diameter of the aforementioned crystal is 100 nm or more and 500 nm or less. The pore diameter of the pores formed by the intertwined crystals is 10 nm or more and 200 nm or less. Gas diffusion layer for fuel cells.

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