JP4062133B2 - Method for producing gas diffusion layer of membrane-electrode assembly, membrane-electrode assembly, and fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a gas diffusion layer of a membrane-electrode assembly in which a proton exchange membrane, an electrode catalyst layer, and a gas diffusion layer are laminated, a membrane-electrode assembly, and a polymer electrolyte fuel cell using the same. It is about.
[0002]
[Prior art]
There are various types of fuel cells such as a solid polymer type, a phosphoric acid type, a solid oxide type, a molten carbonate type, and an alkaline type depending on the type of electrolyte used. In particular, solid polymer fuel cells have features such as lower operating temperatures, shorter start-up times, higher output, easier downsizing and weight reduction, and resistance to vibration than other fuel cells. Suitable for body power supply.
[0003]
Solid polymer fuel cells are expected as one of the pillars of future new energy technologies. A polymer electrolyte fuel cell (PEFC or PEMFC) using an ion exchange membrane made of a polymer as an electrolyte can be operated at a low temperature and can be reduced in size and weight. The application of is being considered. In particular, fuel cell vehicles equipped with polymer electrolyte fuel cells are gaining social interest as the ultimate ecological car.
[0004]
A solid polymer electrolyte is a solid polymer material having an electrolyte group such as a sulfonic acid group in a polymer chain, and has a property of binding firmly to a specific ion or selectively transmitting a cation or an anion. Have. In particular, a fluorine-based electrolyte membrane typified by a perfluorosulfonic acid membrane is awarded as an ion exchange membrane for fuel cells used under severe conditions because of its very high chemical stability.
[0005]
For example, a reformed gas fuel cell is provided with a pair of electrodes on both sides of a proton-conductive ion exchange membrane and hydrogen gas obtained by reforming low-molecular hydrocarbons such as methane and methanol as fuel gas. Is supplied to the other electrode (fuel electrode), and oxygen gas or air is supplied as an oxidizing agent to a different electrode (air electrode) to obtain an electromotive force.
[0006]
In the case of a fuel cell, peroxide is generated in the electrode catalyst layer formed at the interface between the ion exchange membrane and the electrode, and the generated peroxide diffuses into peroxide radicals to cause a degradation reaction. It is not possible to use a hydrocarbon-based electrolyte membrane having poor chemical properties. Therefore, perfluorosulfonic acid membranes having high proton conductivity are generally used in fuel cells and water electrolysis.
[0007]
Currently, ion-exchange membranes used in polymer electrolyte fuel cells include perfons represented by DuPont Nafion (registered trademark), Asahi Glass Flemion (registered trademark), and Asahi Kasei Aciplex (registered trademark). In order to apply these ion exchange membranes using a fluorocarbon sulfonic acid membrane to a polymer electrolyte fuel cell, an electrode catalyst layer having a fuel oxidizing ability and an oxidizing agent reducing ability is provided on both surfaces of the ion exchange membrane. And a membrane-electrode assembly having a structure in which a gas diffusion layer is arranged on the outside.
[0008]
That is, the structure forms an electrode catalyst layer mainly composed of carbon powder carrying a platinum-based metal catalyst on both surfaces of an ion exchange membrane made of a polymer electrolyte membrane that selectively transports hydrogen ions. Next, a gas diffusion layer having both fuel gas permeability and electron conductivity is formed on the outer surface of the electrode catalyst layer. In general, in the gas diffusion layer, a paste containing a powder of fluororesin, silicon, carbon or the like is formed on a carbon paper or carbon cloth substrate. The electrode catalyst layer and the gas diffusion layer described above are collectively referred to as an electrode.
[0009]
Next, in order to prevent leakage of the fuel gas to be supplied and to prevent mixing of the two types of fuel gas, a gas seal material and a gasket are arranged around the electrode with an ion exchange membrane interposed therebetween. This gas seal material or gasket is integrated with an electrode and an ion exchange membrane and assembled in advance, and is called a membrane-electrode assembly (MEA).
[0010]
On the outside of the MEA, a separator having electrical conductivity and airtightness for mechanically fixing the MEA and electrically connecting adjacent MEAs to each other in series is disposed. In the portion of the separator that contacts the MEA, a reaction gas is supplied to the electrode surface to form a gas flow path for carrying away the generated gas and surplus gas. Although the gas channel can be provided separately from the separator, a method of providing a gas channel by providing a groove on the surface of the separator is generally used. A structure in which the MEA is fixed by the pair of separators is referred to as a unit cell as a basic unit.
A plurality of the unit cells are connected in series, and a manifold which is a piping jig for supplying fuel gas is arranged to constitute a fuel cell.
[0011]
For the gas diffusion layer, a base material such as carbon paper or carbon cloth uses a powder of fluororesin, silicon, carbon, etc., but the powder of fluororesin, silicon, carbon, etc. originally has water repellency. In this state, it is impossible to form a film as a paste. Therefore, it is necessary to make the paste containing these powders hydrophilic in order to make these powders familiar with water to form a uniform paste and form a film on the substrate.
[0012]
For this reason, hydrophilization of powders such as fluororesin, silicon, and carbon is performed by adding a surfactant to the gas diffusion layer paste. Patent Document 1 below discloses hydrophilizing the surface of a gas diffusion layer by spraying a surfactant on the gas diffusion layer.
[0013]
When the paste is hydrophilized by such a method, the water repellency of the gas diffusion layer is insufficient, and the performance of the fuel cell is lowered due to the flooding phenomenon. In other words, the gas diffusion layer must be a passage for hydrogen gas and air, and must be a passage for efficiently releasing generated water molecules, and the gas diffusion layer is hydrophilic due to the remaining surfactant. Is an undesirable condition.
[Patent Document 1]
Japanese Patent Laid-Open No. 7-161359
[Problems to be solved by the invention]
In the case of the method disclosed in Patent Document 1, a surfactant is used to impart hydrophilicity to the gas diffusion layer paste. For this reason, it was necessary to remove this surfactant. For example, there is a method of decomposing by heating, but it is difficult to completely decompose, and a long-time heat treatment is required, and productivity is lowered.
Therefore, an object of the present invention is to produce a gas diffusion layer that is hydrophilic as a paste but exhibits water repellency after film formation.
[0015]
[Means for Solving the Problems]
The inventor has found a method for producing a gas diffusion layer that does not use a surfactant, and has reached the present invention.
That is, first, the present invention provides a process for subjecting powder to a hydrophilization treatment in a method for producing a gas diffusion layer of a membrane-electrode assembly formed by laminating a proton exchange membrane, an electrode catalyst layer, and a gas diffusion layer. A step of mixing the hydrophilized powder together with a polymer electrolyte and a solvent to form a paste, a step of forming the paste on a base material sheet, and water repellency on the surface of the formed paste And a step of applying a treatment. A method for producing a gas diffusion layer of a membrane-electrode assembly.
[0016]
Examples of the hydrophilic treatment for the powder include plasma irradiation, immersion in hydrogen peroxide solution, immersion in an inorganic acid aqueous solution, and the like. Among these, plasma irradiation is preferable in terms of workability and efficiency.
Examples of the water repellency treatment for the powder in the paste formed into a film include infrared irradiation, particularly far infrared irradiation. Among far-infrared rays, those having a wavelength of about 2 μm are preferable because they break the H—OH bond of water molecules attached to the powder.
As the powder used in the present invention, those used for producing a gas diffusion layer are used. In particular, a powder selected from any one of fluororesin, silicon, and carbon, or a mixture thereof is preferable.
[0017]
Second, the present invention relates to a membrane-electrode assembly formed by laminating a proton exchange membrane, an electrode catalyst layer, and a gas diffusion layer, wherein a hydrophilized powder, a polymer electrolyte, and a solvent are mixed. The film-electrode assembly includes a gas diffusion layer in which the paste is formed on a substrate sheet, and the surface of the formed paste is subjected to water repellency treatment.
As in the first invention, the hydrophilic treatment is preferably plasma irradiation, the water repellent treatment is preferably far infrared irradiation, and the powder is one of fluororesin, silicon, carbon, or Powders selected from these mixtures are preferred.
The proton exchange membrane used in the present invention preferably has a perfluorosulfonic acid group.
[0018]
3rdly, this invention is a polymer electrolyte fuel cell using the membrane-electrode assembly of the said 2nd invention.
In FIG. 1, the schematic diagram of the hydrophilic treatment and water-repellent treatment with respect to the powder of the gas diffusion layer of this invention is shown. FIG. 1 (a) shows the hydrophilization (improvement of wettability) of the powder surface for making a paste. Plasma treatment is performed in an atmosphere of oxygen gas or the like on the surface of the powder that is difficult to adapt to a liquid such as water. By this plasma treatment, oxygen molecules 2 are imparted to the surface of the powder 1. FIG. 1B shows a state in which water molecules 3 having affinity with oxygen molecules 2 applied to the surface of the powder 1 are compatible. FIG. 1 (c) shows how the water molecules 3 are removed from the powder 1. That is, the H—OH bond of the water molecule 3 that has been familiar to the powder 1 via the oxygen molecule 2 is decomposed by irradiation with far infrared rays, and the powder 1 and oxygen are irradiated by irradiation with far infrared rays. The bond with molecule 2 is also broken. As a result, oxygen molecules 2 and water molecules 3 are removed from the powder 1.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
As the gas diffusion layer (electrode substrate) in the present invention, a gas diffusion layer generally used in a fuel cell is used without any particular limitation. For example, a porous conductive sheet containing a conductive substance as a main constituent material can be used. Examples of the conductive material include a fired body from polyacrylonitrile, a fired body from pitch, a carbon material such as graphite and expanded graphite, stainless steel, molybdenum, and titanium. The form of the conductive material is not particularly limited, such as a fiber shape or a particulate shape. However, when used in an electrochemical device using a gas as an electrode active material such as a fuel cell, a fibrous conductive inorganic material (from the viewpoint of gas permeability) Inorganic conductive fibers) Carbon fibers are particularly preferred. As the porous conductive sheet using inorganic conductive fibers, either a woven fabric or a non-woven fabric structure can be used. The porous conductive sheet in the present invention is not particularly limited, but it is also a preferred embodiment to add conductive particles such as carbon black or conductive fibers such as carbon fiber as an auxiliary agent for improving conductivity. .
[0020]
In addition to the gas diffusion layer described above, the gas diffusion layer includes carbon fiber paper formed by binding carbon short fibers oriented in a random direction in a substantially two-dimensional plane with a polymer substance. In addition, by binding carbon short fibers with a polymer substance, it becomes strong against compression and tension, and the strength and handling properties of carbon fiber paper are improved, so that the carbon short fibers come off from the carbon fiber paper, and the thickness of the carbon fiber paper. It can be prevented from facing the direction.
[0021]
In a polymer electrolyte fuel cell, water as an electrode reaction product or water that has passed through an electrolyte is generated at a cathode (air electrode, oxygen electrode). In the anode (fuel electrode), fuel is humidified and supplied to prevent drying of the proton exchange membrane. Since the condensation and stagnation of water and swelling of the polymer material by water hinder the supply of the electrode reactant, the water absorption rate of the polymer material should be low.
[0022]
The content of the polymer substance in the gas diffusion layer is preferably in the range of 0.1 to 50% by weight. In order to reduce the electrical resistance of the carbon fiber paper, it is better that the content of the polymer substance is small. However, if the content is less than 0.1% by weight, the strength to withstand handling is insufficient, and the short carbon fibers drop off. Conversely, if it exceeds 50% by weight, there arises a problem that the electrical resistance of the carbon fiber paper increases. More preferably, it is in the range of 1 to 30% by weight.
[0023]
Examples of the carbon fiber include polyacrylonitrile (PAN) -based carbon fiber, phenol-based carbon fiber, pitch-based carbon fiber, and rayon-based carbon fiber. Of these, PAN-based carbon fibers are preferable.
[0024]
The gas diffusion layer used in the present invention is also preferably made of a porous conductive sheet in which conductive particles having flexibility are arranged in a sheet shape. As a result, it is possible to provide a gas diffusion layer that has less dropout of constituent components or is less likely to be broken even when mechanical force is applied, has low electrical resistance, and is inexpensive. In particular, the above object can be achieved by using expanded graphite particles as conductive particles having flexibility. Here, the expanded graphite particles refer to graphite particles obtained by making graphite particles intercalated with sulfuric acid, nitric acid or the like and then expanding them by rapid heating.
[0025]
The porous conductive sheet used in the gas diffusion layer of the present invention is also a preferred embodiment including other conductive particles and conductive fibers in addition to the conductive fine particles having flexibility. When both the conductive particles and the conductive particles are made of an inorganic material, an electrode substrate excellent in heat resistance, oxidation resistance, and elution resistance can be obtained.
[0026]
The proton exchange membrane used in the present invention is not particularly limited. Specific examples of the proton exchange group include those having a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and the like. Among these, a sulfonic acid group is preferably used in order to express fuel cell performance.
[0027]
Proton exchange membranes include hydrocarbon proton exchange membranes such as styrene-divinylbenzene copolymers, and perfluoro proton exchange membranes of fluoroalkyl copolymers having fluoroalkyl ether side chains and perfluoroalkyl main chains. Preferably used. These should be appropriately selected according to the use and environment in which the fuel cell is used, but a perfluoro type is preferable from the viewpoint of the life of the fuel cell. For hydrocarbons, a partial fluorine film partially substituted with fluorine atoms is also preferably used. Examples of perfluoro proton exchange membranes include DuPont Nafion, Asahi Kasei Aciplex, Asahi Glass Flemion, Japan Gore-Tex Gore-Select, etc. There are those in which a sulfonic acid group is introduced into vinylidene chloride.
[0028]
Proton exchange membranes are not only one type of polymer, but also a copolymer or blend polymer of two or more types of polymers, a composite membrane in which two or more types of membranes are bonded together, and a membrane in which the proton exchange membrane is reinforced with a nonwoven fabric or porous film Etc. can also be used.
[0029]
The electrode catalyst layer in the present invention has at least a catalyst or a catalyst-carrying medium (for example, catalyst-carrying carbon is preferable. Hereinafter, the catalyst-carrying carbon will be described as an example, but the invention is not limited thereto). Do it. Although not particularly limited, for example, the electrode catalyst layer in the present invention binds the catalyst-carrying carbon and the catalyst-carrying carbon to each other or the catalyst-carrying carbon and the electrode substrate or the catalyst-carrying carbon and the proton exchange membrane, It consists of a polymer that forms the catalyst layer.
[0030]
The catalyst contained in the catalyst-supported carbon is not particularly limited, but a precious metal catalyst such as platinum, gold, palladium, ruthenium and iridium is preferably used because the activation overvoltage in the catalytic reaction is small. Two or more elements such as alloys and mixtures of these noble metal catalysts may be contained.
[0031]
The carbon contained in the catalyst-supported carbon is not particularly limited, but carbon blacks such as oil furnace black, channel black, lamp black, thermal black, and acetylene black are preferred from the viewpoints of electron conductivity and specific surface area. It is. Oil furnace black includes Vulcan XC-72, Vulcan P, Black Pearls 880, Black Pearls 1100, Black Pearls 1300, Black Pearls 2000, Legal 400, Lion Ketjen Black EC, Mitsubishi Chemical Corporation # 3150. , # 3250, etc., and acetylene black includes Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd.
[0032]
The polymer contained in the electrode catalyst layer is not particularly limited, but a polymer that does not deteriorate in an oxidation-reduction atmosphere in the fuel cell is preferable. Examples of such polymers include polymers containing fluorine atoms, and are not particularly limited. For example, polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polyhexafluoropropylene (FEP), poly Tetrafluoroethylene, polyperfluoroalkyl vinyl ether (PFA), or the like, copolymers thereof, copolymers of these monomer units with other monomers such as ethylene and styrene, and blends can also be used.
[0033]
The polymer contained in the electrode catalyst layer is also preferably a polymer having a proton exchange group in order to improve proton conductivity in the electrode catalyst layer. Proton exchange groups contained in such polymers include sulfonic acid groups, carboxylic acid groups, and phosphoric acid groups, but are not particularly limited. The polymer having such a proton exchange group is also selected without any particular limitation, but a fluoroalkyl copolymer having a fluoroalkyl ether side chain with a proton exchange group is preferably used. For example, Nafion manufactured by DuPont is also preferable. Further, it may be a polymer containing the above-described fluorine atom having a proton exchange group, another polymer such as ethylene or styrene, a copolymer or a blend thereof.
[0034]
As the polymer contained in the electrode catalyst layer, it is also preferable to use a polymer containing a fluorine atom or a polymer containing a proton exchange group by copolymerization or blending. In particular, blending a polymer such as polyvinylidene fluoride, poly (hexafluoropropylene-vinylidene fluoride) copolymer and a polymer such as Nafion having a fluoroalkyl ether side chain and a fluoroalkyl main chain in the proton exchange group is From the point of view, it is preferable.
[0035]
The main components of the electrode catalyst layer are preferably catalyst-supported carbon and polymer, and the ratio thereof should be appropriately determined according to the required electrode characteristics and is not particularly limited. A weight ratio of 5/95 to 95/5 is preferably used. In particular, when used as an electrode catalyst layer for a polymer electrolyte fuel cell, the catalyst-supporting carbon / polymer weight ratio is preferably 40/60 to 85/15.
[0036]
In addition to the above-mentioned carbon supporting the catalyst-supporting carbon, it is also preferable to add various conductive agents to the electrode catalyst layer in order to improve electronic conductivity. Examples of such a conductive agent include, in addition to carbon black of the same type as the carbon used for the catalyst-supporting carbon described above, various graphite and carbonaceous carbon materials, metals and metalloids, but are particularly limited. It is not a thing. Examples of such a carbon material include artificial graphite and carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, and furan resin in addition to the above-described carbon black. As the form of these carbon materials, not only particles but also fibers can be used. It is also possible to use carbon materials obtained by post-processing these carbon materials. The addition amount of these conductive materials is preferably 1 to 80%, more preferably 5 to 50% as a weight ratio with respect to the electrode catalyst layer.
[0037]
In the present invention, the method for forming the electrode catalyst layer on the gas diffusion layer or proton exchange membrane is not particularly limited. The catalyst-supporting carbon and the polymer contained in the electrode catalyst layer are kneaded into a paste, and the electrode catalyst layer is formed into a gas diffusion layer by methods such as brush coating, brush coating, bar coater coating, knife coater coating, screen printing, and spray coating. Alternatively, it may be directly added to and formed on the proton exchange membrane, or an electrode catalyst layer may be once formed on another substrate (transfer substrate) and then transferred to the gas diffusion layer or proton exchange membrane. As the transfer substrate in this case, a polytetrafluoroethylene (PTFE) sheet, or a glass plate or a metal plate whose surface is treated with a fluorine or silicone release agent is also used.
[0038]
In this invention, it is preferable that it is 1-10 MPa, and, as for the pressure applied at the time of joining of a membrane-electrode assembly, it is more preferable that it is 2-10 MPa. When the applied pressure is 1 MPa or less, the proton exchange membrane and the electrode catalyst layer or the electrode catalyst layer and the gas diffusion layer are not sufficiently joined, and the ionic resistance at the interface between the proton exchange membrane and the electrode catalyst layer is increased. Alternatively, the electronic resistance at the interface between the electrode catalyst layer and the electrode substrate is undesirably high, and when the applied pressure is 10 MPa or more, the electrode catalyst layer is crushed and the diffusibility of the reaction gas in the electrode catalyst layer is reduced. It is not preferable because it is inhibited.
[0039]
Also, the processing time for heating and pressurization can vary depending on the temperature and pressure. In general, the higher the temperature and the higher the pressure, the shorter the processing time. Preferably it is 10 minutes or more, More preferably, it is 30 minutes or more, More preferably, it is 60 minutes or more.
[0040]
The membrane-electrode assembly comprising the proton exchange membrane, electrode catalyst layer, and gas diffusion layer of the present invention can be applied to various electrochemical devices. Among these, a fuel cell is preferable, and among the fuel cells, a solid polymer fuel cell is preferable. Fuel cells include those using hydrogen as fuel and those using hydrocarbons such as methanol as fuel, but can be used without any particular limitation.
[0041]
The application of the fuel cell using the membrane-electrode assembly of the present invention is not particularly limited, but an automobile power supply source that is useful in a polymer electrolyte fuel cell is preferable. .
[0042]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
[Example 1]
Fluorine resin and carbon black were used as powders, and plasma was irradiated for 1 to 2 kW · sec and 30 to 60 sec in an oxygen atmosphere while stirring.
100 g of the powder hydrophilized with the above plasma was put in 400 g of water and stirred with a stirrer having stirring blades to make a paste.
[0043]
The paste thus obtained was applied onto a carbon sheet that continuously traveled on the roller. The carbon paste coated with the paste was continuously passed through a drying apparatus irradiated with far infrared rays having a wavelength of 2 μm.
A membrane-electrode assembly (MEA) was produced using the obtained gas diffusion layer. In the fuel cell using this membrane-electrode assembly (MEA), since the gas diffusion layer has sufficient water repellency, no flooding phenomenon occurs during operation, and the performance of the fuel cell is reduced. There wasn't.
[0044]
[Comparative Example 1]
For comparison, a gas diffusion layer was produced in the same manner as in Example 1 except that the powder was irradiated with plasma to perform the hydrophilic treatment, but the water repellent treatment with far infrared rays was not performed. A membrane-electrode assembly (MEA) was produced using this gas diffusion layer. In the fuel cell using this membrane-electrode assembly (MEA), since the gas diffusion layer does not have water repellency, a flooding (water clogging) phenomenon occurred during operation, and the performance of the fuel cell was deteriorated.
[0045]
[Comparative Example 2]
About 3% of a surfactant was added to the powder and a hydrophilic treatment was performed to prepare a paste. After applying this paste to the substrate, it was fired for about 30 minutes to produce a gas diffusion layer. A membrane-electrode assembly (MEA) was produced using this gas diffusion layer. In the fuel cell using this membrane-electrode assembly (MEA), since the surfactant remains in the gas diffusion layer, a flooding phenomenon occurs during operation, and the performance of the fuel cell is lowered. did.
[0046]
【The invention's effect】
According to the present invention, since the hydrophilized powder and the water-repellent gas diffusion layer are used, the membrane-electrode assembly (MEA) produced using this gas diffusion layer was used. In the fuel cell, since the gas diffusion layer has sufficient water repellency, a flooding (water clogging) phenomenon does not occur during operation, and the performance of the fuel cell can be maintained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a hydrophilic treatment and a water repellency treatment for a powder of a gas diffusion layer according to the present invention. Fig. 1 (a) shows plasma treatment of powder, Fig. 1 (b) shows how water branches are adapted to the powder via oxygen molecules, and Fig. 1 (c) shows water molecules by far infrared treatment. Shows the state of dissociation.
[Explanation of symbols]
1: powder, 2: oxygen molecule, 3: water molecule.

Claims (8)

In a method for producing a gas diffusion layer of a membrane-electrode assembly formed by laminating a proton exchange membrane, an electrode catalyst layer, and a gas diffusion layer, a step of hydrophilizing the powder, and the powder subjected to the hydrophilic treatment Mixing with a polymer electrolyte and a solvent to form a paste, forming the paste on a substrate sheet, applying a water repellent treatment to the formed paste surface by far infrared radiation , A method for producing a gas diffusion layer of a membrane-electrode assembly comprising:   The method for producing a gas diffusion layer according to claim 1, wherein the hydrophilization treatment is plasma irradiation. The method for producing a gas diffusion layer according to claim 1 or 2 , wherein the powder is a powder selected from any one of fluororesin, silicon, and carbon, or a mixture thereof. In a membrane-electrode assembly formed by laminating a proton exchange membrane, an electrode catalyst layer, and a gas diffusion layer, a paste in which a hydrophilized powder, a polymer electrolyte, and a solvent are mixed is formed on a base sheet. A membrane-electrode assembly comprising a gas diffusion layer which is formed and the paste surface formed is subjected to a water repellency treatment by irradiation with far infrared rays . The membrane-electrode assembly according to claim 4 , wherein the hydrophilization treatment is plasma irradiation. The membrane-electrode assembly according to claim 4 or 5 , wherein the powder is a powder selected from one of fluororesin, silicon, and carbon, or a mixture thereof. The membrane-electrode assembly according to any one of claims 4 to 6 , wherein the proton exchange membrane has a perfluorosulfonic acid group. A polymer electrolyte fuel cell using the membrane-electrode assembly according to any one of claims 4 to 7 .

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