JP4403634B2 - Composite catalyst for solid polymer electrolyte fuel cell. - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a solid polymer electrolyte fuel cell.Composite catalystIt is about.
[0002]
[Prior art]
  A solid polymer electrolyte fuel cell uses a solid ion-exchange membrane as an electrolyte, supplies hydrogen by supplying, for example, hydrogen as a fuel to the anode, and supplying oxygen as an oxidant, for example, to the cathode, and reacts electrochemically on the catalyst surface. Device.
[0003]
  The electrochemical reaction at each electrode in this case is shown below.
[0004]
  Anode: H₂→ 2H⁺+ 2e⁻
  Cathode: 1 / 2O₂+ 2H⁺+ 2e⁻→ H₂O
  Total reaction: H₂+ 1 / 2O₂→ H₂O
  As shown in the above equation, the reaction at the anode and cathode involves supplying oxygen and hydrogen gases, protons (H⁺) And electrons (e⁻), And all reactions proceed only at the three-phase interface in the catalyst layer included in the electrode for the solid polymer electrolyte fuel cell in which they are simultaneously filled.
[0005]
  Therefore, in the catalyst layer, the solid polymer electrolyte and the catalyst particles are three-dimensionally distributed with a plurality of pores, the proton conduction path formed by the solid polymer electrolyte, the conductive agent such as carbon particles, and the catalyst particles. And the gas diffusion path formed by the pores form innumerable three-phase interfaces.
[0006]
  A solid polymer electrolyte fuel cell electrode includes a gas diffusion electrode composed of the above-described catalyst layer and a conductive porous substrate serving as a current collector, and an anode and a cathode on both sides of the solid polymer electrolyte membrane. A membrane-electrode assembly bonded as follows is used. In order to obtain a high-power electrode for a fuel cell, the catalyst layer needs to have high proton conductivity, electron conductivity, and gas diffusivity. For this purpose, each of the three paths described above is provided in the catalyst layer. It is necessary to form in communication.
[0007]
  Further, since the solid polymer electrolyte used as the proton conductor exhibits good proton conductivity only in a water-containing state, the gas supplied to the anode and cathode is humidified to prevent the solid polymer electrolyte from drying.
[0008]
[Problems to be solved by the invention]
  As described above, a continuous gas flow path, proton conduction path, and electron conduction path are required in the catalyst layer in order to obtain a high output electrode for a solid polymer electrolyte fuel cell.
[0009]
  However, since humidified gas is supplied and water is also generated by reaction at the cathode, when the solid polymer electrolyte fuel cell is operated at a high current density, the surface of the catalyst layer and the pores are formed. There is a problem that the water is stagnated, the gas diffusibility is inhibited, and the output is significantly reduced.
[0010]
  In general, in order to prevent generation of water and retention of water due to gas humidification, polytetrafluoroethylene (PTFE) particles having water repellency at the time of forming a catalyst layer are mixed together with catalyst particles, The electrode is applied to the surface of the porous porous body to impart water repellency to the electrode. In order to prevent retention of water in the electrode during high current density operation, it is necessary to further increase the water repellency by increasing the amount of PTFE mixed, but although PTFE has strong water repellency, In addition, since it does not have proton diffusivity as well as proton conductivity, the electron conduction path, proton conduction path, and gas diffusion path are blocked, and the output of the fuel cell is reduced.
[0011]
  In addition, in order to give proton conductivity to the entire catalyst layer, a mixed paste of catalyst particles and a solid polymer electrolyte solution is used at the time of forming the catalyst layer, or the catalyst layer is impregnated with a solid polymer electrolyte solution, The molecular electrolyte is included. However, it is difficult to evenly distribute the ion exchange resin solution having a certain viscosity to the deep part of the electrode, and a sufficient three-phase interface is not formed in the deep part of the electrode, causing problems such as a decrease in catalyst utilization. .
[0012]
  In view of the above, the present invention is to improve the above problems and to improve the performance of a solid polymer electrolyte fuel cell.
[0013]
[Means for solving problems]
  Claim 1In the composite catalyst for a solid polymer electrolyte fuel cell, the invention comprises a catalyst particle comprising carbon carrying a catalyst metal, the catalyst particle surface comprising a first resin and a second resin,SaidThe first resin is an ion exchange resin,SaidThe second resin is porousThe amount of catalyst metal supported on the surface of the carbon particles that do not have proton conductivity and is in contact with the proton conduction path of the ion exchange resin exceeds 50% of the total amount of catalyst metal supported.It is characterized by that.
[0014]
  Of the present inventionIn the composite catalyst for a solid polymer electrolyte fuel cell, the second resin is a fluororesinIs preferred.
[0015]
  Of the present inventionIn the composite catalyst for solid polymer electrolyte fuel cell, the ion exchange resin must be porous.Is preferred.
[0016]
  The present inventionA second resin is provided in the hole of the ion exchange resinIs preferred.
[0017]
  The present inventionAn ion exchange resin in the hole of the second resinIs preferred.
[0018]
  Of the present inventionComposite catalyst for solid polymer electrolyte fuel cellIsThe composite having the porous ion exchange resin on the surface of the catalyst particles is obtained by the first step of phase-separating the ion exchange resin after the solution in which the ion exchange resin is dissolved in the solvent is attached to the surface of the catalyst particles. Fabricate, and then go through a second step of arranging a second resin on the surface of the compositeCan be manufactured by.
[0019]
  The present inventionComposite catalysts for solid polymer electrolyte fuel cellsIsA porous second resin is provided on the surface of the catalyst particles by the first step of phase-separating the second resin after adhering a solution in which the second resin is dissolved in the solvent to the surface of the catalyst particles. Producing a composite, followed by a second step of disposing an ion exchange resin on the surface of the compositeCan be manufactured by.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, structural examples of the composite catalyst for a solid polymer electrolyte fuel cell according to the present invention will be described more specifically with reference to the drawings.
[0021]
  1 ~FIG.These are the schematic diagrams which showed the structural example of the composite catalyst for solid polymer electrolyte type fuel cells provided with the ion exchange resin and 2nd resin based on this invention.1 to 4These are schematic diagrams when the ion exchange resin and the second resin are porous. Also,FIG.Indicates a state in which the catalytic metal is mainly supported on the surface of the carbon particles in contact with the proton conduction path of the ion exchange resin.
[0022]
Also,1 and 3Shows a state where the ion exchange resin and the second resin are provided on the surface of each catalyst particle,2 and 4These show the state with which the ion exchange resin and 2nd resin are equipped over the surface of the catalyst particle which formed the secondary particle.
[0023]
1 ~FIG.In, 31, 41, 51, 61, 71 are catalyst particles, 3242, 52, 62 and 72 are ion exchange resins, 3343, 53, 63, 73 are second resins, 74 is a proton conduction path of the ion exchange resin, and 75 is a catalyst metal. In addition,1 to 4The ion exchange resins 32, 42, 52, 62 and the second resins 33, 43, 53, 63 have a structure with holes.
[0024]
  1 and 2Shows the structure of a composite catalyst comprising porous ion exchange resins 32, 42 on the catalyst particle surface and second resins 33, 43 in the pores and on the surface,FIG.Then, the porous ion exchange resin 32 is formed on the surface of each catalyst particle 31, andFIG.Then, the porous ion exchange resin 42 is provided over the surface of the catalyst particle 41 which formed the secondary particle. The second resins 33 and 43 provided in and on the surfaces of the porous ion exchange resins 32 and 42 do not have to have holes, but are porous to obtain high gas diffusibility. Preferably there is.
[0025]
  3 and 4Shows the structure of a composite catalyst comprising the second resin 52, 62 on the surface of the catalyst particles, and the porous ion exchange resins 53, 63 in the pores and on the surface,FIG.Then, the second resin 52 is formed on the surfaces of the individual catalyst particles 51, andFIG.Then, the 2nd resin 62 is provided over the surface of the catalyst particle 61 which formed the secondary particle. The ion exchange resins 52 and 62 need not have pores, but are preferably porous in order to obtain high gas diffusibility.
[0026]
  The porous ion exchange resin and the porous second resin may have a porous structure or a structure in which the resin is formed in a net shape. Furthermore, you may have the structure where the hole communicated in three dimensions.
[0027]
  further,FIG.As shown in FIG. 3, the composite catalyst in which the catalytic metal particles according to the present invention are mainly supported on the surface of the carbon particles in contact with the proton conduction path of the cation exchange resin is the Teflon skeleton 72 of the ion exchange resin on the surface of the carbon particles 71. The ion-exchange resin proton conduction path 75, the second resin 73, and the catalyst metal 75 have a structure, and the catalyst metal particles exceeding 50% of the total catalyst metal amount are the ion-exchange resin on the surface of the carbon particles. Is supported on the proton conduction path.
[0028]
  Here, various resins can be used as the second resin, but in order to obtain excellent water repellency, it is preferable to use a fluororesin.
[0029]
  The composite catalyst for a solid polymer electrolyte fuel cell according to the present invention includes an ion exchange resin that imparts proton conductivity and a second resin that imparts water repellency to the catalyst particle surface. In the catalyst layer, the ion exchange resin that bears the proton conduction path and the second resin having water repellency are distributed uniformly throughout the details of the catalyst layer, and the gas diffusivity and proton conductivity enhanced by the water repellency are It also serves as a binder between the catalyst particles.
[0030]
  In addition, when the ion exchange resin or the second resin is porous, it is possible to maintain higher gas diffusibility and electronic conductivity of the catalyst.
[0031]
  In addition, by providing the second resin in the pores of the porous ion exchange resin or the ion exchange resin in the pores of the porous second resin, sufficient proton conductivity and water repellency are provided for the catalyst particles. The catalyst layer can be formed together, and the resin covering the surface of the catalyst particles is porous, so that the electron conductivity between the catalyst particles can be maintained.
[0032]
  In such a composite catalyst, since the catalyst particle surface has a large number of holes, the catalyst particle is not completely covered, and the catalytic activity can be maintained. For this reason, since the catalyst layer using the composite catalyst for fuel cells according to the present invention has high mechanical strength and is excellent in water repellency and proton conductivity, a high-power fuel cell can be provided.
[0033]
  The catalyst particles of the composite catalyst for a solid polymer electrolyte fuel cell according to the present invention are those in which a catalyst metal containing a platinum group metal such as platinum, rhodium, ruthenium, iridium, palladium, osmium, or an alloy thereof is supported on carbon. It is preferable to use it. However, when producing a composite catalyst for a fuel cell in which a catalytic metal is mainly supported on the carbon particle surface in contact with the proton conduction path of the ion exchange resin, the carbon particles are provided with an ion exchange resin, or an ion exchange resin and a second resin. Then, the catalyst metal may be supported on the surface of the carbon particles in contact with the proton conduction path of the ion exchange resin.
[0034]
  As carbon, carbon black such as acetylene black and furnace black, graphite particles, activated carbon and the like are preferable, and carbon black is particularly preferable because of excellent electron conductivity and high dispersion of catalyst particles.
[0035]
  The ion exchange resin provided in the composite catalyst for a solid polymer electrolyte fuel cell according to the present invention preferably uses a proton exchange resin, and among them, a perfluorocarbon sulfonic acid or a styrene-divinylbenzene sulfonic acid type. It is preferable to use a solid polymer electrolyte from the viewpoint of good proton conductivity.
[0036]
  Further, the fluororesin provided in the composite catalyst for a solid polymer electrolyte fuel cell according to the present invention does not need to have proton conductivity, such as polyvinylidene fluoride (PVdF), vinyl fluoride polymer (PVF), etc. Fluorine-containing homopolymer or ethylene trifluoride chloride copolymer (PCTFE), ethylene / tetrafluoroethylene copolymer, vinylidene fluoride / hexafluoropropylene polymer (P (VdF-HEP)), vinylidene fluoride A fluorine-containing copolymer such as a tetrafluoroethylene copolymer (P (VdF-TFP)) is preferable, or a mixture thereof may be used. Among them, a vinylidene fluoride polymer (PVdF) excellent in water repellency or a vinylidene fluoride / hexafluoropropylene copolymer (P (VdF-TFP)) that is soft and easy to handle is preferable.
[0037]
  Here, in the ion exchange resin provided in the catalyst particles, the porosity of the ion exchange resin is 50% or more and the supported amount is 70 wt% or less with respect to the weight of the catalyst particles so that the electron conductivity between the catalyst particles does not decrease. More preferably, the porosity is 75% or more and the loading is 50 wt% or less.
[0038]
  Furthermore, the porosity of the fluororesin provided in the catalyst particles is such that the fluororesin covers the catalyst particles so that the activity of the catalyst does not decrease, and the electron conductivity between the catalyst particles does not decrease. The supported amount is preferably 50% or more and 30 wt% or less with respect to the catalyst particles, and more preferably the porosity is 75% or more and the supported amount is 15 wt% or less.
[0039]
  A method for producing a composite catalyst for a solid polymer electrolyte fuel cell according to the present invention will be described below. First, a method for producing a composite having an ion exchange resin on the catalyst particle surface and further having a second resin on the surface of the composite will be described.
[0040]
  In the first step, a solution in which an ion exchange resin is dissolved in a solvent is attached to the surface of the catalyst particles to produce a composite having the ion exchange resin on the surface of the catalyst particles. In this composite, if the ion exchange resin on the surface of the catalyst particles does not have pores, the solvent can be removed from the attached solution by evaporation, etc. In order to make the ion exchange resin porous, this composite What is necessary is just to phase-separate ion-exchange resin from the solution adhered to the body.
[0041]
  Phase separation of the ion exchange resin from the solution adhering to the catalyst particle surface utilizes changes in the solubility of the ion exchange resin in the solvent by heating or cooling, and changes in the concentration of the ion exchange resin in the solution by evaporating the solvent. And a method using a solvent extraction method.
[0042]
  Among these phase separation methods, in order to provide a porous ion exchange resin having uniform pores on the surface of the catalyst particles, it is preferable to use a solvent extraction method. In this method, a catalyst particle having a solution obtained by dissolving an ion exchange resin in a first solvent adhered to the surface is immersed in a second solvent in which the ion exchange resin is insoluble and compatible with the first solvent, The first solvent is extracted to obtain a composite having a porous ion exchange resin on the surface of the catalyst particles.
[0043]
  In the second step, a solution in which the second resin is dissolved in a solvent is attached to the surface of the composite prepared in the first step, and the second resin is provided on the surface of the composite prepared in the first step. A composite catalyst is obtained. In this composite catalyst, when the second resin on the surface of the composite obtained in the first step does not have pores, the solvent may be removed from the attached solution by evaporation or the like. In order to achieve porosity, the ion exchange resin may be phase-separated from the solution attached to the surface of the composite prepared in the first step.
[0044]
  As the phase separation method, the method using the change in solubility and the concentration as described in the first step, and the solvent extraction method can be used.
[0045]
  Furthermore, the composite catalyst of the present invention can also be obtained by a preparation method in which a composite having the second resin on the surface of the catalyst particles is prepared, and an ion exchange resin is provided on the surface of the composite. In this method, in the above-described method for producing a composite catalyst having an ion exchange resin on the surface of catalyst particles and further having a second resin on the surface of the composite, in the first step, an ion is used in the first step. A second resin is used instead of the exchange resin, and an ion exchange resin is used instead of the second resin in the second step.usedo it.
[0046]
  In order to make the ion exchange resin or the second resin porous, the same phase separation method as described in the first step can be used.
[0047]
  In such a method for producing a composite catalyst of the present invention, the ion exchange resin or the second resin provided on the catalyst particle surface in the first step is made porous, so that the ion exchange resin provided on the catalyst particle surface is made porous. The composite catalyst according to the present invention can be produced in which the second resin is provided in the holes or the ion exchange resin is provided in the holes of the second resin provided on the surface of the catalyst particles.
[0048]
  In addition, as a method of attaching the solution in which the ion exchange resin is dissolved or the solution in which the second resin is dissolved to the surface of the catalyst particle or the composite obtained in the first step, for example, the catalyst particle or the composite is used. Is immersed in the solution, or the solution is sprayed on the catalyst particles or the composite by spraying or the like.
[0049]
  In particular, a method of immersing the catalyst particles in the solution under a reduced pressure of 50 Torr or less, more preferably 1 Torr or less in order to include the solution in the pores of the catalyst particles or in the pores between the secondary particles of the catalyst particles. Is this.
[0050]
  As the solvent for dissolving the ion exchange resin of the present invention, alcohol or a mixed solvent of alcohol and water can be used. This solution is particularly preferably a solution obtained by dissolving a perfluorocarbon sulfonic acid resin in alcohol with good dispersibility of particles and appropriate viscosity.
[0051]
  In the solvent extraction method of the method for producing a composite catalyst of the present invention, the solvent having a polar group other than the alcoholic hydroxyl group used as the second solvent has a carbon chain having an alkoxycarbonyl group in the molecule having a carbon number of 1 to 1. 7 organic solvents such as propyl formate, butyl formate, isobutyl formate, ethyl acetate, propyl acetate, isopropyl acetate, allyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, methyl propionate, ethyl propionate, propionic acid Propyl, methyl acrylate, butyl acrylate, isobutyl acrylate, methyl butyrate, methyl isobutyrate, ethyl butyrate, ethyl isobutyrate, methyl methacrylate, propyl butyrate, isopropyl isobutyrate, 2-ethoxyethyl acetate, 2- (2 acetate Ethoxyethoxy) ethyl alone, Mixture properly, it is preferable to use.
[0052]
  In the method for producing a composite catalyst of the present invention, the solvent used for dissolving the second resin includes methyl ethyl ketone (MEK), ketones such as acetone, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl. Carbonates such as carbonate, ethers such as dimethyl ether, diethyl ether, ethyl methyl ether, tetrahydrofuran (THF), dimethylformamide, dimethylacetamide, 1-methyl-pyrrolidinone, n-methyl-pyrrolidone (NMP), dimethylformamide (DMF), Examples thereof include dimethyl sulfoxide (DMSO).
[0053]
  In particular, when a fluororesin is used as the second resin in the method for producing a porous resin by phase separation utilizing the change in solubility, ketones such as MEK and acetone are preferable as the solvent for dissolving the fluororesin.
[0054]
  In the method for producing a porous resin by phase separation using the solvent extraction method described above, when a fluororesin is used as the second resin, examples of the first solvent for dissolving the fluororesin include NMP and DMF. DMSO is preferable, and among them, NMP is preferable because fine and uniform pores can be obtained. That is, when a solution obtained by dissolving PVdF in NMP is used as a solution in which the fluororesin used in the present invention is dissolved in a solvent, a porous fluororesin having uniform and fine pores can be produced. Here, as the second solvent compatible with the first solvent, water or a mixed solution of water and alcohol is preferable because it is inexpensive.
[0055]
  Here, the catalyst particle in the method for producing a composite catalyst for a solid polymer electrolyte fuel cell refers to a carbon particle carrying a catalyst metal, and is on the surface of the carbon particle in contact with the proton conduction path of the cation exchange resin. When producing a composite catalyst for a fuel cell in which the amount of supported catalyst metal exceeds 50% of the total amount of supported catalyst metal, an ion exchange resin and / or a fluorine resin is disposed on carbon particles not supporting the catalyst metal. It is preferable to go through a step of supporting catalyst particles later.
[0056]
  The catalyst particles for a fuel cell comprising an ion exchange resin and a second resin produced using the production method of the present invention are all proton-conductive by ion exchange resin and water repellency by fluororesin. Is a catalyst particle that combines excellent proton conductivity and water repellency in every detail, preventing water from staying on the surface of the catalyst particle and improving gas diffusivity. This resin serves as a binder between the catalyst particles, and prevents the catalyst particles from being detached. Further, when the ion exchange resin 7 or the fluororesin is porous, the surface of the catalyst particles is not covered, and the electron conductivity and higher gas diffusibility are ensured.
[0057]
【Example】
  The present invention will be described below with reference to preferred embodiments.
[0058]
  [Example1]
  First, carbon particles (Valcan XC-72) are immersed in an ion exchange resin solution (manufactured by Aldrich, Nafion 5 wt% solution) in a state where the carbon particles (Valcan XC-72) are kept under reduced pressure, and then an excess ion exchange resin solution is sucked from the mixture. Removed by filtration.
[0059]
  Subsequently, the carbon particles with the ion exchange resin solution attached are immersed in butyl acetate to phase separate the ion exchange resin, and then the butyl acetate is removed by suction filtration and dried at 70 ° C. with a porous ion exchange resin. Carbon particles with a coated surface were produced.
[0060]
  After this step, the weight of the carbon particles provided with the ion exchange resin was measured to determine the amount of the cation exchange resin supported on the carbon (wt%). And the process was repeated so that the load of ion exchange resin might be 35 wt%.
[0061]
  Subsequently, a mixture of the carbon particles provided with the ion exchange resin was mixed with 50 mmol / l [Pt (NH₃)₄] Cl₂It is immersed in an aqueous solution for 2 days, and [Pt (NH₃)₄]²⁺Is preferentially adsorbed, washed thoroughly with purified water and dried, then reduced in a hydrogen atmosphere at 1 atm and 180 ° C. for about 4 hours, and the platinum provided in the carbon particles is proton-conducted by the cation exchange resin. Preferentially supported on the surface of the carbon particles in contact with the path.
[0062]
  Next, it is immersed in 0.2 mol / l sulfuric acid for 3 hours, and unnecessary [Pt (NH₃)₄]²⁺Was eluted to obtain carbon particles in which the amount of platinum supported on the surface of the carbon particles in contact with the proton conduction path of the ion exchange resin exceeded 50% of the total amount of platinum supported.
[0063]
  Next, the carbon particles including the porous ion exchange resin and the platinum particles are kept in a reduced pressure state and immersed in a PVdF-NMP solution in which 5 wt% of PVdF is dissolved in 95 wt% of NMP. The PVdF-NMP solution was removed by suction filtration.
[0064]
  Subsequently, after the platinum-supported carbon particles with the PVdF-NMP solution adhering in the pores of the porous ion exchange resin were immersed in water to separate the PVdF, the water was removed by suction filtration and further dried at 100 ° C. A porous ion exchange resin is provided on the surface of the carbon particles, and the amount of platinum supported on the surface of the carbon particles in contact with the proton conduction path of the porous ion exchange resin exceeds 50% of the total amount of platinum supported. A composite catalyst C having PVdF in the pores of the ion exchange resin was obtained.
[0065]
  The obtained composite catalyst C was joined by hot pressing (95 ° C.) on both surfaces of an ion exchange resin membrane (manufactured by DuPont, Nafion, film thickness 150 μm), and carbon paper as a gas diffusion layer was further joined. -Electrode assembly C was obtained. Then, the membrane-electrode assembly C was incorporated into a single cell of a fuel cell to obtain a cell C. The amount of platinum in the membrane-electrode assembly C was about 0.04 mg / cm2 according to a separate analysis.²It has been confirmed that.
[0066]
  [Comparative example]
  Platinum-supported carbon (manufactured by Tanaka Kikinzoku, TEC-10V-30E: ValcanXC-72 with 30 wt% platinum supported), ion-exchange resin solution (manufactured by Aldrich, Nafion 5 wt% solution) and PTFE particle dispersion solution (Mitsui DuPont Fluorochemicals) A paste made of Teflon 30J) is prepared, and the paste is applied on a polymer film (FEP film: tetrafluoroethylene-hexafluoropropylene copolymer sheet, manufactured by Daikin Industries, Ltd .: 25 μm) at room temperature. Air dried for about 1 hour.
[0067]
  in this wayThe catalyst layer thus obtained was bonded to both sides of a solid polymer electrolyte membrane (manufactured by DuPont, Nafion, film thickness 150 μm) by hot pressing (95 ° C.), and a PTFE dispersion solution was further applied to both sides and dried. A conductive porous body (carbon paper: 0.5 mm) imparted with water repellency was joined by hot pressing (135 ° C.) to obtain a membrane-electrode assembly D.
[0068]
  The membrane-electrode assembly D has a structure in which the gas diffusion electrode D is bonded to both surfaces of the solid polymer electrolyte membrane. The platinum amount of the membrane-electrode assembly D is about 1.0 mg / cm.²Thus, the amount of platinum-supported carbon during paste production was adjusted. The obtained membrane-electrode assembly D was incorporated into a single cell of a fuel cell to obtain a cell D.
[0069]
  Using these cells, the current-voltage characteristics when using hydrogen as the anode supply gas and oxygen as the cathode supply gas are shown.
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The current-voltage characteristics when using hydrogen as the anode supply gas and air as the cathode supply gas
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It was shown to. Each feed gas pressure was 1 atm and was humidified by bubbling in a 70 ° C. closed water bath. The cell operating temperature was 60 ° C., and the holding time during measurement at each current value was 2 minutes.
[0070]
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and
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As is apparent from the present inventionCell CCompared with the conventional cell D, a high output voltage was obtained at each current density. In particular
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As can be seen, the difference was remarkable when air was used as the cathode side supply gas. Cell C has a very small amount of catalyst supported.,outputThere was no decrease in
[0071]
  This is because the conventional gas diffusion electrode D includes a large amount of PTFE particles in the catalyst layer and the gas diffusion layer, but has water repellency, but the electron conduction path and the gas diffusion path are cut off and the output is reduced. In contrast, a gas diffusion electrode using the composite catalyst for a fuel cell according to the present inventionCHas improved the gas diffusibility by eliminating the retention of water in the gas diffusion electrode while maintaining good electron conductivity and proton conductivity. This is because the output is significantly improved compared to the conventional electrodes.
[0072]
  Further, the composite catalyst C used for the gas diffusion electrode C not only has high gas diffusibility and proton conductivity, but also because platinum particles are reliably supported on the three-phase interface of the electrode. The rate is remarkably high, and a higher performance electrode than before can be obtained even with a small amount of platinum supported.
[0073]
【The invention's effect】
  The composite catalyst for a solid polymer electrolyte fuel cell according to the present invention comprises an ion exchange resin and a catalyst particle on the surface of the catalyst particles.Porous and not proton conductiveA second resin,The amount of catalyst metal supported on the surface of the carbon particles in contact with the proton conduction path of the ion exchange resin exceeds 50% of the total amount of catalyst metal supported.Especially by ion exchangeResinBy making it porous, it is possible to obtain a highly active catalyst having both proton conductivity and water repellency, and also having catalytic activity and electron conductivity due to the presence of many pores.
[0074]
  By using this composite catalyst as a catalyst for a solid polymer electrolyte fuel cell, water retention is prevented by the provided water repellency and high gas diffusibility is secured to the inside of the catalyst layer. Even in a fuel cell that supplies low air, high performance can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view showing the surface state of a composite catalyst for a fuel cell of the present invention.
FIG. 2 is a schematic view showing the surface state of the composite catalyst for a fuel cell of the present invention.
FIG. 3 is a schematic view showing the surface state of the composite catalyst for a fuel cell of the present invention.
FIG. 4 is a schematic view showing the surface state of the composite catalyst for a fuel cell of the present invention.
[Figure 5]The schematic diagram which shows the surface state of the composite catalyst for fuel cells of this invention.
[Fig. 6]The figure which shows the electric current-voltage characteristic of a cell at the time of using hydrogen for an anode and oxygen for a cathode.
[Fig. 7]The figure which shows the electric current-voltage characteristic of a cell at the time of using hydrogen for an anode and air for a cathode.
[Explanation of symbols]
  31, 41, 51, 61, 71 Catalyst particles
  32, 42, 52, 62, 72 Ion exchange resin
  33, 43, 53, 63, 73 Second resin
  74 Proton Conduction Path of Ion Exchange Resin
  75 catalytic metal

Claims (1)

A carbon catalyst particles carrying a catalytic metal, comprising a first and second resins in the surface of the catalyst particles in the first resin is an ion exchange resin, said second resin is porous The solid polymer electrolyte type is characterized in that the amount of catalyst metal supported on the surface of the carbon particles in contact with the proton conduction path of the ion exchange resin exceeds 50% of the total amount of catalyst metal supported. Composite catalyst for fuel cells.