JP2006344424A - Manufacturing method of catalyst mixture for solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of catalyst mixture for a solid polymer fuel cell excellent in productivity by heating it in cheap and safe gas atmosphere without using inflammable gas like hydrogen or hydrazine, at a third process of manufacturing catalyst carrying very small amount of catalytic metal, and by setting most optimum range of heating temperature, and to provide a solid polymer fuel cell including the above catalyst. <P>SOLUTION: The manufacturing method of the catalyst mixture for the solid polymer fuel cell comprises a first process preparing a mixture containing cation exchange resin and carbon, a second process making fixed ion of the cation exchange resin in the mixture store catalytic metal cation, and a third process decomposing the catalytic metal cation in an atmosphere of nitrogen, carbon dioxide, helium, neon, or argon at a temperature of not lower than 150°C and not higher than 200°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a catalyst mixture for a polymer electrolyte fuel cell.

  A single cell of a polymer electrolyte fuel cell has a structure in which a membrane / electrode assembly is sandwiched between a pair of gas flow plates. The membrane / electrode assembly is obtained by joining an anode to one surface of a polymer electrolyte membrane and a cathode to the other surface. A gas flow path is processed in the gas flow plate. For example, electric power can be obtained by supplying hydrogen as fuel to the anode and oxygen as oxidant to the cathode. In the anode and the cathode, the following electrochemical reaction proceeds.

Anod: 2H ₂ → 4H ⁺ + 4e ⁻
Cathode: O ₂ + 4H ⁺ + 4e ⁻ → H ₂ O
The above electrochemical reaction requires a catalyst. In the catalyst, protons (H ⁺ ) and electrons (e ⁻ ) are transferred. That is, the electrochemical reaction proceeds at the reaction interface where the electron conductor, electrolyte, and reactant are in contact. Therefore, the power density of the fuel cell is improved by increasing the reaction interface. In order to form a large number of reaction interfaces, it is necessary to fabricate an electrode in which a reactant transfer channel, a proton conduction channel, and an electron conduction channel are three-dimensionally formed.

  As disclosed in Patent Document 1, the electrode having such a structure includes a catalyst-supporting carbon particle in which catalyst metal particles such as platinum are supported in a highly dispersed manner on a carbon particle support, and PTFE (polytetrafluoroethylene). The mixture with the particle dispersion solution is applied to a polymer film or a carbon electrode substrate, heated and dried, then coated with a cation exchange resin solution, impregnated and then dried. It was.

  However, in the electrode manufactured using this conventional manufacturing method, a problem that the utilization rate of the catalytic metal supported on carbon is low, for example, about 15 to 20%, is reported in Non-Patent Document 1. ing.

  In order to solve the problem, the catalyst support that significantly improves the utilization rate of the catalyst metal by supporting the catalyst metal mainly on the contact surface between the surface of the carbon and the proton conduction path called the ion cluster of the cation exchange resin. A method for producing a powder is reported in Patent Document 2. This ultra-small catalyst metal-supported catalyst is hereinafter referred to as “ULLPLC” (Ultra-low Platinum Loading Carbon).

  ULPLC prepares a mixture containing a cation exchange resin and carbon particles, then ion-exchanges the counter ion of the cation exchange resin and the catalytic metal ion, and further converts the catalytic metal ion into a reducing agent such as hydrogen or hydrazine. Produced by chemical reduction in an atmosphere containing In ULPLC, a catalytic metal having a particle size of 3 nm to 4 nm is mainly supported on the contact surface between the ion cluster of the cation exchange resin and the carbon, so that the utilization rate of the catalytic metal is high and the catalyst is formed by the aggregation of the catalytic metal. Degradation of performance is remarkably suppressed.

  Therefore, the polymer electrolyte fuel cell using the electrode including ULPLC exhibits high output and long life with a very small amount of platinum supported.

  The reduction step of the ULPLC production method preferably uses a chemical reduction method using a reducing agent suitable for mass production. Patent Document 2 includes a method of gas phase reduction with hydrogen gas or a hydrogen-containing gas or hydrazine. It is described that a gas phase reduction method using an inert gas is preferable, and in the examples, reduction is performed for about 30 minutes with nitrogen gas containing anhydrous hydrazine (obtained by bubbling nitrogen gas into hydrazine).

  In Patent Document 3, it is preferable that the reduction step of the ULPLC production method is a gas phase reduction method using hydrogen gas or a gas containing hydrogen or a gas phase reduction method using an inert gas containing hydrazine, or a gas containing hydrogen gas. Is preferably a mixed gas of hydrogen gas and an inert gas such as nitrogen, helium, or argon, and preferably contains 10 vol% or more of hydrogen gas. Examples of the inert gas include helium gas, neon gas, It is described that argon gas and nitrogen gas can be used. It is also described that the reduction temperature is preferably 100 ° C. or higher and 200 ° C. or lower because the reduction reaction proceeds sufficiently.

  Specific conditions for the reduction step are described in Patent Document 4 as “about 4 hours in a hydrogen atmosphere at 1 atm and 180 ° C.”, and in Patent Document 5 “leave in a hydrogen atmosphere at 200 ° C. for 7 hours. Is described.

JP-A-11-086882 JP 2000-012041 A JP 2002-134119 A JP 2001-319661 A JP 2002-358971 A Edson A. Ticianelli, J .; Electroanal. Chem. 251, 275 (1988)

  In the above-described method for producing an ultra-small catalyst metal-supported catalyst (ULPLC) for a polymer electrolyte fuel cell in which a catalytic metal is supported on the contact surface between the proton conduction path of the cation exchange resin and the carbon surface, hydrogen or hydrazine is used. Since heating is performed in a highly flammable gas atmosphere such as the above, equipment for preventing leakage of the gas is necessary. Therefore, there is a problem that it is not suitable for mass production because the cost for the equipment for improving safety is high. Moreover, although the optimal value of the reduction temperature when using hydrogen was 100-200 degreeC, the optimal temperature range at the time of using nitrogen etc. as atmosphere gas is not disclosed.

  An object of the present invention is to heat in a safe gas atmosphere without using a highly flammable gas such as hydrogen and hydrazine in a reduction process for producing a conventional ULPLC, and to determine the optimum range of the heating temperature. Provided is a method for producing a catalyst mixture for a polymer electrolyte fuel cell excellent in productivity, and further includes an electrode containing the catalyst mixture obtained by the production method of the present invention as an electrode for a polymer electrolyte fuel cell. The object is to provide a polymer electrolyte fuel cell used.

  The invention of claim 1 is a method for producing a catalyst mixture for a polymer electrolyte fuel cell, wherein the first step of producing a mixture containing a cation exchange resin and carbon, and the cation exchange resin in the mixture A second step of adsorbing the catalytic metal cation on the fixed ions; and the catalytic metal cation is pyrolyzed at a temperature of 150 ° C. or higher and 200 ° C. or lower in a nitrogen, carbon dioxide, helium, neon or argon atmosphere. The third step is performed.

  In the ULLPLC production method according to the present invention, since a large amount of hydrogen gas does not have to be used, the safety of the production process and mass productivity are excellent, and the apparatus for the thermal decomposition process is simple, so that the productivity is excellent. The manufacturing process becomes low cost.

  In addition, in the catalyst mixture for a polymer electrolyte fuel cell obtained by the production method of the present invention, a catalytic metal is mainly supported on the contact surface between the carbon surface and a proton conduction path called an ion cluster of the cation exchange resin. Therefore, the utilization factor of the catalyst metal is remarkably improved, and a polymer electrolyte fuel cell having excellent characteristics using an extremely small amount of the catalyst metal can be obtained.

  The present invention relates to a method for producing a catalyst mixture for a polymer electrolyte fuel cell in which a catalytic metal is mainly supported on a contact surface between a carbon surface and a proton conduction path called an ion cluster of a cation exchange resin. A first step of preparing a mixture containing a resin and carbon, a second step of adsorbing a cation of a catalytic metal to a fixed ion of a cation exchange resin in the mixture, and a cation of the catalytic metal, A third step of thermal decomposition is performed at a temperature of 150 ° C. or higher and 200 ° C. or lower in a nitrogen, carbon dioxide, helium, neon, or argon atmosphere.

  That is, in the conventional ULPLC production method, the cation of the catalytic metal is reduced to a catalytic metal by using hydrogen, hydrazine, or the like, whereas in the present invention, the catalytic metal is not a reduction reaction. It is characterized in that cations are converted to catalytic metals by thermal decomposition on the carbon surface.

  It is essential that the catalytic metal contained in the catalyst mixture of the present invention is mainly supported on the contact surface between the carbon surface and the proton conduction path of the cation exchange resin. The contact surface between the carbon surface and the proton conduction path of the cation exchange resin is a place where electrons and protons can be exchanged at the same time, so the catalytic metal supported on this contact surface is efficient for electrode reactions. Involved. Therefore, the usage amount of the catalyst metal can be reduced by increasing the ratio of the catalyst metal supported on the contact surface.

  In the catalyst layer of the polymer electrolyte fuel cell electrode of the present invention, “the catalytic metal is mainly provided at the contact surface between the proton conduction path of the cation exchange resin and the surface of the carbon material” It means that the amount of catalyst metal supported on the surface of carbon particles in contact with the proton conduction path of the resin is 50% by mass or more of the total amount of catalyst metal supported. That is, 50% by mass or more of the total catalytic metal loading is a catalytic metal active for the electrode reaction, so that the utilization rate of the catalytic metal is remarkably increased.

  In the present invention, the ratio of the amount of the catalyst metal supported on the surface of the carbon particles in contact with the proton conduction path of the cation exchange resin to the total amount of the catalyst metal supported is preferably as high as possible, particularly exceeding 80% by mass. preferable. In this way, the electrode is highly activated by supporting the catalytic metal at a high rate on the contact surface between the proton conduction path and the carbon particles.

  In the catalyst mixture of the present invention, the catalyst metal is mainly supported on the contact surface between the carbonaceous material and the proton conduction path of the cation exchange resin. This can be seen from the mass activity in the high current density region of the fuel cell equipped with this catalyst mixture and the volume ratio between the proton conduction path of the cation exchange resin and the hydrophobic skeleton (M. Kohmoto et al. , GS Yuasa Technical Report, 1, 48 (2004)). This mass activity is obtained by dividing the current density at a certain voltage by the amount of catalyst metal supported per unit area.

  In the first step of the method for producing a catalyst mixture for a polymer electrolyte fuel cell of the present invention, the mixture containing a cation exchange resin and carbon may be in the form of a sheet or powder. Good. When the mixture containing a cation exchange resin and carbon is in the form of a sheet, a paste containing carbon and a cation exchange resin solution and, if necessary, a dispersion solution of a fluororesin such as PTFE, is applied onto the polymer film. (Preferably a thickness of 3 to 50 μm) followed by drying, a paste containing carbon and a fluororesin dispersion solution is applied onto a polymer film (preferably a thickness of 3 to 50 μm), dried, A method of applying, impregnating and drying an ion exchange resin solution, or applying a paste containing carbon and a cation exchange resin solution and, if necessary, a PTFE particle dispersion solution on a carbon electrode substrate of a conductive porous body. After drying, a paste containing carbon and a PTFE particle dispersion solution is applied onto a carbon electrode base material of a conductive porous body and dried by heating. After drying, it can be produced by a method of applying, impregnating and drying a cation exchange resin solution. As the coating means, a spray method, a screen printing method, a doctor blade method, or the like can be used.

  On the other hand, when the mixture containing a cation exchange resin and carbon is in a powder form, for example, a mixed solution containing a cation exchange resin solution, carbon, and an alcohol solvent is used at 120 ° C. or higher and 200 ° C. using a spray dryer. A mixture can be manufactured by granulating at the following temperature. At this time, before granulating using a spray drier, the dispersion of carbon may be enhanced by irradiating the mixed solution with ultrasonic waves using an ultrasonic disperser. Further, a dispersion of a fluororesin such as PTFE or FEP can be added to the mixed solution.

  In the second step, the counter ion of the cation exchange resin and the catalyst metal ion in the mixture are ion-exchanged to adsorb the catalyst metal cation to the fixed ion of the cation exchange resin. This ion exchange reaction is performed by immersing a mixture containing a cation exchange resin and carbon in a solution containing catalytic metal ions. A solution containing catalytic metal ions can be prepared by dissolving a compound that generates a cation in an aqueous solution or in a solution containing an alcohol in a solution containing water or an alcohol.

  In the third step, the catalytic metal cations in the mixture are thermally decomposed at a temperature of 150 ° C. or higher and 200 ° C. or lower in a nitrogen, carbon dioxide, helium, neon, or argon atmosphere to form carbon surfaces and cations. A catalyst mixture in which a catalytic metal is supported on the contact surface of the exchange resin with the proton conduction path is manufactured.

  In the third step of the method for producing the catalyst mixture for a polymer electrolyte fuel cell of the present invention, the catalyst metal ion in the mixture containing the cation exchange resin and carbon is converted into nitrogen, carbon dioxide, helium, neon or argon. Thermally decomposes in atmosphere. Here, “in a nitrogen, carbon dioxide, helium, neon or argon atmosphere” means a nitrogen, helium, neon or argon atmosphere alone or a mixed gas atmosphere thereof. Further, it is preferable that other gases contained in these gases be as small as possible, but they may be contained in a volume ratio of several percent.

  However, when the content of an oxidizing agent such as oxygen gas increases, carbon and cation exchange resin are oxidized, and when the content of hydrogen gas increases, handling must be handled carefully.

  The thermal decomposition temperature in the third step needs to be 150 ° C. or higher at which the decomposition of the catalytic metal ions starts, and further must be 200 ° C. or lower in order to prevent deterioration of the cation exchange resin. The catalytic metal ions in the vicinity of the carbon surface are preferentially reduced to the catalytic metal by the thermal decomposition of the catalytic metal ions, and a catalytic metal is generated on the contact surface between the carbon surface and the proton conduction path of the cation exchange resin.

  In this third step, the particle size and surface properties of the catalytic metal produced on the surface of the carbon can be controlled by adjusting the pressure and time during thermal decomposition as appropriate.

  The pressure at the time of thermal decomposition is not particularly limited. However, when the pressure is lower than 0.1 MPa, the heat conduction to the mixture containing the cation exchange resin and the carbon is deteriorated, and the thermal decomposition time becomes long. When the pressure is higher than 1 MPa, the apparatus becomes large and the manufacturing cost increases.

  The thermal decomposition time is not particularly limited, but is preferably 5 hours or longer. When the thermal decomposition time is shorter than 5 hours, the thermal decomposition is insufficient, and the generated catalytic metal is reduced. Even when the thermal decomposition time exceeds 72 hours, the characteristics hardly change. do not have to.

  The catalytic metal used in the catalyst mixture for the polymer electrolyte fuel cell of the present invention has high catalytic activity for electrochemical oxygen reduction reaction and hydrogen oxidation reaction, such as platinum, rhodium, ruthenium, iridium, palladium, osmium, etc. Platinum group metals and alloys thereof. In the second step, by using two or more types of catalytic metal ions to be ion-exchanged, two or more types of catalytic metal ions can be adsorbed on the fixed ions of the cation exchange resin in the mixture.

  Catalytic metal ions used in the production of the solid polymer fuel cell catalyst mixture of the present invention are not easily adsorbed on the exposed carbon surface, and cation exchange is performed by an ion exchange reaction with a counter ion of a cation exchange resin. Those that preferentially adsorb to the fixed ions of the cation exchange resin present in the proton conduction path of the resin are preferred.

As a cation containing a platinum group metal having such an adsorption characteristic, platinum that can be expressed as a complex ion of a platinum group metal, particularly [Pt (NH ₃ ) ₄ ] ²⁺ or [Pt (NH ₃ ) ₆ ] ⁴⁺ Or [Ru (NH ₃ ) ₆ ] ²⁺ or [Ru (NH ₃ ) ₆ ] ³⁺ is preferable. In addition to the ammine complex, a platinum group metal complex ion coordinated with a nitrate group or a nitroso group can be used.

  The shape of the electrode for the polymer electrolyte fuel cell using the catalyst mixture of the present invention is preferably a thin film, and the thickness thereof is preferably 50 μm or less because gas diffusion is sufficiently promoted. More preferably, it is 30 μm or less. Therefore, after mixing the catalyst mixture and a binder mainly composed of a fluororesin such as PTFE or FEP, the mixture is sprayed, screen-printed, doctor-blade, etc. It is desirable to form into a thin film.

  As the cation exchange resin contained in the catalyst mixture for a polymer electrolyte fuel cell of the present invention, an ion exchange resin that conducts protons can be used. Preferably, the operating conditions of the polymer electrolyte fuel cell are used. Perfluorocarbon sulfonic acid type or styrene-divinylbenzene type sulfonic acid type cation exchange resin is preferable because it is relatively stable and has a long life. Furthermore, the ion exchange capacity of the cation exchange resin is preferably 0.9 meq / g or more because high proton conductivity is obtained.

  As the cation exchange resin solution used in the production of the catalyst mixture for a polymer electrolyte fuel cell of the present invention, it is preferable to use a solution obtained by dissolving an ion exchange resin in alcohol or alcohol and water or water.

  Carbon black, acetylene black, furnace black, activated carbon, etc. can be used as the carbon used in the production of the catalyst mixture for a polymer electrolyte fuel cell of the present invention, and in particular, the supported catalytic metal is highly dispersed in carbon black. This is preferable.

  In the catalyst mixture for a polymer electrolyte fuel cell of the present invention, the ratio of the mass of the cation exchange resin to carbon is desirably 0.25 or more and 1.2 or less. When the ratio exceeds 1.2, the contact between the carbon particles carrying the catalyst is hindered by the excessive cation exchange resin adhering to the carbon surface, so that the number of catalyst metals that cannot accept and receive electrons increases. As a result, the utilization rate of the catalyst metal is lowered. On the other hand, when the ratio is smaller than 0.25, the amount of ion exchange resin adhering to the carbon surface is insufficient, so that the formation of the proton conduction path of the electrode becomes insufficient, and as a result, the proton transfer resistance increases. .

  The present invention will be described below with reference to preferred embodiments.

[Examples 1 to 6 and Comparative Example 1]
[Example 1]
A catalyst mixture for a polymer electrolyte fuel cell of the present invention, a polymer electrolyte fuel cell positive electrode containing this catalyst mixture, and a polymer electrolyte fuel cell using this electrode were produced by the following method.

  The manufacturing method of the fuel cell catalyst mixture of the present invention is as follows. First, in the first step, 37.5 g of carbon (manufactured by Cabot, Vulcan XC-72), 500 g of a 5% by mass cation exchange resin solution (manufactured by Aldrich, Nafion Soution SE-5142) and 250 g of isopropanol were mixed with a vacuum mixer ( A mixed solution containing carbon and a cation exchange resin was produced by stirring for 30 minutes with SMT (HV-1 Type).

  Next, a mixed solution with high carbon dispersion was produced by irradiating the mixed solution with ultrasonic waves using an ultrasonic disperser (manufactured by SMT, UH-600SR). The irradiation conditions were 1 minute for 150 g of the mixture.

  Furthermore, the mixed solution obtained by adding isopropyl alcohol to the mixed solution is granulated using a spray dryer (manufactured by Fujiki Electric, spray dryer MDL-050), thereby forming a powdery mixture of the cation exchange resin and carbon. Produced. The amount of isopropanol added was 1.86 g per 1 g of the mixture, and granulation conditions using a spray dryer were a temperature of 150 ° C. and a feed rate of 6 g / min. It was.

Next, in the second step, the cation exchange in the powdery mixture is performed by immersing the powdery mixture in a 0.05 mol / l concentration [Pt (NH ₃ ) ₄ ] Cl ₂ aqueous solution prepared in advance for 6 hours. [Pt (NH ₃ ) ₄ ] ²⁺ was adsorbed on a fixed ion (—SO ₃ ⁻ ) of the resin. Thereafter, the powdery mixture was thoroughly washed with deionized water and then sufficiently dried to produce a mixture in which [Pt (NH ₃ ) ₄ ] ²⁺ was adsorbed. This is referred to as mixture A.

  Subsequently, in the third step, the mixture A was placed in a reaction vessel and filled with 1.5 atm of nitrogen. And the reaction container was hold | maintained for 24 hours in the state heated to 180 degreeC.

After that, the mixture taken out from the reaction vessel was immersed in 0.5 mol / l sulfuric acid for 1 hour to elute the [Pt (NH ₃ ) ₄ ] ²⁺ that was not decomposed by the heat treatment, and then the mixture was removed. By thoroughly washing with ionized water, a catalyst mixture for a polymer electrolyte fuel cell of the present invention in which a catalytic metal was supported on the contact surface between the proton conduction path of the cation exchange resin and the carbon surface was obtained. This is designated as catalyst mixture A for polymer electrolyte fuel cells.

  Further, a paste was prepared by mixing 3.0 g of the solid polymer fuel cell mixture A and 21 g of N-methyl-2-pyrrolidone (NMP) using a hybrid mixer. The paste is formed into a thin film using a 250 μm applicator on a Ti sheet (manufactured by Katsuta Greching Co., Ltd., thickness 50 μm), and then dried at 80 ° C. to apply the catalyst mixture A of the present invention. A polymer fuel cell electrode was fabricated. This is designated as a polymer electrolyte fuel cell electrode A.

The manufacturing method of the polymer electrolyte fuel cell to which the electrode A for the polymer electrolyte fuel cell is applied is as follows. First, the polymer electrolyte fuel cell electrode A produced by the above-described method was cut into a size of 5 cm × 5 cm. This electrode supported 0.045 mg / cm ² of platinum as a catalyst metal. On the other hand, a polymer electrolyte membrane (DuPont, Nafion 112, thickness of about 50 μm) was boiled with 0.5 mol / l sulfuric acid for 1 hour, then washed with deionized water 5 times and boiled for 1 hour. .

Next, two polymer electrolyte fuel cell electrodes A used as an anode and a cathode are arranged on both sides of the polymer electrolyte membrane, respectively, and then subjected to thermocompression bonding (135 ° C., 50 kg / cm ² ), The polymer electrolyte membrane and the polymer electrolyte fuel cell electrode A were joined together. Thereafter, the Ti foil was removed from the joined body.

  Finally, a conductive porous carbon paper imparted with water repellency is disposed on both surfaces of the joined body, and then sandwiched between a pair of gas flow plates, so that the solid high-temperature fuel catalyst of the present invention is provided. A molecular fuel cell was fabricated. This is referred to as a single cell A.

[Example 2]
In the third step, the catalyst mixture B for the polymer electrolyte fuel cell of Example 2 was used in the same manner as in Example 1 except that the reaction vessel containing the mixture A was filled with carbon dioxide at 1.5 atm. Then, a polymer electrolyte fuel cell electrode B and a single cell B were produced.

[Example 3]
In the third step, the catalyst mixture C for polymer electrolyte fuel cell of Example 3 was prepared in the same manner as in Example 1 except that the reaction vessel containing the mixture A was filled with 1.5 atm of argon. A polymer electrolyte fuel cell electrode C and a single cell C were produced.

[Example 4]
In the third step, in the same manner as in Example 1 except that the reaction vessel containing the mixture A was filled with 1.5 atm of helium, the catalyst mixture D for the polymer electrolyte fuel cell of Example 4, A polymer electrolyte fuel cell electrode D and a single cell D were produced.

[Example 5]
In the third step, the catalyst mixture E for the polymer electrolyte fuel cell of Example 5 was used in the same manner as in Example 1 except that the reaction vessel containing the mixture A was filled with 1.5 atm of neon. A polymer electrolyte fuel cell electrode E and a single cell E were produced.

[Example 6]
In the third step, in the same manner as in Example 1 except that the reaction vessel containing the mixture A was filled with a 1.5 atm nitrogen / hydrogen mixed gas (hydrogen content 2 vol%). A catalyst mixture F for a polymer electrolyte fuel cell, an electrode F for a polymer electrolyte fuel cell, and a single cell F were produced.

[Example 7]
In the third step, in the same manner as in Example 1 except that the reaction vessel containing the mixture A was filled with a mixed gas of nitrogen and oxygen of 1.5 atm (oxygen content 2 vol%). A catalyst mixture G for a polymer electrolyte fuel cell, an electrode G for a polymer electrolyte fuel cell, and a single cell G were produced.

[Comparative Example 1]
In the third step, the catalyst mixture H for the polymer electrolyte fuel cell of Comparative Example 1 was prepared in the same manner as in Example 1 except that the reaction vessel containing the mixture A was filled with 1.5 atm of hydrogen. A polymer electrolyte fuel cell electrode H and a single cell H were produced. The solid polymer fuel cell electrode G supported 0.040 mg / cm ² of platinum as a catalyst metal.

  The output performances of the polymer electrolyte fuel cells A to H of Examples 1 to 7 and Comparative Example 1 were evaluated. Measurement conditions were such that the battery temperature was 70 ° C., and air and hydrogen humidified by a bubbler humidifier at 70 ° C. were supplied to the cathode and the cathode at flow rates of a stoichiometric ratio of 2.5 and 1.25, respectively.

  FIG. 1 shows the polarization curves of the single cell A of Example 1 and the single cell H of Comparative Example 1. In FIG. 1, the symbol ◯ indicates the polarization curve of the single cell A, and the symbol Δ indicates the polarization of the single cell H. The curve is shown. From FIG. 1, in the third step, the output performance of the single cell A using the catalyst mixture A for polymer electrolyte fuel cells manufactured by heat treatment in a nitrogen atmosphere was manufactured by heat treatment in a hydrogen atmosphere. It turned out that it is the substantially same thing as the output performance of the single cell H using the catalyst mixture H for polymer electrolyte fuel cells.

  In the third step, argon, carbon dioxide, helium, neon, a mixed gas of nitrogen and hydrogen (hydrogen content 2 vol%) or a mixed gas of nitrogen and oxygen (oxygen content 2 vol%) is used as the heating atmosphere. The polymer polymer fuel cell catalyst mixtures B to G were manufactured, and the output performance of the polymer electrolyte fuel cells B to G using these catalyst mixtures was equal to or better than that of Comparative Example 1. I understood it.

  Therefore, in the method for producing a catalyst mixture for a polymer electrolyte fuel cell in which a catalytic metal is supported on the contact surface between the proton conduction path of the cation exchange resin and the carbon surface, the thermal decomposition of the third step is performed. It was found that by using nitrogen, carbon dioxide, helium, neon, argon, or a gas containing a small amount of hydrogen or oxygen as the atmosphere, a polymer electrolyte fuel cell exhibiting high performance can be obtained.

[Examples 8 to 10 and Comparative Examples 2 to 4]
[Example 8]
In the third step, in the same manner as in Example 1 except that the reaction vessel was heated to 150 ° C., the solid polymer fuel cell catalyst mixture I and the solid polymer fuel cell electrode I of Example 8 were used. And the single cell I was produced.

[Example 9]
In the third step, in the same manner as in Example 1 except that the reaction vessel was heated to 160 ° C., the polymer mixture J for the polymer electrolyte fuel cell of Example 9, the electrode J for the polymer electrolyte fuel cell of Example 9 And the single cell J was produced.

[Example 10]
In the third step, the solid polymer fuel cell catalyst mixture K and the solid polymer fuel cell electrode K of Example 10 were the same as in Example 1 except that the reaction vessel was heated to 200 ° C. And the single cell K was produced.

[Comparative Example 2]
In the third step, the solid polymer fuel cell catalyst mixture L and the solid polymer fuel cell electrode L of Comparative Example 2 were the same as in Example 1 except that the reaction vessel was heated to 100 ° C. And the single cell L was produced.

[Comparative Example 3]
In the third step, the solid polymer fuel cell catalyst mixture M and the solid polymer fuel cell electrode M of Comparative Example 3 were the same as in Example 1 except that the reaction vessel was heated to 130 ° C. And the single cell M was produced.

[Comparative Example 4]
In the third step, in the same manner as in Example 1 except that the reaction vessel was heated to 220 ° C., the solid polymer fuel cell catalyst mixture N and the polymer electrolyte fuel cell electrode N of Comparative Example 4 And the single cell N was produced.

  The output performance of the single cells I to N of Examples 8 to 10 and Comparative Examples 2 to 4 was evaluated. The measurement conditions were the same as in Example 1.

FIG. 2 shows the relationship between the heat treatment temperature and the cell voltage in the third step when the single cells I to N are operated at a current density of 300 mA / cm ² . In FIG. 2, the results of Example 1 are also shown. From FIG. 2, it was found that a high cell voltage was obtained when the heat treatment temperature was 150 ° C. or higher and 200 ° C. or lower.

When the heat treatment temperature is lower than 150 ° C., [Pt (NH ₃ ) ₄ ] ²⁺ of the catalytic metal ion is not sufficiently decomposed, and when the thermal decomposition temperature exceeds 200 ° C., the solid polymer This is thought to be due to the thermal decomposition of the cation exchange resin contained in the catalyst mixture for a fuel cell.

[Examples 11 to 13]
[Example 11]
Example 1 except that in the second step, a 0.05 mol / l concentration [Pt (NH ₃ ) ₆ ] Cl ₄ aqueous solution was used as the solution for immersing the powdery mixture of the cation exchange resin and carbon. In the same manner as in Example 11, a polymer electrolyte fuel cell catalyst mixture O, a polymer electrolyte fuel cell electrode O and a single cell O of Example 11 were produced.

[Example 12]
Example 1 except that an aqueous solution of [Ru (NH ₃ ) ₆ ] Cl ₂ having a concentration of 0.05 mol / l was used as a solution for immersing the powdery mixture of the cation exchange resin and carbon in the second step. In the same manner as described above, the polymer mixture fuel cell catalyst mixture P, the polymer electrolyte fuel cell electrode P and the single cell P of Example 12 were produced.

[Example 13]
In the second step, 0.02 mol / l concentration of [Ru (NH ₃ ) ₆ ] Cl ₂ and 0.04 mol / l concentration of [Pt] are used as a solution for immersing the powdery mixture of cation exchange resin and carbon. Except that an aqueous solution containing (NH ₃ ) ₄ ] Cl ₂ was used, in the same manner as in Example 1, the solid polymer fuel cell catalyst mixture Q of Example 13 and the polymer electrolyte fuel cell electrode Q and single cell Q were produced.

The output performance of the single cells O to Q of Examples 11 to 13 was evaluated. The measurement conditions were the same as in Example 1. Table 1 summarizes the relationship between the type of the catalyst and the cell voltage when the single cells O to Q were operated at a current density of 300 mA / cm ² . Table 1 also shows the results of Example 1 for comparison.

  From the results in Table 1, it was found that the cell voltage hardly changed depending on the type of the catalyst metal.

[Examples 14 to 17]
[Example 14]
In the third step, in the same manner as in Example 1 except that the pressure of nitrogen gas during pyrolysis was set to 0.05 MPa, the solid polymer fuel cell catalyst mixture R of Example 14, solid polymer type A fuel cell electrode R and a single cell R were produced.

[Example 15]
In the third step, in the same manner as in Example 1 except that the pressure of the nitrogen gas at the time of thermal decomposition was set to 0.1 MPa, the solid polymer fuel cell catalyst mixture S of Example 15 and the solid polymer type A fuel cell electrode S and a single cell S were produced.

[Example 16]
In the third step, in the same manner as in Example 1 except that the pressure of nitrogen gas at the time of thermal decomposition was set to 0.5 MPa, the solid polymer fuel cell catalyst mixture T of Example 16, solid polymer type A fuel cell electrode T and a single cell T were produced.

[Example 17]
In the third step, in the same manner as in Example 1 except that the pressure of the nitrogen gas at the time of thermal decomposition was 1.05 MPa, the solid polymer fuel cell catalyst mixture U of Example 17 and the solid polymer type Fuel cell electrodes U and single cells U were produced.

The output performance of the single cells R to U of Examples 14 to 17 was evaluated. The measurement conditions were the same as in Example 1. Table 2 summarizes the relationship between the pressure of the nitrogen gas and the cell voltage during the pyrolysis in the third step when the single cells R to U were operated at a current density of 300 mA / cm ² . Table 2 also shows the results of Example 1 for comparison.

  From the results in Table 2, it was found that the cell voltage hardly changed depending on the pressure of nitrogen gas.

[Examples 18 to 21]
[Example 18]
In the third step, in the same manner as in Example 1 except that the thermal decomposition time was 2 hours, the polymer polymer fuel cell catalyst mixture V, the polymer electrolyte fuel cell electrode V of Example 18 and A single cell V was produced.

[Example 19]
In the third step, in the same manner as in Example 1 except that the thermal decomposition time was 5 hours, the polymer mixture fuel cell catalyst mixture W, polymer electrolyte fuel cell electrode W of Example 19 and A single cell W was produced.

[Example 20]
In the third step, in the same manner as in Example 1 except that the thermal decomposition time was set to 10 hours, the solid polymer fuel cell catalyst mixture X, the solid polymer fuel cell electrode X of Example 20 and A single cell X was produced.

[Example 21]
In the third step, the solid polymer fuel cell catalyst mixture Y, the solid polymer fuel cell electrode Y of Example 21 and A single cell Y was produced.

The output performance of the single cells V to Y of Examples 18 to 21 was evaluated. The measurement conditions were the same as in Example 1. Table 3 summarizes the relationship between the thermal decomposition time in the third step and the cell voltage when the single cells V to Y were operated at a current density of 300 mA / cm ² . Table 3 also shows the results of Example 1 for comparison.

  From the results in Table 3, the cell voltage of Example 18 with a pyrolysis time of 2 hours was slightly low, but the cell voltages of Examples 19 to 21 and Example 1 with a pyrolysis time of 5 hours or more were almost the same. It was found that the change in the cell voltage due to the thermal decomposition time was small.

The figure which shows the polarization curve of the single cell A of Example 1, and the single cell H of the comparative example 1. FIG. The figure which shows the relationship between the heat processing temperature of a 3rd process, and a cell voltage when it drive | operates with the current density of 300 mA / cm < ² >.

Claims (1)

A first step of preparing a mixture containing a cation exchange resin and carbon; a second step of adsorbing a cation of a catalyst metal on a fixed ion of the cation exchange resin in the mixture; and a cation of the catalyst metal. A catalyst mixture for a polymer electrolyte fuel cell comprising a third step of thermally decomposing ions at a temperature of 150 ° C. or higher and 200 ° C. or lower in a nitrogen, carbon dioxide, helium, neon or argon atmosphere Production method.

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