JP2016072000A - Gas diffusion layer for fuel cell, fuel cell and method of manufacturing gas diffusion layer for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for enhancing gas diffusivity in a gas diffusion layer for fuel cell.SOLUTION: A gas diffusion layer for fuel gas includes a porous layer containing a plurality of conductive fibers 28, 48 having a length of 30 μm or more, and thermosetting resins 30, 50 having a melt viscosity of 1000 Pa s or less and binding the conductive fibers each other, and groove-like fluid passages 24, 44 provided in one principal surface of the porous layer.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fuel cell gas diffusion layer, a fuel cell having a fuel cell gas diffusion layer, and a method for producing a fuel cell gas diffusion layer.

  A fuel cell is a device that generates electrical energy from hydrogen and oxygen, and can achieve high power generation efficiency. The main features of the fuel cell are direct power generation that does not go through the process of thermal energy or kinetic energy as in the conventional power generation method, so high power generation efficiency can be expected even on a small scale, and emissions of nitrogen compounds, etc. There are few, and noise and vibration are also small, and environmental properties are good. In this way, fuel cells can be used effectively for the chemical energy of fuel and have environmentally friendly characteristics, so they are expected as energy supply systems for the 21st century, and are widely used in space, automobiles and portable devices. It is attracting attention as a promising new power generation system that can be used for various applications from scale power generation to small-scale power generation, and technological development is in full swing toward practical use.

  Patent Document 1 discloses a fuel cell in which a catalyst layer, a gas diffusion layer, and a separator are sequentially laminated on both surfaces of a polymer electrolyte membrane. The gas diffusion layer of the fuel cell is made of a conductive carbon sheet, and has a fluid flow path on the surface in contact with the separator.

International Publication No. 11/045889 Pamphlet

  As a result of intensive studies on the above-described fuel cell, the present inventors have come to recognize that the gas diffusion layer of a conventional fuel cell has room for improving gas diffusibility.

  This invention is made | formed in view of such a condition, The objective is to provide the technique which aims at the improvement of the gas diffusibility in the gas diffusion layer for fuel cells.

  One embodiment of the present invention is a gas diffusion layer for a fuel cell. The fuel cell gas diffusion layer includes a plurality of conductive fibers having a length of 30 μm or more, and a porous layer having a melt viscosity of 1000 Pa · s or less and containing a thermoplastic resin that binds the conductive fibers to each other. And a groove-like fluid flow path provided on one main surface of the porous layer.

  Another aspect of the present invention is a gas diffusion layer for a fuel cell. The gas diffusion layer for a fuel cell includes a first porous layer having a groove-like fluid channel on one main surface, and a second porous layer disposed on the other main surface side of the first porous layer, . The first porous layer contains conductive fibers having a length of 30 μm or more. In the second porous layer, the occupied area ratio of the conductive fibers per unit area in the cross section is smaller than the occupied area ratio in the cross section of the first porous layer.

  Another embodiment of the present invention is a fuel cell. The fuel cell includes a membrane electrode assembly including an electrolyte membrane, an anode catalyst layer disposed on one surface side of the electrolyte membrane, and a cathode catalyst layer disposed on the other surface side of the electrolyte membrane, and a membrane electrode An anode gas diffusion layer disposed on the anode catalyst layer side of the assembly, and a cathode gas diffusion layer disposed on the cathode catalyst layer side of the membrane electrode assembly. At least one of the anode gas diffusion layer and the cathode gas diffusion layer is composed of the fuel cell gas diffusion layer of the above-described embodiment.

  Another aspect of the present invention is a method for producing a fuel cell gas diffusion layer. The manufacturing method of the fuel cell gas diffusion layer includes a plurality of conductive fibers having a length of 30 μm or more, and a thermoplastic resin having a melt viscosity of 1000 Pa · s or less and binding the conductive fibers to each other. A step of preparing a porous sheet, and a step of heating and pressurizing the porous sheet to form a groove-like fluid flow path on one main surface of the porous sheet.

  ADVANTAGE OF THE INVENTION According to this invention, the improvement of the gas diffusibility in the gas diffusion layer for fuel cells can be aimed at.

1 is a perspective view schematically showing the structure of a fuel cell according to an embodiment. It is a schematic sectional drawing along the AA line of FIG. It is sectional drawing which shows typically the structure of the gas diffusion layer for fuel cells. 4A to 4D are process cross-sectional views schematically showing a method for manufacturing a fuel cell gas diffusion layer according to an embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  FIG. 1 is a perspective view schematically showing the structure of a fuel cell according to an embodiment. FIG. 2 is a schematic cross-sectional view along the line AA in FIG. The fuel cell 1 of the present embodiment includes a substantially flat membrane electrode assembly 10 and an anode gas diffusion layer 20 and a cathode gas diffusion layer 40 as gas diffusion layers for a fuel cell. Hereinafter, when the anode gas diffusion layer 20 and the cathode gas diffusion layer 40 are not distinguished, they are collectively referred to as a fuel cell gas diffusion layer. The anode gas diffusion layer 20 and the cathode gas diffusion layer 40 are provided so that their main surfaces face each other with the membrane electrode assembly 10 interposed therebetween. In addition, separators 2 and 4 are provided on the main surface sides of the anode gas diffusion layer 20 and the cathode gas diffusion layer 40 opposite to the membrane electrode assemblies 10. In the present embodiment, a set of membrane electrode assemblies 10, an anode gas diffusion layer 20, and a cathode gas diffusion layer 40 are shown, but a plurality of sets are stacked via separators 2 and 4, thereby forming a fuel cell stack. Also good.

  The membrane electrode assembly 10 includes an electrolyte membrane 12, an anode catalyst layer 14 disposed on one surface side of the electrolyte membrane 12, and a cathode catalyst layer 16 disposed on the other surface side of the electrolyte membrane 12.

  The electrolyte membrane 12 exhibits good ion conductivity in a wet state, and functions as an ion exchange membrane that moves protons between the anode catalyst layer 14 and the cathode catalyst layer 16. The electrolyte membrane 12 is formed of a solid polymer material such as a fluorine-containing polymer or a non-fluorine polymer. As a material of the electrolyte membrane 12, a sulfonic acid type perfluorocarbon polymer, a polysulfone resin, a perfluorocarbon polymer having a phosphonic acid group or a carboxylic acid group, or the like can be used. Examples of the sulfonic acid type perfluorocarbon polymer include Nafion (manufactured by DuPont: registered trademark) 112. Examples of the non-fluorine polymer include sulfonated aromatic polyetheretherketone and polysulfone. The thickness of the electrolyte membrane 12 is, for example, not less than 10 μm and not more than 200 μm.

  The anode catalyst layer 14 and the cathode catalyst layer 16 have ion exchange resin and catalyst particles, and optionally carbon particles supporting the catalyst particles. The ion exchange resin included in the anode catalyst layer 14 and the cathode catalyst layer 16 connects the catalyst particles and the electrolyte membrane 12 and plays a role of transmitting protons therebetween. This ion exchange resin can be formed from the same polymer material as the electrolyte membrane 12. Catalyst particles include Sc, Y, Ti, Zr, V, Nb, Fe, Co, Ni, Ru, Rh, Pd, Pt, Os, Ir, alloys selected from lanthanoid elements and actinoid elements, A catalytic metal such as a simple substance can be mentioned. As the carbon particles, acetylene black, ketjen black, carbon nanotubes and the like can be used. The thicknesses of the anode catalyst layer 14 and the cathode catalyst layer 16 are, for example, 10 μm or more and 40 μm or less, respectively.

  The anode gas diffusion layer 20 is disposed on the anode catalyst layer 14 side of the membrane electrode assembly 10. The anode gas diffusion layer 20 includes a first porous layer 22, a fluid flow path 24, and a second porous layer 26. The thickness of the anode gas diffusion layer 20 is, for example, not less than 50 μm and not more than 500 μm.

  FIG. 3 is a cross-sectional view schematically showing the structure of the fuel cell gas diffusion layer. The first porous layer 22 contains a plurality of conductive fibers 28 having a length of 30 μm or more and the thermoplastic resin 30. As the conductive fibers 28, for example, polyacrylonitrile-based carbon fibers, rayon-based carbon fibers, pitch-based carbon fibers, carbon fibers such as carbon nanotubes, metal fibers, or the like can be used. The length of the conductive fiber 28 is 30 μm or more. If the length of the conductive fiber 28 is less than 30 μm, the contact point between the conductive fibers increases, and the conductivity and tensile strength of the first porous layer 22 may be reduced. Moreover, desired gas diffusibility can be imparted to the first porous layer 22 by setting the length of the conductive fibers 28 to 30 μm or more.

  The method for measuring the length of the conductive fiber 28 is as follows. That is, first, the first porous layer 22 is cut to form a cross section. After the section is polished, the section is imaged with a scanning electron microscope (SEM). Then, the length of the conductive fiber 28 is measured in the obtained cross-sectional image. Moreover, the following method can be mentioned as another measuring method. That is, a part of the first porous layer 22 is cut out, and the part is put into a solvent that dissolves the thermoplastic resin. Thereby, the thermoplastic resin in the first porous layer 22 is dissolved. Then, the conductive fibers 28 separated from each other are recovered from the solvent by a known operation such as filtration. For example, 400 separated conductive fibers 28 are randomly extracted, and the length of each conductive fiber 28 is measured using an optical microscope or SEM. As a method for separating the conductive fibers 28, a method that does not use a solvent that dissolves the thermoplastic resin may be employed. In this method, a part of the cut out first porous layer 22 is heated at, for example, a temperature of 500 ° C. for 30 minutes. Thereby, the thermoplastic resin is burned off, and the conductive fibers 28 are separated.

  The thermoplastic resin 30 has a function of binding conductive fibers together. Further, the thermoplastic resin 30 has a melt viscosity of 1000 Pa · s or less at a molding processing temperature. Examples of such a thermoplastic resin 30 include PPS (polyphenylene sulfide). The “melt viscosity at the molding temperature” is the viscosity of the resin as measured with a capillary rheometer. A capillary rheometer detects the shear rate and shear stress when the molten thermoplastic resin flows out through the capillary, and measures the melt viscosity of the thermoplastic resin. The melt viscosity of PPS is about 500 Pa · s at a molding temperature of 310 ° C.

  By binding the conductive fibers 28 with the thermoplastic resin 30, it is possible to maintain a state in which a large number of pores are included in the first porous layer 22. For this reason, the gas diffusibility of the first porous layer 22 can be improved. In addition, since the thermoplastic resin 30 has the above-described physical properties, a porous sheet press molding method can be employed as a method of forming the fluid flow path 24.

  The first porous layer 22 is made of a material mainly composed of conductive fibers 28 and a thermoplastic resin 30. The total mass of the conductive fibers 28 and the thermoplastic resin 30 with respect to the total mass of the first porous layer 22 is 50 mass% or more, preferably 80 mass% or more. By setting the total mass to 50% by mass or more, desired gas diffusibility can be more reliably imparted to the first porous layer 22. The thickness of the first porous layer 22 is, for example, not less than 30 μm and not more than 480 μm.

  The fluid flow path 24 has a groove shape and is provided on one main surface of the first porous layer 22. The fluid flow path 24 is configured by a recess provided on the main surface of the first porous layer 22. The fluid flow path 24 is disposed on the separator 2 side and functions as a fuel gas flow path. A fuel gas such as hydrogen gas is distributed from a manifold for fuel supply (not shown) to the fluid flow path 24, and passes through the first porous layer 22 and the second porous layer 26 from the fluid flow path 24 to the membrane electrode. It is supplied to the anode catalyst layer 14 of the joined body 10. The dimensions of the fluid channel 24 are, for example, a depth of 500 μm to 1000 μm, a width of 500 μm to 1000 μm, and a distance between adjacent fluid channels 24 of 500 μm to 1000 μm. In the present embodiment, five fluid flow paths 24 are provided, but the number is not particularly limited, and may be appropriately set according to the size of the anode gas diffusion layer 20 and the fluid flow path 24. Can do.

  The second porous layer 26 is disposed on the other main surface side of the first porous layer 22, that is, on the main surface side on the anode catalyst layer 14 side. The second porous layer 26 contains a plurality of conductive particles and a binder resin that binds the conductive particles. In FIG. 3, the conductive particles and the binder resin are not drawn separately, and a state where both are mixed is illustrated.

As the conductive particles, for example, carbon particles such as carbon black, artificial graphite, natural graphite, and expanded graphite, metal particles, and the like can be used. The average particle diameter of the conductive particles is, for example, 0.01 μm or more and 50 μm or less for primary particles. Binder resins include PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), ETFE (tetrafluoroethylene / ethylene copolymer). Fluorine resin such as (polymer) can be used. The melt viscosity of PTFE is about 1 × 10 ¹⁰ Pa · s at a molding temperature of 380 ° C. The melt viscosity of PFA is 4000 to 30000 Pa · s at a molding temperature of 360 ° C. The melt viscosity of FEP is 7000-50000 Pa · s at a molding temperature of 380 ° C. The melt viscosity of ETFE is about 2000 at a molding temperature of 300 ° C.

  The 2nd porous layer 26 is comprised with the material which has electroconductive particle and binder resin as a main component. The total mass of the conductive particles and the binder resin with respect to the total mass of the second porous layer 26 is 50% by mass or more, preferably 80% by mass or more. By making the total mass 50% by mass or more, the desired current collecting performance can be more reliably imparted to the fuel cell 1. In addition, by providing the second porous layer 26, the possibility that the anode catalyst layer 14 is damaged by the conductive fibers 28 in the first porous layer 22 can be suppressed, and the power generation efficiency of the fuel cell 1 is reduced. Can be suppressed. The thickness of the second porous layer 26 is, for example, not less than 20 μm and not more than 200 μm.

  The content of the conductive fiber 28 in the second porous layer 26 is smaller than the content in the first porous layer 22. For example, in the second porous layer 26, the occupied area ratio of the conductive fibers 28 per unit area in the cross section is smaller than the occupied area ratio in the cross section of the first porous layer 22. The occupied area ratio of the conductive fibers 28 in the first porous layer 22 is, for example, 50% or more and 95% or less, and the occupied area ratio of the conductive fibers 28 in the second porous layer 26 is, for example, 0% or more and 50%. Is less than. Since the occupied area ratio of the conductive fibers 28 in the second porous layer 26 is smaller than the occupied area ratio of the conductive fibers 28 in the first porous layer 22, the first porous layer 22 is the second porous layer. Air permeability is higher than 26. Thus, by combining the first porous layer 22 having a high air permeability and the second porous layer 26 having a low air permeability, the gas diffusibility of the anode gas diffusion layer 20 is improved, and the fuel cell 1 is provided. The current collecting performance can be improved.

  The occupation area ratio of the conductive fibers 28 can be obtained as follows. That is, first, a cross section of the first porous layer 22 is photographed using a scanning electron microscope (SEM). Then, in the obtained SEM image, the area of the conductive fiber 28 in a predetermined measurement region on the cross section is measured. The area of the conductive fiber 28 is measured by detecting the fiber by image processing and calculating the area of the fiber on the cross section. Then, the ratio of the area of the conductive fiber 28 to the area of the measurement region is calculated, and the occupation area ratio per unit area of the conductive fiber 28 is obtained. The magnification of the SEM image is, for example, 100 times, and the size of the measurement region in the SEM image photographed at this magnification is 1000 μm × 1000 μm.

  Further, the first porous layer 22 is conductive particles derived from the second porous layer 26 and does not contain conductive particles discontinuous with the second porous layer 26. For this reason, the pores of the first porous layer 22 are not blocked by the conductive particles derived from the second porous layer 26, and high gas diffusibility can be imparted to the first porous layer 22. . Further, the contact resistance at the interface between the first porous layer 22 and the second porous layer 26 can be reduced, and high conductivity of the anode gas diffusion layer 20 can be ensured.

  As shown in FIGS. 1 and 2, the cathode gas diffusion layer 40 is disposed on the cathode catalyst layer 16 side of the membrane electrode assembly 10. The cathode gas diffusion layer 40 includes a first porous layer 42, a fluid flow path 44, and a second porous layer 46. The thickness of the cathode gas diffusion layer 40 is, for example, not less than 50 μm and not more than 500 μm.

  As shown in FIG. 3, the first porous layer 42 contains a plurality of conductive fibers 48 having a length of 30 μm or more and a thermoplastic resin 50. Examples of the conductive fiber 48 and the thermoplastic resin 50 include the same ones as the conductive fiber 28 and the thermoplastic resin 30 included in the anode gas diffusion layer 20. The composition and dimensions of the first porous layer 42 are the same as those of the first porous layer 22.

  The fluid flow path 44 has a groove shape and is provided on one main surface of the first porous layer 42. The fluid flow path 44 is configured by a recess provided on the main surface of the first porous layer 42. The fluid channel 44 functions as a channel for oxidizing gas. Oxidant gas such as air is distributed from the manifold (not shown) for supplying oxidant to the fluid flow path 44, passes through the first porous layer 42 and the second porous layer 46 from the fluid flow path 44, and the membrane It is supplied to the cathode catalyst layer 16 of the electrode assembly 10. The fluid flow path 44 also functions as a drainage path for water generated in the cathode catalyst layer 16. The dimensions of the fluid channel 44 are the same as those of the fluid channel 24. In the present embodiment, five fluid flow paths 44 are provided, but the number is not particularly limited, and may be set as appropriate according to the size of the cathode gas diffusion layer 40, the fluid flow path 44, and the like. Can do.

  The second porous layer 46 is disposed on the other main surface side of the first porous layer 42, that is, on the main surface side on the cathode catalyst layer 16 side. The second porous layer 46 contains a plurality of conductive particles and a binder resin that binds the conductive particles. As the conductive particles and the binder resin, the same materials as those used for the second porous layer 26 can be used. The composition and dimensions of the second porous layer 46 are the same as those of the second porous layer 26.

  Since the cathode gas diffusion layer 40 has the second porous layer 46, the cathode gas diffusion layer 40 can be provided with a desired current collecting performance more reliably, and the cathode catalyst layer 16 is formed by the conductive fibers 48. The risk of damage can be suppressed. Further, the first porous layer 42 efficiently causes the water generated in the cathode catalyst layer 16 by the electrochemical reaction or the water moved from the electrolyte membrane 12 to the cathode catalyst layer 16 by the second porous layer 46 by capillary action. Or can be pumped into the fluid flow path 44. The pumped water is discharged by the oxidant gas flowing through the first porous layer 42 and the fluid flow path 44. Thereby, generation | occurrence | production of the flooding phenomenon can be suppressed more reliably.

  As in the case of the anode gas diffusion layer 20, the second porous layer 46 has an occupation area ratio of the conductive fibers 48 per unit area in its cross section that is higher than the occupation area ratio in the cross section of the first porous layer 42. small. The first porous layer 42 has a higher air permeability than the second porous layer 46. Further, the first porous layer 42 is conductive particles derived from the second porous layer 46 and does not contain conductive particles discontinuous with the second porous layer 46.

  A structure in which the anode catalyst layer 14 and the anode gas diffusion layer 20 are stacked may be referred to as an anode, and a structure in which the cathode catalyst layer 16 and the cathode gas diffusion layer 40 are stacked may be referred to as a cathode.

In the polymer electrolyte fuel cell 1 described above, the following reaction occurs. That is, when hydrogen gas as a fuel gas is supplied to the anode catalyst layer 14 through the anode gas diffusion layer 20, a reaction represented by the following formula (1) occurs in the anode catalyst layer 14, and hydrogen is decomposed into protons and electrons. Is done. Protons move through the electrolyte membrane 12 toward the cathode catalyst layer 16 side. The electrons move to an external circuit (not shown) and flow into the cathode catalyst layer 16 from the external circuit. On the other hand, when air as an oxidant gas is supplied to the cathode catalyst layer 16 through the cathode gas diffusion layer 40, a reaction represented by the following formula (2) occurs in the cathode catalyst layer 16, and oxygen in the air is converted into protons and oxygen. It reacts with electrons to become water. As a result, electrons flow from the anode toward the cathode in the external circuit, and electric power can be taken out.
Anode catalyst layer 14: H ₂ → 2H ⁺ + 2e ⁻ (1)
Cathode catalyst layer 16: 2H ⁺ + (1/2) O ₂ + 2e ⁻ → H ₂ O (2)

(Manufacturing process of gas diffusion layer for fuel cells)
Then, the manufacturing method of the gas diffusion layer for fuel cells which concerns on embodiment is demonstrated. 4A to 4D are process cross-sectional views schematically showing a method for manufacturing a fuel cell gas diffusion layer according to an embodiment. Here, the manufacturing method of the fuel cell gas diffusion layer will be described by taking the anode gas diffusion layer 20 as an example.

  First, as shown in FIG. 4A, a first porous sheet 21 and a second porous sheet 25 are prepared. The first porous sheet 21 is a sheet containing a plurality of conductive fibers 28 (see FIG. 3) and a thermoplastic resin 30 (see FIG. 3). The second porous sheet 25 contains a plurality of conductive particles and a binder resin, and the occupied area ratio of the conductive fibers 28 is a sheet smaller than the occupied area ratio in the cross section of the first porous sheet 21.

  Next, as shown in FIG. 4B, the first porous sheet 21 and the second porous sheet 25 are overlapped and disposed between the first mold 70 and the second mold 72. The first porous sheet 21 is disposed on the first mold 70 side, and the second porous sheet 25 is disposed on the second mold 72 side. The first mold 70 is provided with a convex portion 74 corresponding to the shape of the fluid flow path 24. The surface of the second mold 72 facing the convex portion 74 is flat.

  Next, as shown in FIG. 4C, the first mold 70 and the second mold 72 are closed, and the first porous sheet 21 and the second porous sheet 25 are moved to a predetermined temperature and pressure. Heat and pressurize with Thereby, the thermoplastic resin 30 in the first porous sheet 21 is plastically deformed, and a groove-like fluid flow path 24 is formed on one main surface of the first porous sheet 21. When the thermoplastic resin 30 is PPS, the temperature and pressure at the time of molding are 10 MPa and 300 ° C. At the same time, the first porous sheet 21 and the second porous sheet 25 are pressure-bonded to each other. After a predetermined time has elapsed, the first mold 70 and the second mold 72 are opened.

  Through the above steps, as shown in FIG. 4D, the first porous layer 22 having the fluid flow path 24 on one main surface and the first main layer laminated on the other main surface of the first porous layer 22 are stacked. The anode gas diffusion layer 20 including the two porous layers 26 is obtained.

  As described above, the fuel cell gas diffusion layer of the present embodiment includes the first porous layer containing the conductive fibers and the thermoplastic resin, and the fluid provided on the main surface of the first porous layer. A flow path. In addition, the fuel cell gas diffusion layer includes a second porous layer that contains less or no conductive fiber than the first porous layer. Since the second porous layer has less conductive fiber content than the first porous layer, the first porous layer has higher air permeability.

  Thereby, gas can be diffused more reliably to the first porous layer, particularly to the convex portion between the two adjacent fluid flow paths and the lower portion thereof. Therefore, compared with the fuel cell gas diffusion layer made of only the material constituting the second porous layer, the gas can be uniformly diffused throughout the fuel cell gas diffusion layer. For this reason, the diffusion overvoltage can be reduced. Moreover, since the gas diffusibility of the first porous layer is high, the interval between two adjacent fluid flow paths can be increased while maintaining the desired gas diffusivity. Thereby, the contact area of a separator and the gas diffusion layer for fuel cells can be increased, and the current collection performance of a fuel cell can be improved. Moreover, the drainage property of the water produced | generated by the cathode catalyst layer is improved by the 2nd porous layer arrange | positioned between a 1st porous layer and a cathode catalyst layer. Therefore, a fuel cell having a high cell voltage in a high current density region can be obtained.

  Further, in the method for manufacturing the fuel cell gas diffusion layer according to the present embodiment, the first porous sheet is heated and pressurized to form a fluid flow path. For this reason, a fluid flow path can be formed more easily. Therefore, it is possible to simplify the manufacturing process of the fuel cell gas diffusion layer and thus the fuel cell. Furthermore, in the manufacturing method of the present embodiment, the second porous sheet is formed by laminating the second porous sheet on the first porous sheet. For this reason, a 1st porous layer is an electroconductive particle derived from a 2nd porous layer, Comprising: A 2nd porous layer does not contain a conductive particle discontinuous. Therefore, the first porous layer is kept in a highly gas diffusive state as compared with the case where the slurry of the conductive particles and the binder resin is spray-coated on the first porous sheet to form the second porous layer. be able to.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. Embodiments to which such modifications are added Can also be included in the scope of the present invention.

  In the above-described embodiment, both the anode gas diffusion layer 20 and the cathode gas diffusion layer 40 include the first porous layers 22 and 42, the fluid flow paths 24 and 44, and the second porous layers 26 and 46. It has a configuration. However, it is not particularly limited to this, and only one of the anode gas diffusion layer 20 and the cathode gas diffusion layer 40 may have the above-described configuration.

  In the embodiment described above, the step of forming the fluid flow path 24 and the step of laminating the second porous sheet 25 on the first porous sheet 21 are performed simultaneously. For this reason, compared with the case where both processes are implemented separately, the manufacturing process of the gas diffusion layer for fuel cells can be simplified. However, it is not particularly limited to this manufacturing process, and the step of laminating the second porous sheet 25 on the first porous sheet 21 may be before or after the step of forming the fluid flow path 24.

  When the step of laminating the second porous sheet 25 is performed after the step of forming the fluid flow path 24, only the first porous sheet 21 is first disposed between the first mold 70 and the second mold 72. The fluid flow path 24 is formed by press molding. Next, the first porous sheet 21 and the second porous sheet 25 provided with the fluid flow path 24 are overlapped and placed between the first mold 70 and the second mold 72, and press-molded. The second porous sheet 25 is laminated on the first porous sheet 21.

  When the step of laminating the second porous sheet 25 is performed before the step of forming the fluid flow path 24, the first porous sheet 21 and the second porous sheet 25 are first overlapped to form the first mold 70. And the second mold 72 are press-molded. At this time, the first mold 70 is a flat mold that does not have the convex portion 74. Thereby, the second porous sheet 25 is laminated on the first porous sheet 21. Next, the obtained laminate is placed between the first mold 70 and the second mold 72 and press-molded. At this time, the first mold 70 is a mold having a convex portion 74. Thereby, the fluid flow path 24 is formed in the first porous sheet 21.

  DESCRIPTION OF SYMBOLS 1 Fuel cell, 10 Membrane electrode assembly, 12 Electrolyte membrane, 14 Anode catalyst layer, 16 Cathode catalyst layer, 20 Anode gas diffusion layer, 22, 42 1st porous layer, 24, 44 Fluid flow path, 26, 46 1st 2 porous layers, 28, 48 conductive fibers, 30, 50 thermoplastic resin, 40 cathode gas diffusion layer.

Claims (8)

A plurality of conductive fibers having a length of 30 μm or more, and a porous layer having a melt viscosity of 1000 Pa · s or less and containing a thermoplastic resin that binds the conductive fibers;
A groove-like fluid flow path provided on one main surface of the porous layer;
A gas diffusion layer for a fuel cell, comprising: When the porous layer is a first porous layer,
A second porous layer disposed on the other main surface side of the first porous layer,
The second porous layer contains a plurality of conductive particles and a binder resin that binds the conductive particles, and the occupation area ratio of the conductive fibers per unit area in the cross section is the first porous layer. The gas diffusion layer for a fuel cell according to claim 1, wherein the gas diffusion layer is smaller than the occupied area ratio in the cross section of the mass layer. A first porous layer having a groove-like fluid flow path on one main surface;
A second porous layer disposed on the other main surface side of the first porous layer;
With
The first porous layer contains conductive fibers having a length of 30 μm or more,
The gas diffusion for a fuel cell, wherein the second porous layer has a smaller occupied area ratio of the conductive fibers per unit area in the cross section than the occupied area ratio in the cross section of the first porous layer. layer. The second porous layer contains a plurality of conductive particles and a binder resin that binds the conductive particles.
4. The fuel cell gas diffusion layer according to claim 2, wherein the first porous layer does not contain the conductive particles discontinuous with the second porous layer. 5.   The gas diffusion layer for a fuel cell according to any one of claims 2 to 4, wherein the first porous layer has a higher air permeability than the second porous layer. A membrane electrode assembly comprising an electrolyte membrane, an anode catalyst layer disposed on one surface side of the electrolyte membrane, and a cathode catalyst layer disposed on the other surface side of the electrolyte membrane;
An anode gas diffusion layer disposed on the anode catalyst layer side of the membrane electrode assembly;
A cathode gas diffusion layer disposed on the cathode catalyst layer side of the membrane electrode assembly,
6. The fuel cell according to claim 1, wherein at least one of the anode gas diffusion layer and the cathode gas diffusion layer includes the fuel cell gas diffusion layer according to claim 1. Preparing a porous sheet containing a plurality of conductive fibers having a length of 30 μm or more, and a melt viscosity of 1000 Pa · s or less and containing a thermoplastic resin that binds the conductive fibers;
Heating and pressurizing the porous sheet to form a groove-like fluid flow path on one main surface of the porous sheet; and
A method for producing a gas diffusion layer for a fuel cell, comprising: When the porous sheet is a first porous sheet,
Before, after or simultaneously with the step of forming the fluid flow path, further comprising the step of laminating the second porous sheet on the other main surface of the first porous sheet;
The second porous sheet contains a plurality of conductive particles and a binder resin that binds the conductive particles, and the occupied area ratio of the conductive fibers per unit area in the cross section is the first porous sheet. The manufacturing method of the gas diffusion layer for fuel cells of Claim 7 smaller than the said occupied area rate in the cross section of a quality sheet.