JP3714766B2 - Electrode and membrane / electrode assembly for polymer electrolyte fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polymer electrolyte fuel cell, and more particularly to an electrode and a membrane / electrode assembly.
[0002]
[Prior art]
The fuel cell is one that converts the chemical energy of the fuel directly into electrical energy by electrochemically oxidizing hydrogen, methanol, or the like in the cell, and has attracted attention as a clean electrical energy supply source. In particular, the polymer electrolyte fuel cell is expected to be an alternative power source for automobiles because it operates at a lower temperature than others.
[0003]
In such a polymer electrolyte fuel cell, a pair of gas diffusion electrodes are joined to both surfaces of a polymer electrolyte membrane. That is, an anode catalyst layer is provided on one side of the solid polymer electrolyte membrane, a cathode catalyst layer is provided on the other side, and a pair of gas diffusion layers are adjacent to each other on both sides. Conventionally, the anode and cathode catalyst layers are formed by sheeting a mixture of carbon black powder supporting an electrode catalyst, a polymer having proton conductivity, and a polymer having water repellency. Are joined by hot pressing.
[0004]
Fuel (for example, hydrogen) is supplied to the gas diffusion electrode side as the anode, and an oxidant (for example, oxygen or air gas) is supplied to the gas diffusion electrode side as the cathode, and the two electrodes are connected by an external circuit. Operates as a battery. That is, in the anode, protons and electrons are generated by oxidation of the fuel, and the protons pass through the solid electrolyte and move to the cathode side. On the other hand, electrons reach the cathode through an external circuit. At the cathode, water is generated by such protons and electrons and oxygen in the oxidizing agent, and at this time, electric energy can be taken out.
[0005]
[Problems to be solved by the invention]
In order for protons to move smoothly in the solid polymer electrolyte membrane, water is required, so the fuel is humidified and supplied to the anode together with water. Excess water generated at the cathode and moving through the membrane is released outside the electrode together with the oxidizing agent. In the catalyst layer, in order to obtain a high catalyst utilization rate, as described in JP-A-6-333574, for example, “Nafion (5% by weight solution)” manufactured by Aldrich, USA, which is commercially available, is used. A proton conductive polymer having a high water content is uniformly dispersed. Therefore, even when a water-repellent polymer is included, it is difficult for water to be smoothly discharged from the catalyst layer to the outside of the layer or the gas diffusion layer. While the fuel cell continues to operate, water gradually accumulates in the catalyst layer and gas diffusion layer, and the higher the current density, the more water accumulates and the oxidant is supplied to the catalyst layer. Is greatly disturbed. As a result, the resistance of the electrochemical reaction becomes extremely large, causing a problem that the battery voltage that can be taken out is greatly reduced, and that voltage variation between cells is increased in the stack.
[0006]
By operating the fuel and oxidant under pressure and increasing the fuel cell operating pressure, the reaction efficiency of the electrode increases, but the discharge capacity of produced water and the like decreases conversely due to a decrease in gas flow rate. Improvement in characteristics cannot be expected.
Increasing the amount of the water-repellent polymer dispersed in the catalyst layer is constrained to cause a significant decrease in the catalyst utilization rate and a decrease in output voltage, and a significant improvement in water repellency cannot be expected. In addition, since a proton conductive polymer is contained, a high temperature treatment as described in, for example, Japanese Patent Publication No. 5-20868 is performed after a water repellent polymer such as PTFE is dispersed in the catalyst layer. Cannot be used to form an effective matrix of water repellent polymer.
The present invention has been made paying attention to such problems of the prior art, and improves the water discharge capacity in the catalyst layer, eliminates the influence of water on the diffusion of the reaction gas in the catalyst layer, An object of the present invention is to provide an electrode and a membrane / electrode assembly for a polymer electrolyte fuel cell that exhibits a stable battery voltage even in a current density region.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention provides an electrode characterized in that in the gas diffusion electrode for a polymer electrolyte fuel cell, the catalyst layer contains at least two kinds of proton conductive polymers having different EWs. To do. Also, in membrane / electrode assemblies for polymer electrolyte fuel cells,
Provided is a membrane / electrode assembly comprising a solid polymer membrane having an EW of 700 to 1500 and an electrode having a catalyst layer containing at least two types of proton conducting polymers having different EWs. By producing these electrodes and membrane / electrode assemblies, it was found that a stable battery voltage can be obtained, and the present invention has been achieved.
  That is, the present invention
  1. In the gas diffusion electrode for a polymer electrolyte fuel cell, both the anode catalyst layer and the cathode catalyst layer have at least two kinds of sulfonic acid groups in which the difference in EW uniformly dispersed in the catalyst layer is 20 to 800. An electrode comprising a perfluorocarbon polymer;
2. 1. The perfluorocarbon polymer having at least two types of sulfonic acid groups is uniformly dispersed in the catalyst layer by sequentially or simultaneously adding to the catalyst dispersion. The described electrode,
3. The difference in EW is 50 to 600. Or the electrode according to 2,
4). In the membrane / electrode assembly for a polymer electrolyte fuel cell, the difference in EW in which the solid polymer membrane having an EW of 700 to 1500 and the anode catalyst layer and the cathode catalyst layer are both uniformly dispersed in the catalyst layer A membrane-electrode assembly comprising an electrode having a catalyst layer containing a perfluorocarbon polymer having at least two kinds of sulfonic acid groups of which is 20 to 800,
5. 3. The perfluorocarbon polymer having at least two kinds of sulfonic acid groups is uniformly dispersed in the catalyst layer by sequentially or simultaneously adding the perfluorocarbon polymer to the catalyst dispersion in advance. The membrane-electrode assembly described,
  6). 3. The difference in EW is 50 to 600. Or the membrane / electrode assembly according to 5,
7). 3. The above-mentioned 4. having a proton conductive polymer layer of EW different from the solid polymer membrane at the interface where the solid polymer membrane and the catalyst layer contact. ~ 6. The membrane / electrode assembly according to any one of
It is.
[0008]
The operation of dispersing the proton conductive polymer in the catalyst layer is for greatly improving the utilization rate of the catalyst, but in order to exert the effect more, a polymer having high proton conductivity, that is, EW. It is desirable to use lower polymers. As the proton conductive polymer, perfluorosulfonic acid polymers represented by the above-mentioned Nafion are widely used. For example, in this perfluorosulfonic acid polymer, a polymer having a lower proton conductivity and a higher proton conductivity exhibits a relatively high hydrophilicity and has a high water content. In the battery reaction, protons oxidized on the anode catalyst reach the membrane through the polymer having high proton conductivity, move through the membrane having the same conductivity to the cathode side, and again, It reaches the cathode catalyst through the highly proton conducting polymer dispersed in the catalyst layer. Using this as a three-phase interface, it reacts again with oxygen gas as an oxidant reaction gas and electrons that have passed through an external circuit to produce water. Here, the generated water quickly moves from above the catalyst active point to a polymer having a higher EW and a lower water content, which is also dispersed in the catalyst layer. The gas diffusion layer is discharged out of the electrode. In this way, at the cell reaction catalyst active point, an electrode having a high product water discharge capability can be obtained while maintaining a high reaction rate.
[0009]
Here, EW mentioned above represents the equivalent weight of the exchange group having proton conductivity. The equivalent weight is the dry weight of the ion exchange membrane per equivalent of ion exchange group, and is expressed in units of “g / ew”. The difference between the highest EW and the lowest EW of the proton conductive polymer referred to in the present invention is preferably 20 or more, more preferably 50 or more, and more preferably 100 or more. Particularly preferred. The effect of the present invention can be enjoyed if the difference in EW between the closest numerical values in the case of including three or more proton conductive polymers is 20 or more. The upper limit of the EW difference is preferably 800 or less, more preferably 600 or less, and particularly preferably 400 or less.
[0010]
The EW of the proton conductive polymer may be at least 700 or more, more preferably 800 or more. And it is preferable that it is 1500 or less, and it is more preferable that it is 1300 or less. If it is 700 or less, the hydrophilicity is too high and water cannot move smoothly, and if it is 1500 or more, the proton conductivity is too low, the effect of the present invention cannot be shown.
The proton conductive polymer may be any polymer that conducts protons, and preferably has at least one of a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, and a phosphoric acid group with a fluorine-containing polymer as a skeleton. Is. In addition, those having a hydrocarbon skeleton such as polyolefin can also be used.
[0011]
Examples of the fluorine-containing polymer include tetrafluoroethylene, trifluoromonochloroethylene, trifluoroethylene, vinylidene fluoride, 1,1-difluoro-2,2-dichloroethylene, 1,1-difluoro-2-chloroethylene, hexa A first group of monomers such as fluoropropylene, 1,1,1,3,3-pentafluoropropylene, octafluoroisobutylene, ethylene, vinyl chloride, and alkyl vinyl ester, and the following general formula (1),
Y- (CF₂)_a-(CFR_f)_b-(CFR '_f)_c-O-[CF (CF₂X) -CF₂-O]_n-CF = CF₂  (1)
(Where Y is -SO₂F, -SO_ThreeNH, -COOH, -CN, -COF, -COOR (R is an alkyl group having 1 to 10 carbon atoms), -PO_ThreeH₂, -PO_ThreeH, a is an integer of 0-6, b is an integer of 0-6, c is 0 or 1, provided that a + b + c cannot be equal to 0. X is Cl, Br, F or a mixture thereof when n> 1, and n is 0-6. R_fAnd R '_fAre independently selected from the group consisting of F, Cl, a perfluoroalkyl group having about 1-10 carbon atoms and a fluorochloroalkyl group having 1-10 carbon atoms. ), A copolymer of 2 or 3 or more monomers essential for the second group monomer, one or more polymers of the second group, etc. . In particular, a perfluorocarbon polymer having a sulfonic acid group is preferable.
[0012]
Although the polymer should just couple | bond two or more molecules of monomers, the molecular weight is preferable 5000 or more from a durable viewpoint. Furthermore, EW can be adjusted as appropriate by using a mixture of a polymer and a low molecular weight compound.
Proton conducting polymers as described above include polar solvents such as alcohols such as methanol, ethanol, propanol and butanol, N, N′-dimethylacetamide, N, N′-dimethylformamide, dimethyl sulfoxide, sulfolane and the like. And a cyclic ether such as tetrahydrofuran, and a mixture of two or more selected from the above solvent group, or a mixture of the above solvent group and water. In particular, a lower alcohol such as ethanol, 1-propanol, or 2-propanol alone or a mixture of two or more solvents and water is preferable. Furthermore, a mixed solvent of at least one of the above solvent groups and a fluorine-containing compound such as a fluorocarbon or a fluorine-containing alcohol can also be used.
[0013]
The concentration of the dissolved proton conductive polymer solution is preferably in the range of 3 to 20% by weight, when an appropriate proton conductive polymer coating is easily formed on the catalyst surface when dispersed in the catalyst layer of the gas diffusion electrode. . If this concentration is too high, the dispersibility of the polymer in the catalyst layer will deteriorate, the coating thickness will become too large, the three-phase interface will become non-uniform, and the catalyst utilization will decrease, and the effects of the present invention will be reduced. You may not be able to demonstrate. On the other hand, if the concentration is too low, a uniform and sufficient thickness of the proton conductive polymer coating on the catalyst surface cannot be obtained, or the proton conductive polymer solution is applied to the surface of the porous catalyst layer sheet to In the case of dispersing in the polymer, the viscosity of the liquid is too low, and therefore the polymer is concentrated locally, which is not preferable.
[0014]
The electrode catalyst material used for the anode and cathode catalyst layers may be any material that has a catalytic action on the oxidation reaction of hydrogen and the reduction reaction of oxygen, such as platinum, ruthenium, iridium, rhodium, palladium, osnium, tungsten, lead, It can be selected from metals such as iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, or alloys thereof.
[0015]
The particle size of the catalyst is preferably 10 to 300 mm, more preferably 15 to 100 mm. If it is less than 10 mm, it is practically difficult to manufacture, and if it is more than 300 mm, the catalyst utilization rate decreases, and a high battery voltage cannot be obtained. These catalyst particles may be supported on a conductive material such as carbon black. The amount of catalyst supported is 0.01 to 5 mg / cm with the catalyst layer sheet formed.²And more preferably 0.1-1 mg / cm²It is. 0.01mg / cm²Less than 5 mg / cm, the catalyst performance cannot be exhibited effectively.²In the above, the cost becomes very large, and the effect corresponding to the amount cannot be seen in terms of performance.
[0016]
The catalyst layer referred to in the present invention is composed of a conductive material such as the catalyst material, proton conductive polymer, and carbon black, and includes a water repellent material such as PTFE and a binder as necessary. May be. As a method for dispersing the proton conductive polymer in the catalyst layer, the catalyst layer constituent materials may be mixed and molded to form a catalyst layer, or other constituent materials other than the proton conductive polymer may be mixed and molded in advance to form a catalyst layer. Then, a proton conductive polymer may be impregnated.
The conductive material may be any electron conductive material. For example, carbon black such as furnace black, channel black, and acetylene black listed above as the carbon material, activated carbon, graphite, and various metals can be applied. .
[0017]
Proton conductive polymers such as perfluorosulfonic acid also have a function as a binder in the polymer itself, and form a sufficiently stable matrix with catalyst particles and conductive particles in the catalyst layer. Is possible. For the purpose of imparting water repellency in addition to the function as a binder, for example, various resins containing fluorine can also be used. The fluororesin preferably has a melting point of 400 ° C. or lower, and examples thereof include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the like.
[0018]
In addition, when an EW proton conducting polymer layer different from the proton conducting polymer in the catalyst layer or the solid polymer membrane is formed at the interface where the catalyst layer and the solid polymer membrane are in contact with each other, especially on the cathode side By making the EW higher than that of the polymer membrane and lower EW than that of the solid polymer membrane on the anode side, the difference in hydrophilicity or hydrophobicity is utilized, and the fuel or oxidizer is insufficiently humidified or the battery Even when the operating current density is low or when the operation is stopped, it is possible to maintain water in the membrane and maintain high proton conductivity. The thickness of this layer is 0.05 to 30 μm, more preferably 0.1 to 10 μm. When the thickness is 0.05 μm or less, the above-described sufficient function effect cannot be obtained. On the other hand, when the thickness is 30 μm or more, the resistance increases, which is not suitable. The EW of the proton conductive polymer layer may be at least 700 or more, more preferably 800 or more. And it is preferable that it is 1500 or less, and it is more preferable that it is 1300 or less. If it is 700 or less, the hydrophilicity is too high and water cannot move smoothly, and if it is 1500 or more, the proton conductivity is too low, the effect of the present invention cannot be shown. The difference in EW between the proton conductive polymer layer and the solid polymer membrane at the interface is preferably 20 or more, more preferably 50 or more, and particularly preferably 100 or more. . In addition, when the EW difference between the closest numerical values in the case of including three or more kinds of proton conductive polymers is 20 or more, the effect of the present invention can be enjoyed. The upper limit of the EW difference is preferably 800 or less, more preferably 600 or less, and particularly preferably 400 or less.
[0019]
In the present invention, the same material as the proton conductive polymer can be used for the membrane used as the solid polymer electrolyte. That is, those having at least one of a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, and a phosphoric acid group with a fluorine-containing polymer as a skeleton are preferable. A film in which a monomer having a sulfonic acid group or a carboxylic acid group is introduced into a polyolefin film such as polyethylene by a graft polymerization reaction can also be used. The fluorine-containing film is, for example, a copolymer of 2 or more, usually 2 to 3, which is selected from the first group of monomers and the second group of monomers and essentially requires the second group of monomers. In addition to the method of reinforcing the mechanical strength by laminating with a film having a higher EW, these membranes may be reinforced with a perfluorocarbon polymer in a fibril shape, a woven fabric shape, a nonwoven fabric shape, or a porous sheet, The membrane surface can be reinforced by coating with an inorganic oxide or metal.
The EW of these films may be 700 or more, more preferably 800 or more. And it is preferable that it is 1500 or less, and it is more preferable that it is 1300 or less. If it is less than 700, the proton conductivity is improved, but the mechanical strength of the membrane is lowered, which is not practical. Above 1500, the mechanical strength is further improved, but the proton conductivity is lowered and the battery voltage is lowered.
[0020]
  The EW of the solid polymer electrolyte membrane may be 800 or less, more preferably 600 or less, with respect to the EW of the proton conductive polymer dispersed in the catalyst layer in contact with both surfaces of the membrane. If it is 800 or more, the adhesion between the membrane and the catalyst layer is not sufficient, which is not preferable. The catalyst layer can be produced by various generally known methods-spraying method, transfer method, screen printing method, rolling method and the like. After sufficiently stirring a catalyst dispersion liquid composed of a proton conductive polymer, a catalyst, a conductive material, and / or a water-repellent polymer dissolved in a solvent mainly composed of a lower alcohol such as ethanol, for example, in the transfer method, PTFE A catalyst layer is formed on such a smooth sheet by applying and drying the catalyst dispersion to a certain area. At this time, at least two or more types of proton conductive polymers can be added to the catalyst dispersion liquid sequentially or simultaneously in advance to form a catalyst layer in which the proton conductive polymers are uniformly dispersed.
[0021]
The amount of the proton conductive polymer dispersed in the catalyst layer is in the range of 0.1 to 10 by weight with respect to the amount of catalyst supported. When the weight ratio to the catalyst is 0.1 or less, a sufficient catalyst utilization rate cannot be obtained due to a decrease in the reaction active point. On the other hand, when the weight ratio is 10 or more, the influence of hydrophilicity due to the proton conductive polymer increases, and the effect of the present invention cannot be obtained.
Next, the catalyst layer surface of the sheet on which the catalyst layer is formed is superimposed on both surfaces of the solid polymer electrolyte membrane, and the catalyst layer is bonded to the solid polymer electrolyte membrane under heating and heating. The pressure and temperature at the time of joining are selected from the conditions under which the solid polymer electrolyte membrane, the proton conductive polymer, the catalyst, and the conductive material add sufficient adhesion to each other. In particular, when a perfluorosulfonic acid polymer is used as the solid polymer electrolyte membrane, it may be at least the glass transition point, and the preferred joining temperature is 120 to 200 ° C.
[0022]
Proton conducting polymer can not obtain sufficient conductivity unless it is finally proton type, but in order to improve the heat resistance of solid polymer membrane and proton conducting polymer at the time of bonding, sodium or potassium It is also effective to substitute a monovalent metal ion or the like, or a divalent or trivalent metal, heat treatment, and finally form a proton type.
[0023]
After the catalyst layer is bonded to the solid polymer membrane, the fuel is further used as a membrane / electrode assembly by bonding or overlapping with an electrically conductive porous woven fabric / nonwoven fabric such as carbon paper or carbon cloth as a catalyst layer support. Can be incorporated into battery cells. Carbon paper and carbon cloth can impart water repellency as needed by impregnating with a polytetrafluoroethylene resin, like the diffusion layer. If the porosity of the electrically conductive porous woven fabric or nonwoven fabric is 50% or more, it has a sufficient material exchange function.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not restrict | limited to an Example.
【Example】
Example 1
40 wt% platinum catalyst-supported carbon (manufactured by E-TEK, USA), 5 wt% solution of proton type perfluorosulfonic acid polymer resin (Asahi Kasei Kogyo Co., Ltd., EW = 910, solvent composition: ethanol / water = 50/50) was added so that the weight ratio of the platinum catalyst to the polymer was 4 to 1, and evenly dispersed to form a paste, and then 5% of proton type perfluorosulfonic acid polymer resin with EW = 1030. A weight percent solution (manufactured by Asahi Kasei Kogyo Co., Ltd., solvent composition is the same as above) was added in the same amount as the polymer weight, and uniformly dispersed again to prepare a paste. This paste was applied onto a polytetrafluoroethylene sheet using a 200 mesh screen, and then dried and fixed at 100 ° C. in an air atmosphere to obtain a platinum loading of 0.2 mg / cm 2.²The catalyst sheet was obtained.
[0025]
Two catalyst layer sheets thus obtained were faced to each other, and a perfluorosulfonic acid membrane (made by Asahi Kasei Kogyo Co., Ltd.) having an EW = 950 and a thickness of 100 μm was sandwiched between them, 150 ° C., pressure 50 kg / cm.²After hot pressing, the polytetrafluoroethylene sheets on both sides were peeled off to produce a membrane / electrode assembly.
As a catalyst layer support, a carbon cloth having a thickness of about 400 μm (manufactured by E-TEK) was immersed in a tetrafluoroethylene dispersion (60% by weight) and sintered at 340 ° C. 40% by weight impregnation was performed. The porosity was 50%.
[0026]
These membrane / electrode assembly and catalyst layer support were incorporated into a fuel cell single cell evaluation device, and hydrogen gas was used as the fuel and air gas was used as the oxidant, and a single cell characteristic test was conducted at normal pressure and a cell temperature of 70 ° C. . Hydrogen gas was humidified at 80 ° C., and air gas was supplied to the cell as it was without humidification. 0.5, 1.0 A / cm²When the current density was 0.66V and 0.51V, respectively. The following examples and comparative examples were also tested under the same membrane / electrode joining method, diffusion layer, and single cell operating conditions.
[0027]
(Example 2)
40 wt% platinum catalyst-supported carbon (manufactured by E-TEK, USA) and 5 wt% solution of proton type perfluorosulfonic acid polymer resin (Asahi Kasei Kogyo Co., Ltd., EW = 950, solvent composition is ethanol / water = 50/50) was mixed and stirred at a weight ratio of 4 to 1 between the platinum catalyst and the polymer, and then dried in vacuum at 100 ° C. to prepare a polymer-coated platinum catalyst in advance. Further, this polymer-coated platinum catalyst and a 5% by weight solution of proton type perfluorosulfonic acid polymer resin having an EW = 1030 (made by Asahi Kasei Kogyo Co., Ltd., the solvent composition is the same as the above), the weight ratio of platinum catalyst to polymer 4 A paste was prepared by mixing in a pair and dispersing uniformly. Thereafter, a catalyst sheet was formed in the same manner as in Example 1, and the platinum loading was 0.2 mg / cm.²Got. The anode catalyst layer was produced in the same procedure as in Example 1.
0.5, 1.0 A / cm²When the current density was 0.66V and 0.51V, respectively.
[0028]
(Example 3)
On the cathode catalyst sheet of Example 1, only a 5% by weight solution of proton type perfluorosulfonic acid polymer resin with EW = 1030 (same as above) was applied using the same screen and dried at 100 ° C. in an air atmosphere. 0.20mg / cm²The polymer layer was formed.
On the other hand, on the anode catalyst sheet of Example 1, a 5 wt% solution of proton type perfluorosulfonic acid polymer resin with EW = 910 (same as above) was applied, dried at 100 ° C. in an air atmosphere, 20 mg / cm²The polymer layer was formed.
The following procedures and methods after the production of the membrane / electrode assembly were the same as those in Examples 1 and 2.
0.5, 1.0 A / cm²When the current density was 0.67 V and 0.53 V, respectively. A schematic diagram of the cell structure of Example 3 is shown in FIG.
[0029]
(Comparative Example 1)
40 wt% platinum catalyst-supported carbon (manufactured by E-TEK, USA), 5 wt% solution of proton type perfluorosulfonic acid polymer resin (Asahi Kasei Kogyo Co., Ltd., EW = 910, solvent composition: ethanol / water = 50/50) was added so that the weight ratio of the platinum catalyst to the polymer was 2 to 1, and dispersed uniformly to prepare a paste. This paste was applied onto a polytetrafluoroethylene sheet using a 200-mesh screen, and then dried and fixed at 100 ° C. in an air atmosphere to obtain a platinum loading of 0.2 mg / cm 2.²The catalyst sheet was obtained.
0.5, 1.0 A / cm²When the current density was 0.53V and 0.25V, respectively.
[0030]
【The invention's effect】
As described above, by using a catalyst layer containing at least two types of proton conductive polymers having different EWs, the high proton conductive low EW polymer near the catalytic active point has an effect of smoothly promoting the cell reaction, The high EW polymer indicates that the generated water in the catalyst layer is quickly discharged out of the layer and the gas supply to the catalyst is maintained. Accordingly, a stable battery voltage can be obtained from a low current density to a high current density. In particular, even when the electrode area is increased and the gas humidification conditions fluctuate in the cell, the use of the electrode or the membrane / electrode assembly of the present invention greatly improves the electrode area.
[Brief description of the drawings]
FIG. 1 is a schematic view of a cell structure of a polymer electrolyte fuel cell to which a membrane / electrode assembly of the present invention is applied.
[Explanation of symbols]
1 Solid polymer membrane
2 Anode
3 Cathode
4 Membrane / electrode assembly
5 Catalyst layer support
6 Separator
7 Catalyst layer
8 Proton conductive polymer layer

Claims (7)

In the gas diffusion electrode for a polymer electrolyte fuel cell, both the anode catalyst layer and the cathode catalyst layer have at least two kinds of sulfonic acid groups in which the difference in EW uniformly dispersed in the catalyst layer is 20 to 800. An electrode comprising a perfluorocarbon polymer . 2. The perfluorocarbon polymer having at least two kinds of sulfonic acid groups is uniformly dispersed in the catalyst layer by sequentially or simultaneously adding to the catalyst dispersion. Electrodes. The electrode according to claim 1 or 2, wherein the difference in EW is 50 to 600. In the solid polymer type fuel cell membrane electrode assembly, and a solid polymer membrane EW is 700 to 1500, an anode catalyst layer and cathode catalyst layer are both difference uniformly distributed EW in the catalyst layer A membrane-electrode assembly comprising: an electrode having a catalyst layer containing a perfluorocarbon polymer having at least two kinds of sulfonic acid groups having a saponification value of 20 to 800 . 5. The perfluorocarbon polymer having at least two kinds of sulfonic acid groups is uniformly dispersed in the catalyst layer by sequentially or simultaneously charging the catalyst dispersion liquid. Membrane / electrode assembly. 6. The membrane / electrode assembly according to claim 4, wherein the difference in EW is 50 to 600. The membrane / electrode assembly according to any one of claims 4 to 6, further comprising an EW proton conductive polymer layer different from the solid polymer membrane at an interface where the solid polymer membrane and the catalyst layer are in contact with each other .

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