JP5614468B2 - Manufacturing method of gas diffusion electrode for fuel cell - Google Patents

Description

  The present invention relates to a method for producing a gas diffusion electrode used for a polymer electrolyte fuel cell.

  In a fuel cell, a fuel gas such as hydrogen gas and an oxidizing gas containing oxygen are electrochemically reacted through an electrolyte, and electric energy is directly taken out between electrodes provided on both surfaces of the electrolyte. In particular, a polymer electrolyte fuel cell using a polymer electrolyte has attracted attention as a power source for a mobile body because it has a low operating temperature and is easy to handle.

  In the polymer electrolyte fuel cell, a catalyst layer containing platinum or the like is provided on both surfaces of a hydrogen ion conductive solid polymer electrolyte membrane, and a gas diffusion layer having electron conductivity and air permeability is provided thereon. The catalyst layer and the gas diffusion layer serve as a fuel electrode (anode or negative electrode) and an oxidant electrode (cathode or positive electrode) (for example, Patent Document 1). Then, a fuel gas containing hydrogen and an oxidant gas containing oxygen are supplied to the fuel electrode and the oxidant electrode from gas supply grooves provided in the separator, respectively, and electricity is generated by the following electrochemical reaction.

[Fuel electrode reaction]: H ₂ → 2H ⁺ + 2e ⁻ (Formula 1)
[Oxidant electrode reaction]: 2H ⁺ + 2e ⁻ + 1 / 2O ₂ → H ₂ O (chemical formula 2)
During the power generation reaction of the fuel cell, the fuel gas and oxidant gas supplied from the separator channel pass through the gas diffusion layer to reach the catalyst layer, and the electrode reaction is promoted by the action of the catalyst. The gas diffusion layer has various functions such as a reaction gas supply path to the catalyst layer, a conductive path from the catalyst layer to the separator, moisture retention of the polymer electrolyte membrane, and discharge of excess generated water.

  Normally, carbon paper or carbon cloth is used for the gas diffusion layer, but the surface of the gas diffusion layer has fluff or unevenness of carbon fibers. Therefore, gas diffusion is caused by the clamping pressure when a fuel cell stack is formed by stacking a separator and a membrane electrode assembly (MEA) in which a solid polymer electrolyte membrane in which a catalyst layer is formed and a gas diffusion layer are joined. In order to avoid the fluff and unevenness of the layer from damaging the solid polymer electrolyte membrane, a technique for providing a protective adhesive layer between the catalyst layer and the gas diffusion layer is known (patent) Reference 1). This protective adhesive layer is composed of conductive carbon and a hydrogen ion conductive polymer electrolyte.

Japanese Patent Laying-Open No. 2005-216834 (page 6, FIG. 1)

  However, in the above conventional fuel cell structure, the protective adhesive layer is inferior in gas permeability to the gas diffusion layer. Therefore, if the protective adhesive layer is thickened with an emphasis on the protective function, the gas supply performance to the catalyst layer decreases. On the other hand, if the protective adhesive layer is thinned, the contact performance with the catalyst layer decreases and the contact resistance increases, or the function of protecting the catalyst layer from the fluff and irregularities of the gas diffusion layer is not sufficiently fulfilled. There was a point.

  The first invention provides a fuel comprising a first conductive porous layer having a first porosity and a second conductive porous layer having a second porosity lower than the first porosity. A method for producing a gas diffusion electrode for a battery, wherein a hydrophilic layer is made hydrophilic by immersing the porous layer in a hydrophilic treatment solution, and a conductive substance and polytetrafluoroethylene fine particles are added to the hydrophilic porous layer. A fuel cell gas comprising: a coating step of coating an ink slurry containing; and a heat treatment step of heat treating a porous layer coated with the conductive material and the polytetrafluoroethylene fine particles. It is a manufacturing method of a diffusion electrode.

  In addition, the second invention includes a first conductive porous layer having a first porosity and a second conductive porous layer having a second porosity lower than the first porosity. A fuel cell gas diffusion electrode manufacturing method, comprising: a first porous layer having a third porosity; and a second porous layer having a fourth porosity lower than the third porosity; Are laminated by thermocompression bonding to form a laminated porous layer, a hydrophilicizing step of hydrophilizing the laminated porous layer by immersing the laminated porous layer in a hydrophilization treatment solution, and the hydrophilicized laminate A fuel comprising: a coating step of coating an ink slurry containing a conductive substance on a porous layer; and a heat treatment step of heat-treating the laminated porous layer coated with the conductive substance. It is a manufacturing method of the gas diffusion electrode for batteries.

  Furthermore, the third invention includes a first conductive porous layer having a first porosity and a second conductive porous layer having a second porosity lower than the first porosity. A method for producing a gas diffusion electrode for a fuel cell, comprising: forming a conductive porous layer in which the first conductive porous layer and the second conductive porous layer are integrated; and And a step of heat bonding a gas diffusion layer base material to the first conductive porous layer of the porous porous layer.

  According to the first aspect of the present invention, a conductive porous layer having a relatively low porosity formed of a conductive material and polytetrafluoroethylene fine particles is formed on the surface of the porous layer, and a relatively low porosity. A conductive porous layer with a relatively high porosity is formed by providing conductivity to the inside of the porous layer with a high porosity, and a simple process avoids a decrease in gas supply performance to the catalyst layer as much as possible. However, there is an effect that it is possible to manufacture a gas diffusion electrode for a fuel cell that can sufficiently protect the catalyst layer from fluff and unevenness of the gas diffusion layer.

  According to the second aspect of the present invention, a fuel cell gas in which a conductive porous layer having a desired porosity and a relatively high porosity is integrated with a conductive porous layer having a relatively low porosity. There is an effect that a diffusion electrode can be manufactured.

  According to the third invention, since the gas diffusion layer base material is heat-bonded to the first conductive porous layer having a relatively high porosity, the adhesion between the conductive porous layer and the gas diffusion layer base material is improved. Can be improved.

It is a schematic cross section explaining the structure of the single cell using the gas diffusion electrode for fuel cells which concerns on this invention. It is an expansion schematic cross section explaining Example 1 of the gas diffusion electrode for fuel cells which concerns on this invention. It is an expansion schematic cross section explaining Example 2 of the gas diffusion electrode for fuel cells which concerns on this invention. It is a manufacturing-process figure explaining Example 1 of the manufacturing method of the electroconductive porous layer from which the at least 2 type of porosity which comprises the gas diffusion electrode for fuel cells which concerns on this invention differs. It is a manufacturing process figure explaining Example 2 of the manufacturing method of the electroconductive porous layer from which the porosity which comprises at least 2 types of porosity which comprises the gas diffusion electrode for fuel cells which concerns on this invention is different.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

[Example 1]
FIG. 1 is a schematic cross-sectional view of a polymer electrolyte fuel cell using Example 1 of a gas diffusion electrode for a fuel cell according to the present invention. In the figure, a unit cell 1 of a solid molecular fuel cell comprises an oxidant electrode (cathode) 3 and a fuel electrode (anode) 4 on both sides of a polymer electrolyte membrane 2, and these polymer electrolyte membrane 2 and oxidant. The electrode 3 and the fuel electrode 4 constitute a membrane electrode assembly (MEA) 5.

  The oxidant electrode 3 includes a catalyst layer 6 formed on one surface of the polymer electrolyte membrane 2, a conductive porous layer 7 having a relatively low porosity, and a conductive porous having a relatively high porosity. It has a layer 8 and a gas diffusion layer substrate 9. Similarly, the fuel electrode 4 includes a catalyst layer 10 formed on the other surface of the polymer electrolyte membrane 2, a conductive porous layer 11 having a relatively low porosity, and a conductivity having a relatively high porosity. A porous layer 12 and a gas diffusion layer substrate 13 are provided.

  An oxidant electrode side separator 14 is disposed on the back surface of the gas diffusion layer base material 9 of the oxidant electrode 3. A fuel electrode-side separator 16 is disposed on the back surface of the gas diffusion layer base material 13 of the fuel electrode 4. The oxidant electrode side separator 14 is provided with an oxidant gas flow path 15. The fuel electrode side separator 16 is provided with a fuel gas flow path 17. Further, seal members 18 are provided between the polymer electrolyte membrane 2 and the oxidant electrode side separator 14 and between the polymer electrolyte membrane 2 and the fuel electrode side separator 16, respectively. Is prevented from leaking from the side surface of the single cell 1.

  The polymer electrolyte membrane 2 is a hydrogen ion conductive polymer membrane such as a perfluorosulfonic acid group polymer or an aromatic hydrocarbon polymer. The catalyst layers 6 and 10 are formed of a catalyst in which platinum fine particles are supported on carbon particles and an ionomer (which may be a perfluorosulfonic acid group polymer).

  The conductive porous layers 7 and 11 having a relatively low porosity are in contact with the catalyst layers 6 and 10, and the conductive porous layers 8 and 12 having a relatively high porosity are used as the gas diffusion layer base materials 9 and 13. Is in contact with

  The conductive porous layers 7 and 11 having a relatively low porosity and the conductive porous layers 8 and 12 having a relatively high porosity have, for example, a three-dimensional porous structure having a relatively high porosity. It is obtained by heat-treating a polytetrafluoroethylene (PTFE) film coated with ink containing carbon particles as a conductive substance and PTFE particles as a water repellent material.

  Thus, the material PTFE film becomes the conductive porous layer 8 having a relatively high porosity, and the conductive porous layer 7 having a relatively low porosity is formed on the surface thereof. Similarly, the conductive porous layer 11 having a relatively low porosity and the conductive porous layer 12 having a relatively high porosity are formed.

  For the gas diffusion layer base materials 9 and 13, carbon paper or carbon cloth is used. The separators 14 and 16 are made of carbon or a metal plate subjected to corrosion resistance treatment.

  In an actual fuel cell, a plurality of single cells 1 in FIG. 1 are stacked to form a stacked body, and end plates for fixing and current extraction are provided at both ends of the stacked body. Then, the end plates are tightened with a predetermined tightening force so that the contact resistance between the constituent elements in each cell and the cells is reduced. When the fuel cell stack is configured by tightening both end plates in this way, the unevenness and fluff on the surface of the carbon paper and carbon cloth constituting the gas diffusion layer base materials 9 and 13 13 is absorbed by the conductive porous layers 8 and 12 having a relatively high porosity in contact with the gas diffusion layer base material 9, and the gas diffusion layer base materials 9 and 13 are in close contact with the conductive porous layers 8 and 12 having a relatively high porosity. The contact resistance can be lowered while ensuring gas permeability.

  Here, the thickness of the conductive porous layers 8 and 12 having a relatively high porosity is desirably 15 [μm] or more and 100 [μm] or less. When the thickness of the conductive porous layers 8 and 12 having a relatively high porosity is less than 15 [μm], the surface roughness such as surface irregularities and fluff of the gas diffusion layer base materials 9 and 13 cannot be absorbed. The carbon fibers may pierce the catalyst layers 6 and 10 and the polymer electrolyte membrane 2 to cause an electrical short circuit or a gas cross leak between both electrodes. Further, the rigidity in the direction perpendicular to the surface of the cell is lowered, and the durability of the gas diffusion electrode for a fuel cell is lowered. On the other hand, when the thickness exceeds 100 [μm], the gas permeability decreases, the reaction gas supplied to the catalyst layer at the time of large output becomes insufficient, and the power generation output performance decreases.

  The catalyst layers 6 and 10 having relatively flat surfaces are in contact with the conductive porous layers 7 and 11 having relatively low porosity, respectively. The conductive porous layers 7 and 11 having a relatively low porosity are formed thinner than the conductive porous layers 8 and 12 having a relatively high porosity. For example, the thickness of the conductive porous layers 7 and 11 having a relatively low porosity is desirably 2 [μm] or more and 50 [μm] or less. If the thickness of the conductive porous layers 7 and 11 having a relatively low porosity is less than 2 [μm], the surface irregularities of the catalyst layers 6 and 10 cannot be absorbed, and the conductivity having a relatively low porosity. The contact resistance between the porous layers 7 and 11 and the catalyst layers 6 and 10 increases. On the contrary, if the thickness of the conductive porous layers 7 and 11 having relatively low porosity exceeds 50 [μm], the gas permeability decreases, and the reaction gas supplied to the catalyst layer at the time of large output becomes insufficient. Power generation output performance is reduced.

  Next, an enlarged schematic cross-sectional view of the oxidant electrode 3 in FIG. 2 will be described. The structure of the fuel electrode 4 is the same. In FIG. 2, the three-dimensional porous PTFE membrane (23, 24) having a relatively high porosity is composed of PTFE particles 23 and bridging portions 24 that connect the PTFE particles 23 to each other. The PTFE membranes (23, 24) are coated with ink containing carbon particles 21 as conductive materials and PTFE particles 22, and are dried and fired. As a result, the carbon particles 21 and the PTFE particles 22 that are ink components enter the PTFE membrane (23, 24) to form the conductive porous layer 8 having a relatively high porosity, and the surface (in FIG. 2). On the lower surface), a high-density layer composed of carbon particles 21 and PTFE particles 22 is formed, and this becomes the conductive porous layer 7 having a relatively low porosity.

  Next, referring to the manufacturing process diagram of FIG. 4, a method for manufacturing the conductive porous layer 7 having a relatively low porosity and the conductive porous layer 8 having a relatively high porosity in the first embodiment. Will be explained. Note that the conductive porous layer 11 having a relatively low porosity and the conductive porous layer 12 having a relatively high porosity constituting the fuel electrode 4 are also manufactured by the same manufacturing method.

  The outline of this production method is as follows: (1) a hydrophilic step for hydrophilizing the porous PTFE membrane, (2) an ink coating step for penetrating and adhering ink containing carbon and PTFE particles to the hydrophilic PTFE membrane, (3) A drying step for drying the ink, and (4) a baking step for fixing the ink particles and the PTFE particles to the PTFE film by heat treatment.

  In step S1 of FIG. 4, a porous PTFE membrane having a relatively high porosity is first prepared as a porous layer having a relatively high porosity. This porous PTFE membrane is provided with products adjusted to various thicknesses and porosity (ratio of pores or voids relative to the total volume) by controlling, for example, the uniaxial or biaxial distraction conditions (For example, trade name: Poaflon membrane, manufactured by Sumitomo Electric Fine Polymer Co., Ltd.). The porous PTFE membrane used for the material of the conductive porous layers 8 and 12 having a relatively high porosity in the present invention has a thickness of 15 to 100 [μm], a pore diameter of 1 to 30 [μm], and a porosity of Is preferably 70% or more.

  Next, in step S2, a hydrophilic treatment solution for improving ink adhesion of the porous PTFE film is prepared. As a hydrophilic treatment solution, 4 g of a nonionic surfactant (trade name: Triton X-100, manufactured by Dow Chemical Co.) is mixed with 200 g of ethanol.

  Next, in step S3, the porous PTFE membrane is hydrophilized. For example, the porous PTFE membrane is horizontally fixed with a frame-shaped jig, and the hydrophilization solution is poured into the jig and immersed therein.

  Next, in step S4, an ink slurry containing carbon particles and PTFE particles is prepared. The ink slurry contains a surfactant, pure water, carbon particles, and PTFE particles as main components. The ink slurry was prepared by mixing carbon black (Denka) with a solution obtained by previously mixing and stirring 3 g of a nonionic surfactant (trade name: Triton Triton X-100, manufactured by Dow Chemical Co., Ltd.) and 200 g of pure water as a surfactant. 20 g of carbon particles obtained by pulverizing acetylene black AB-6) manufactured by a company to an average particle size of about 1 [μm] with a jet mill are added and stirred. In order to further add PTFE particles, 30 g of Polyflon D-1E (solid content: 64%) manufactured by Daikin Industries, Ltd. was added and mixed as a PTFE dispersion, and stirred to obtain an ink slurry.

  Next, in step S5, the ink slurry is brought into contact with the porous PTFE membrane fixed on the jig and subjected to the hydrophilic treatment, and suctioned under reduced pressure from under the porous PTFE membrane. Thereby, the hydrophilization treatment solution in the porous PTFE membrane is sucked out from the inside of the porous PTFE membrane, and the ink slurry penetrates into the porous PTFE membrane.

  Next, in step S6, the porous PTFE film coated with the ink slurry is placed in a drying furnace, and water in the ink is evaporated and dried under drying conditions of a temperature of 50 to 120 [° C.] and a time of 5 to 20 [min].

  Next, in step S7, the porous PTFE film from which the ink slurry has been dried is placed in a baking furnace, and baking is performed under baking conditions of a temperature of 250 to 350 [° C.] and a time of 5 to 20 [min] to remove the surfactant. In addition, by fixing the carbon particles and PTFE particles to the inside and the surface of the porous PTFE membrane, the conductive porous layer having a relatively high porosity and the conductivity having a relatively low porosity formed on the surface thereof. A conductive porous layer in which the porous layer is integrated is obtained.

  Thereafter, in step S8, the outer periphery of the conductive porous layer is trimmed to a predetermined dimension to complete the manufacture of the conductive porous layer. The finished thickness of the relatively high porosity conductive porous layers 8 and 12 of the conductive porous layer manufactured by the above manufacturing process is preferably 15 [μm] or more and 100 [μm] or less. The finished thickness of the relatively low porosity conductive porous layers 7 and 11 is preferably 2 [μm] or more and 50 [μm] or less.

  A gas diffusion layer for a fuel cell is formed by stacking and joining the gas diffusion layer base material 9 (13) to the conductive porous layer 8 (12) side having a relatively high porosity of the conductive porous layer thus obtained. A layer is obtained. This heat bonding can be performed by, for example, a hot press machine under conditions of a temperature of 150 to 200 [° C.], a pressure of 0.5 to 4 [MPa], and a time of 0.5 to 10 [min].

  According to the present embodiment described above, between the gas diffusion layer base materials 9 and 13 and the catalyst layers 6 and 10, the conductive porous layers 8 and 12 having a relatively high porosity, and the relatively empty By providing the conductive porous layers 7 and 11 having a low porosity, the surface unevenness of the gas diffusion layer substrate can be reduced while ensuring the contact area between the catalyst layer and the gas diffusion layer substrate and reducing the contact resistance. There is an effect that gas diffusibility can be secured while avoiding local pressure on the catalyst layer and the polymer electrolyte membrane by the fluff or perforation of the catalyst layer and the polymer electrolyte membrane.

  1, the gas diffusion layer bases 9 and 13 are removed, and the conductive porous layers 8 and 12 having a relatively high porosity are in direct contact with the separators 14 and 16 in the present invention. Is valid. That is, the conductive porous layers 8 and 12 having a relatively high porosity absorb the pressure distribution due to the unevenness of the gas flow paths 15 and 17 formed in the separators 14 and 16, and the conductivity having a relatively low porosity. The porous porous layers 7 and 11 can make good contact with the catalyst layers 6 and 10.

  Further, according to the present example, the thickness of the conductive porous layers 7 and 11 having a relatively low porosity is made thinner than the thickness of the conductive porous layers 8 and 12 having a relatively high porosity. Therefore, there is an effect that the contact resistance with the catalyst layer can be sufficiently reduced while suppressing the decrease in gas diffusibility as much as possible.

  In addition, according to the present embodiment, the conductive porous layers 7 and 11 having a relatively low porosity include carbon as at least a conductive material and PTFE particles as a water repellent material, so that they are inexpensive and durable. There is an effect that it is possible to provide a gas diffusion electrode.

  Further, according to this embodiment, the fuel cell having a gas diffusion layer including the first conductive porous layer having a relatively high porosity and the second conductive porous layer having a relatively low porosity. A method for producing a gas diffusion electrode, wherein a porous layer having a relatively high porosity is hydrophilized with a hydrophilization treatment liquid, and a conductive substance and polytetrafluoroethylene are added to the hydrophilic layer. The method includes a coating step of coating an ink slurry containing fine particles, and a heat treatment step of heat-treating the porous layer to which the conductive substance and the polytetrafluoroethylene fine particles are adhered, so that the porosity is relatively high. There is an effect that it is possible to easily form a thin film structure having a uniform thickness and a relatively low porosity on a film structure having a high thickness.

  In addition, according to the present example, the gas diffusion layer base material is heat-bonded to the first conductive porous layer having a relatively high porosity, and thus the adhesion between the conductive porous layer and the gas diffusion layer base material. There is an effect that can be improved.

[Example 2]
Next, a second embodiment of the gas diffusion electrode for a fuel cell according to the present invention will be described with reference to FIGS. In addition, the structure of the single cell 1 of the fuel cell using the gas diffusion electrode for a fuel cell of the present embodiment is the same as that of the first embodiment shown in FIG.

  FIG. 3 is an enlarged schematic cross-sectional view of the oxidizer electrode 3 in the second embodiment. The structure of the fuel electrode 4 is the same. In FIG. 3, the three-dimensional porous PTFE membrane (34, 35) having a relatively high porosity is composed of PTFE particles 34 and bridging portions 35 that connect the PTFE particles 34 to each other. The three-dimensional porous PTFE membrane (32, 33) having a relatively low porosity is composed of PTFE particles 32 and a bridging portion 33 that connects the PTFE particles 32 to each other. After the PTFE film (34, 35) and the PTFE film (32, 33) are thermocompression bonded, an ink slurry containing the carbon particles 31 is applied and heat-treated, thereby conducting a relatively high porosity. The porous layer 8 and the conductive porous layer 7 having a relatively low porosity are formed.

  Next, referring to the manufacturing process diagram of FIG. 5, the manufacturing method of the conductive porous layer 7 having a relatively low porosity and the conductive porous layer 8 having a relatively high porosity in the second embodiment. Will be explained. Note that the conductive porous layer 11 having a relatively low porosity and the conductive porous layer 12 having a relatively high porosity constituting the fuel electrode 4 are also manufactured by the same manufacturing method.

  The outline of this production method is as follows: (1) A porous PTFE membrane having layers with different porosity by thermocompression bonding of a porous PTFE membrane having a relatively high porosity and a porous PTFE membrane having a relatively low porosity. (2) a hydrophilization process for hydrophilizing the thermo-bonded porous PTFE membrane, and (3) an ink coating that permeates and adheres ink containing carbon particles to the hydrophilized PTFE membrane. An adhesion process, (4) a drying process for drying the ink, and (5) a baking process for fixing the ink particles to the PTFE film by heat treatment.

  In step S10 of FIG. 5, a PTFE membrane having a three-dimensional porous structure having a relatively high porosity is prepared. In step S11, a three-dimensional porous PTFE membrane having a relatively low porosity is prepared. These porous PTFE membranes, for example, have products adjusted to various thicknesses and porosity (ratio of pores or voids to the total volume) by controlling the distraction conditions in uniaxial or biaxial distraction. (For example, trade name: Porefluoron membrane, manufactured by Sumitomo Electric Fine Polymer Co., Ltd.).

  In step S12, the three-dimensional porous structure PTFE membrane having a relatively high porosity and the three-dimensional porous structure PTFE membrane having a relatively low porosity are overlapped and set in a hot press machine. Heat-pressure bonding is performed under press conditions of 150 to 200 [° C.], pressure of 0.5 to 4 [MPa], and time of 0.5 to 10 [min] to obtain a porous PTFE membrane.

  In step S13, a hydrophilic treatment solution for improving the ink adhesion of the porous PTFE membrane is prepared. As a hydrophilic treatment solution, 4 g of a nonionic surfactant (trade name: Triton X-100, manufactured by Dow Chemical Co.) is mixed with 200 g of ethanol.

  In step S14, the porous PTFE membrane is hydrophilized. For example, the porous PTFE membrane is horizontally fixed with a frame-shaped jig, and the hydrophilization solution is poured into the jig and immersed therein.

  In step S15, an ink slurry containing carbon particles is prepared. The ink slurry contains a surfactant, pure water, and carbon particles as main components. The ink slurry was prepared by mixing carbon black (Denka) with a solution obtained by previously mixing and stirring 3 g of a nonionic surfactant (trade name: Triton Triton X-100, manufactured by Dow Chemical Co., Ltd.) and 200 g of pure water as a surfactant. 20 g of carbon particles obtained by pulverizing acetylene black AB-6) manufactured by a company to an average particle size of about 1 [μm] with a jet mill are added and stirred.

  In step S16, the ink slurry is brought into contact with the porous PTFE film fixed to the jig and subjected to the hydrophilic treatment, and suctioned under reduced pressure from under the porous PTFE film. Thereby, the hydrophilization treatment solution in the porous PTFE membrane is sucked out from the inside of the porous PTFE membrane, and the ink slurry penetrates into the porous PTFE membrane.

  Next, in step S17, the porous PTFE film coated with the ink slurry is put in a drying furnace, and water in the ink is evaporated and dried under drying conditions of a temperature of 50 to 120 [° C.] and a time of 5 to 20 [min].

  Next, in step S18, the porous PTFE membrane from which the ink slurry has been dried is placed in a baking furnace, and baking is performed under baking conditions of a temperature of 250 to 350 [° C.] and a time of 5 to 20 [min] to remove the surfactant. In addition, by fixing the carbon particles inside the porous PTFE membrane, the conductive porous layer in which the conductive porous layer having a relatively high porosity and the conductive porous layer having a relatively low porosity are integrated. A layer is obtained.

  Thereafter, in step S19, the outer periphery of the conductive porous layer is trimmed to a predetermined dimension, thereby completing the manufacture of the conductive porous layer. The finished thickness of the relatively high porosity conductive porous layers 8 and 12 of the conductive porous layer manufactured by the above manufacturing process is preferably 15 [μm] or more and 100 [μm] or less. The finished thickness of the relatively low porosity conductive porous layers 7 and 11 is preferably 2 [μm] or more and 50 [μm] or less.

  A gas diffusion layer for a fuel cell is formed by stacking and joining the gas diffusion layer base material 9 (13) to the conductive porous layer 8 (12) side having a relatively high porosity of the conductive porous layer thus obtained. A layer is obtained. This heat bonding can be performed by, for example, a hot press machine under conditions of a temperature of 150 to 200 [° C.], a pressure of 0.5 to 4 [MPa], and a time of 0.5 to 10 [min].

  According to the present embodiment described above, between the gas diffusion layer base materials 9 and 13 and the catalyst layers 6 and 10, the conductive porous layers 8 and 12 having a relatively high porosity, and the relatively empty By providing the conductive porous layers 7 and 11 having a low porosity, the surface unevenness of the gas diffusion layer substrate can be reduced while ensuring the contact area between the catalyst layer and the gas diffusion layer substrate and reducing the contact resistance. There is an effect that gas diffusibility can be secured while avoiding local pressure on the catalyst layer and the polymer electrolyte membrane by the fluff or perforation of the catalyst layer and the polymer electrolyte membrane.

  1, the gas diffusion layer bases 9 and 13 are removed, and the conductive porous layers 8 and 12 having a relatively high porosity are in direct contact with the separators 14 and 16 in the present invention. Is valid. That is, the conductive porous layers 8 and 12 having a relatively high porosity absorb the pressure distribution due to the unevenness of the gas flow paths 15 and 17 formed in the separators 14 and 16, and the conductivity having a relatively low porosity. The porous porous layers 7 and 11 can make good contact with the catalyst layers 6 and 10.

  Further, according to the present example, the thickness of the conductive porous layers 7 and 11 having a relatively low porosity is made thinner than the thickness of the conductive porous layers 8 and 12 having a relatively high porosity. Therefore, there is an effect that the contact resistance with the catalyst layer can be sufficiently reduced while suppressing the gas diffusibility reduction margin as much as possible.

  In addition, according to the present embodiment, the conductive porous layers 7 and 11 having a relatively low porosity include carbon as at least a conductive material and PTFE particles as a water repellent material, so that they are inexpensive and durable. There is an effect that it is possible to provide a gas diffusion electrode.

  Further, according to this example, the porosity of each of the porous layer having a relatively high porosity and the porous layer having a relatively low porosity is optimally selected, and after joining them, the carbon particles are bonded. Since it adheres, there exists an effect that the porosity of each of the conductive porous layer having a relatively high porosity and the conductive porous layer having a relatively low porosity can be set optimally.

DESCRIPTION OF SYMBOLS 1 Single cell 2 Polymer electrolyte membrane 3 Oxidant electrode 4 Fuel electrode 5 MEA (membrane electrode assembly)
6,10 Catalyst layer 7,11 Low porosity conductive porous layer 8,12 High porosity conductive porous layer 9,13 Gas diffusion layer base material 14,16 Separator 15 Oxidant gas flow path 17 Fuel gas flow path 18 Seal member

Claims (3)

A first conductive porous layer having a first porosity and a first thickness; a second porosity lower than the first porosity; and a second thickness less than the first thickness. A conductive porous layer comprising a second conductive porous layer, and disposed between the gas diffusion layer and the catalyst layer, the reaction gas supplied from the gas diffusion layer is transferred to the surface of the solid polymer electrolyte membrane A gas diffusion electrode for a fuel cell that is supplied to the catalyst layer formed on the electrode and serves as an electrode for current extraction,
A hydrophilization step of hydrophilizing by immersing the porous layer in a hydrophilization solution;
An application step of applying an ink slurry containing a conductive substance and polytetrafluoroethylene fine particles to the hydrophilic porous layer;
A heat treatment step of heat treating the porous layer coated with the conductive material and the polytetrafluoroethylene fine particles;
The fuel cell , wherein the porous layer is a first conductive porous layer, and a second conductive porous layer is formed on the surface of the first conductive porous layer. Method for manufacturing gas diffusion electrode. A first conductive porous layer having a first porosity and a first thickness; a second porosity lower than the first porosity; and a second thickness less than the first thickness. A conductive porous layer comprising a second conductive porous layer, and disposed between the gas diffusion layer and the catalyst layer, the reaction gas supplied from the gas diffusion layer is transferred to the surface of the solid polymer electrolyte membrane A gas diffusion electrode for a fuel cell that is supplied to the catalyst layer formed on the electrode and serves as an electrode for current extraction,
A laminated porous body in which a first porous layer having a third porosity and a second porous layer having a fourth porosity lower than the third porosity are laminated by thermocompression bonding. A thermocompression bonding step to form a layer;
A hydrophilization step of immersing the laminated porous layer in a hydrophilization treatment solution to make it hydrophilic;
An application step of applying an ink slurry containing a conductive substance to the hydrophilic porous layer;
A heat treatment step of heat treating the laminated porous layer coated with the conductive material;
By providing the laminated porous layer as a first conductive porous layer, a fuel is characterized in that a second conductive porous layer is formed on the surface of the first conductive porous layer. A method for producing a gas diffusion electrode for a battery. A first conductive porous layer having a first porosity and a first thickness; a second porosity lower than the first porosity; and a second thickness less than the first thickness. A conductive porous layer comprising a second conductive porous layer, and disposed between the gas diffusion layer and the catalyst layer, the reaction gas supplied from the gas diffusion layer is transferred to the surface of the solid polymer electrolyte membrane A gas diffusion electrode for a fuel cell that is supplied to the catalyst layer formed on the electrode and serves as an electrode for current extraction,
By forming the second conductive porous layer on the surface of the first conductive porous layer,
Forming a conductive porous layer in which the first conductive porous layer and the second conductive porous layer are integrated;
Heat bonding a gas diffusion layer substrate to the first conductive porous layer of the conductive porous layer;
A method for producing a gas diffusion electrode for a fuel cell, comprising: