CN100454623C

CN100454623C - Membrane-electrode assembly for fuel cell and fuel cell using same

Info

Publication number: CN100454623C
Application number: CNB2005800134556A
Authority: CN
Inventors: 山本伸司
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2004-04-28
Filing date: 2005-04-22
Publication date: 2009-01-21
Anticipated expiration: 2025-04-22
Also published as: CN1947291A

Abstract

Disclosed is a membrane-electrode assembly for fuel cells which is improved in durability to repeated starting and stopping operations. Specifically disclosed is a membrane-electrode assembly for fuel cells comprising a cathode catalyst layer containing a cathode catalyst composed of platinum or an platinum alloy, a conductive carbon material for supporting the cathode catalyst and a proton conductive polymer electrolyte; a solid polymer electrolyte membrane; and an anode catalyst layer containing an anode catalyst, a conductive carbon material for supporting the anode catalyst and a proton conductive polymer electrolyte. In this membrane-electrode assembly for fuel cells, the average thickness (Ya) of the anode catalyst layer is smaller than the average thickness (Yc) of the cathode catalyst layer.

Description

Membrane-electrode assembly for fuel cell and fuel cell using same

Technical Field

The present invention relates to a membrane-electrode assembly for a fuel cell, and more particularly to an electrode catalyst layer of a membrane-electrode assembly for a fuel cell.

Background

In recent years, in response to social demands and trends in the background of energy and environmental problems, fuel cells have attracted attention as a drive source for vehicles and a stationary power source. The fuel cell may be classified into various types according to the kind of electrolyte, the kind of electrode, and the like, and representative examples thereof include an alkaline type, a phosphoric acid type, a molten carbonate type, a solid electrolyte type, and a solid polymer type. Among them, a Polymer Electrolyte Fuel Cell (PEFC) capable of operating at a low temperature (usually 100 ℃ or lower) is attracting attention, and has been developed and put into practical use as a low-pollution power source for automobiles in recent years (japanese patent laid-open No. 2004-79457).

The PEFC is generally configured to sandwich a membrane-electrode assembly (MEA) between separators. The MEA generally has a structure in which a gas diffusion layer, a cathode catalyst layer, a solid polymer electrolyte membrane, an anode catalyst layer, and a gas diffusion layer are laminated.

In the MEA, the following electrochemical reactions occur. First, hydrogen contained in the fuel gas supplied to the anode (fuel electrode) side is oxidized by a catalyst, generating protons and electrons. The generated protons pass through the polymer electrolyte contained in the anode-side catalyst layer, further pass through the solid polymer electrolyte membrane in contact with the anode-side catalyst layer, and reach the cathode (air electrode) side catalyst layer, and the electrons generated in the anode-side catalyst layer pass through the conductive carrier constituting the anode-side catalyst layer, and further pass through the gas diffusion layer, the gas separator, and the external circuit in contact with the anode-side catalyst layer on the side opposite to the solid polymer electrolyte membrane, and reach the cathode-side catalyst layer. Then, the protons and electrons that have reached the cathode-side catalyst layer react with oxygen contained in the oxidant gas supplied to the cathode-side catalyst layer to generate water. In the fuel cell, electric energy can be released to the outside by the electrochemical reaction.

As applications of the PEFC, a driving source for a vehicle or a stationary power source are studied, and durability over a long period of time is required for application to these applications. Among them, in the case of use as a drive source for a vehicle, it is required not to cause degradation of battery characteristics due to frequent start-up and stop.

In particular, in an electrode catalyst layer containing a catalyst composed of platinum or a platinum alloy, a conductive carbon material such as carbon black supporting the catalyst, and a proton conductive polymer electrolyte, there is a tendency that corrosion of the conductive carbon material and decomposition degradation of the polymer electrolyte, decrease in gas diffusion and water discharge of the electrode, increase in concentration overvoltage, and decrease in battery characteristics are easily caused by repeated start-up and stop.

Therefore, many attempts have been made to improve the corrosion resistance of the conductive carbon material. For example, Japanese patent laid-open publication No. H05-129023 and Japanese patent laid-open publication No. 2005-26174 disclose conductive carbon materials having improved corrosion resistance by controlling the crystallinity of the carbon by heat treatment.

Disclosure of Invention

As described above, the PEFC is required to exhibit high power generation performance over a long period of time. However, in the conventional membrane-electrode assembly, sufficient power generation performance cannot be obtained even with the conductive carbon material whose corrosion resistance is improved by heat treatment as described in patent documents 2 and 3 and the like.

Of membrane-electrode assemblies resulting from repeated start-stopOne of the causes of the reduction in power generation characteristics is considered to be caused by hydrogen gas remaining on the anode side at the time of stop. On the anode side, hydrogen gas is supplied as a fuel, and when the membrane-electrode assembly is stopped, a gas such as air is supplied to the anode side to replace the hydrogen gas remaining on the anode side. However, if hydrogen is not removed from the anode and a certain amount of hydrogen remains on the anode side, a local cell is formed on the anode side at the time of starting, and the cathode side is exposed to a high potential state. As a result, electrolysis of water occurs at platinum as a catalyst support to generate oxygen, and the carbon material passes through C + O₂→CO₂The reaction of (2) causes oxidation corrosion. The carbon material corrodes, and the electrode catalyst layer of the membrane-electrode assembly deforms and deteriorates, thereby increasing the concentration overvoltage and significantly reducing the performance of the PEFC. In the membrane-electrode assembly, repeated activation and deactivation causes platinum to melt in the solid polymer electrolyte membrane and cause decomposition of the polymer electrolyte, which all cause degradation of the performance of the PEFC.

Accordingly, an object of the present invention is to improve the durability of a membrane-electrode assembly for a fuel cell against repeated start-up and stop.

The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, have found that the durability of the membrane-electrode assembly for a fuel cell against the cathode catalyst layer at the time of start-up and shutdown can be improved by making the anode catalyst layer thinner than the cathode catalyst layer.

That is, the above problem is solved by the following (1) to (3).

(1) A membrane-electrode assembly for a fuel cell, comprising:

a cathode catalyst layer containing a cathode catalyst formed of platinum or a platinum alloy, an electrically conductive carbon material supporting the cathode catalyst, and a proton-conductive polymer electrolyte;

a solid polymer electrolyte membrane;

an anode catalyst layer containing an anode catalyst, an electrically conductive carbon material supporting the anode catalyst, and a proton-conductive polymer electrolyte,

wherein,

the average thickness (Ya) of the anode catalyst layer is smaller than the average thickness (Yc) of the cathode catalyst layer.

(2) A polymer electrolyte fuel cell using the membrane-electrode assembly for a fuel cell.

(3) A vehicle equipped with the polymer electrolyte fuel cell.

Detailed Description

The following describes embodiments of the present invention in detail.

A first aspect of the present invention is a membrane-electrode assembly for a fuel cell, comprising:

a solid polymer electrolyte membrane;

wherein,

In the membrane-electrode assembly for a fuel cell of the present invention, the average thickness (Ya) of the anode catalyst layer is made smaller than the average thickness (Yc) of the cathode catalyst layer. Thus, the hydrogen gas remaining on the anode side at the time of stopping can be effectively replaced with other gas. As a result, formation of a local cell on the anode side at the time of startup can be suppressed, and deterioration of the membrane-electrode assembly can be prevented.

Further, if the anode catalyst layer is thin, the moisture content of the anode catalyst layer is likely to be reduced when a gas such as air is purged to replace the hydrogen gas on the anode side during stoppage. That is, the anode catalyst layer is easily dried. As a result, in order to replenish the moisture reduced in the anode catalyst layer, the moisture is caused to move from the solid polymer electrolyte membrane having a relatively high moisture content. At the same time, moisture is caused to move from the cathode catalyst layer to the solid polymer electrolyte membrane, and the moisture content of the cathode catalyst layer decreases. At the time of startup, even if the cathode catalyst layer is exposed to a high potential, oxygen is not generated as long as water is not present in the vicinity of the platinum catalyst. Thus, the occurrence of carbon corrosion accompanying start-up and stop can be suppressed.

However, the above-described mechanism between the configuration and the effect of the present invention is presumed, and the technical scope of the present invention is not limited to only the embodiment utilizing the above-described mechanism.

As described above, in the membrane-electrode assembly of the present invention, the average thickness (Ya) of the anode catalyst layer is smaller than the average thickness (Yc) of the cathode catalyst layer. Specifically, Ya and Yc preferably satisfy a relationship of Ya/Yc of 0.01 to 0.9, and more preferably of 0.03 to 0.86. By controlling the thickness of the catalyst layer in such a relation, a membrane-electrode assembly having good durability can be obtained.

The average thickness (Ya) of the anode catalyst layer is preferably 0.3 to 10 μm, more preferably 0.3 to 8 μm, and particularly preferably 2 to 6 μm. The average thickness (Yc) of the cathode catalyst layer is preferably 7 to 20 μm, and more preferably 7 to 15 μm. By controlling the amount within this range, carbon corrosion and platinum melting at the time of start/stop or at the time of load change can be effectively suppressed. The thinner the catalyst layer is, the better the gas diffusibility and permeability and the drainage of humidified water and produced water are, but if the catalyst layer is too thin, it is difficult to maintain durability, and therefore a preferable thickness should be determined in order to balance the two.

In the present invention, the thicknesses of the respective catalyst layers of the anode and the cathode are measured at 20 to 50 sites in an electron micrograph (magnification: 3000 times) of a cross section of the catalyst layer taken under an acceleration voltage of 3kV using a scanning electron microscope, and the average value is taken.

Next, the components of the PEFC of the present invention will be described.

The cathode catalyst layer includes a cathode catalyst formed of platinum or a platinum alloy, an electrically conductive carbon material supporting the cathode catalyst, and a proton-conductive polymer electrolyte. In the cathode catalyst layer, a cathode catalyst may be supported on a conductive carbon material to serve as a cathode electrode catalyst.

The cathode catalyst is a material that promotes a reaction on the cathode side (air electrode) of the membrane-electrode assembly, and at least platinum or a platinum alloy can be used. The platinum alloy is not particularly limited, and preferably includes an alloy of platinum and iridium and an alloy of platinum and rhodium from the viewpoint of obtaining high catalytic activity. Further, the platinum alloy preferably includes an alloy of platinum and at least 1 or more base metals selected from chromium, manganese, iron, cobalt, and nickel, for the purpose of improving heat resistance, resistance to carbon monoxide poisoning, and the like. The mixing ratio of the platinum and the base metal in the platinum alloy is preferably 1/1-5/1, and particularly preferably 2/1-4/1 in terms of mass ratio. Thus, a cathode catalyst having resistance to poisoning, corrosion, and the like while maintaining high catalytic activity can be obtained.

The average particle diameter of the cathode catalyst is not particularly limited, but is preferably 1 to 20nm, more preferably 2 to 10 nm. Although it is presumed that the smaller the average particle diameter of the catalyst particles, the larger the specific surface area and the higher the catalyst activity, in practice, even if the particle diameter of the catalyst particles is extremely small, the catalytic activity commensurate with the degree of increase in the specific surface area cannot be obtained.

In the present invention, the average particle diameters of the cathode catalyst and the anode catalyst are the average values of the crystallite particle diameters obtained from the half width of the diffraction peak of the cathode catalyst or the anode catalyst in X-ray diffraction or the particle diameters of the cathode catalyst or the anode catalyst obtained from a transmission electron microscope image.

The conductive carbon material is a carbon material having a function as a carrier of the cathode catalyst and having conductivity, and is also referred to as conductive carbon. The transfer of electrons to and from the site where the electrode reaction actually proceeds is performed by the conductive carbon material. The conductive carbon material of the cathode catalyst layer is not particularly limited, and carbon black subjected to graphitization treatment is preferably used. Although general carbon black has higher hydrophobicity than oxide, it has hydrophilicity because a small amount of functional groups such as hydroxyl groups and carboxyl groups are present on the surface. In contrast, graphitized carbon black has a reduced hydrophilic functional group and thus has an increased hydrophobicity. By using carbon black having improved hydrophobicity, the water-draining property of the electrode catalyst layer is improved, and further, the cell performance of the PEFC is improved.

The carbon black is not particularly limited as long as it is a conventional usual carbon black, and preferable examples thereof include channel black, furnace black, pyrolytic carbon black, ketjen black, BlackPearl and the like. Further, as the carbon Black, commercially available products such as Vulcan XC-72, Vulcan P, Black Pearls880, Black Pearls1100, Black Pearls 1300, Black Pearls 2000, Re gal400 manufactured by Cabot corporation, Ketjen Black EC manufactured by Lion corporation, and oil furnace carbon blacks such as #3150, #3250 manufactured by Mitsubishi chemical corporation; acetylene black such as electrochemical carbon black manufactured by electrochemical industries.

The graphitization treatment is not particularly limited as long as it is a conventionally used treatment generally used, such as a heat treatment. The heat treatment is preferably performed in an inert gas atmosphere such as nitrogen, argon, or helium. The heat treatment temperature and the heat treatment time vary depending on the carbon material used, and the heat treatment can be carried out at 2000 to 3000 ℃ for 5 to 20 hours, as long as the desired surface area of the B ET or the like is obtained in the graphitized carbon black.

The graphitization ratio of the graphitized carbon black may be 75% or more, preferably 80 to 95%. Thus, not only can water resistance be ensured by reducing the surface functional groups of the carbon black, but also corrosion resistance and electrical conductivity can be improved by changing the crystal structure.

The graphitized carbon black preferably has a true density of 1.80 to 2.11g/cm³Interplanar spacing d₀₀₂Is 3.36 to 3.55

The carbon black of (1).

In the present invention, the crystal face spacing d of the above-mentioned graphitized carbon black₀₀₂The average value of the 1/2 interlayer spacing is expressed by the distance of the crystal plane of the hexagonal network plane of the carbon black graphite structure and the lattice constant in the c-axis direction perpendicular to the hexagonal network plane.

The carbon black subjected to graphitization treatment by heat treatment or the like has a graphitized layer formed of three-dimensional lattices having a structure similar to that of graphite on the surface thereof, and as graphitization progresses, fine void portions between the lattices decrease, and the crystal structure of the conductive carbon material approximates to that of graphite. In addition to water resistance, corrosion resistance and the like are considered, and it is preferable that the degree of crystallization of the conductive carbon material to be used is high.

When the true density of the above graphitized carbon black is less than 1.80g/cm³Interplanar spacing d₀₀₂Over 3.55

In many cases, the graphite structure is not sufficiently developed, and high corrosion resistance and electron conductivity may not be obtained. In addition, when the true density is more than 2.11g/cm³Interplanar spacing d₀₀₂Less than 3.36When there are more thanIn several cases, the graphite structure excessively develops, and a sufficient specific surface area may not be obtained.

Therefore, the graphitized carbon black preferably has a true density of 1.80 to 2.11g/cm³Interplanar spacing d₀₀₂Carbon black having a true density of 3.36 to 3.55, more preferably 1.90 to 2.11g/cm³Interplanar spacing d₀₀₂Is 3.38 to 3.53

The carbon black of (2) is particularly preferably used in a true density of 1.90 to 2.11g/cm³Interplanar spacing d₀₀₂Is 3.40 to 3.51

The carbon black of (1).

In the present invention, the true density is a value measured by a gas phase displacement method using helium, and the interplanar spacing d₀₀₂Measured by the X-ray diffraction method "Kangshu method (standard method-translation method approved by Nissan society)" (Kingchow, carbon Nos. 36, 25 to 34 (1963)).

The graphitized carbon black may have an electric conductivity of 50 to 1000S/cm, preferably 100 to 1000S/cm.

In addition, the graphitized carbon black is required to have not only a function of supporting a cathode catalyst but also a function of a current collector for outputting electrons to an external circuit or inputting electrons from the external circuit in order to be used for an electrode catalyst of a high-performance fuel cell. If the conductivity of the graphitized carbon black is less than 50S/cm, the internal resistance of the fuel cell increases and the cell performance decreases, and if it exceeds 1000S/cm, crystallization of the carbon occurs and the BET surface area decreases.

In the present invention, the conductivity of the graphitized carbon black is a value measured at 25 ℃ after compression molding of the graphitized carbon black under a pressure of 14 to 140MPa, heat treatment at 1000 ℃ under a nitrogen atmosphere, and the like as in the conventional method.

In the present invention, the graphitized carbon black may contain a BET surface area of preferably 100m²More preferably 100 to 300 m/g or more²Per g, particularly preferably 120 to 250m²A graphitized carbon black (A) in a gram of carbon black. The carbon black (a) obtained by the graphitization treatment is excellent not only in water repellency but also in corrosion resistance, and further, the supported cathode catalyst has high dispersibility, so that a cathode electrode catalyst having excellent catalytic activity can be obtained.

The catalyst supporting amount of the graphitized carbon black (A) is not particularly limited. The amount of the supported carbon black (a) may be appropriately determined depending on the kind of the cathode catalyst, the performance of the membrane-electrode assembly, the kind of the graphitized carbon black (a), and the like, so as to obtain desired power generation characteristics. Specifically, when the graphitized carbon black (a) supporting the cathode catalyst is used as the cathode electrode catalyst (C), the amount of the cathode catalyst supported in the cathode electrode catalyst (C) is preferably 20 to 80% by mass, more preferably 40 to 60% by mass, based on the total amount of the cathode electrode catalyst (C). If the catalyst loading amount of the graphitization-treated carbon black (A) is within this range, it is possible to suppress oxygen generated in the vicinity of the platinum catalyst from contacting the carbon surface and causing oxidative corrosion when it is at a high potential.

The conductive carbon material for the cathode catalyst layer preferably further contains a BET surface area of preferably less than 100m in addition to the above graphitized carbon black (A)²(ii) g, more preferably 80 to 100m²A graphitized carbon black (B) in a gram of carbon black. The graphitized carbon black (B) is excellent not only in water repellency but also in corrosion resistance. Therefore, by using the graphitized carbon black (a) and the graphitized carbon black (B) as the carrier of the cathode catalyst, it is possible to obtain a high catalytic activity by the graphitized carbon black (a) and further improve the corrosion resistance by the graphitized carbon black (B), and to obtain a membrane-electrode assembly excellent in power generation performance and durability.

The catalyst supporting amount of the graphitized carbon black (B) is not particularly limited, and specifically, when the graphitized carbon black (B) supporting the cathode catalyst is used as the cathode electrode catalyst (D), the supporting amount of the cathode catalyst in the cathode electrode catalyst (D) is preferably 10 to 50% by mass, more preferably 10 to 30% by mass, based on the total amount of the cathode electrode catalyst (D). If the catalyst loading of the graphitized carbon black (B) is within this range, a cathode catalyst having both corrosion resistance and catalytic activity can be obtained.

When the above-mentioned graphitized carbon black (a) and graphitized carbon black (B) are used as the conductive carbon material of the cathode catalyst support, it is preferable that the cathode catalysts supported on the graphitized carbon black (a) and the graphitized carbon black (B) are supported with their average particle diameters adjusted so as to achieve both durability and catalytic activity of the cathode electrode catalyst and further reduce the extent of decrease in catalytic activity with time.

Specifically, the average particle diameter of the cathode catalyst in the graphitized carbon black (A) may be 2 to 8nm, preferably 3 to 6 nm. If the average particle diameter is less than 2nm, high catalytic activity cannot be obtained at the initial stage of power generation, and if it exceeds 8nm, the particle diameter of the supported cathode catalyst becomes too large, the active surface area becomes small, and the catalytic activity is rather lowered. The cathode catalyst in the graphitized carbon black (B) has an average particle diameter of 4 to 10nm, preferably 4 to 8 nm. When the average particle diameter is less than 4nm, the decrease in catalytic activity with time cannot be sufficiently reduced, and when it exceeds 8nm, the particle diameter of the supported cathode catalyst becomes too large, the active surface area decreases, and the catalytic activity decreases conversely.

In the cathode catalyst layer, in order to further improve the durability and the power generation performance of the membrane-electrode assembly, it is more preferable that the cathode electrode catalyst (C) in which the cathode catalyst is supported by the graphitized carbon black (a) and the cathode electrode catalyst (D) in which the cathode catalyst is supported by the graphitized carbon black (B) are mixed at a predetermined ratio.

That is, in the cathode catalyst layer, the cathode electrode catalyst (C) and the cathode electrode catalyst (D) may be mixed in a mass ratio (C)/(D) of preferably 60/40 or more, more preferably 60/40 to 99/1, particularly preferably 80/20 to 99/1, and further preferably 85/15 to 95/5. If the mixing mass ratio (C)/(D) of the electrode catalyst (C) to the electrode catalyst (D) is less than 60/40, it may cause a decrease in power generation performance, and thus it is preferable to control within the above range.

In the cathode catalyst layer, moisture generated along with the progress of the electrode reaction easily moves with the flow of the supplied fuel gas. Under operating conditions such as high current density and high humidification, a large amount of generated water stays in the vicinity of the gas discharge portion of the cathode catalyst layer, hindering the progress of the electrode reaction, and for these reasons, the deterioration of the cathode electrode catalyst becomes severe from the upstream to the downstream of the gas flow path in the cathode catalyst layer. Therefore, when the cathode electrode catalyst (C) and the cathode electrode catalyst (D) are contained in the cathode catalyst layer, the composition of the cathode electrode catalyst is preferably optimized from the upstream to the downstream of the gas flow path.

That is, the mass ratio (C)/(D) of the cathode electrode catalyst (C) to the cathode electrode catalyst (D) on the downstream side of the gas flow path of the cathode catalyst layer may be smaller than the mass ratio (C)/(D) on the upstream side of the gas flow path of the cathode catalyst layer.

Specifically, the mass ratio (C)/(D) of the cathode electrode catalyst (C) to the cathode electrode catalyst (D) on the upstream side of the gas flow path of the cathode catalyst layer is (R ═ R)_up) A mass ratio (C)/(D) of the cathode electrode catalyst (C) to the cathode electrode catalyst (D) on a downstream side of the gas flow path of the cathode catalyst layer (R ═ R)_down) In a ratio of R_up/R_downThe content of the organic solvent is not less than 1/1, preferably 2/1-9/1, and particularly preferably 3/1-6/1.

Thus, a cathode catalyst layer which can maintain desired performance for a long period of time without any difference in electrode reaction in the cathode catalyst layer can be obtained.

The upstream side of the gas flow path of the cathode catalyst layer means the vicinity of the fuel gas inlet, and the downstream side of the gas flow path of the cathode catalyst layer means the vicinity of the fuel gas outlet, and specific ranges and the like may be determined in consideration of the characteristics of the cathode catalyst layer.

In the present invention, carbon black further subjected to hydrophobic treatment with a fluorine compound can be used as the conductive carbon material of the cathode catalyst layer. Thus, the hydrophobicity of the cathode catalyst layer can be further increased. The amount of carbon black subjected to hydrophobization treatment using a fluorine compound is preferably 1 to 20% by mass based on the total mass of the conductive carbon material of the cathode catalyst layer. By mixing the amount within this range, it is possible to achieve high power generation performance over a long period of time from the initial stage, to a range from a low current density to a high current density, to improve durability, and to realize a long life characteristic. Further, as an example of the hydrophobic treatment, a method of treating carbon black with polytetrafluoroethylene may be mentioned.

In addition, as the conductive Carbon material of the cathode catalyst layer, Carbon nanotubes, Carbon nanofibers, or Carbon nanohorns (Carbon nanohorns) are more preferably used. By adding carbon nanotubes, carbon nanofibers, or carbon nanohorns having a higher graphitization degree than carbon black, the hydrophobicity in the cathode catalyst layer can be increased, and the destruction of the three-phase structure that causes deterioration can be suppressed. As the case may be, 2 or 3 of carbon nanotubes, carbon nanofibers, or carbon nanohorns may be mixed and used. The amount of the carbon nanotubes, carbon nanofibers or carbon nanohorns used is 1 to 20 mass% based on the total mass of the conductive carbon material of the cathode catalyst layer. By mixing the amount within this range, high power generation performance is exhibited over a long period of time from the initial stage, and the durability is improved, and high life characteristics are achieved.

The proton-conductive polymer electrolyte used in the cathode catalyst layer and the anode catalyst layer has an effect of improving the mobility of protons that migrate between the cathode (air electrode) and the anode (fuel electrode) in power generation of the PEFC.

The polymer electrolyte is not particularly limited as long as it is a polymer electrolyte generally used for a catalyst layer. Specifically, Nafion can be mentioned^TMPerfluorocarbon polymers having sulfonic acid groups (manufactured by dupont), hydrocarbon polymer compounds doped with inorganic acids such as phosphoric acid, organic/inorganic hybrid polymers partially substituted with proton conductive functional groups, and proton conductors or other polymer electrolytes in which a phosphoric acid solution or a sulfuric acid solution is impregnated into a polymer matrix.

The solid polymer electrolyte membrane is an ion-conductive membrane present between a cathode catalyst layer and an anode catalyst layer. The solid polymer electrolyte membrane is not particularly limited, and a membrane formed of the same proton-conductive electrolyte as that used for the electrode catalyst layer may be used. For example, various Nafion products manufactured by DuPont may be used^TMOr by Flemion^TMTypical examples of the electrolyte membrane include a common commercially available solid polymer electrolyte membrane such as a perfluorosulfonic acid membrane. A membrane in which a liquid electrolyte is impregnated in a microporous polymer membrane, a membrane in which a porous body is filled with a polymer electrolyte, or the like may be used. The polymer electrolyte used in the solid polymer electrolyte membrane may be the same as or different from the proton-conductive electrolyte used in the electrode catalyst layer, and the same is preferably used from the viewpoint of improving the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane.

The thickness of the solid polymer electrolyte membrane may be appropriately determined in consideration of the characteristics of the MEA to be obtained, and is preferably not excessively thin from the viewpoint of strength at the time of membrane formation and durability at the time of use, and is preferably not excessively thick from the viewpoint of power characteristics at the time of use. Specifically, the thickness of the solid polymer electrolyte membrane is preferably 5 to 300. mu.m, more preferably 10 to 200. mu.m, and particularly preferably 15 to 100. mu.m.

The anode catalyst layer contains an anode catalyst, an electrically conductive carbon material supporting the anode catalyst, and a proton-conductive polymer electrolyte.

The anode catalyst is a material having a function of promoting a reaction on the anode side (fuel electrode) of the PEF C. The kind thereof is not particularly limited as long as it has the function of an anode catalyst. As with the cathode catalyst, platinum or a platinum alloy may be used, and other catalysts may also be used. For example, a catalyst selected from metals such as platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum, and alloys thereof can be used. More than 2 catalysts may be used in combination.

The conductive carbon material for the anode catalyst layer is not particularly limited, and carbon black is preferably used, and graphitized carbon black is more preferably used. Since carbon corrosion is less likely to occur in the anode catalyst layer than in the cathode catalyst layer, even carbon black which has not been subjected to graphitization treatment can exhibit high power generation performance at low to high current densities over a long period of time from the initial stage, improve durability, and realize long-life characteristics. Since the hydrophilic functional groups of the graphitized carbon black are reduced, the hydrophobicity is improved. When carbon black having improved hydrophobicity is used, the amount of moisture in the anode catalyst layer is likely to decrease, that is, to dry, during the operation of purging air to the anode catalyst layer when the PEFC is stopped.

The catalyst loading amount of the conductive carbon material in the anode catalyst layer is not particularly limited. The amount of the supported catalyst can be appropriately determined depending on the kind of the anode catalyst, the performance of the membrane-electrode assembly, the kind of the conductive carbon material, and the like so as to obtain desired power generation characteristics. For example, when an anode catalyst-supporting conductive carbon material is used as the anode electrode catalyst, the amount of the anode catalyst supported in the anode electrode catalyst is preferably 30 to 70% by mass based on the total amount of the anode electrode catalyst. If the catalyst supporting amount is within this range, the utilization efficiency of platinum is improved, and therefore the anode catalyst layer can be made thin.

The basic structure of the membrane-electrode assembly of the present invention is preferably a structure in which a cathode catalyst layer, a solid polymer electrolyte membrane, and an anode catalyst layer are arranged in this order. As a more preferable configuration of the membrane-electrode assembly, a gas diffusion layer is preferably disposed on the outer side of either one of the cathode catalyst layer and the anode catalyst layer, and a gas diffusion layer is more preferably disposed on the outer side of both the cathode catalyst layer and the anode catalyst layer. In this way, the gas supplied from the outside can be more uniformly supplied to the electrode catalyst layer, and the power generation performance of the membrane-electrode assembly can be further improved.

There is no particular limitation on the constituent material of the gas diffusion layer. Examples thereof include sheet-like materials having conductivity and porosity, such as carbon woven fabrics, paper-made paper bodies, felts, and nonwoven fabrics. More specifically, carbon paper (carbon paper), carbon cloth, carbon nonwoven fabric, and the like can be cited. It is preferable to use a carbon paper subjected to water repellent treatment.

As a water repellent treated sheet material suitable for use in a gas diffusion layer such as water repellent treated carbon paper, a sheet material containing a water repellent agent is exemplified. The water repellent is preferably a fluorine-based polymer material such as Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polypropylene, polyethylene, or the like.

The gas diffusion layer is preferably carbon paper having a thickness of 400 μm or less or carbon paper subjected to water repellent treatment, and may be appropriately determined in consideration of the characteristics of the obtained gas diffusion layer. In consideration of the water resistance of the gas diffusion layer, it is more preferable to use a gas diffusion layer having a thickness of 200 μm or less. The lower limit of the thickness of the gas diffusion layer is not particularly limited, but if it is too thin, sufficient mechanical strength cannot be obtained, and a thickness of 100 μm or more is suitable.

In order to prevent flooding of the membrane-electrode assembly, a mil layer may be provided between the gas diffusion layer and the cathode catalyst layer and between the gas diffusion layer and the anode catalyst layer. The mil layer is a mixture layer formed on the surface of the gas diffusion layer and made of carbon and a water-repellent fluororesin such as polytetrafluoroethylene.

A second aspect of the present invention is a Polymer Electrolyte Fuel Cell (PEFC) using the membrane-electrode assembly for a fuel cell according to the first aspect of the present invention. The PEFC of the present invention is less likely to deteriorate the catalyst layer of the membrane-electrode assembly, and has excellent durability. That is, the PEFC of the present invention has a small voltage drop even when the PEFC is used for a long time. Such properties are particularly beneficial in applications requiring long-term durability. Such applications include vehicle applications such as automobiles. Since the PEFC of the present invention can maintain the power generation characteristics for a long period of time, the life of a vehicle on which the PEFC of the present invention is mounted can be extended and the vehicle value can be improved. The PEFC of the present invention is preferably used as various power sources, and particularly preferably used as a power source for a vehicle.

The structure of the PEFC is not particularly limited, and conventionally known techniques can be appropriately used, and the PEFC generally has a structure in which the M EA is sandwiched by separators. Specifically, the separator, the gas diffusion layer, the cathode catalyst layer, the solid polymer electrolyte membrane, the anode catalyst layer, the gas diffusion layer, and the separator are arranged in this order. However, the present invention is not limited to such a basic configuration, and PEFCs having other configurations may be applied to the present invention.

The material of the separator is not particularly limited, and known separators such as carbon separators made of dense carbon graphite, carbon plates, and the like, and metal separators made of stainless steel, and the like can be used. The thickness and size of the separator, the shape of the flow channel, and the like are not particularly limited, and may be appropriately determined in consideration of the power characteristics and the like of the obtained fuel cell.

Further, in order to obtain a desired voltage or the like for the fuel cell, a stack may be formed in which a plurality of MEAs are connected in series by stacking separators. The shape of the fuel cell or the like is not particularly limited, and may be appropriately determined so as to obtain desired cell characteristics such as voltage.

Examples

Example 1

1. Preparation of anode electrode catalyst

4.0g of carbon Black (Ketjen Black manufactured by Ketjen Black International Co., Ltd.) was prepared^TMEC, BET surface area 800m²As a conductive carbon material, 400g of an aqueous dinitrodiammine platinum solution (Pt concentration 1.0%) was added thereto and stirred for 1 hour. Further, 50g of methanol was mixed as a reducing agent and stirred for 1 hour. Then heated to 80 ℃ over 30 minutes and stirred at 80 ℃ for 6 hours, then cooled to room temperature over 1 hour. The precipitate was filtered, and the obtained solid was dried at 85 ℃ for 12 hours under reduced pressure and pulverized using a mortar to obtain an anode electrode catalyst (average particle diameter of Pt particles was 2.6nm, Pt loading concentration was 50 mass%).

2. Preparation of cathode electrode catalyst

By subjecting carbon Black (Ketjen Black manufactured by Ketjen Black International Co., Ltd.) to a heating treatment at 2700 deg.C^TMEC) was subjected to graphitization treatment for 10 hours to obtain graphitized carbon Black (graphitized Ketjen Black EC having a BET surface area of 130m²G, true density 1.93g/cm³Interplanar spacing d₀₀₂3.51

Conductivity 200S/cm). To 4.0g of graphitized Ketjen black, 400g of an aqueous dinitrodiammine platinum solution (Pt concentration 1.0%) was added and stirred for 1 hour. Further, 50g of formic acid was mixed as a reducing agent and stirred for 1 hour. Then, it was heated to 40 ℃ over 30 minutes and stirred at 40 ℃ for 6 hours. Heated to 60 ℃ over 30 minutes, stirred at 60 ℃ for 6 hours and then cooled to room temperature over 1 hour. The precipitate was filtered, and the obtained solid was dried at 85 ℃ for 12 hours under reduced pressure and pulverized using a mortar to obtain a cathode electrode catalyst (average particle diameter of Pt particles was 4.8nm, Pt load concentration is 50 mass%).

3. Manufacture of anode catalyst layer

Purified water was added in an amount of 5 times the mass of the anode electrode catalyst, and the degassing was performed under reduced pressure for 5 minutes. To this was added n-propanol in an amount of 0.5 times the amount of the mixture, and further added a solution containing a proton-conductive polymer electrolyte (containing 20 wt% Nafion manufactured by DuPont Co., Ltd.)^TM). The content of the polyelectrolyte in the solution is as follows: the mass ratio of the solid component to the mass of the anode electrode catalyst carbon was 1.0/0.9.

The obtained mixed slurry was sufficiently dispersed by an ultrasonic homogenizer, and a catalyst slurry was prepared by performing a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing, and an amount of catalyst paste corresponding to a desired thickness was printed and dried at 60 ℃ for 24 hours. The anode catalyst layer was formed to have a size of 5cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt became 0.05mg/cm²。

4. Manufacture of cathode catalyst layer

Purified water was added in an amount 5 times the mass of the cathode electrode catalyst, and the vacuum degassing operation was performed for 5 minutes. To this was added n-propanol in an amount of 0.5 times the amount of the mixture, and further added a solution containing a proton-conductive polymer electrolyte (containing 20 wt% Nafion manufactured by DuPont Co., Ltd.)^TM). The content of the polyelectrolyte in the solution is as follows: the solid content mass ratio with respect to the carbon mass of the cathode electrode catalyst was 1.0/0.9.

The obtained mixed slurry was sufficiently dispersed by an ultrasonic homogenizer, and a catalyst slurry was prepared by performing a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing, and an amount of catalyst paste corresponding to a desired thickness was printed and dried at 60 ℃ for 24 hours. The size of the formed cathode catalyst layer was 5cm × 5 cm. Further, polytetrafluoroethylene was adjustedCoating layer on vinyl sheet so that Pt amount becomes 0.35mg/cm²。

5. Production of Membrane Electrode Assembly (MEA)

Nafion as solid polymer electrolyte membrane^TM111 (film thickness 25 μm) was superposed on the electrode catalyst layer formed on the polytetrafluoroethylene sheet previously manufactured. In this case, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer are laminated in this order. Then, the resulting laminate was hot-pressed at 130 ℃ and 2.0MPa for 10 minutes to peel off only the polytetrafluoroethylene sheet, thereby obtaining an MEA.

The thickness of the cathode catalyst layer transferred to the solid polymer electrolyte membrane was about 12 μm, and the Pt loading was 1cm per unit²Has an apparent electrode area of 0.35mg and an electrode area of 25cm². The thickness of the anode catalyst layer was about 1.5 μm, and the Pt loading was 1cm per layer²The apparent electrode area of (2) was 0.05mg and the electrode area was 25cm²。

6. Performance evaluation of Membrane Electrode Assembly (MEA)

Carbon paper (size: 6.0 cm. times.5.5 cm, thickness 320 μm) as a gas diffusion layer and a gas separator plate with a gas flow path were placed on both surfaces of the MEA obtained above, and sandwiched by gold-plated stainless collector plates to obtain a single cell for evaluation. Hydrogen gas was supplied as a fuel to the anode side of the evaluation unit cell, and air was supplied as an oxidant to the cathode side. The supply pressure of both gases was atmospheric pressure, hydrogen gas was 58.6 ℃ and relative humidity was 60%, air was 54.8 ℃ and relative humidity was 50%, and the cell temperature was set to 70 ℃. Further, the hydrogen utilization rate was 67%, and the air utilization rate was 40%. Under these conditions, the measurement was carried out at 1.0A/cm²The cell voltage at the time of power generation is set as the initial cell voltage.

Then, after power generation for 60 seconds, power generation was stopped. After the stop, the supply of hydrogen gas and air was stopped, and the cells were replaced with air and stood by for 50 seconds. Then, hydrogen gas was supplied to the anode side at 1/5 of the above utilization rate for 10 seconds. Then in the same manner as aboveHydrogen gas was supplied to the anode side and air was supplied to the cathode side under the conditions of 1.0A/cm again²The current density of (2) generated electricity for 60 seconds. In addition, the load current at this time was from 0A/cm within 30 seconds²Increase to 1A/cm². The power generation and stop operation was performed, and the battery voltage was measured to evaluate the power generation performance. 1.0A/cm²The number of cycles at which the cell voltage reached 0.45V at the current density of (a) was taken as a value for durability evaluation. The composition and the results are shown in Table 1-1. The heat treatment temperature, BET specific surface area, true density, and interplanar spacing d of the graphitization treatment of the conductive carbon material used in the cathode electrode catalyst₀₀₂The conductivities are summarized in Table 4.

Examples 2 to 25 and reference examples 1 to 5

An MEA was produced and durability was evaluated in the same manner as in example 1, except that the configuration of the fuel cell was changed as shown in tables 1-1 and 1-2. The constitution and the results are shown in tables 1-1 and 1-2. The heat treatment temperature, BET specific surface area, true density, and interplanar spacing d of the graphitization treatment of the conductive carbon material used in the cathode electrode catalyst₀₀₂The conductivities are summarized in Table 4.

Example 26

1. Preparation of cathode electrode catalyst

A cathode electrode catalyst was produced in the same manner as in example 1, and used as the cathode electrode catalyst (C).

Then, the carbon black (vulcan x C-72 manufactured by Cabot corporation) was graphitized at 2700 ℃ for 10 hours to obtain a graphitized carbon black (graphitized vulcan x C-72 having a BET surface area of 113m²G, true density 2.01g/cm³Interplanar spacing d₀₀₂3.46

Conductivity 300S/cm). To 4.0g of the graphitized carbon black, 400g of an aqueous dinitrodiammineplatinum solution (Pt concentration 1) was added.0%) and stirred for 1 hour. Further, 50g of formic acid was mixed as a reducing agent and stirred for 1 hour. Then, it was heated to 40 ℃ over 30 minutes and stirred at 40 ℃ for 6 hours. Heated to 60 ℃ over 30 minutes, stirred at 60 ℃ for 6 hours and then cooled to room temperature over 1 hour. The precipitate was filtered, and the obtained solid was dried at 85 ℃ for 12 hours under reduced pressure and pulverized using a mortar to obtain a cathode electrode catalyst (D) (the average particle diameter of Pt particles was 4.8nm, the Pt loading concentration was 50 mass%).

2. Manufacture of cathode catalyst layer

The electrode catalyst (C) and the electrode catalyst (D) produced above were mixed at a mass ratio of (C)/(D) of 2/1, and purified water was added in an amount of 5 times the mass of the obtained mixture to conduct a vacuum degassing operation for 5 minutes. To this was added n-propanol in an amount of 0.5 times the amount of the mixture, and further added a solution containing a proton-conductive polymer electrolyte (containing 20 wt% Nafion manufactured by DuPont Co., Ltd.)^TM). The content of the polyelectrolyte in the solution is as follows: the solid content mass ratio with respect to the carbon mass of the mixture (electrode catalysts (C) and (D)) was 1.0/0.9. The obtained mixed slurry was sufficiently dispersed by an ultrasonic homogenizer, and a catalyst slurry was prepared by performing a vacuum degassing operation.

A cathode catalyst layer was formed on one surface of a polytetrafluoroethylene sheet in the same manner as in example 1 except that the above catalyst slurry was used, and an MEA was prepared using the cathode catalyst layer, and the evaluation thereof was performed. The compositions and results are shown in table 2. The heat treatment temperature, BET specific surface area, true density, and interplanar spacing d of the graphitization treatment of the conductive carbon material used in the cathode electrode catalyst₀₀₂The conductivities are shown in Table 5.

Examples 27 to 33

An MEA was produced and durability was evaluated in the same manner as in example 26, except that the configuration of the fuel cell was changed as shown in table 2. The compositions and results are shown in table 2. In addition, the conductive carbon material used in the cathode electrode catalystHeat treatment temperature, BET specific surface area, true density, interplanar spacing d of graphitization treatment of₀₀₂The conductivities are shown in Table 5.

Example 34

1. Manufacture of cathode catalyst layer

The electrode catalyst (C) produced in example 1 and the electrode catalyst (D) produced in example 26 were mixed at a mass ratio of (C)/(D) of 9/1, and a catalyst slurry for the gas upstream side was prepared in the same manner as in example 26 using the resulting mixture.

A catalyst slurry for gas downstream side was prepared in the same manner as in example 26, using a mixture obtained by mixing the electrode catalyst (C) produced in example 1 and the electrode catalyst (D) produced in example 26 in a mass ratio (C)/(D) of 8/2.

In the same manner as in example 1 except for using the above catalyst slurry, a catalyst slurry for gas upstream side was applied to one half (size 5.0cm × 2.5cm) of one surface of a polytetrafluoroethylene sheet, and dried at 60 ℃ for 24 hours to prepare an upstream side cathode catalyst layer.

Next, the remaining other half (size 5.0cm × 2.5cm) of one surface of the polytetrafluoroethylene sheet was coated with a catalyst slurry for gas downstream, and dried at 60 ℃ for 24 hours to prepare a downstream cathode catalyst layer.

The MEA was produced using this, and evaluated. The compositions and results are shown in table 3. The heat treatment temperature, BET specific surface area, true density, and interplanar spacing D of the graphitization treatment of the conductive carbon material used for the cathode electrode catalysts (C) and (D)₀₀₂The conductivities are shown in Table 6.

In the cathode catalyst layer, the electrode areas formed by applying the catalyst slurry for the gas upstream side and the catalyst slurry for the gas downstream side were 12.5cm each²The thickness of each layer was 12 μm, and the Pt loading was 1cm²Apparent electrode surfaceThe product was 0.35 mg.

In the durability evaluation of the evaluation unit cell, the cathode catalyst layer was provided with a portion coated with the catalyst slurry for the gas upstream side on the gas introduction side and a portion coated with the catalyst slurry for the gas downstream side on the gas outlet side.

Examples 35 to 41

An MEA was produced and durability was evaluated in the same manner as in example 34, except that the configuration of the fuel cell was changed as shown in table 3. The compositions and results are shown in table 3. The heat treatment temperature, BET specific surface area, true density, and interplanar spacing D of the graphitization treatment of the conductive carbon material used in the cathode electrode catalysts (C) and (D)₀₀₂The conductivities are shown in Table 6.

TABLE 4

TABLE 5

TABLE 6

As shown in tables 1 to 3, the PEFC of the present invention has very good durability against repeated start-stop.

The above embodiments are intended to explain the present invention more specifically, but the present invention is not limited to the above embodiments.

In addition, the present application is based on Japanese patent application No. 2004-.

Claims

1. A membrane-electrode assembly for a fuel cell, comprising:

a solid polymer electrolyte membrane;

wherein,

the average thickness Ya of the anode catalyst layer is smaller than the average thickness Yc of the cathode catalyst layer.

2. The membrane-electrode assembly for a fuel cell according to claim 1, wherein Ya and Yc satisfy a relationship of Ya/Yc of 0.01 to 0.9.

3. The membrane-electrode assembly for a fuel cell according to claim 1 or 2, wherein Ya is 0.3 μm to 10 μm, and Yc is 7 μm to 20 μm.

4. The membrane-electrode assembly for a fuel cell according to claim 1, wherein the conductive carbon material as the cathode catalyst layer comprises graphitized carbon black.

5. The membrane-electrode assembly for a fuel cell according to claim 4, wherein the graphitized carbon black has a true density of 1.80 to 2.11g/cm³Interplanar spacing d₀₀₂Is 3.36 to 3.55

The conductivity is 50 to 1000S/cm.

6. The membrane-electrode assembly for a fuel cell according to claim 4, wherein the graphitized carbon black contains a BET surface area of 100m²The above graphitized carbon black A.

7. The membrane-electrode assembly for a fuel cell according to claim 6, wherein the carbon black A has a BET surface area of 100 to 300m²/g。

8. The membrane-electrode assembly for a fuel cell according to claim 6, wherein the carbonThe BET surface area of the black A is 120 to 250m²/g。

9. The membrane-electrode assembly for a fuel cell according to any one of claims 6 to 8, wherein the cathode catalyst is supported on the carbon black A to form a cathode electrode catalyst C, and the amount of the cathode catalyst supported in the cathode electrode catalyst C is 20 to 80% by mass.

10. The membrane-electrode assembly for a fuel cell according to claim 4, wherein the graphitized carbon black further comprises a BET surface area of less than 100m²A graphitized carbon black B per g.

11. The membrane-electrode assembly for a fuel cell according to claim 10, wherein the carbon black B has a BET surface area of 80 to 100m²/g。

12. The membrane-electrode assembly for a fuel cell according to claim 10, wherein the cathode catalyst is supported on the carbon black B to form a cathode electrode catalyst D, and the amount of the cathode catalyst supported in the cathode electrode catalyst D is 10 to 50 mass%.

13. The membrane-electrode assembly for a fuel cell according to claim 4, wherein the cathode catalyst layer comprises the cathode catalyst supported at a BET surface area of 100m²A cathode electrode catalyst C formed on the graphitized carbon black A having a BET surface area of less than 100m, and the cathode electrode catalyst²A cathode electrode catalyst D formed on/g of the graphitized carbon black B, wherein a mixing ratio of the cathode electrode catalyst C to the cathode electrode catalyst D is 60/40 or more in terms of a mass ratio C/D.

14. The membrane-electrode assembly for a fuel cell according to claim 13, wherein a mixing ratio of the cathode electrode catalyst C to the cathode electrode catalyst D is 60/40 to 99/1 in terms of a mass ratio C/D.

15. The membrane-electrode assembly for a fuel cell according to claim 13, wherein a mixing ratio R of the cathode electrode catalyst C and the cathode electrode catalyst D on an upstream side of a gas flow path of the cathode catalyst layer_upAnd a mixing ratio R of the cathode electrode catalyst C to the cathode electrode catalyst D on the downstream side of the gas flow path of the cathode catalyst layer_downIn a ratio of R_up/R_down1/1 or more.

16. The membrane-electrode assembly for a fuel cell according to claim 1, further comprising carbon black subjected to a hydrophobic treatment with a fluorine compound in an amount of 1 to 20 mass% based on the total mass of the conductive carbon materials of the cathode catalyst layer.

17. The membrane-electrode assembly for a fuel cell according to claim 1, further comprising carbon nanotubes, carbon nanofibers, or carbon nanohorns as the conductive carbon material of the cathode catalyst layer, in an amount of 1 to 20 mass% based on the total mass of the conductive carbon material of the cathode catalyst layer.

18. The membrane-electrode assembly for a fuel cell according to claim 1, wherein the platinum alloy is an alloy of at least 1 or more base metals selected from chromium, manganese, iron, cobalt, and nickel with platinum.

19. The membrane-electrode assembly for a fuel cell according to claim 18, wherein a mixing ratio of the platinum to the base metal in the platinum alloy is 1/1 to 5/1 in terms of a mass ratio.

20. The membrane-electrode assembly for a fuel cell according to claim 1, wherein the conductive carbon material as the anode catalyst layer contains carbon black.

21. The membrane-electrode assembly for a fuel cell according to claim 20, wherein a graphitized carbon black is contained as the conductive carbon material of the anode catalyst layer.

22. The membrane-electrode assembly for a fuel cell according to claim 1, wherein the anode catalyst is supported on the conductive carbon material to form an anode electrode catalyst, and the amount of the anode catalyst supported in the anode electrode catalyst is 30 to 70 mass%.

23. The membrane-electrode assembly for a fuel cell according to claim 1, wherein a gas diffusion layer having a thickness of 200 μm or less formed of water repellent treated carbon paper is provided on the outer side of the cathode catalyst layer and the anode catalyst layer.

24. The membrane-electrode assembly for a fuel cell according to claim 23, wherein a mil layer is provided between the gas diffusion layer and the cathode catalyst layer and the anode catalyst layer.

25. A polymer electrolyte fuel cell using the membrane-electrode assembly for a fuel cell according to any one of claims 1 to 24.

26. A vehicle equipped with the solid polymer fuel cell according to claim 25.