JP2011175772A - Catalyst for polymer electrolyte fuel cell and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst for a polymer electrolyte fuel cell having a small particle diameter of the catalyst carrier capable of mass-producing, and to provide a method of manufacturing the same. <P>SOLUTION: To manufacture the catalyst for a polymer electrolyte fuel cell which is so composed that a platinum catalyst material is carried on a titanium oxide catalyst carrier coated with a carbon layer, paste is prepared by mixing and stirring titanium oxide particles, PVA and water, then titanium oxide particles coated with the carbon layer is prepared by reduction-baking the paste to crush and pulverize it. Then, ethanol and chloroplatinic acid solution are mixed with the particles and put under heating and drying distillation to obtain platinum catalyst-carrying particles. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte fuel cell catalyst and a method for producing the same, and more particularly to a polymer electrolyte fuel cell catalyst having a carrier that exhibits high durability in a highly oxidizing atmosphere and a method for producing the same.

  The catalyst layer of the air electrode and the hydrogen electrode of a conventional polymer electrolyte fuel cell is a porous body composed of a catalyst, a catalyst carrier, and an electrolyte membrane, and a noble metal catalyst such as platinum or a platinum alloy is used as the catalyst. The catalyst particle size is ultrafine particles of several nanometers. Carbon black is generally used as a material for supporting this catalyst, and an ideal electrode reaction interface is formed by uniformly supporting platinum fine particles on the surface of carbon particles. The supported catalyst is obtained by adding a chloroplatinic acid aqueous solution to a solution in which carbon black is dispersed in ethanol or water, dropping a sodium hydrogen carbonate aqueous solution, reducing by heating and stirring, and washing and removing sodium components and the like. . Reduction of the catalyst can also be obtained by heating in a hydrogen atmosphere. An electrode paste obtained by sufficiently mixing a mixed aqueous solution or ethanol solution containing a supported catalyst and an electrolyte component is thinly applied to an electrode substrate such as carbon paper to produce an electrode.

  The electrode and the electrolyte membrane are heat-laminated to complete an electrolyte membrane-electrode complex (MEA). The electrode layer is integrated with the carbon paper, and the carbon paper is sometimes referred to by the functional name of the gas diffusion layer because hydrogen is diffused in the fuel electrode at the fuel electrode and air is diffused and supplied to the electrode at the air electrode. . A gas is supplied to the electrode through an uneven channel formed on the separator surface. A fuel cell is a basic unit of a single cell composed of an MEA, a fuel electrode flow channel plate, and an air electrode flow channel plate. The single cell voltage in an unloaded state is about 1 V, and the load voltage depends on the current. It is around 0.7V. The system is operated by a stack in which single cells are stacked in series, and the total voltage is generally about 35 V for 50 cells in series.

  At the air electrode, the supplied oxygen reacts with protons that have moved from the hydrogen electrode side through the electrolyte membrane, and water is generated by an electrochemical reduction reaction. At the hydrogen electrode, the supplied hydrogen is oxidized to generate protons. Water generated at the air electrode passes through the gap of the gas diffusion layer and is discharged to the air electrode channel. When the water vapor dew point in the air supplied to the air electrode is low, the water produced by the electrode reaction is discharged as a gas, but when the water vapor dew point in the air supplied is high, the water is produced as a liquid. The gas diffusion layer and the gas flow path are discharged as liquid water.

  The proton conductive electrolyte membrane is not limited to a fluorine-based or hydrocarbon-based one, and the proton conductivity is higher as the humidity is higher. In addition, the higher the humidity, the higher the durability against the deterioration of the membrane due to the anion radical generated by the side reaction. Therefore, high humidification conditions are preferable from the viewpoint of power generation performance and life, but from the viewpoint of fuel cell system efficiency, low humidification operation with less energy required for gas humidification is preferable. Then, the generated water and heat are recovered by using a total heat exchange type water heat exchanger or the like, and returned to the inlet for circulation.

  Since the polymer electrolyte fuel cell system is operated at a relatively low temperature of about 80 ° C., the influence of the corrosion deterioration of the constituent materials is small. However, the electrode has a high oxidation potential on the catalyst surface, and it is in a harsh environment where heat generation and moisture generation due to electrochemical reactions proceed simultaneously, and the corrosion reaction proceeds over the long term. Sex is required. In general, carbon black having a relatively high durability is used for the catalyst carrier of the electrode layer, but it is not sufficient.

  In addition to high durability, the catalyst carrier must have electronic conductivity. An electrochemical reaction involving the movement of electrons proceeds on the surface of the Pt catalyst supported on the catalyst support. However, in order for electrons to flow from the outside of the cell and contribute to the electrochemical reaction on the catalyst surface, the support must be used. Have to go through. Further, in order to uniformly support a catalyst having a small particle diameter on a support, the support surface area must be large. Thus, the catalyst carrier needs to have high corrosion resistance, high electron conductivity, and high surface area.

  As a material having higher corrosion resistance than carbon, it has been proposed to use titanium oxide, which is a metal oxide having electronic conductivity, as a catalyst carrier. This conductive metal oxide is excellent in corrosion resistance as compared with carbon, but it needs electron conductivity and is usually subjected to a reduction treatment. However, since reduction firing at a high temperature close to 1,000 ° C. is necessary, the oxide is sintered and the particle size increases simultaneously with the reduction. In order to support platinum with a high surface area, it is necessary to reduce the carrier particle diameter and increase the surface area (see, for example, Patent Document 1).

  As a method for reducing oxides without causing an increase in particle size, attempts have been made to make fine particles using an ultraviolet laser (see, for example, Non-Patent Document 1).

JP 2005-149742 A

Abstracts of the 76th Annual Meeting of the Electrochemical Society of Japan P396-1Q28 (2009)

  However, while it is possible to reduce the particle size by ultraviolet laser irradiation without increasing the temperature, it is difficult to reduce a large amount of titanium oxide at a low cost at one time by this method. Application was difficult. Therefore, the method is not suitable for a method of reducing titanium oxide that does not cause an increase in particle diameter that can be mass-produced. Further, there is a problem that it is difficult to control the composition ratio of titanium and oxygen in the reduced titanium oxide.

  Accordingly, an object of the present invention is to provide a polymer electrolyte fuel cell catalyst capable of mass production and having a small catalyst carrier particle size and a method for producing the same.

  The polymer electrolyte fuel cell catalyst of the present invention is a polymer electrolyte fuel cell catalyst in which an electrode-reactive catalyst substance is supported on a catalyst carrier that is metal oxide particles having electronic conductivity. The surface is covered with a carbon layer.

  The method for producing a polymer electrolyte fuel cell catalyst according to the present invention includes a polymer electrolyte fuel cell catalyst in which an electrode-reactive catalyst substance is supported on a catalyst carrier that is metal oxide particles having electronic conductivity. In order to manufacture, a catalyst in which the metal oxide particles, polyvinyl alcohol and water are mixed and stirred to prepare a paste, the paste is reduced and fired to pulverize and pulverize, and the metal oxide particles are coated with a carbon layer. A carrier powder is prepared, and the catalyst carrier powder, ethanol and a chloroplatinic acid solution are mixed and heated to dry distillation to produce a platinum catalyst-supported powder.

  According to this invention, it is possible to produce a solid polymer fuel cell catalyst that can be reduced without causing an increase in the particle size of the titanium oxide catalyst carrier and can be industrially mass-produced.

It is a cross-sectional schematic diagram of one embodiment of a single cell of a fuel cell using the polymer electrolyte fuel cell catalyst of the present invention. It is a schematic plan view which shows the separator flow path of FIG. FIG. 2 is a schematic sectional view showing only half of the catalyst-carrying particles of the fuel cell of FIG. 1 together with an electrolyte layer. It is a flowchart which shows the manufacturing method of the fuel cell using the manufacturing method of the polymer electrolyte fuel cell catalyst of this invention.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings in order to explain the present invention in more detail. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
FIGS. 1 and 2 schematically show a single cell fuel cell using a polymer electrolyte fuel cell catalyst according to Embodiment 1 of the present invention. FIG. 3 shows the structure according to Embodiment 1 of the present invention. Half of the catalyst-carrying particles of the polymer electrolyte fuel cell catalyst are shown in a schematic cross-sectional view, and FIG. 4 is a flowchart showing a fuel cell manufacturing method using the polymer electrolyte fuel cell catalyst manufacturing method of the present invention. It is shown.

  1 and 2, a solid polymer fuel cell includes a solid polymer electrolyte membrane 1 having proton conductivity, an anode catalyst layer 2 disposed on the surface of the anode side (right side in FIG. 1), a cathode And a cathode catalyst layer 3 disposed on the surface of the side (left side in FIG. 1). On the outer surfaces of the anode catalyst layer 2 and the cathode catalyst layer 3, that is, on the surface opposite to the surface in contact with the solid polymer electrolyte membrane 1, the anode-side and cathode-side intermediate layers 4a and 4b are respectively disposed. Anode-side and cathode-side gas diffusion layers 5a and 5b are disposed outside the intermediate layers 4a and 4b, respectively, and gas passages 6a and 6b for supplying gas are provided outside the gas diffusion layers 5a and 5b, respectively. The anode-side and cathode-side separator plates 7a and 7b on which 6b is formed are arranged. Between the separator plates 7a and 7b and the intermediate layers 4a and 4b, gas is surrounded by the gas diffusion layers 5a and 5b. Gas seals 8a and 8b are provided for preventing leakage.

  The anode catalyst layer 2 and the cathode catalyst layer 3 are each formed by the polymer electrolyte fuel cell catalyst of the present invention, and the polymer electrolyte fuel cell catalyst carries an electrode-reactive catalyst substance 9 such as platinum. A three-dimensional porous structure is constituted by catalyst-supporting granules composed of a number of granular catalyst carriers 10 which are metal oxide particles having electronic conductivity such as titanium oxide. Since the anode catalyst layer 2 and the cathode catalyst layer 3 are in contact with the solid polymer electrolyte membrane 1, a three-phase interface is formed inside by a catalyst, a polymer electrolyte, and pores, and an electrochemical reaction occurs. It acts as a fuel cell.

  FIG. 3 shows such a polymer electrolyte fuel cell catalyst, and only one of the catalyst-carrying particles comprising the catalyst substance 9 and the particulate catalyst carrier 10 carrying the catalyst substance 9 is shown. Only half of it is drawn with the surrounding structure. The catalyst carrier 10 has a particle diameter of about 20 nm to 100 nm, and the catalyst substance 9 has a particle diameter of about 2 nm to 10 nm. The catalyst carrier 10 is made of metal oxide particles such as titanium oxide or a titanium oxide reducing substance, and the surface thereof is covered with a carbon layer 11 which is a carbon thin film. Since the carbon layer 11 has high electronic conductivity, the electronic conductivity in the catalyst layer can be increased.

  Some of the catalyst materials 9 are supported on the surface of the carbon layer 11, and some of the catalyst materials 9 are supported in contact with the catalyst carrier 10 through the carbon layer 11. Can increase the sex. The surface of the carbon layer 11 is covered with a water-repellent layer 12 made of silica or fluorine material, so that the electrode can be prevented from being submerged by electrode reaction product water. The water repellent layer 12 is exposed to the outside without covering the catalyst material 9. The catalyst carrier 10 is further covered with an electrolyte layer 13 that is a proton conductor.

  Thus, by disposing the carbon layer 11 and the water repellent layer 12 on the surface of the catalyst carrier 10, the catalyst carrier 10 and the strongly acidic electrolyte layer 13 are less likely to be in direct contact, and damage to the catalyst carrier 10 can be reduced. In addition, it is possible to suppress deterioration of characteristics due to water wetting on the surface of the catalyst carrier 10.

  In this embodiment, the polymer electrolyte fuel cell catalyst of the present invention is used for both the anode catalyst layer 2 and the cathode catalyst layer 3, but at least one of the anode catalyst layer 2 and the cathode catalyst layer 3 is used. Can also be according to the invention. The anode catalyst layer 2 and the cathode catalyst layer 3 contain a strongly acidic electrolyte. However, since the carbon layer 11 is present on the surface of the catalyst carrier 10, the electronic conductivity is high and the water repellent layer 12 is present. Therefore, even if the material of the catalyst carrier 10 is relatively low in acid resistance, it is not easily damaged by the electrolyte or the catalyst. Further, the surface of the fuel cell catalyst is hardly wetted by the generated water due to the effect of the water repellent layer 12, so that the gas diffusibility of the anode catalyst layer 2 and the cathode catalyst layer 3 is sufficiently ensured.

  The carbon layer 11 has a thickness of several nanometers to several tens of nanometers on the surface of the catalyst carrier 10, assists electronic conduction in the surface layer of the oxide metal catalyst carrier 10 having relatively low electronic conductivity, and supports the catalyst carrier in the electrode. Reduce the resistance of 10 electron conduction networks. As will be described in detail later, the carbon layer 11 can be formed, for example, by reducing and firing a paste of polyvinyl alcohol (PVA), water, and the catalyst carrier 10 in a hydrogen atmosphere to leave carbon on the surface of the catalyst carrier 10. If the carbon layer 11 is thinner than a range of several nanometers to several tens of nanometers, the contribution to assisting electronic conductivity becomes insufficient, and if it is too thick, the catalyst carrier of oxide metal such as titanium oxide having excellent corrosion resistance. The advantage of using 10 is impaired.

  The water-repellent layer 12 is formed of, for example, a long-chain organic acid such as stearic acid, a silica-based material, a fluorine-based material, or the like, and a silica-based material and a fluorine-based material are preferable in terms of more excellent water repellency. . Among them, a material having a siloxane bond having a high binding force and containing at least one of a methyl group and a fluoro group has a high surface adsorptivity and is excellent in water repellency. This is preferable in that a catalyst support for a fuel cell capable of stably holding the catalyst substance 9 for a long period of time can be obtained. Furthermore, the water-repellent layer 12 can be more strongly adsorbed to the surface of the catalyst carrier 10 by directly adsorbing the water-repellent layer 12 to the surface of the catalyst carrier 10 via a siloxane bond.

The catalyst carrier 10 may be a fine powder made of an inorganic material, but a metal oxide fine powder having excellent oxidation resistance is preferably used. From the viewpoint of further increasing the electrical conductivity of the anode catalyst layer 2 and the cathode catalyst layer 3, it is preferable to use an inorganic material having a volume resistivity of 1 MΩcm or less. Specifically, the material of the catalyst carrier 10 is indium oxide, tin oxide, titanium oxide, zirconium oxide, selenium oxide, tungsten oxide, zinc oxide, vanadium oxide. Products, niobium-based oxides and rhenium-based oxides. More preferable materials for the catalyst carrier 10 include tin-containing indium oxide, antimony-containing tin oxide, magnetic phase-containing tin oxide, and magnetic phase-containing titanium oxide (for example, Ti _n O _2n-1 (n = 2 to 9)). And the like).

  From the viewpoint of supporting the catalyst material 9 on a higher specific surface area, the average primary particle size of the catalyst carrier 10 is desirably in the range of 1 nm to 500 nm.

  As the catalyst carrier 10 described above, tin-containing indium oxide (ITO), antimony-containing tin oxide, tin oxide and the like, which are fine particles of conductive oxide, are commercially available, and these can be obtained and used. Is possible. It is also possible to increase the conductivity by heat-treating the fine powder of titanium oxide. For example, by treating a fine powder of titanium oxide for several hours at a high temperature in a hydrogen reduction atmosphere, the electron conductivity can be improved by 3 digits or more.

  Examples of the catalytic substance 9 that can be supported on the catalyst carrier 10 include platinum, an alloy of platinum and noble metals (ruthenium, rhodium, iridium, etc.), platinum and a base metal (vanadium, chromium, cobalt, nickel, iron, etc.). An alloy etc. are mentioned.

  Since the catalyst material 9 such as platinum can efficiently generate power even in a small amount by increasing the specific surface area, it is desirable that the catalyst material 9 exists in the form of fine particles on the catalyst carrier 10. More specifically, the average particle diameter of the catalyst substance 9 is desirably 1 nm to several tens of nm. Further, the presence of the particulate metal catalyst material dispersed on the surface of the catalyst carrier 10 has an effect of supplementing the conductivity of the catalyst carrier 10 itself.

As a method for supporting the catalyst material 9 on the surface of the catalyst carrier 10, a method known in the art can be adopted without limitation. For example, chloroplatinic acid hexahydrate (H ₂ PtCl ₆ .6H ₂ O), dinitrodiammine platinum (Pt (NH ₃ ) ₂ (NO ₂ ) ₂ ) or the like is used as a precursor, and these are subjected to a liquid phase chemical reduction method. Platinum can be supported on the catalyst carrier 10 by reduction by a known method such as a gas phase chemical reduction method, an impregnation-reduction pyrolysis method, a surface-modified colloid pyrolysis reduction method. The supported amount of the catalyst substance 9 is preferably in the range of 5% by mass to 70% by mass with respect to the catalyst support for the fuel cell.

  Examples of other materials constituting the anode catalyst layer 2 and the cathode catalyst layer 3 include electrolytes. The anode catalyst layer 2 and the cathode catalyst layer 3 are made of a water-repellent material such as polytetrafluoroethylene (PTFE) particles, a binder that binds powders together, a conductive material that improves conductivity such as carbon black, and the like. May be included.

  These anode catalyst layer 2 and cathode catalyst layer 3 may be formed on the solid polymer electrolyte membrane 1, may be formed on the gas diffusion layers 5a and 5b, or may be formed on the gas diffusion layer. You may form in the surface of intermediate | middle layer 4a, 4b. Further, the anode catalyst layer 2 and the cathode catalyst layer 3 are formed into a sheet shape, which is formed between the solid polymer electrolyte membrane 1 and the intermediate layers 4a and 4b or between the solid polymer electrolyte membrane 1 and the gas diffusion layers 5a and 5b. You may arrange | position between.

  As a means for forming the anode catalyst layer 2 and the cathode catalyst layer 3, a method known in the technical field can be adopted without limitation. For example, screen printing coating, doctor blade coating, spray coating, slit die coating, reverse coating Common application means such as coating and bar coating can be employed.

  The solid polymer electrolyte membrane 1 may be any material that is chemically stable in the environment within the fuel cell, has high proton conductivity and gas barrier properties, and does not have electronic conductivity. As such a material, in general, a polymer electrolyte membrane having a sulfonic acid group in a perfluoro main chain is often used, but the material is not limited to this, and a hydrocarbon type or the like can also be used. is there.

  The gas diffusion layers 5a and 5b may be any material having electronic conductivity and a structure capable of diffusing the reaction gas from the gas flow paths 6a and 6b to the anode catalyst layer 2 and the cathode catalyst layer 3. As such a material, a porous body mainly made of a carbon-containing material is often used, and specifically, porous carbon formed of carbon fibers such as carbon paper, carbon cloth, and carbon nonwoven fabric is used. . Further, those obtained by subjecting these materials to surface treatment such as water repellent treatment or hydrophilic treatment can also be used.

  The separator plates 7a and 7b on which the gas flow paths 6a and 6b are formed are not particularly limited as long as they have electronic conductivity and can form the gas flow paths 6a and 6b and the cooling water flow path. Examples of such a material include metals such as stainless steel, carbon, a mixture of carbon and resin, and the like.

  The intermediate layers 4a and 4b that can be disposed between the gas diffusion layers 5a and 5b and the catalyst layers 2 and 3 reduce the contact resistance between the gas diffusion layers 5a and 5b and the catalyst layers 2 and 3, and allow moisture permeation. It has functions such as managing sex. The intermediate layers 4a and 4b include a conductive filler such as carbon black, and if necessary, a binder for forming the conductive filler, a water repellent for water repellency, and a hydrophilizing agent for hydrophilicity. Etc. can be included. Among them, it is preferable to use a fluorine-based resin as the water repellent and the binder because an intermediate layer having excellent stability in the environment within the fuel cell can be obtained. In particular, polytetrafluoroethylene (PTFE) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP) are more preferable because of their excellent water repellency and heat resistance. The intermediate layers 4a and 4b may contain a perfluorosulfonic acid-based polymer electrolyte component in order to impart hydrophilicity.

  Hereinafter, the solid polymer fuel cell catalyst of the present invention and the method for producing the same will be described more specifically with reference to the flowchart shown in FIG.

(S1: Reduction treatment of titanium oxide powder)
As a first step for producing the catalyst carrier, a titanium oxide fine powder as a metal oxide placed in a quartz glass container in a hydrogen tubular furnace was subjected to reduction treatment at 1,050 ° C. for 5 hours in a hydrogen stream. The reduction-treated titanium oxide powder changed from white to black, and was identified as oxygen-deficient Ti ₄ O ₇ , Ti ₂ O ₅ , Ti ₅ O _{9 and the} like by powder X-ray diffraction. When the powder was solidified into a pellet and the resistance was measured, the powder that was an insulator before the reduction showed a conductivity of ¹ KScm ⁻¹ . Particle growth due to sintering was observed as well as conductivity improvement, confirming a decrease in the surface area of the carrier.

(S2: Paste preparation)
Next, the reduced titanium oxide powder and polyvinyl alcohol (PVA) as the organic polymer resin are mixed in a weight ratio of 1: 3, 1: 2, 1: 1, 2: 1, respectively, and the total weight is equal to the total weight. A milky white paste was prepared by dispersing in water and stirring. In order to increase the solubility of polyvinyl alcohol, 60 ° C. warm water was used as a dispersion solvent.

(S3: Preparation of mixed sheet)
The paste was thinly applied on a mylar sheet, and moisture was removed by natural drying to prepare a mixed sheet of titanium oxide and polyvinyl alcohol. There is no particular limitation on the thickness of the sheet, but a thickness of about several hundred μm is easy to fire.

(S4: Small piece production)
This sheet was cut into square pieces having a side of about 5 mm.

(S5: Reduced firing fine powder)
The cut sheet is subjected to a reduction baking treatment at 1,050 ° C. for 5 hours in a hydrogen / inert gas (N ₂ , Ar, etc.) mixed gas in the same manner as in the above step S 1, and after complete removal of hydrogen at room temperature. The catalyst carrier powder which is the catalyst carrier 10 covered with the carbon thin film, that is, the carbon layer 11, was pulverized and pulverized. In the sheet after reduction firing, titanium oxide is reduced and left and dispersed in a state of being taken up in carbon having a large number of three-dimensionally continuous pores. Since the carbon bridging between the bodies is broken, a catalyst carrier powder that is a catalyst carrier 10 that is finely powdered and coated with the carbon layer 11 can be produced. Thus, sintering between oxide powders can be prevented by reducing and firing a uniform mixture of oxide powder (titanium oxide) and resin (PVA) in a high-temperature hydrogen atmosphere. Thus, it becomes possible to obtain a catalyst carrier powder having a small particle size.

  The organic polymer resin mixed with the titanium oxide powder in S2 may be polyphenol, polypyrrole, polyaniline, or the like. The average particle diameter obtained from the X-ray diffraction chart of the titanium oxide particles manufactured by the above-described steps S1 to S5 by changing the mixing weight ratio of titanium oxide and polyvinyl alcohol is reduced as the amount of resin in S2 is increased. When / PVA was changed to 1/3, 1/2, 1/1 and 2/1, the average particle diameters of the titanium oxide particles were 45 nm, 60 nm, 80 nm and 105 nm, respectively.

(S6: Water repellent treatment)
In order to prepare a platinum catalyst-supported powder, a titanium oxide catalyst carrier 10 manufactured as in S1 to S5 and coated with a carbon layer 11 was used. 3 g (special reagent grade) was added and mixed well. This pasty liquid was dried at 60 ° C. for 5 hours, and further vacuum-dried at 120 ° C. for 5 hours to obtain 5.1 g of titanium oxide powder coated with the water-repellent layer 12 by the hexamethyldisilazane treatment. Hexamethyldisilazane is not subjected to the reaction other than adsorbing to the adsorbable site of the titanium oxide powder, and evaporates by drying. Therefore, in the obtained hexamethyldisilazane-treated titanium oxide powder, 0.5% by mass of hexamethyldisilazane, which is a water-repellent surface protective substance, is adsorbed to the titanium oxide powder, which is a catalyst carrier. It will be.

(S7: Production of platinum catalyst-supported powder)
After 5 g of this hexamethyldisilazane-treated titanium oxide powder was dispersed in 50 g of ethanol, 45 g of water and 25 g of a 5 mass% chloroplatinic acid aqueous solution were added and stirred well. This solution was heated and refluxed in a reflux apparatus for 2 hours, and platinum was supported on hexamethyldisilazane-treated titanium oxide powder. The solution was then washed by repeating the centrifugation several times. After washing, it was dried at 60 ° C. for 5 hours, and further vacuum-dried at 120 ° C. for 5 hours to obtain a catalyst carrier 10 carrying platinum particles as the catalyst material 9. As a result of ICP analysis of the platinum catalyst-supported powder, the amount of platinum supported was about 11% by mass.

  In order to perform the acid solution immersion test of the platinum catalyst-supported powder, the platinum catalyst-supported powder obtained in S7 was placed in a 1M sulfuric acid aqueous solution and immersed at 80 ° C. for 100 hours. Then, as a result of performing the ion analysis in a solution, the amount of ions was ppm or less.

(S8: Preparation of catalyst layer containing platinum catalyst-supported powder)
To the platinum catalyst-supported powder obtained in S7, a perfluorosulfonic acid polymer electrolyte solution (manufactured by DuPont, Nafion (registered trademark) solution) and a solvent are added and mixed by stirring to obtain a uniform catalyst layer paste. It was. The catalyst layer paste was screen-printed on a polyethylene terephthalate (PET) film having a thickness of 50 μm and then dried at 60 ° C.

(S9: Formation of catalyst layer on polymer electrolyte membrane)
A polymer electrolyte membrane (for example, DuPont, Nafion (registered trademark) 112 membrane) is sandwiched between catalyst layers containing platinum catalyst-supported powders formed on the two PET films obtained in S8, and 2 at 130 ° C. The cathode catalyst layer and the anode catalyst layer were formed on both sides of the polymer electrolyte membrane by hot pressing for minutes and removing the PET film. Each catalyst layer was formed in a square shape having a length and width of 50 mm.

(S10: Production of battery)
The polymer electrolyte membrane with a catalyst layer obtained in S9 is sandwiched between a pair of gas diffusion layers with an intermediate layer, and further sandwiched between a pair of carbon plates in which a gas flow path is formed, and has the same configuration as that shown in FIG. A polymer electrolyte fuel cell was produced.

(Battery operation)
Hydrogen gas was supplied to the anode electrode side of the polymer electrolyte fuel cell, and atmospheric air was supplied to the cathode electrode side. The flow rate was set so that the utilization rate of hydrogen gas was 75% and the oxygen utilization rate on the air side was 40%. Both gases were humidified by an external humidifier and then supplied to the polymer electrolyte fuel cell. The temperature of the polymer electrolyte fuel cell was adjusted to 80 ° C. Regarding the humidity of the supplied gas, an external humidifier was adjusted so that the dew point was 75 ° C. on the anode electrode side and the dew point was 70 ° C. on the cathode electrode side. This solid polymer fuel cell was operated at a current density of 200 mA / cm ² , and the output voltage after 24 hours from the start was measured. As a result, almost the same performance as a cell using a carbon-supported catalyst as a comparative example was obtained. It was. Moreover, in the low humidification condition where the dew point of the air supplied to the cell temperature of 80 ° C. was lowered to 65 ° C., the performance was higher than that of the battery using the carbon supported catalyst.

  Thus, according to the present invention, it is possible to provide a polymer electrolyte fuel cell catalyst capable of mass production and having a small catalyst carrier particle size and a method for producing the same.

  The polymer electrolyte fuel cell catalyst and the method for producing the same illustrated and described above are merely examples, and various modifications are possible, and all the features of the specific examples may be used in combination. it can.

  The present invention can be used as a polymer electrolyte fuel cell catalyst and a method for producing the same.

  1 solid polymer electrolyte membrane, 2 anode catalyst layer, 3 cathode catalyst layer, 4a, 4b intermediate layer, 5a, 5b gas diffusion layer, 6a, 6b gas flow path, 7a, 7b separator plate, 8a, 8b gas seal, 9 Catalyst material, 10 catalyst carrier (metal oxide particles), 11 carbon layer, 12 water repellent layer, 13 electrolyte layer.

Claims (12)

In a polymer electrolyte fuel cell catalyst in which an electrode-reactive catalyst substance is supported on a catalyst carrier that is metal oxide particles having electronic conductivity,
A polymer electrolyte fuel cell catalyst, wherein the surface of the catalyst carrier is coated with a carbon layer.   The catalyst carrier is an indium oxide, tin oxide, titanium oxide, zirconium oxide, selenium oxide, tungsten oxide, zinc oxide, vanadium oxide, niobium oxide and 2. The polymer electrolyte fuel cell catalyst according to claim 1, wherein the catalyst is at least one selected from the group consisting of rhenium-based oxides.   2. The catalyst carrier according to claim 1, wherein the catalyst carrier is at least one selected from the group consisting of tin-containing indium oxide, antimony-containing tin oxide, magnetic phase-containing tin oxide, and magnetic phase-containing titanium oxide. The polymer electrolyte fuel cell catalyst described.   2. The polymer electrolyte fuel cell catalyst according to claim 1, wherein the catalyst carrier is a titanium oxide reducing substance.   The polymer electrolyte fuel cell catalyst according to any one of claims 1 to 4, wherein the catalyst substance is supported on the surface of the carbon layer or in contact with the catalyst carrier. .   6. The polymer electrolyte fuel cell catalyst according to claim 1, wherein the carbon layer has a thickness of several nanometers to several tens of nanometers.   The solid polymer fuel cell catalyst according to any one of claims 1 to 6, wherein the carbon layer is coated with a water repellent layer.   8. The polymer electrolyte fuel cell catalyst according to claim 7, wherein the water repellent layer is a silica-based or fluorine-based material. In order to produce a polymer electrolyte fuel cell catalyst in which an electrode-reactive catalyst material is supported on a catalyst carrier that is metal oxide particles having electronic conductivity,
The catalyst carrier, organic polymer resin and water are mixed and stirred to produce a paste,
The paste is reduced and fired to pulverize and pulverize to produce a catalyst carrier powder in which the catalyst carrier is coated with a carbon layer,
A method for producing a polymer electrolyte fuel cell catalyst, comprising mixing the catalyst carrier powder, ethanol, and a chloroplatinic acid solution, followed by heating to dry distillation to produce catalyst-carrying particles.   The method for producing a polymer electrolyte fuel cell catalyst according to claim 9, wherein the organic polymer resin is polyvinyl alcohol.   11. The polymer electrolyte fuel cell catalyst according to claim 9 or 10, wherein after the step of producing the catalyst carrier powder, the surface of the catalyst carrier powder is subjected to water repellent treatment with a silica-based or fluorine-based material. Manufacturing method.   The catalyst carrier is an indium oxide, tin oxide, titanium oxide, zirconium oxide, selenium oxide, tungsten oxide, zinc oxide, vanadium oxide, niobium oxide and The method for producing a polymer electrolyte fuel cell catalyst according to any one of claims 9 to 11, wherein the method is at least one selected from the group consisting of rhenium-based oxides.

Images