JP5426830B2 - Gas diffusion electrode for polymer electrolyte fuel cell, membrane-electrode assembly using the same, method for producing the same, and polymer electrolyte fuel cell using the same - Google Patents

Description

  The present invention relates to a gas diffusion electrode for a polymer electrolyte fuel cell, a membrane-electrode assembly using the same, a method for producing the same, and a polymer electrolyte fuel cell using the same.

  A fuel cell is a power generation system that continuously supplies fuel and an oxidant, and extracts chemical energy as electric power when the fuel and an oxidant react with each other. Fuel cells using this electrochemical power generation method use the reverse reaction of water electrolysis, that is, a mechanism in which hydrogen and oxygen are combined to produce electrons and water, and have high efficiency and excellent environmental characteristics. In recent years it has been in the spotlight.

  Fuel cells are classified into phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, alkaline fuel cells and solid polymer fuel cells depending on the type of electrolyte. In recent years, solid polymer fuel cells that have advantages such as startup at room temperature and extremely short startup time have attracted attention. The basic structure of a single cell constituting this polymer electrolyte fuel cell is such that a gas diffusion electrode having a catalyst layer is bonded to both sides of a polymer electrolyte membrane, and separators are arranged on both outer surfaces thereof.

  In such a polymer electrolyte fuel cell, first, hydrogen supplied to the fuel electrode side is guided to the gas diffusion electrode through the gas flow path in the separator. Next, the hydrogen is uniformly diffused by the gas diffusion electrode and then led to the catalyst layer on the fuel electrode side, where it is separated into hydrogen ions and electrons by a catalyst such as platinum. Then, the hydrogen ions are guided through the electrolyte membrane to the catalyst layer in the oxygen electrode on the opposite side across the electrolyte membrane. On the other hand, electrons generated on the fuel electrode side are led to a gas diffusion layer on the oxygen electrode side through a circuit having a load, and further to a catalyst layer on the oxygen side. At the same time, oxygen introduced from the separator on the oxygen electrode side passes through the gas diffusion electrode on the oxygen electrode side and reaches the catalyst layer on the oxygen electrode side. Then, water is generated from oxygen, electrons, and hydrogen ions to complete the power generation cycle. In addition, examples of the fuel other than hydrogen used in the polymer electrolyte fuel cell include alcohols such as methanol and ethanol, and these can be directly used as fuel.

  Conventionally, carbon paper or carbon cloth made of carbon fiber has been used as a gas diffusion layer of a polymer electrolyte fuel cell. In this carbon paper or carbon cloth, for the purpose of preventing flooding due to humidified water during fuel cell operation or water generated by electrode reaction at the cathode, such as polytetrafluoroethylene (PTFE) is formed on the surface or inside the gap. Water repellent treatment is performed with a water repellent binder. However, since these carbon paper and carbon cloth have a very large pore diameter, water may stay in the pores without obtaining a sufficient water repellent effect.

  In order to improve this point, for example, as shown in Patent Document 1, a gas diffusion electrode in which a porous resin containing a conductive filler made of carbon or the like is included in carbon paper has been proposed. However, the gas diffusion electrode as shown in Patent Document 1 is applied directly on the surface of carbon paper with a paint constituting a porous resin containing a conductive filler made of carbon or the like, impregnated, solvent extracted, and dried. Therefore, many gaps in the carbon paper are blocked, and therefore, gas permeability inside the voids is deteriorated, and the battery performance is deteriorated.

  Patent Document 2 describes that a water repellent layer is formed by applying a mixture of carbon black and PTFE to a stainless steel mesh. However, those formed by applying such a mixture have a problem that many of the gaps in the stainless steel mesh are blocked, resulting in poor gas permeability inside the gaps and a decrease in battery performance. Furthermore, when manufacturing the fuel cell, it is necessary to make the gas diffusion electrode adhere to the electrolyte or to use an adhesive. When pressure is applied to the gas diffusion electrode, the porous film of the gas diffusion electrode There was also a problem that the gap of the gas was crushed and gas / water discharge was hindered.

Patent Document 3 describes a solid polymer membrane fuel cell including a gas diffusion layer in which at least two types of carbon particles having different particle size distribution centers are mixed. Graphite is used as the carbon particles having a larger particle size. It is described that the diffusion layer is formed by using carbon particles coated with a fluororesin to impart water repellency. However, this polymer electrolyte fuel cell has a problem that the formed diffusion layer has low strength and the water repellency of the diffusion layer is not sufficient.
JP 2003-303595 A JP 2000-58072 A JP 2001-57215 A

  The present invention has been made for the purpose of improving the above problems. That is, an object of the present invention is to provide a gas diffusion electrode for a polymer electrolyte fuel cell that can maintain good gas diffusibility through a porous membrane and thereby maintain good cell characteristics. Another object of the present invention is to provide a membrane-electrode assembly using the gas diffusion electrode for a polymer electrolyte fuel cell and a simple production method thereof. Still another object of the present invention is to provide a polymer electrolyte fuel cell having excellent cell performance using the gas diffusion electrode for a polymer electrolyte fuel cell.

The gas diffusion electrode for a polymer electrolyte fuel cell of the present invention that solves the above problems is a gas diffusion electrode for a polymer electrolyte fuel cell in which a nonwoven fabric is included in a conductive porous body, and the conductive porous quality body, to a carbon material, the following as (a) or (b), characterized in that it consists of.
(A) Ternary fluoropolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride (b) Binary fluoropolymer of tetrafluoroethylene and vinylidene fluoride Also for the polymer electrolyte fuel cell of the present invention The membrane-electrode assembly is characterized in that the gas diffusion electrode for a solid polymer fuel cell is laminated on both sides of a polymer electrolyte membrane via a catalyst layer.
The first method for producing a membrane-electrode assembly for a polymer electrolyte fuel cell includes the steps of forming a catalyst layer on the gas diffusion electrode for the polymer electrolyte fuel cell, and providing the gas diffusion electrode with a catalyst layer. A first step of obtaining, a catalyst layer surface of the gas diffusion electrode with a catalyst layer being disposed on both sides of the polymer electrolyte membrane, and joining the gas diffusion electrode with a catalyst layer and the polymer electrolyte membrane by hot pressing It has two steps.

The second method for producing a membrane-electrode assembly for a polymer electrolyte fuel cell is a first step of obtaining a polymer electrolyte membrane with a catalyst layer by forming catalyst layers on both sides of the polymer electrolyte membrane. And the gas diffusion electrode for the polymer electrolyte fuel cell so that the conductive porous body of the gas diffusion electrode for the polymer electrolyte fuel cell is in contact with each catalyst layer surface of the polymer electrolyte membrane with the catalyst layer. And a second step of joining the polymer electrolyte membrane with a catalyst layer and the gas diffusion electrode by hot pressing.
In the solid polymer fuel cell of the present invention, the gas diffusion electrode for a solid polymer fuel cell is provided on both sides of the polymer electrolyte membrane via a catalyst layer, and a separator is disposed on the outside thereof. Features.

  The gas diffusion electrode for a polymer electrolyte fuel cell according to the present invention has a conductive porous body made of a porous fluororesin film containing a carbon material, and has water repellency and drainage by the conductive porous body. And having a smooth surface with conductivity due to the carbon material. However, since only the conductive porous body has a problem that the voids are crushed during the hot pressing in the manufacturing process, a nonwoven fabric is used as the reinforcing material. Since the nonwoven fabric in this invention is excellent in compression resistance, the space | gap of the electroconductive porous body included by the inside of the space | gap of a nonwoven fabric is protected by a nonwoven fabric, and is not crushed by a hot press. Since the gas diffusion electrode for a polymer electrolyte fuel cell of the present invention has the above-mentioned characteristics, flooding due to humidified water or generated water during operation of the fuel cell is prevented, and supply and removal of the reaction gas are promptly performed. It is excellent in water repellency for conducting the heat and the conductivity that efficiently transmits the generated electricity. Further, due to the function of the non-woven fabric, the voids of the porous gas diffusion electrode are not crushed and the permeation of water and gas is not hindered by the pressure applied to the gas diffusion electrode that is loaded when the fuel cell is manufactured.

Further, since the conductive porous body has good adhesion to the catalyst layer and no gap is formed, water does not accumulate between the catalyst layer and the conductive porous body.
In addition, conductivity is maintained by using a carbon material. On the other hand, a fuel cell using the gas diffusion electrode for a polymer electrolyte fuel cell of the present invention is excellent in gas / water discharge and conductivity in a power generation cycle. In addition, since the gas diffusion electrode for a solid polymer fuel cell of the present invention has a smooth surface, the catalyst layer and the polymer solid electrolyte membrane may be damaged or destroyed as compared with the case of using a conventional carbon fiber sheet. There is also an effect that there is nothing to do.

Hereinafter, the present invention will be specifically described.
The gas diffusion electrode for a polymer electrolyte fuel cell of the present invention (hereinafter also referred to as a gas diffusion electrode) has a conductive porous body containing a carbon material, and uses a nonwoven fabric as a structure-retaining (void collapse prevention) material. The conductive porous body includes a nonwoven fabric. The thickness of the conductive porous body is preferably larger than the thickness of the nonwoven fabric, and the conductive porous body preferably has a smooth surface. The gas diffusion electrode for a polymer electrolyte fuel cell according to the present invention has a smooth surface having water repellency / drainage, conductivity by a carbon material, strength by a nonwoven fabric because the conductive porous body contains a fluoropolymer. Can have.

The conductive porous body needs to contain at least one of the following (a) and (b). (A) ternary fluoropolymer of tetrafluoroethylene (TFE), hexafluoropropylene (HFP) and vinylidene fluoride (VdF) (hereinafter this polymer is also referred to as THV) (b) tetrafluoroethylene (TFE) Binary fluoropolymer with vinylidene fluoride (VdF) (hereinafter this polymer is also referred to as TV)
That is, in addition to the case where these polymers (a) or (b) (hereinafter these two types of polymers are collectively referred to as fluoropolymers) are used alone, two or more types of resins should be used in combination. Are also encompassed by the present invention.

  Said (a) and (b) consist of tetrafluoroethylene (TFE) 5-80 mass%, hexafluoropropylene (HFP) 0-60 mass%, vinylidene fluoride (VdF) 5-95 mass%. It is preferable. If the amount of tetrafluoroethylene (TFE) is less than 5% by mass, the water repellency tends to decrease. When there is more tetrafluoroethylene (TFE) than 80 mass%, the binding property to a nonwoven fabric will fall easily and the binding property to the fluoropolymer of a carbon material will fall easily. Further, when the vinylidene fluoride (VdF) is less than 5% by mass, the binding property of the fluoropolymer to the nonwoven fabric and the binding property of the carbon material to the fluoropolymer are liable to be lowered. If the vinylidene fluoride (VdF) is more than 95% by mass, the water repellency tends to decrease. That is, TFE contributes to water repellency, and VdF contributes to the binding properties of nonwoven fabrics and carbon materials. HFP has a harmonious role of TFE and VdF, and is not necessarily included. Hexafluoropropylene (HFP) is preferably in the range of 0 to 60% by mass. In the present invention, since the above fluoropolymer is used, the nonwoven fabric, the fluoropolymer, and the carbon material can be bound to each other.

  Any carbon material can be used, and examples thereof include particulate carbon materials. For example, so-called carbon black represented by furnace black, channel black, acetylene black and the like can be used. Carbon black can be used in any grade regardless of the specific surface area and particle size. For example, Lion Akzo: Ketjen EC, Cabot: Vulcan XC72R, Electrochemical Industry: For example, Denka Black. Among these, carbon black is preferably used from the viewpoint of high conductivity and dispersibility in the coating liquid, and acetylene black is particularly preferably used. In the present invention, these carbon materials preferably have an average primary particle diameter in the range of 10 to 100 nm.

  In the gas diffusion electrode of the present invention, a fibrous carbon material (hereinafter referred to as carbon fiber) may be used in addition to the fine particle carbon material. Carbon fibers include carbon fibers, Showa Denko's carbon nanofibers (trade name: VGCF), and carbon nanotubes. The aspect ratio of the carbon fiber (the diameter of the cross section of the fiber and the length of the fiber (the bent length if bent)) is preferably 5 to 1000. Since the carbon fiber used in the present invention has high conductivity with advanced graphitization, it is effective in reducing the resistance of the gas diffusion electrode.

  In the present invention, a filler other than the above carbon material may be further included. In particular, those that improve water repellency such as polytetrafluoroethylene particles are preferred. As the particle size of the filler, any particle size can be used. However, when the particle size is very large, there is a problem that the porous pores are blocked. Therefore, generally, a particle size range comparable to the particle size of the particulate carbon material, that is, a range of 10 to 500 nm is preferable.

  The mass ratio of the nonwoven fabric, the fluoropolymer (THV or TV), and the carbon material is desirably at least one of nonwoven fabric: THV or TV: carbon material = 100: 5-150: 15-80. Outside this range, the fuel cell performance is lowered for the following reasons, which is not preferable. When the amount of fluoropolymer is less than 5 parts by mass with respect to 100 parts by mass of the nonwoven fabric, binding and water repellency are likely to be insufficient, and the binding property of the carbon material is liable to be deteriorated. The drainage of the generated water is unfavorable. Further, when the amount of the carbon material is less than 15 parts by mass with respect to 100 parts by mass of the nonwoven fabric, the conductivity is insufficient, and when it is more than 80 parts by mass, the porosity is insufficient and the drainage of generated water at the time of power generation is not preferable.

  In the gas diffusion electrode of the present invention, a sheet-like conductive porous film may be laminated on the conductive porous body. Examples of the conductive porous film include carbon paper and carbon cloth made of carbon fiber, nickel foam, titanium fiber sintered body, and the like. Since the gas diffusion electrode in which the conductive porous film is laminated has a laminated structure of the conductive porous body and the conductive porous film, the gas diffusion for fuel cells described in Patent Document 1 is used. Unlike the electrodes, the voids of the conductive porous film are not blocked by the fluoropolymer and the carbon material constituting the conductive porous body. Therefore, the gas permeability inside the voids is good, and the problem of reducing battery performance is eliminated.

  In the present invention, the thickness of the gas diffusion electrode is preferably 5 μm to 200 μm, more preferably 10 μm to 150 μm, and still more preferably 15 μm to 70 μm. If the thickness is smaller than 5 μm, the water retention effect is not sufficient, and if it is larger than 200 μm, it is too thick and the gas diffusing capacity and drainage capacity are lowered, and the fuel cell performance is likely to be lowered. Moreover, it is preferable that the thickness of the conductive porous body is the same as or thicker than that of the nonwoven fabric. Since the conductive porous body has better adhesion to the catalyst layer than the nonwoven fabric, it is desirable that the conductive porous body be slightly thicker than the thickness of the nonwoven fabric to be an adhesive layer during hot pressing. Thereby, there is no gap between the catalyst layer and the conductive porous body according to the present invention. Since the conductive porous body is slightly thicker than the nonwoven fabric, it has a smooth surface.

  As the nonwoven fabric, carbon fiber, glass fiber, aramid fiber, polyethylene fiber, polypropylene fiber, polyethylene terephthalate fiber, polybutyl terephthalate fiber, polyarylate fiber, polyvinyl alcohol fiber, benzazole fiber, polyparaphenylene benzobisoxazole fiber, Nonwoven fabrics made of fibers such as polyphenylene sulfide fibers and polytetrafluoroethylene fibers can be mentioned. Among these, non-woven fabrics obtained from polyarylate fibers which are excellent in fixability of carbon materials and fluoropolymers and do not decompose at a high temperature or under a high pressure and have very little deformation are preferred.

  In the gas diffusion electrode of the present invention, a conductive porous body is formed in a non-woven fabric by the above-mentioned fluoropolymer, and there are density, porosity, and pore diameter as scales for measuring the structure of such a porous film. The porosity of the gas diffusion electrode of the present invention is preferably in the range of 60% to 95%, more preferably 70% or more, and particularly preferably 80% or more. If the porosity is less than 60%, the gas diffusing capacity and water discharge are insufficient, and if it exceeds 95%, the mechanical strength is remarkably lowered, and the fuel cell is easily damaged in the process until it is assembled.

In addition, said porosity is x = (specific gravity of fluoropolymer in conductive porous body) × (mass content of fluoropolymer in conductive porous body), y = (specific gravity of carbon material) × (conductivity) Substituting the mass content of the carbon material in the porous body), z = (specific gravity of the nonwoven fabric) × (mass content of the nonwoven fabric in the conductive porous body), and the density of the conductive porous body into the following equation: It can ask for. Here, the fluoropolymers include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), vinylidene fluoride (VdF) ternary fluoropolymer (THV), tetrafluoroethylene (TFE) and vinylidene fluoride (VdF). The porosity can be calculated by substituting the specific gravity and mass content of the binary fluoropolymer (TV) with
Porosity (%) = [{(x + y + z) −density of conductive porous body} / (x + y + z)] × 100

The density can be determined by the film thickness of the conductive porous body of the gas diffusion electrode and the mass per unit area as shown below, and the range of 0.10 to 0.65 g / cm ³ is the same as above. It is preferable for the reason.
Density (g / cm ³ ) = mass per unit area / (film thickness × unit area)

  The pore diameter of the conductive porous body is preferably in the range of 0.5 μm to 10 μm, more preferably 3 μm to 10 μm, and still more preferably 5 μm to 10 μm. When the pore diameter is less than 0.5 μm, gas diffusion performance and water discharge tend to be insufficient.

The gas diffusion electrode for a polymer electrolyte fuel cell of the present invention can be produced as follows. First, a carbon mixture is dispersed in at least one fluoropolymer solution of (a) and (b) to prepare a solvent mixture (paint). As the solvent in which the fluoropolymer is dissolved, various organic solvents such as ketones, esters, acetone, ethyl acetate, butyl acetate, 1-methyl-2-pyrrolidone can be selected.
In order to disperse and mix the carbon material in the fluoropolymer solution, a commercially available stirrer or disperser can be used. The obtained paint can be applied to a nonwoven fabric and dried to form a conductive porous body, whereby the gas diffusion electrode of the present invention can be obtained. As another method, the nonwoven fabric is impregnated into the solvent mixture (paint) in which the carbon material is dispersed in the above-described fluoropolymer solution, and the excess paint is scraped off with a gap such as a roll having an appropriate interval. The conductive porous body can be formed by drying later to obtain the gas diffusion electrode of the present invention.

As another method, a conductive porous body is formed by applying a solvent mixture (paint) in which a carbon material is dispersed in the above-mentioned fluoropolymer solution to a suitable substrate, then transferring it to a nonwoven fabric and drying it. Thus, the gas diffusion electrode of the present invention can be obtained. At this time, the substrate is peeled off after drying or removed when a membrane-electrode assembly is produced. For example, a polyimide film or a polyethylene naphthalate film (PEN) is preferably used as the substrate.
Alternatively, a nonwoven fabric in which the fluoropolymer is fixed to a nonwoven fabric fiber is prepared by impregnating or applying at least one fluoropolymer solution of (a) and (b) to the nonwoven fabric, and then heated and dried to form the nonwoven fabric. The gas diffusion electrode of the present invention can be obtained by making it water-repellent and then impregnating or applying a dispersion of a carbon material onto a nonwoven fabric and drying to form a conductive porous body.

  In addition, when the gas diffusion electrode for a polymer electrolyte fuel cell according to the present invention has a structure in which a sheet-like conductive porous film is laminated on the conductive porous body, it is formed as described above. It can be produced by stacking a sheet-like conductive porous film on a conductive porous body and pressurizing and joining them by hot pressing or the like.

  In the membrane-electrode assembly for a polymer electrolyte fuel cell of the present invention, the gas diffusion electrode for a polymer electrolyte fuel cell produced as described above is laminated on both sides of the polymer electrolyte membrane via a catalyst layer. It has a structured. This membrane-electrode assembly for a polymer electrolyte fuel cell can be produced as follows. In one of the manufacturing methods, first, a conductive porous body made of a fluoropolymer containing a carbon material is formed on a substrate in the same manner as described above to produce a gas diffusion electrode, and a catalyst layer is formed thereon. A gas diffusion electrode with a catalyst layer is prepared by applying a coating material for formation, and then the obtained two gas diffusion electrodes with a catalyst layer are placed so that the catalyst layers are in contact with both surfaces of the polymer electrolyte membrane. A membrane-electrode assembly for a polymer electrolyte fuel cell can be produced by joining the polymer electrolyte membrane and the gas diffusion electrode with catalyst by hot pressing.

  In the other method, a catalyst layer-forming coating material is applied to both surfaces of the polymer electrolyte membrane to form a catalyst layer, thereby producing a polymer electrolyte membrane with a catalyst layer. Next, the gas diffusion electrodes prepared as described above are disposed on both sides of the catalyst layer of the polymer electrolyte membrane with the catalyst layer, and the polymer electrolyte membrane with the catalyst layer and the gas diffusion electrode are joined by hot pressing. Thus, a membrane-electrode assembly for a polymer electrolyte fuel cell can be produced.

  In the method for producing a membrane-electrode assembly of the present invention, a gas diffusion electrode with a catalyst layer or a polymer electrolyte membrane with a catalyst layer is prepared as described above, and bonded to the polymer electrolyte membrane or the gas diffusion electrode by hot pressing, respectively. Therefore, the membrane-electrode assembly can be manufactured very easily. Further, since the formed membrane-electrode assembly is provided with the gas diffusion electrode described above, the gas / water discharge is good and the conductivity is excellent.

  In addition, a solid polymer fuel cell can be obtained by providing the gas diffusion electrode for a solid polymer fuel cell on both sides of the polymer electrolyte membrane via a catalyst layer and arranging a separator on the outside thereof. .

  Therefore, the polymer electrolyte fuel cell of the present invention composed of cells in which separators are arranged on both surfaces of the membrane-electrode assembly has excellent power generation characteristics. Moreover, the structure of the cell which distribute | arranged carbon paper and cloth on both surfaces of the membrane-electrode assembly, and has arrange | positioned the separator on the outer side may be sufficient. As the separator, any known separator used in solid polymer fuel cells can be used.

  The present invention will be described more specifically with reference to examples. A gas diffusion electrode was prepared as follows, and then a polymer electrolyte fuel cell in which the gas diffusion electrode was disposed on both the fuel electrode side and the oxygen electrode side was manufactured and evaluated.

Examples 1-11
(Manufacture of gas diffusion electrode)
A 20 mass% methyl ethyl ketone solution of a fluoropolymer of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (VdF) having the composition ratio shown in Table 1 was prepared. Next, acetylene black having an average primary particle diameter of 40 nm was dispersed in 1-methyl-2-pyrrolidone so as to have a mass part shown in Table 1, and mixed with a methyl ethyl ketone solution of the above fluoropolymer to obtain 5 mass%. A mixed solution (paint) was obtained. The obtained paint was applied to a polyarylate non-woven fabric using an applicator to obtain a coating film, and dried to obtain a gas diffusion electrode made of a conductive porous material described in Table 1. No substrate is present on both sides of the polyarylate nonwoven during drying. (The parts by mass of the fluoropolymer and acetylene black in Table 1 are shown as values with respect to 100 parts by mass of the polyarylate nonwoven fabric. The composition ratio in the fluoropolymer shown in Table 1 is shown in Table 2.)

Comparative Example 1
(Manufacture of gas diffusion electrode)
A solution was prepared by dispersing 30 parts by mass of polyvinylidene fluoride (PVdF) in 600 parts by mass of 1-methyl-2-pyrrolidone. Next, acetylene black having an average primary particle diameter of 40 nm and polytetrafluoroethylene (PTFE) having an average primary particle diameter of 400 nm are dispersed in 1-methyl-2-pyrrolidone so as to have a mass part shown in Table 1, and the above PVdF solution By mixing, a 5 mass% mixed solution (paint) was obtained. The obtained paint was applied to a polyarylate non-woven fabric using an applicator to obtain a coating film, and dried to obtain a gas diffusion electrode made of a porous fluororesin film described in Table 1. (The mass parts of PTFE, PVdF and acetylene black in Table 1 are shown as values relative to 100 mass parts of the polyarylate nonwoven fabric.)

(Physical property measurement and surface water repellency confirmation test)
The film thickness and the mass per unit area of the gas diffusion electrode in Examples 1 to 11 and Comparative Example 1 were measured. The density was calculated from the measured mass, and the porosity was calculated from the result. Subsequently, the pure water contact angle was measured using a contact angle meter, and the results are shown in Table 1.

  As is clear from the results in Table 1, Examples 1 to 10 have a pure water contact angle of 148 ° or more and a porosity of 80% or more, which is a suitable range having both water repellency and high porosity. Comparative Example 1 is different from Example 2 in that the mass parts of PTFE (TFE) and PVdF (VdF) are approximately the same, but are not copolymerized. Such Comparative Example 1 has a pure water contact angle as low as 139 °. The reason why the contact angle of pure water in Comparative Example 1 is low is considered to be that PTFE responsible for high water repellency is included in PVdF or unevenly distributed, and the contribution to water repellency is not sufficiently extracted. On the other hand, in the examples, since TFE and VdF are copolymerized, TFE is difficult to be included in VdF, so that water repellency is considered to be improved.

(Production of polymer electrolyte fuel cell)
(1) Fabrication of polymer electrolyte fuel cell 1
Two 50 mm square gas diffusion electrodes obtained in Examples 1 to 11 and Comparative Example 1 were prepared. A catalyst coating consisting of a carbon / ion conductive resin carrying platinum catalyst and a mixed solvent of water and ethanol is applied and dried on the porous membrane surfaces of the two gas diffusion electrodes to form a catalyst layer. A gas diffusion electrode with a layer was obtained. The amount of each platinum catalyst was 0.3 mg / cm ² . Next, the gas diffusion electrode with the catalyst layer is arranged so that the catalyst layer surface is in contact with the electrolyte membrane (manufactured by DuPont, trade name: Nafion 117), and the gas with the catalyst layer is formed by hot pressing (120 ° C., 10 MPa, 10 minutes). The diffusion electrode and the electrolyte membrane were joined to obtain a membrane-electrode assembly. A carbon paper is arranged on both sides of the obtained membrane-electrode assembly, a graphite separator is arranged on the outside thereof, and the polymer electrolyte fuel cell for evaluation (Examples 1-1 to 11-) is incorporated into a single cell. 1 and Comparative Example 1-1) were obtained. Examples 1-1 to 11-1 are solid polymer fuel cells using the gas diffusion electrodes of Examples 1 to 11, respectively. Comparative Example 1-1 is a gas diffusion electrode of Comparative Example 1. It is the used polymer electrolyte fuel cell.

(2) Fabrication of polymer electrolyte fuel cell 2
Applying and drying a catalyst coating made of carbon, an ion conductive resin and a solvent carrying a platinum catalyst on both sides of a polymer electrolyte membrane (manufactured by DuPont, trade name: Nafion 117) to form a catalyst layer, A polymer electrolyte membrane with a catalyst layer was obtained. The amount of each platinum catalyst was 0.3 mg / cm ² . Next, the gas diffusion electrodes obtained in Examples 1 to 11 and Comparative Example 1 were arranged so that the gas diffusion electrode surface was in contact with the polymer electrolyte membrane with a catalyst layer, and hot pressing (120 ° C., 10 MPa, 10 minutes). ), The polymer electrolyte membrane with a catalyst layer and the gas diffusion electrode were joined together to obtain a membrane-electrode assembly. A carbon paper is arranged on both surfaces of the obtained membrane-electrode assembly, a graphite separator is arranged on the outside thereof, and the polymer electrolyte fuel cell for evaluation (Examples 2-1 to 11-) is incorporated into a single cell. 2, Comparative Example 1-2) was obtained. Examples 1-2 to 11-2 are polymer electrolyte fuel cells using the gas diffusion electrodes of Examples 1 to 11, respectively. Comparative Example 1-2 is a gas diffusion electrode of Comparative Example 1. It is the used polymer electrolyte fuel cell.

(Evaluation of polymer electrolyte fuel cells)
The power generation characteristics of the 24 types of polymer electrolyte fuel cells (Examples 1-1 to 11-1, Comparative Example 1-1) (Examples 1-2 to 11-2, Comparative Example 1-2) are as follows. I evaluated it in the way. Hydrogen gas was used on the fuel electrode side and oxygen gas was used on the oxygen electrode side as the supply gas for the polymer electrolyte fuel cell. Hydrogen gas was supplied at a humidification temperature of 85 ° C. so as to be 500 mL / min and 0.1 MPa, and oxygen gas was supplied so as to be 1000 mL / min and 0.1 MPa at a humidification temperature of 70 ° C. Under this condition, the voltage at a current density of 1 A / cm ² was measured. The results are shown in Table 3.

As shown in Table 3, polymer electrolyte fuel cells (Example 1-1 to Example 11-1, Example 1-2 to Example 11) provided with the gas diffusion electrodes obtained in Examples 1 to 11 -2) is a voltage at a current density of 1 A / cm ² than the polymer electrolyte fuel cell (Comparative Example 1-1, Comparative Example 1-2) provided with the gas diffusion electrode obtained in Comparative Example 1. High power generation characteristics. This is because the gas diffusion electrode of the present invention is made of a terpolymer fluoropolymer (THV) or tetrafluoroethylene (THV), tetrafluoroethylene (TFE), hexafluoropropylene, (HFP), vinylidene fluoride (VdF) containing a nonwoven fabric. TFE), vinylidene fluoride (VdF) binary fluoropolymer (TV), and conductive porous bodies made of carbon materials have excellent water repellency, so flooding with humidified water or generated water during fuel cell operation Since the gas permeability is increased, the battery performance represented by the power generation characteristics of the solid polymer fuel cell is improved. On the other hand, in Comparative Example 1, since tetrafluoroethylene (TFE) and vinylidene fluoride (VdF) were not copolymerized as in the examples, water repellency was not improved and sufficient power generation performance was not obtained.

Claims (15)

A gas diffusion electrode for a polymer electrolyte fuel cell in which a nonwoven fabric is included in a conductive porous body, wherein the conductive porous body includes a carbon material and the following (a) or (b) : A gas diffusion electrode for a polymer electrolyte fuel cell.
(A) ternary fluoropolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride (b) binary fluoropolymer of tetrafluoroethylene and vinylidene fluoride   The said (a) and (b) consist of 5-80 mass% of tetrafluoroethylene, 0-60 mass% of hexafluoropropylene, and 5-95 mass% of vinylidene fluorides, It is characterized by the above-mentioned. A gas diffusion electrode for a polymer electrolyte fuel cell as described.   The gas diffusion electrode for a polymer electrolyte fuel cell according to claim 1, wherein the carbon material is in the form of particles.   The gas diffusion electrode for a polymer electrolyte fuel cell according to claim 1, wherein the carbon material is carbon black.   The gas diffusion electrode for a polymer electrolyte fuel cell according to claim 4, wherein the carbon black is acetylene black.   The mass ratio of the nonwoven fabric to at least one component of (a) and (b) and the carbon material is at least one component of nonwoven fabric: (a) and (b): carbon material = 100: 5 to 150: It is 15-80, The gas diffusion electrode for polymer electrolyte fuel cells of Claim 1 characterized by the above-mentioned.   The gas diffusion electrode for a polymer electrolyte fuel cell according to claim 1, wherein a conductive porous membrane is laminated on the conductive porous body.   2. The gas diffusion electrode for a polymer electrolyte fuel cell according to claim 1, wherein the conductive porous body is thicker than the nonwoven fabric.   The gas diffusion electrode for a polymer electrolyte fuel cell according to claim 1, wherein the nonwoven fabric contains polyarylate fibers.   2. The solid polymer according to claim 1, wherein the conductive porous body is formed by applying or impregnating a nonwoven fabric with a paint in which a carbon material and at least one of (a) and (b) are dispersed. Diffuser gas diffusion electrode.   The conductive porous body is obtained by impregnating or applying a carbon material dispersion to a nonwoven fabric obtained by impregnating or applying at least one fluoropolymer solution of (a) and (b) in advance. The gas diffusion electrode for a polymer electrolyte fuel cell according to claim 1, wherein the gas diffusion electrode is a solid polymer fuel cell.   The solid polymer fuel cell gas diffusion electrode according to any one of claims 1 to 11, wherein the gas diffusion electrode is laminated on both surfaces of a polymer electrolyte membrane via a catalyst layer. Membrane-electrode assembly for molecular fuel cell.   A first step of forming a catalyst layer on the gas diffusion electrode for a polymer electrolyte fuel cell according to claim 1 to obtain a gas diffusion electrode with a catalyst layer, and a catalyst layer surface of the gas diffusion electrode with a catalyst layer is provided with a polymer electrolyte. A membrane-electrode assembly for a polymer electrolyte fuel cell, comprising a second step of joining the gas diffusion electrode with a catalyst layer and the polymer electrolyte membrane by hot pressing, respectively, on both sides of the membrane Manufacturing method.   A gas diffusion electrode for a polymer electrolyte fuel cell according to claim 1, wherein a catalyst layer is formed on both sides of the polymer electrolyte membrane to obtain a polymer electrolyte membrane with a catalyst layer; The conductive porous body of the fuel cell gas diffusion electrode is placed in contact with the catalyst layer surface of the polymer electrolyte membrane with the catalyst layer, and the polymer electrolyte membrane with the catalyst layer and the gas diffusion electrode are joined by hot pressing. A method for producing a membrane-electrode assembly for a polymer electrolyte fuel cell.   The gas diffusion electrode for a polymer electrolyte fuel cell according to any one of claims 1 to 11 is provided on both surfaces of the polymer electrolyte membrane via a catalyst layer, and a separator is disposed on the outside thereof. A solid polymer fuel cell.