JP2006164535A - Polyelectrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyelectrolyte fuel cell with the utilization efficiency of a catalyst improved. <P>SOLUTION: The polyelectrolyte fuel cell is formed with a hydrogen-ion conductive polyelectrolyte film and a pair of electrodes pinching the polyelectrolyte film. The electrode is formed with a catalyst layer in contact with the polyelectrolyte film, and the catalyst layer contains a hydrogen-ion conductive polyelectrolyte and a catalyst metal with the density of an ion-conductive group in the vicinity of the catalyst layer larger than the average density of the electrode as a whole. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polymer electrolyte fuel cell.

  Basically, a fuel cell is a power generation device that generates electricity by reacting hydrogen and oxygen, and has the excellent property that only water is generated by the power generation reaction. It is attracting attention as an energy-saving technology that addresses environmental issues.

  Fuel cells include solid polymer fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, and solid oxide fuel cells. Among these, the polymer electrolyte fuel cell has an advantage that the operating temperature is low and the electrolyte is solid (polymer thin film). There are two types of polymer electrolyte fuel cells: a reforming type that converts methanol into hydrogen using a reformer, and a direct type that uses methanol directly without using a reformer (DMFC, Direct Methanol Polymer Fuel Cell). It is divided roughly into. Since DMFC does not require a reformer, it can be reduced in size and weight, and it can be used as a battery or a dedicated battery for personal digital assistants (PDAs) for the coming ubiquitous society. Is expected.

  DMFC uses a proton-conducting solid polymer membrane as an electrolyte membrane, and through this electrolyte membrane, an anode electrode and a cathode electrode formed by applying a catalyst on porous carbon paper serving as a diffusion layer are joined, and the anode electrode side Is provided with an anode electrode side separator having a channel groove for supplying a methanol aqueous solution as a fuel, and a cathode electrode side separator having a channel groove for supplying air as an oxidant gas on the cathode electrode side. In general, the structure is provided with.

When an aqueous methanol solution is supplied to the anode electrode and air is supplied to the cathode electrode, carbon dioxide gas is generated and hydrogen ions and electrons are released (CH ₃ OH + H ₂ O → CO ₂₎ by the oxidation reaction of methanol and water at the anode electrode. + 6H ⁺ + 6e ⁻ ), water is generated by the reduction reaction between the hydrogen ions that have passed through the electrolyte membrane and air at the cathode (6H ⁺ + (3/2) O ₂ + 6e ⁻ → 3H ₂ O), and the anode Electrical energy can be obtained in an external circuit connecting the pole and the cathode pole. Therefore, the total reaction of DMFC is a reaction in which water and carbon dioxide are generated from methanol and oxygen.

  In general, the anode and cathode are composed of a mixture containing a metal catalyst such as platinum and conductive carbon such as carbon black or catalyst-supporting carbon and a polymer electrolyte. Since the cost of the platinum catalyst used for the fuel cell electrode occupies several tens of percent of the entire fuel cell, it is necessary to reduce the amount of platinum catalyst used in order to reduce the cost of the fuel cell.

  On the other hand, in the conventional method for producing a catalyst layer, only 20 to 30% of platinum used as the catalyst layer is involved in the electrode reaction. Proton conduction after the reaction occurs only at the three-phase interface where the polymer electrolyte contacts. Fuel is supplied to the three-phase interface, and after the reaction, carbon conducts electrons, and the polymer electrolyte conducts protons. However, in the conventional method for producing the catalyst layer, since the ratio of the polymer electrolyte present around the platinum catalyst is small, it is difficult to perform rapid mass transfer.

  In order to increase the utilization rate of the catalyst, a core-shell type catalyst metal in which the core catalyst metal is coated with a catalyst metal different from the core catalyst metal is used, and supported on the surface of carbon particles in contact with the proton conduction path of the polymer electrolyte. A technology for setting the amount of catalyst metal to 50% by mass or more of the total amount of catalyst metal (see, for example, Patent Document 1), and carbon of the catalyst-supporting carbon has an organic group capable of hydrogen ion dissociation such as a sulfonic acid group. A technique using carbon (for example, see Patent Document 2), an electrode catalyst in which a catalyst is supported on a carbon material having at least one ionic functional group on the surface of primary particles of carbon black (for example, see Patent Document 3). Is disclosed.

  In addition, in order to sufficiently and uniformly contact the polymer electrolyte and the catalyst and increase the reaction area inside the electrode, the molecular length of the hydrogen ion conductive polymer electrolyte is set to 30 to 200 nm, and this is passed through the catalyst-supporting carbon and the solvent. It is disclosed that it is important to appropriately select the dielectric constant of the solvent when mixing (see, for example, Patent Document 4).

  In addition, a technique in which a molecule containing an ion conductive functional group that functions as an electrolyte is chemically bonded to a surface selected from catalyst particles, other particles, and a porous membrane (see, for example, Patent Document 5).

  Further, as a technique for increasing the utilization efficiency of the platinum catalyst, a grafted platinum-supported catalyst in which an electrolyte polymer is immobilized on the carbon surface by reacting the monomer on the carbon surface and chemically bonding is disclosed (for example, non-patent document). 1).

In these techniques, a proton transfer path is not necessarily formed in the vicinity of the catalyst, and the efficiency improvement range is small. Development of an electrode with high production efficiency of proton conduction path and high catalyst utilization is desired.
JP 2001-118582 A JP 2004-79420 A JP 2004-22346 A JP 2002-63912 A JP 2004-172098 A Summary of Next Generation Fuel Cell Technology Development Report Meeting (December 14, 2003) New Energy and Industrial Technology Development Organization, Fuel Cell and Hydrogen Technology Development Department

  As described above, in order to increase the power generation efficiency of the fuel cell, an epoch-making technology development for increasing the utilization efficiency of the catalyst has been desired. The present invention solves these problems, and an object of the present invention is to provide a polymer electrolyte fuel cell in which the utilization efficiency of a catalyst is enhanced.

  The above object of the present invention has been achieved by the following constitution.

(Claim 1)
A hydrogen ion conducting polymer electrolyte membrane and a pair of electrodes sandwiching the hydrogen ion conducting polymer electrolyte membrane, the electrodes comprising a catalyst layer in contact with the hydrogen ion conducting polymer electrolyte membrane, and the catalyst The layer includes a hydrogen ion conductive polymer electrolyte and a catalyst metal, and the density of the ion conductive group in the vicinity of the catalyst metal is larger than the average density of the entire electrode.

(Claim 2)
A hydrogen ion conducting polymer electrolyte membrane and a pair of electrodes sandwiching the hydrogen ion conducting polymer electrolyte membrane, the electrodes comprising a catalyst layer in contact with the hydrogen ion conducting polymer electrolyte membrane, and the catalyst The layer includes a hydrogen ion conductive polymer electrolyte and carbon carrying a catalyst metal, and the density of the ion conductive group in the vicinity of the catalyst metal is larger than the average density of the carbon surface. battery.

(Claim 3)
The polymer electrolyte fuel cell according to claim 1 or 2, wherein the catalytic metal has gold adsorbed on the surface thereof.

  According to the present invention, it was possible to provide a polymer electrolyte fuel cell in which the utilization efficiency of the catalyst was increased and the current-voltage characteristics were improved.

  The present invention comprises a hydrogen ion conductive polymer electrolyte membrane and a pair of electrodes sandwiching the hydrogen ion conductive polymer electrolyte membrane, the electrodes being in contact with the hydrogen ion conductive polymer electrolyte membrane, In a polymer electrolyte fuel cell having a catalyst layer including a conductive polymer electrolyte and a catalyst metal, or a hydrogen ion conductive polymer electrolyte and a catalyst metal-supported carbon, the density of ion conductive groups in the vicinity of the catalyst metal is an average. It has been found that the utilization efficiency of the catalyst is improved when the density of the ion conductive group in the vicinity of the catalyst metal is larger than the average density.

  In order to increase the density of the ion conductive group in the vicinity of the catalyst metal, it has a sulfide group, a disulfide group, a mercapto group, an amino group, etc. having an affinity for the catalyst metal, and the carboxyl group, phosphate group as the ion conductive group A compound having a phosphorous acid group, a sulfonic acid group, or the like can be used.

  Hereinafter, an embodiment of a fuel cell of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing a single cell I of a fuel cell according to the present invention. The hydrogen ion conductive polymer electrolyte membrane 1 is disposed so as to be sandwiched between the anode electrode side catalyst layer 2 and the cathode electrode side catalyst layer 3. The anode electrode side catalyst layer 2 and the cathode electrode side catalyst layer 3 are respectively provided on diffusion layers 4 and 5 formed of a porous conductive sheet such as carbon paper. Here, for the sake of convenience, the diffusion layer 4 and the anode electrode side catalyst layer 2 provided thereon are referred to as an anode electrode, and the diffusion layer 5 and the cathode electrode side catalyst layer 3 provided thereon are referred to as a cathode electrode. Called.

  At least one of the anode electrode side catalyst layer 2 and the cathode electrode side catalyst layer 3 must contain a catalyst or catalyst-supporting carbon. In the present invention, the anode electrode side catalyst layer 2 preferably contains the catalyst or catalyst-supporting carbon according to the present invention, but both the anode electrode side catalyst layer 2 and the cathode electrode side catalyst layer 3 have the catalyst according to the present invention. Or it is more preferable that the catalyst-supported carbon is included.

  Examples of the catalyst metal that can be used in the catalyst according to the present invention include platinum, ruthenium, rhodium, palladium, iridium, gold, silver, iron, cobalt, nickel, chromium, tungsten, magazine, vanadium, molybdenum oxide, or these. It is a multi-component alloy. Among these, the catalyst metal that can be preferably used in the present invention is platinum or a metal having gold adsorbed on the platinum surface.

  In the present invention, catalyst metal-supported carbon obtained by supporting these catalyst metals on carbon particles can be used.

  As the carbon particles supporting the catalyst metal, activated carbon, carbon black, graphite and a mixture thereof can be preferably used. Examples of carbon black include acetylene black, ketjen black, furnace black, lamp black, and thermal black. Ketjen black is particularly preferable. Examples of commercially available carbon blacks include Denka BLACK (manufactured by Denki Kagaku Kogyo Co., Ltd.), Valcan XC-72 (manufactured by Cabot), Black Pearl 2000 (same as above), Ketjen Black EC300J (manufactured by Ketjen Black International), and the like. Can be mentioned. Also, the carbon particles can be used after being hydrophilized. In particular, those treated with a compound having a carboxyl group and carboxylated and those treated with a compound having a sulfonic acid group and sulfonated are preferred.

  Examples of the method of supporting the metal catalyst on the carbon particles include a method of adding a salt of a metal catalyst such as platinum or ruthenium to the carbon black dispersion liquid, and then reducing with hydrazine or the like, filtering and drying. In the present invention, heat treatment may be further performed after drying. It is also possible to use Valcan XC-72 commercially available as carbon particles (Platinum-Platinum-Ruthenium catalyst) supported on Platinum XC-72 (manufactured by Tanaka Kikinzoku Co., Ltd.).

  The electrode for a polymer electrolyte fuel cell according to the present invention contains a hydrogen ion conductive polymer electrolyte in addition to the catalyst-supporting carbon according to the present invention. The hydrogen ion conductive polymer electrolyte that can be contained is not particularly limited as long as it is an electrolyte having ion conductivity, and examples thereof include a fluorine-based electrolyte, a partial fluorine-based electrolyte, and a hydrocarbon-based electrolyte. For example, an ion exchange resin having an organic fluorine-containing polymer as a skeleton, for example, a perfluorocarbon sulfonic acid resin or the like can be used. As perfluorocarbon sulfonic acid resins, DE520, DE521, DE1020, DE1021 (manufactured by DuPont) and the like are commercially available. In addition, sulfonated polyether ketone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, sulfonated polysulfone, sulfonated polysulfide, sulfonated polyphenylene and other sulfonated plastic electrolytes, sulfoalkylated polyetheretherketone, sulfone Examples thereof include sulfoalkylated plastic electrolytes such as alkylated polyethersulfone, sulfoalkylated polyetherethersulfone, sulfoalkylated polysulfone, sulfoalkylated polysulfide, and sulfoalkylated polyphenylene.

  The use ratio of the catalyst metal-supporting carbon and the polymer electrolyte according to the present invention should be appropriately determined according to the required electrode characteristics, and is not particularly limited. For example, the mass ratio of catalytic metal-supported carbon / polymer electrolyte according to the present invention is preferably 5/95 to 95/5, and more preferably 40/60 to 85/15.

  Various additives can be added to the catalyst layer. Examples thereof include additives such as a conductive agent such as carbon for improving electronic conductivity, a polymer binder for improving binding property, and a water repellency imparting agent for improving water repellency. Examples of the water repellency-imparting agent include fluorine-containing compounds such as polytetrafluoroethylene (PTFE) such as Teflon (registered trademark), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer. Resin.

  The diffusion layers 4 and 5 are layers for supplying reaction gas to and receiving electrons from the anode electrode side catalyst layer 2 and the cathode electrode side catalyst layer 3 and transferring electrons to and from the current collecting layer, and are generally porous. A material having high quality and electron conductivity is used. As a material that is porous and has electronic conductivity, any material having a low electrical resistance and a function of collecting current may be used. Examples include those mainly composed of conductive substances, such as calcined products from polyacrylonitrile, calcined products from pitch, carbon materials such as graphite and expanded graphite, nanocarbon materials, stainless steel, molybdenum, and titanium. .

  The form of the conductive substance is not particularly limited, and for example, it can be used in the form of fibers or particles. From the viewpoint of gas permeability, fibrous conductive inorganic substances such as inorganic conductive fibers such as carbon fibers are preferable. As the inorganic conductive fiber, a woven fabric or non-woven fabric structure can be used. For example, carbon paper TGP series, SO series manufactured by Toray Industries, Inc., carbon cloth manufactured by E-TEK, etc. are used. As the woven fabric, a plain weave, a twill weave, a satin weave, a crest weave, a binding weave and the like are used without particular limitation. The nonwoven fabric can be used without any particular limitation, such as a paper making method, a needle punch method, a spun bond method, a water jet punch method, a melt blow method, and the like. Moreover, a knitted fabric may be sufficient.

  When carbon fiber is used, a woven fabric obtained by carbonizing or graphitizing a plain fabric using flame-resistant spun yarn, a nonwoven fabric obtained by carbonizing or graphitizing a flame-resistant yarn after processing the nonwoven fabric by a needle punch method or a water jet punch method, A mat nonwoven fabric produced by a paper making method using flame-resistant yarn, carbonized yarn or graphitized yarn is preferably used. In particular, it is preferable to use a non-woven fabric because a thin and strong fabric can be obtained. It is also effective to use carbon nanofibers as described in Japanese Patent Application Laid-Open No. 2003-109618.

  When inorganic conductive fibers made of carbon fibers are used, examples of the carbon fibers include polyacrylonitrile (PAN) -based carbon fibers, phenol-based carbon fibers, pitch-based carbon fibers, and rayon-based carbon fibers. Of these, PAN-based carbon fibers are preferred.

  The anode electrode can be produced by applying the anode electrode side catalyst layer 2 to the diffusion layer 4 and then performing heat treatment. Similarly, the cathode electrode side catalyst layer 3 is applied to the diffusion layer 5 and then subjected to heat treatment to produce a cathode electrode.

  As the hydrogen ion conductive polymer electrolyte membrane 1 having proton conductivity, a known material such as a sulfonated polyimide polymer electrolyte membrane, a fluorine polymer electrolyte membrane, a hydrocarbon polymer electrolyte membrane, or a composite material is adopted. be able to.

  For example, sulfonated engineering plastic electrolytes such as sulfonated polyetherketone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, sulfonated polysulfone, sulfonated polysulfide, and sulfonated polyphenylene as hydrocarbon polymer electrolyte materials , Sulfoalkylated polyether ether ketone, sulfoalkylated polyethersulfone, sulfoalkylated polyetherethersulfone, sulfoalkylated polysulfone, sulfoalkylated polysulfide, sulfoalkylated engineering plastic electrolytes such as polyphenylene, etc. .

  The sulfonic acid equivalent of these electrolyte materials is 0.5 to 2.0 meq / g dry resin, preferably 0.7 to 1.6 meq / g dry resin. When the sulfonic acid equivalent is less than 0.5 meq / g dry resin, the ionic conduction resistance increases, and when it is greater than 2.0 meq / g dry resin, it tends to swell in water.

  The hydrogen ion conductive polymer electrolyte membrane 1 is sandwiched between the anode electrode and the cathode electrode, and the same electrolyte solution as that of the hydrogen ion conductive polymer electrolyte membrane 1 is placed in each of the anode electrode side catalyst layer 2 and the cathode electrode side catalyst layer 3. An electrolyte membrane-electrode assembly (MEA) can be produced by applying to the substrate and hot pressing.

  A separator 6 (fuel distribution plate) as a current collector in which grooves for forming a fuel flow path and an oxidant flow path are formed outside the electrolyte membrane-electrode assembly (MEA) produced as described above; A fuel cell is constituted by stacking a plurality of single cells via a cooling plate or the like, with a separator 7 and an oxidant distribution plate (oxidant distribution plate) arranged thereon. The fuel cell may be a single cell, or may have a shape in which the current collector is formed by plating or the like without providing a separator.

  Examples of the fuel that can be used in the polymer electrolyte fuel cell of the present invention include hydrogen gas, methanol, ethanol, 1-propanol, dimethyl ether, ammonia, and the like, and methanol is preferable. In the present invention, it is preferable to use air as the oxidant gas.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

<Production of catalyst>
(Preparation of catalyst 1) Adsorption of gold particles on platinum black 0.4 g of platinum ruthenium black (TEC090110 (Tanaka Kikinzoku Co., Ltd.)) was mixed in 1000 ml. Thereafter, 40 ml of a 1 mol / L chloroauric acid aqueous solution was added. A 2 mol / L sodium citrate aqueous solution was added so as to be 100 mmol as a reducing agent. This solution was stirred and mixed at 95 ° C. for 7 hours. Then, filtration drying was performed and gold was deposited on platinum ruthenium black, and the catalyst 1 was produced.

(Preparation of Catalyst 2) Adsorption of gold particles on platinum-ruthenium-supported carbon 0.4 g of platinum-ruthenium-supported carbon catalyst (TEC81E81 (manufactured by Tanaka Kikinzoku Co., Ltd.)) was mixed in 1000 ml. Thereafter, 40 ml of a 1 mol / L chloroauric acid aqueous solution was added. A 2 mol / L sodium citrate aqueous solution was added so as to be 100 mmol as a reducing agent. This solution was stirred and mixed at 95 ° C. for 7 hours. Then, filtration and drying were performed, gold was deposited on the catalyst, and the catalyst 2 was produced.

(Preparation of modified catalysts 1 and 2) Adsorption of sulfonic acid-containing molecules on the surface of gold adsorption catalyst Catalyst 1, 0.4 g was dispersed in 1000 ml of water, and the following compounds shown in Table 1 were added at 1 × 10 ⁻⁴ mol / L. Then, a compound having a proton-accepting group was adsorbed in the vicinity of the catalyst metal. Unadsorbed molecules were removed by decantation, and modified catalyst 1 having adsorbed sulfonic acid-containing molecules was removed by filtration. The same treatment was performed on the catalyst 2 to produce a modified catalyst 2.

(Preparation of Modified Catalysts 3 and 4) Adsorption of sulfonic acid-containing molecules on the surface of gold non-adsorbed catalyst Platinum ruthenium black, 0.4 g is dispersed in 1000 ml of water, and the following compounds shown in Table 1 are 1 × 10 ⁻⁴ mol. / L was added to adsorb a compound having a proton-accepting group in the vicinity of the catalyst metal. Unadsorbed molecules were removed by decantation, and the modified catalyst 3 having adsorbed sulfonic acid-containing molecules was removed by filtration. The same treatment was performed on the platinum-supported carbon to produce a modified catalyst 4.

<Preparation of electrode paste>
(Preparation of negative electrode paste)
The amount of Teflon (registered trademark) is 12% by mass as the solid content of the anode catalyst, distilled water, 60% by mass of Teflon (registered trademark) dispersion, 5% by mass of Nafion solution (manufactured by DuPont) listed in Table 1. Thus, the paste for negative electrodes (Examples 1-4, Comparative Examples 1-4) was produced by uniformly dispersing with ultrasonic waves.

(Preparation of positive electrode paste)
In the preparation of the negative electrode paste, the same operation was performed except that the catalyst was changed to platinum-supported carbon (TEC10E60E (manufactured by Tanaka Kikinzoku Co., Ltd.)), and a positive electrode paste was prepared.

<Production of water-repellent carbon paper>
Carbon paper with a porosity of 75% and a thickness of 0.40 mm is immersed in a Teflon (registered trademark) dispersion (manufactured by Mitsui DuPont Fluorochemical Co., Ltd.), and 0.5 mg / cm ² of Teflon (registered trademark) is attached to the surface. Water-treated carbon paper was produced.

<Preparation of electrolyte membrane / electrode assembly (MEA)>
With the combinations shown in Table 1, a negative electrode paste was uniformly applied to the surface of a water-repellent carbon paper so that the amount of platinum was 3.0 mg / cm ² and dried at 80 ° C. for 1 hour in a nitrogen atmosphere to produce a negative electrode. did. Similarly, a positive electrode paste was applied to the surface of a water-repellent carbon paper so that the amount of platinum was 3.0 mg / cm ² to produce a positive electrode. Next, a Nafion 112 membrane (manufactured by DuPont) was sandwiched between these positive and negative electrodes, and hot pressing was performed to prepare an electrolyte membrane / electrode assembly.

(Evaluation 1)
The state in which the sulfonic acid group is localized on the platinum surface can be confirmed by spot analysis with an analytical transmission electron microscope (ATEM) equipped with a field emission electron gun (ATEM: Analytical Transmission Electron Microscope). Specifically, after confirming a sample placed on a grid mesh with a microgrid by a transmission image, an electron beam focused to about 1 nm is irradiated to an analysis position, and characteristic X-rays generated therefrom are converted into energy dispersive X-rays. The S (sulfur) intensities of the spectra were compared with a line analyzer (EDS: Energy Dispersive X-ray Spectrometer).

  In Examples 1, 2, 3, and 4, the platinum surface had high S strength. In particular, Examples 1 and 2 were remarkable. Moreover, since S is not detected in the comparative example, it can be seen that there are portions where sulfonic acid groups are localized on the platinum surface of the example, and that the ion conductive group is higher than other portions after the electrode is manufactured.

(Evaluation 2)
Using the prepared electrolyte membrane / electrode assembly (MEA), a direct methanol fuel cell unit was assembled, the temperature of the fuel was 60 ° C., the flow rate of fuel at atmospheric pressure was 30 ml / min, and the flow rate of air was 100 ml / min. Then, 2 mol / L of methanol was supplied to the negative electrode side and air was supplied to the positive electrode side, and current-voltage characteristics were measured. Table 1 shows the current value at 0.6V.

  As can be seen from Table 1, the fuel cell of the present invention has better current-voltage characteristics than the comparison.

It is a schematic diagram which shows the single cell I of the fuel cell of this invention.

Explanation of symbols

I Fuel cell unit cell 1 Hydrogen ion conductive polymer electrolyte membrane 2 Anode electrode side catalyst layer 3 Cathode electrode side catalyst layer 4, 5 Diffusion layer 6, 7 Separator

Claims (3)

A hydrogen ion conducting polymer electrolyte membrane and a pair of electrodes sandwiching the hydrogen ion conducting polymer electrolyte membrane, the electrodes comprising a catalyst layer in contact with the hydrogen ion conducting polymer electrolyte membrane, and the catalyst The layer includes a hydrogen ion conductive polymer electrolyte and a catalyst metal, and the density of the ion conductive group in the vicinity of the catalyst metal is larger than the average density of the entire electrode. A hydrogen ion conducting polymer electrolyte membrane and a pair of electrodes sandwiching the hydrogen ion conducting polymer electrolyte membrane, the electrodes comprising a catalyst layer in contact with the hydrogen ion conducting polymer electrolyte membrane, and the catalyst The layer includes a hydrogen ion conductive polymer electrolyte and carbon carrying a catalyst metal, and the density of the ion conductive group in the vicinity of the catalyst metal is larger than the average density of the carbon surface. battery. The polymer electrolyte fuel cell according to claim 1 or 2, wherein the catalytic metal has gold adsorbed on the surface thereof.

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