JP2006134613A - Electrocatalyst for polymer electrolyte fuel cell and fuel cell using the same - Google Patents

Abstract

An electrode catalyst having high catalytic activity and capable of suppressing deterioration of catalytic activity under the use conditions of the fuel cell, a fuel cell air electrode having the electrode catalyst, and a fuel cell are provided.
A polymer electrolyte fuel cell comprising a membrane electrode assembly comprising a solid polymer electrolyte membrane that permeates protons, a fuel electrode having a catalyst layer containing an electrode catalyst, and an air electrode, with a separator interposed therebetween. An electrode catalyst for use in the air electrode, comprising platinum or a noble metal alloy containing platinum and a composite particle comprising a metal oxide other than a noble metal, an electrode catalyst for a polymer electrolyte fuel cell, and a fuel cell having the electrode catalyst Air electrode and fuel cell.
[Selection] Figure 1

Description

  The present invention relates to an electrode catalyst for a polymer electrolyte fuel cell, an electrode for a polymer electrolyte fuel cell, and a polymer electrolyte fuel cell.

  Fuel cells have high energy savings and excellent environmental characteristics such as low noise and vibration, almost no harmful emissions, and the ability to directly convert the chemical energy of the fuel into electrical energy, thus enabling efficient power generation. It is expected as an energy system in a new era. Above all, solid polymer electrolyte fuel cells operate at a low temperature, and have been commercialized in a wide range of fields such as automobiles, household cogeneration, and portables due to their features such as miniaturization, weight reduction, and ease of handling. Development is progressing.

The solid polymer electrolyte fuel cell uses an ion-exchange solid polymer membrane (PEM) that transmits only protons (H ⁺ ) as an electrolyte, and a fuel electrode having a catalyst layer formed on both sides of the PEM and an air electrode. A membrane electrode assembly (MEA) sandwiching each electrode is laminated with a separator. Hydrogen supplied to the fuel electrode is divided into hydrogen ions (protons) and electrons on the catalyst, and oxygen supplied to the air electrode reacts with protons moving through the PEM and electrons moving through the external circuit to form water. become. In this way, electrons move in the external circuit, current flows in the direction opposite to the electrons, and electric energy can be obtained.

  The electromotive reaction that occurs on each electrode catalyst is shown below.

  In an air electrode to which an oxygen-containing gas is supplied, air is supplied as an oxygen-containing gas. However, the oxygen reduction reaction at the air electrode is more than 100 times the hydrogen oxidation reaction at the fuel electrode. Slowly, the oxygen reduction reaction at the air electrode is rate-limiting in the battery reaction, and the development of a highly active air electrode catalyst is important in improving battery power generation efficiency.

  Conventionally, for high activation of an air electrode catalyst, a so-called supported platinum catalyst in which platinum fine particles having an average particle diameter of several nanometers are supported on a carbon support typified by carbon black has been put into practical use (for example, Patent Documents). 1 and 2). Furthermore, as a highly active catalyst, a platinum alloy catalyst has been discovered, and many studies have been made so far. Pt—Ni, Pt—Co, Pt—Fe, Pt—Cr, and Pt—Cu are compared with pure platinum. A large increase in activity has been obtained (see, for example, Non-Patent Document 1 and Patent Document 3).

The platinum alloy fine particle catalyst is more active than pure platinum fine particles, but under the conditions of use of the fuel cell, the alloying element selectively dissolves in the electrolyte, and the remaining platinum on the outermost surface of the fine particles gradually dissolves. (For example, see Non-Patent Document 2 and Patent Document 4) Further, alloying element ions dissolved in the electrolyte are deposited at the interface between the electrolyte and the catalyst layer, leading to deterioration of battery performance (for example, non-patent documents). 3 and 4). For this reason, in order to suppress further performance improvement and performance deterioration of the fuel cell, it is required to realize high activation of platinum by alloying and to suppress elution of alloying elements into the electrolyte. .
U.S. Pat. No. 4,044,193 US Pat. No. 4,136,059 JP 2003-331855 A JP 2003-142112 A “Journal of the Electrochemical Society”, 145, 4185 (1998) “Catalyst”, Vol. 37, no. 5,334 (1995) "NEDO" 2001 report "Research and development of polymer electrolyte fuel cells, research on degradation factors of polymer electrolyte fuel cells, basic research on degradation factors (2) Degradation factors due to operating conditions" “Abstracts of the 43rd Battery Discussion” 1D16, p. 516 (2002)

  The present invention has been made in view of such a background art. An electrode catalyst having high catalytic activity and capable of suppressing deterioration of catalytic activity under the use conditions of the fuel cell, and a fuel cell having the electrode catalyst An object of the present invention is to provide an air electrode and a fuel cell using the fuel cell electrode.

  That is, the present invention relates to the air electrode of a solid polymer fuel cell having a membrane electrode assembly comprising a solid polymer electrolyte membrane that transmits protons, a fuel electrode having a catalyst layer containing an electrode catalyst, and an air electrode. An electrode catalyst for use in a polymer electrolyte fuel cell, characterized by comprising platinum or a composite particle comprising a noble metal alloy containing platinum and a metal oxide other than the noble metal.

  The present invention also relates to a solid polymer type obtained by laminating a membrane electrode assembly comprising a solid polymer electrolyte membrane that permeates protons, a fuel electrode having a catalyst layer containing an electrode catalyst, and an air electrode via a separator. An electrode catalyst for use in the air electrode of a fuel cell, comprising a composite particle comprising platinum or a noble metal alloy containing platinum and a metal oxide other than a noble metal. is there.

The present invention also provides a polymer electrolyte fuel cell electrode comprising the above electrode catalyst as a catalyst component.
Furthermore, the present invention is a polymer electrolyte fuel cell using the above electrode as an air electrode.

  In the fuel cell electrode catalyst of the present invention, platinum or a noble metal alloy phase containing platinum is uniformly mixed with a metal oxide phase other than the noble metal or dispersed on the surface of the metal oxide phase other than the noble metal, Further, composite particles in which platinum or a noble metal alloy phase containing platinum has a large affinity with a metal oxide phase other than the noble metal are used. By using the composite fine particles in such a state as a catalyst, platinum or a noble metal alloy phase containing platinum on the surface of the composite particles of platinum or a noble metal alloy containing platinum and a metal oxide other than noble metal, compared with pure platinum fine particles Has a high catalytic activity, and platinum or a noble metal alloy phase containing platinum has a high affinity with a metal oxide phase other than noble metal, so that elution into the electrolyte can be suppressed. Since this metal element is in an oxide state, elution of metal elements other than noble metals into the electrolyte can be suppressed.

In the present invention, the alloy phase represents a phase in which two or more different component metal elements are mixed with each other on an atomic scale.
In the fuel cell electrode catalyst of the present invention, examples of the platinum or platinum-containing noble metal alloy include platinum or an alloy containing platinum and one or more elements selected from Pd, Ag, and Au.

  In the fuel cell electrode catalyst of the present invention, the metal oxides other than the noble metals include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Sn, In, and Hf. , Ta, W, Re, Ir and one or more metal elements (X) selected from rare earth elements (hereinafter abbreviated as “metal element (X)”). By doing so, the platinum or the noble metal alloy phase containing platinum is uniformly mixed with the oxide phase of the metal element (X) or dispersed on the surface of the metal oxide phase other than the noble metal, and further the metal oxidation of the metal element (X). It can have a great affinity with the physical phase.

In the fuel cell electrode catalyst of the present invention, the metal oxide phase of the metal element (X) exhibits non-stoichiometry with respect to oxygen, and MO _2-a (M: Ti, V, Cr, Mn, Fe, Co, One or more elements selected from Ni, Cu, Zr, Nb, Mo, Ru, Rh, Sn, In, Hf, Ta, W, Re, Ir, and rare earth elements, a represents non-stoichiometry to oxygen The non-stoichiometric composition can be expressed as:

  The electrode catalyst for a fuel cell of the present invention is composed of composite fine particles in which platinum or a noble metal alloy containing platinum and a metal oxide of the metal element (X) are uniformly dispersed or aggregated, and the average particle size is about several tens of nm. Secondary particles are formed.

  In the fuel cell electrode catalyst of the present invention, it is preferable that the fine particles of platinum or the noble metal alloy containing platinum and the metal oxide of the metal element (X) are uniformly dispersed and supported on the carbon material. As the carbon material, a mixture of carbon black, activated carbon, acetylene black and the like and mesoporous carbon particles can be adopted. Titanium oxide or tin oxide can also be used.

According to the present invention, composite fine particles of platinum or a noble metal alloy containing platinum and a metal oxide of metal element (X) are used as the main constituent material of the electrode catalyst layer for fuel cells.
The electrode catalyst layer for a fuel cell in the present invention contains composite fine particles of platinum or a noble metal alloy containing platinum and a metal oxide of the metal element (X), and is therefore suitable for a catalyst electrode of a fuel cell, particularly an air electrode catalyst. Can be used.

  According to the present invention, the catalyst particles are provided on both sides of the solid polymer electrolyte, and the composite fine particles of the platinum or the noble metal alloy containing platinum and the metal oxide of the metal element (X) are the catalyst fine particles for a fuel cell described above. A fuel cell electrode catalyst is provided.

  The present invention is a fuel cell including a fuel electrode, an air electrode, and a solid electrolyte membrane sandwiched between the fuel electrode and the air electrode, wherein the air electrode includes the platinum or a noble metal alloy containing platinum and a metal element. (X) a composite fine particle with a metal oxide, or a carbon material powder carrying a composite fine particle with a platinum or platinum-containing noble metal alloy and a metal element (X) metal oxide, or the platinum or platinum. A catalyst layer formed into a thin film using titanium oxide or tin oxide powder supporting composite fine particles of a noble metal alloy and a metal oxide of metal element (X), and porous carbon paper or carbon supporting the catalyst layer A fuel cell comprised of a fabric is provided.

  According to the present invention, platinum or a noble metal alloy containing noble metal alloy containing platinum and a metal element (X) is manufactured, or platinum oxide or noble metal alloy oxide containing platinum oxide and metal element (X And a noble metal alloy containing platinum and a step of producing composite fine particles of the metal oxide of the metal element (X) by reducing the composite fine particles of the metal oxide of A method for producing battery electrode catalyst particles is provided.

  In the method for producing electrode catalyst particles for a fuel cell of the present invention, composite oxide fine particles of platinum or platinum-containing noble metal or platinum oxide or noble metal alloy oxide containing platinum oxide and metal element (X) are converted into carbon. The step of supporting on the surface of the material, platinum or a noble metal containing platinum supported on the surface of the carbon material, and the composite oxide fine particles of the metal element (X) are reduced, so that the platinum supported on the carbon material or A step of producing a composite fine particle of a noble metal alloy containing platinum and a metal oxide of the metal element (X) can be included.

  The present invention exhibits high catalytic activity by using composite fine particles of platinum or a noble metal alloy containing platinum and a metal oxide other than a noble metal for an electrode catalyst of a solid polymer fuel cell, particularly an air electrode catalyst. In addition, when a platinum catalyst is used, performance degradation due to elution of the platinum alloying element into the electrolyte can be suppressed.

  DESCRIPTION OF EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic view showing one embodiment of the polymer electrolyte fuel cell of the present invention. In FIG. 1, 1 is an air electrode current collector, 2 is an air electrode gas diffusion layer, 3 is an air electrode catalyst layer, 4 is a solid polymer electrolyte membrane, 5 is a fuel electrode catalyst layer, 6 is a fuel electrode gas diffusion layer, Reference numeral 7 denotes a fuel electrode current collector.

The polymer electrolyte fuel cell of the present invention directly generates electrical energy from the chemical energy possessed by hydrogen (H ₂ ) without going through a combustion process, and is not subject to the Carnot cycle.

  This polymer electrolyte fuel cell has a stack structure in which unit cells composed of a flat MEA and two separators are stacked. Further, each unit cell includes a fuel electrode, a solid polymer electrolyte membrane, and an air electrode. This polymer electrolyte fuel cell uses an electrode catalyst containing platinum at the fuel electrode and the above-described electrode catalyst at the air electrode. , The electrode reaction shown in the formula (2) proceeds to generate an electromotive force.

The electrode includes both a fuel electrode and an air electrode, a catalyst layer formed into a thin film containing catalyst fine particles, and a porous gas diffusion layer that supports the catalyst layer.
The gas diffusion layer supplies the fuel gas or air uniformly and sufficiently within the battery surface to the electrode reaction region in the fuel electrode or the catalyst layer of the air electrode in order to efficiently perform the electrode reaction, and (1) The charge generated by the electrode reaction shown in the formula (2) is discharged to the outside of the single cell, and the reaction product water and unreacted gas are efficiently discharged to the outside of the single cell. As a constituent material of the gas diffusion layer, a porous body having electron conductivity such as carbon cloth or carbon paper is used.

The catalyst layer of the air electrode of the polymer electrolyte fuel cell is preferably composed mainly of catalyst powder covered with a thin film electrolyte and PTFE (polytetrafluoroethylene).
The catalyst particles used in the air electrode of the polymer electrolyte fuel cell of the present invention are platinum or a noble metal alloy containing platinum and a composite particle of metal oxide or platinum supported on carbon or a noble metal alloy containing platinum. It is composed of composite particles with metal oxide.

  The average particle diameter of the catalyst composite particles is preferably 30 nm or less, particularly 5 nm to 25 nm in order to form composite particles and to obtain high activity. When the particle diameter exceeds 30 nm, the specific surface area of the catalyst phase becomes relatively small, and the high activity of the catalyst cannot be brought out. If the particle diameter is smaller than 5 nm, it is difficult to obtain composite particles in which platinum or a noble metal alloy phase containing platinum and a metal oxide phase other than the noble metal are uniformly dispersed.

  The size of platinum or a noble metal alloy phase containing platinum in the catalyst composite particles is preferably 1 nm to 15 nm, particularly 2 nm to 10 nm in order to obtain high catalyst activity. If the size of platinum or a noble metal alloy phase containing platinum is less than 1 nm, high activity of the catalyst is not exhibited. On the other hand, when the particle diameter exceeds 15 nm, the specific surface area of platinum or a noble metal alloy phase containing platinum becomes relatively small, and the high activity of the catalyst cannot be brought out.

  From the above viewpoint, the composite particle of platinum or a noble metal alloy containing platinum and a metal oxide other than the noble metal preferably has an average particle size of 5 nm to 25 nm, and platinum which is the main constituent phase of the composite particle Alternatively, the noble metal alloy phase containing platinum preferably has an average size of 2 nm to 10 nm from the above viewpoint.

  Platinum in the composite particles or a noble metal element (Y) constituting a noble metal alloy phase containing platinum (hereinafter abbreviated as “noble metal element (Y)”) and a metal element (X) constituting a metal oxide phase other than the noble metal Is preferably 30 ≦ 100Y / (X + Y) ≦ 95. When the value of 100Y / (X + Y) is less than 30, the ratio of platinum or a noble metal alloy phase containing platinum becomes small, and the high activity of the catalyst cannot be brought out. On the other hand, when the value of 100Y / (X + Y) exceeds 95, there is no significant difference in catalytic activity over pure platinum.

  The metal oxide phases other than the noble metals constituting the catalyst composite particles are Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Sn, In, Hf, Ta, and W. , Re, Ir and at least one metal oxide selected from the group consisting of rare earth elements is preferable.

On the other hand, the catalyst layer of the fuel electrode of the polymer electrolyte fuel cell is preferably composed mainly of catalyst powder covered with a thin film electrolyte and PTFE (polytetrafluoroethylene).
The catalyst particles used in the fuel electrode of the polymer electrolyte fuel cell of the present invention are platinum fine particles or platinum fine particles supported on a carbon support. The catalyst particles used in the fuel electrode have a hydrogen oxidation reaction at the fuel electrode that is 100 times faster than the oxygen reduction reaction at the air electrode, and there is no need to use the same catalyst composite fine particles as in the air electrode. The structure is not particularly limited.

  In addition, an ion-exchange solid polymer membrane (PEM), which is a thin film electrolyte that covers the surface of catalyst fine particles in the catalyst layer of the fuel electrode and the air electrode, and an electrolyte sandwiched between the catalyst layer of the fuel electrode and the air electrode on both sides, A perfluoroalkylsulfonic acid ion exchange membrane having a sulfonic acid group is preferred.

The catalyst layer of the fuel electrode and the air electrode is composed of catalyst particles, an electrolyte, and PTFE (polytetrafluoroethylene).
The thicknesses of the catalyst layers of the fuel electrode and the air electrode are preferably 100 μm or less. When the thickness of the catalyst layer exceeds 100 μm, the diffusibility of the fuel gas at the fuel electrode or the air at the air electrode to the electrode reaction region in the catalyst layer is significantly reduced, and the reaction product water and unreacted gas are supplied to a single cell. Emission efficiency to the outside is significantly reduced. Furthermore, the proton conduction resistance in the catalyst layer of the air electrode increases, the oxygen reduction reaction overvoltage increases, and the battery performance decreases.

The formation method of the fuel electrode and air electrode which consist of such a gas diffusion layer and a catalyst layer is not specifically limited, For example, it manufactures according to the following formation methods.
First, catalyst composite particles are prepared. Fine particles can be produced by a liquid phase method or a gas phase method. Examples of the liquid phase method are shown below, and the liquid phase method may be any of a coprecipitation method, a precipitation method, a metal alkoxide method, a reverse phase micelle method, a sol-gel method, and the like. For example, an aqueous solution of a metal salt of noble metal (Y) containing platinum or platinum and one or more elements selected from Pd, Ag, and Au, and Ti, V, Cr, Mn, Fe, Co, Ni, Cu, An aqueous solution of a metal salt of one or more metal elements (X) selected from Zr, Nb, Mo, Ru, Rh, Sn, In, Hf, Ta, W, Re, Ir and rare earth elements is mixed and appropriate. Platinum or a noble metal containing platinum by adding a precipitating agent or a reducing agent, and then heat-treating as necessary, with the pH adjusted and maintained at an appropriate temperature. Composite particles of an alloy and a metal oxide other than a noble metal, or a composite particle of platinum oxide or a noble metal alloy oxide containing platinum and a metal oxide other than a noble metal can be obtained.

  Next, a manufacturing method by a vapor phase method, for example, an RF thermal plasma method is described below. Platinum or platinum and a noble metal containing one or more elements selected from Pd, Ag and Au, and Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, After uniformly dissolving an alloy of one or more metal elements (X) selected from Sn, In, Hf, Ta, W, Re, Ir and rare earth elements, an alloy powder having an average particle size of 10 to 50 μm is produced by gas atomization. Further, an alloy powder having an average particle diameter of 0.1 to 3 μm is produced by pulverization as necessary, and the alloy powder is supplied into the apparatus from the plasma torch in the RF thermal plasma apparatus, thereby producing argon-oxygen. By vaporizing the alloy powder in the plasma and then rapidly cooling after passing through the plasma, platinum oxide or a noble metal alloy oxide containing platinum and an acid of a metal element (X) other than the noble metal Compound oxide fine particles with the compound are obtained. Furthermore, composite particles of platinum or a noble metal alloy containing platinum and an oxide of metal element (X) can be obtained by reducing the composite oxide fine particles in a hydrogen-containing atmosphere.

  In the case where it is difficult to produce an alloy powder by gas atomization after uniformly dissolving the alloy, an aqueous solution of a metal salt of a noble metal (Y) containing platinum or one or two or more elements selected from platinum and Pd, Ag and Au. And selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Sn, In, Hf, Ta, W, Re, Ir, and rare earth elements By mixing an aqueous solution of a metal salt of two or more metal elements (X), forming the mixed liquid into droplets in the range of several μm to several tens of μm, and supplying the mixture into the apparatus from a plasma torch in the RF thermal plasma apparatus The alloy powder is vaporized in an argon-oxygen plasma, and then rapidly cooled after passing through the plasma, whereby platinum oxide or a noble metal alloy oxide containing platinum and a metal element other than the noble metal (X) Composite oxide fine particles with these oxides are obtained. Furthermore, composite particles of platinum or a noble metal alloy containing platinum and an oxide of metal element (X) can be obtained by reducing the composite oxide fine particles in a hydrogen-containing atmosphere.

  Next, the catalyst composite fine particles, the polytetofluoroethylene (PTFE) suspension (binder and water repellent), the membrane solution in which the electrolyte is dissolved, and the organic solvent are mixed to form a paste or slurry ( Hereinafter, it is adjusted to a catalyst layer forming ink).

  Next, the catalyst layer forming ink is formed into a film thickness of several tens of μm by a screen printing method, a deposition method, a spray method or the like on a polymer electrolyte membrane or carbon paper that has been subjected to a water repellent treatment in advance with a PTFE suspension. A catalyst layer is formed so that the film thickness is uniform over the entire surface, and heat treatment is performed to prepare the catalyst layer.

  Next, the electrolyte membrane is sandwiched between the fuel electrode and the air electrode so that the catalyst layer side of the electrode is in contact with the electrolyte membrane, and the electrode and the membrane are joined by hot pressing with a press machine, and the membrane electrode assembly ( MEA).

The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment.
That is, in the above embodiment, the polymer electrolyte fuel cell having a configuration of only a single cell has been described. However, the polymer electrolyte fuel cell of the present invention is not limited to this, and a plurality of single cells are provided. It may have a so-called stack structure that is laminated.

  Hereinafter, examples and comparative examples of the electrode catalyst for a fuel cell of the present invention, a production method thereof, and a fuel cell using them will be described, but the present invention is not limited thereto.

Example 1
1 mmol (mil mole) of CoCl ₂ .6H ₂ O and 3 mmol of H ₂ PtCl ₆ .6H ₂ O are dissolved in 200 ml of trimethylene glycol, an aqueous NaOH solution is added to bring the pH of the solution to 13, and NaNO is added. 15g of ₃ is added, and it heats up to 180 degreeC, and hold | maintains for 1 hour, stirring at this temperature. After holding, the suspension is cooled to room temperature, and solid-liquid separation is performed to produce composite fine particles of platinum and cobalt oxide having an average particle diameter of 5 nm.

  1 g of the composite fine particles of platinum and cobalt oxide, 0.4 ml of pure water, 1.5 ml of 5% Nafion solution, and 0.2 ml of isopropyl alcohol are mixed to prepare a slurry catalyst for the air electrode.

  Further, 1 g of platinum black, 0.4 ml of pure water, 1.5 ml of 5% Nafion solution, and 0.2 ml of isopropyl alcohol are mixed to prepare a slurry-like catalyst for the fuel electrode. Slurry catalysts for the air electrode and the fuel electrode are formed into sheets by a doctor blade method, respectively, and dried in the air to produce a catalyst sheet for the air electrode and the fuel electrode.

A carbon paper obtained by sandwiching Nafion 112 as a proton conductive solid polymer membrane between the air electrode catalyst sheet and the fuel electrode catalyst sheet and thermocompression bonding by a hot press method. The membrane electrode assembly (MEA) is produced by sandwiching.
A fuel cell having a laminated structure in which the membrane electrode assembly (MEA) is sandwiched between a fuel electrode side separator serving as a fuel gas channel and an air electrode side separator serving as an air channel is manufactured.

Example 2
A membrane electrode assembly (MEA) was produced in the same manner as described in Example 1 except that the air electrode catalyst composite fine particles produced by the method described below were used, and this membrane electrode assembly was used as a fuel. A fuel cell having a laminated structure sandwiched between a fuel electrode side separator serving as a gas flow path and an air side separator serving as an air flow path is manufactured.

Composite fine particles of platinum and copper oxide are produced by the method described below.
First, Pt and Cu are weighed so as to have an atomic concentration ratio of 50:50, put into a melting crucible, dissolved in an Ar gas atmosphere at 1700 ° C. by a gas atomizer, and sprayed with an Ar gas pressure of 6 MPa. A Pt ₅₀ Cu ₅₀ alloy powder having an average particle diameter of 25 μm is prepared. This alloy powder is pulverized in an Ar atmosphere using a planetary ball mill to produce a Pt ₅₀ Cu ₅₀ alloy powder having an average particle size of 0.5 μm. This alloy powder is supplied from the plasma torch in the RF thermal plasma device to the argon-oxygen plasma in the device, and rapidly solidified particles are collected to produce composite particles of platinum and copper oxide with an average particle size of 7 nm. To do.

Comparative Example 1
1 g of platinum black, 0.4 ml of pure water, 1.5 ml of 5% Nafion solution, and 0.2 ml of isopropyl alcohol are mixed to prepare slurry catalysts for the fuel electrode and the air electrode. Slurry catalysts for the air electrode and the fuel electrode are formed into sheets by a doctor blade method, respectively, and dried in the air to produce a catalyst sheet for the air electrode and the fuel electrode.

  A carbon paper obtained by sandwiching Nafion 112 as a proton conductive solid polymer membrane between the air electrode catalyst sheet and the fuel electrode catalyst sheet and thermocompression bonding by a hot press method. The membrane electrode assembly (MEA) is produced by sandwiching. A fuel cell having a laminated structure in which the membrane electrode assembly is sandwiched between a fuel electrode side separator serving as a fuel gas flow path and an air side separator serving as an air flow path is manufactured.

  When the composite fine particles of platinum and platinum and cobalt oxide shown in Examples 1 and 2 and the composite fine particles of platinum and copper oxide are used as the catalyst of the air electrode, compared with the case of using platinum black of the comparative example. Thus, the fuel cell (single cell) is excellent in open circuit voltage, current density-voltage characteristics, and life evaluation based on changes in cell voltage over time.

  Since the fuel cell air electrode of the present invention has high catalytic activity and can suppress deterioration of catalytic activity under the use conditions of the fuel cell, it can be used for a small fuel cell for mobile devices.

It is the schematic which shows one Embodiment of the polymer electrolyte fuel cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air electrode current collector 2 Air electrode gas diffusion layer 3 Air electrode catalyst layer 4 Solid polymer electrolyte membrane 5 Fuel electrode catalyst layer 6 Fuel electrode gas diffusion layer 7 Fuel electrode current collector

Claims (11)

  An electrode catalyst for use in the air electrode of a polymer electrolyte fuel cell having a membrane electrode assembly comprising a solid polymer electrolyte membrane that permeates protons, a fuel electrode having a catalyst layer containing an electrode catalyst, and an air electrode. An electrode catalyst for a polymer electrolyte fuel cell, comprising platinum, a noble metal alloy containing platinum, and composite particles comprising a metal oxide other than the noble metal.   The air electrode of a solid polymer fuel cell comprising a membrane electrode assembly comprising a solid polymer electrolyte membrane that permeates protons, a fuel electrode having a catalyst layer containing an electrode catalyst, and an air electrode, with a separator interposed therebetween. An electrode catalyst for a solid polymer fuel cell, comprising: composite particles comprising platinum or a noble metal alloy containing platinum and a metal oxide other than the noble metal.   The electrode catalyst according to claim 1 or 2, wherein the composite particles have a maximum particle size of 30 nm or less.   4. The electrode catalyst according to claim 1, wherein the platinum-containing noble metal alloy is an alloy of at least one member selected from the group consisting of Pd, Ag, and Au and Pt. 5.   The electrode catalyst according to any one of claims 1 to 4, wherein an average size of platinum or a noble metal alloy phase containing platinum in the composite particles is 20 nm or less.   The electrode catalyst according to any one of claims 1 to 5, wherein platinum in the composite particles or a noble metal alloy phase containing platinum is present on the surface more than inside the composite particles.   Metal oxides other than the noble metals include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Sn, In, Hf, Ta, W, Re, Ir, and rare earths. The electrode catalyst according to any one of claims 1 to 6, wherein the electrode catalyst comprises at least one member selected from the group consisting of elements.   The electrode catalyst according to claim 1, wherein the composite particles are supported on a carbon support or an oxide support.   The composite particles are generated by reducing platinum particles or oxide particles comprising a noble metal alloy oxide containing platinum and a metal oxide other than the noble metal in a mixed gas atmosphere of an inert gas and hydrogen. Item 10. The electrode catalyst according to any one of Items 1 to 8.   An electrode for a polymer electrolyte fuel cell comprising the electrode catalyst according to any one of claims 1 to 9 as a catalyst component.   A polymer electrolyte fuel cell using the electrode according to claim 10 as an air electrode.

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