JP2006004662A - Catalyst for fuel cell and manufacturing method of catalyst layer for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for improving affinity between graphitized carbon used as a catalyst support and an ion exchanging polymer (ionomer) and for preventing flooding in the vicinity of a catalyst. <P>SOLUTION: This catalyst for a fuel cell comprises the graphitized carbon 10 having, on a surface thereof, an affinity functional group 30 disappearing during operation of the fuel cell, and a catalyst metal 20 supported to the graphitized carbon. An affinity compound removable by chemical processing may be arranged instead of the affinity functional group 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a catalyst used in a fuel cell. More specifically, the present invention relates to a catalyst using graphitized carbon as a support. The catalyst of this invention is used for the catalyst layer in a polymer electrolyte fuel cell (PEFC), for example.

  A fuel cell is a clean power generation system in which the product of an electrode reaction is water in principle and has almost no adverse effect on the global environment. Various fuel cells such as a polymer electrolyte fuel cell, a solid oxide fuel cell, a molten carbonate fuel cell, and a phosphoric acid fuel cell have been proposed as fuel cells. Among these, a polymer electrolyte fuel cell (PEFC) can be operated at a relatively low temperature, and thus is expected as a power source for moving bodies such as automobiles, and is being developed.

  In the polymer electrolyte fuel cell, an oxidant such as air is supplied to the oxygen electrode, and hydrogen gas is supplied to the fuel electrode. Electric power is generated by an electrochemical reaction.

  As the catalyst metal that promotes the electrode reaction, a catalyst metal such as platinum is used. In many cases, the catalyst metal is arranged in the catalyst layer in a state of being supported on a conductive support in order to effectively use the catalyst. From the viewpoint of enhancing the durability of the catalyst, graphitized carbon produced by heat treatment is preferably used as the conductive carrier.

  However, the surface of graphitized carbon tends to become hydrophobic due to the graphitization treatment. When the support surface is hydrophobic, the affinity between the catalyst and an ion-exchange polymer (ionomer) and the hydrophilic functional group such as a sulfonic acid group located in the ionomer and the catalyst is lowered. Since the electrode reaction is a reaction that proceeds at the three-phase interface of the catalyst, ionomer, and reaction gas, if the affinity between the ionomer and the catalyst is low, there is a problem that the electrochemical active surface area (ECA) becomes low. . That is, when hydrophobic graphitized carbon is used, the utilization factor of the catalyst metal is lowered, and consequently the power generation efficiency of the fuel cell is lowered. In order to improve the decreased utilization rate, the amount of catalyst metal used may be increased. However, an increase in the amount of catalyst metal such as platinum greatly increases the production cost of the catalyst.

As a method of hydrophilizing the surface of graphitized carbon, there is a method of forming a hydrophilic monomolecular layer on the carbon surface (see, for example, Patent Document 1). However, the hydrophilic portion located on the carbon surface hinders the discharge of water from the vicinity of the catalyst and causes flooding particularly during long-time operation, leading to a decrease in fuel cell performance.
JP 2000-243404 A

  Accordingly, an object of the present invention is to provide means for improving the affinity between graphitized carbon used as a support and an ion-exchange polymer (ionomer) and preventing flooding in the vicinity of the catalyst.

  The present invention has a graphitized carbon having a hydrophilic functional group that disappears during operation of a fuel cell or a hydrophilic compound that can be removed by chemical treatment on the surface, and a catalytic metal supported on the graphitized carbon. And a fuel cell catalyst.

  By providing the hydrophilic part on the surface of the graphitized carbon, the affinity between the graphitized carbon and the ion exchange polymer (ionomer) is improved. In addition, it is possible to eliminate the hydrophilic part located on the surface of the graphitized carbon after combining the catalyst and the ion-exchange polymer, resulting in the hydrophilic part located on the surface of the graphitized carbon. It is also possible to prevent flooding.

  A first aspect of the present invention is a graphitized carbon having a hydrophilic functional group that disappears during operation of the fuel cell or a hydrophilic compound that can be removed by chemical treatment on the surface, and a catalytic metal supported on the graphitized carbon. And a fuel cell catalyst.

  The fuel cell catalyst of the present invention is obtained by hydrophilizing the surface of a carbon support that has been hydrophobized by graphitization. By disposing a hydrophilic portion on the surface of the graphitized carbon, the surface of the graphitized carbon can be hydrophilized, and the affinity between the graphitized carbon and the ionomer in forming the catalyst layer is increased. As a result, the effective area of the three-phase interface of the catalyst, ionomer, and reaction gas increases, and the electrochemically active surface area (ECA) increases. That is, it is possible to effectively utilize the supported catalyst metal. For example, when the ECA of hydrophilic carbon supporting platinum is 1, a fuel cell catalyst having an ECA of 0.8 or more with the same amount of platinum supported can be obtained.

  The improvement in the affinity between graphitized carbon and ionomer by the hydrophilic portion will be described with reference to the drawings. In the drawings, an ionomer having a sulfonic acid group is described as an example, but the technical scope of the present invention is not limited to an ionomer having a sulfonic acid group.

  FIG. 1 is a schematic diagram illustrating the affinity between graphitized carbon and ionomer in graphitized carbon having hydrophilic functional groups arranged on the surface. The graphitized carbon 10 carries a catalyst metal 20. In the state where the graphitized carbon has not been hydrophilized, the sulfonic acid group of the ionomer and the surface of the graphitized carbon are repelled, and the contact between the graphitized carbon and the ionomer is inhibited. On the other hand, as shown in FIG. 1, when the hydrophilic functional group 30 is attached to the surface of the graphitized carbon 10, the sulfonic acid group of the ionomer is brought close to the graphitized carbon by the action of the hydrophilic functional group 30. It comes to exist. As a result, the ECA increases and the power generation characteristics of the fuel cell are improved.

  FIG. 2 is a schematic diagram for explaining the affinity between graphitized carbon and ionomer in graphitized carbon having a hydrophilic compound disposed on the surface. The graphitized carbon 10 carries a catalyst metal 20. Since the hydrophilic compound 40 is attached to the surface of the graphitized carbon 10, the sulfonic acid group possessed by the ionomer is present in the vicinity of the graphitized carbon by the action of the hydrophilic compound 40. As a result, the ECA increases and the power generation characteristics of the fuel cell are improved.

  Hydrophilic sites sometimes cause flooding, but the hydrophilic sites in the catalyst of the present invention can be removed by chemical treatment or disappear during fuel cell operation. The hydrophilic functional group can be lost during operation of the fuel cell. Since the hydrophilic functional group located on the surface of graphitized carbon is generally more susceptible to corrosion than graphitized carbon, it is likely to be selectively deteriorated and lost during operation of the fuel cell. In addition, the hydrophilic compound can be removed by chemical treatment after electrode formation. And if it is after making it complex with an ionomer, even if a hydrophilic part lose | disappears, there will be no big influence on the effective area of a three-phase interface. Therefore, by using the fuel cell catalyst of the present invention, the affinity between the graphitized carbon as a carrier and the ionomer is high, and the occurrence of flooding due to the hydrophilic portion of the graphitized carbon can be prevented.

  Hereinafter, the configuration of the fuel cell catalyst of the present invention will be described in detail.

  Graphitized carbon is a material produced by graphitizing a carbon material. The graphitized carbon is not particularly limited as long as it has conductivity and can support a metal catalyst. Graphitized carbon may be produced by heat-treating a non-graphitized carbon material, or commercially available graphitized carbon may be purchased and used. In some cases, graphitized carbon on which a desired catalyst metal is already supported may be purchased and used as a raw material.

  A hydrophilic functional group that disappears during the operation of the fuel cell or a hydrophilic compound that can be removed by chemical treatment adheres to the surface of the graphitized carbon. In the present application, for the convenience of explanation, “hydrophilic functional group” and “hydrophilic compound” are also collectively referred to as “hydrophilic portion”.

The hydrophilic functional group means a functional group that can improve the hydrophilicity of graphitized carbon by adhering to the graphitized carbon surface. Specific examples of the hydrophilic functional group include, but are not limited to, a carboxyl group, a phenolic hydroxyl group, a hydroxyl group, a carbonyl group, a nitro group, a sulfonic acid group, and an amino group. The phenolic hydroxyl group means an embodiment in which a hydroxyl group is included as a functional group of phenol type (— (C ₆ H ₄ ) OH). The hydrophilic functional group is preferably a hydroxyl group, a carboxyl group, or an amino group that has an excellent function of attracting protons and improving the affinity between the ionomer and the sulfonic acid group. Two or more functional groups may be used as the hydrophilic functional group.

  The amount of hydrophilic functional group attached is not particularly limited. The degree of hydrophilicity of the graphitized carbon surface can be adjusted by controlling the amount of the hydrophilic functional group and the type of the hydrophilic functional group.

  A hydrophilic compound means a compound that can improve the hydrophilicity of graphitized carbon by adhering to the graphitized carbon surface. Specific examples of the hydrophilic compound include, but are not limited to, metal oxidation of a metal selected from the group consisting of silicon, magnesium, tin, aluminum, niobium, ruthenium, tantalum, titanium, zinc, zirconium, and mixtures thereof. Products, metal hydroxides, or metal oxyhydroxides. In this, the metal oxide, metal hydroxide, or metal oxyhydroxide of titanium, silicon, zirconia, or a mixture thereof is preferable. By using these, a compound having a high water holding ability is formed. Specific examples of the hydrophilic compound include titanium oxide, silicon oxide, zirconia oxide, and the like.

  The adhesion amount of the hydrophilic compound is not particularly limited. The degree of hydrophilicity of the graphitized carbon surface can be adjusted by controlling the amount of the hydrophilic compound and the type of the hydrophilic compound.

  The catalyst metal to be supported is not particularly limited. Various catalytic metals used for fuel cell catalysts can be used. For example, platinum is used as the catalyst metal. In order to enhance the catalytic properties, other components such as iridium oxide may be used in combination with platinum.

  The amount of the catalyst metal supported may be determined in consideration of the production cost of the catalyst, the catalyst activity, the type of the support, and the like. For example, when platinum is used as the catalyst metal, high catalytic activity can be expressed by supporting a sufficient amount of platinum. However, since platinum is expensive, it becomes a main factor that increases the manufacturing cost of the catalyst. Preferably, the amount of platinum supported is controlled so that 10 to 50% by mass of platinum is included with respect to the total mass of the catalyst.

  A second aspect of the present invention is a fuel cell in which the first fuel cell catalyst of the present invention and a proton conductive ionomer are disposed in a catalyst layer. The electrode catalyst layer may be an air electrode or a fuel electrode. The catalyst of this invention may be arrange | positioned at both. The type of fuel cell is not particularly limited as long as the catalyst of the present invention is applicable. Preferably, the catalyst of the present invention is used for a polymer electrolyte fuel cell.

  By disposing the catalyst of the present invention, a fuel cell having high power generation performance with a small amount of platinum supported can be obtained. For this reason, it is possible to reduce the manufacturing cost of the fuel cell. In addition, by using graphitized carbon as a carrier, effects such as improved durability of the fuel cell can be obtained.

  The third aspect of the present invention relates to a method for producing a catalyst layer for a fuel cell, using a technique for attaching a hydrophilic functional group to the surface of graphitized carbon. Specifically, the third aspect of the present invention is the step of adding a hydrophilic functional group that disappears during operation of the fuel cell to the surface of graphitized carbon carrying the catalyst metal, and the hydrophilic functional group on the surface. A method for producing a catalyst layer of a fuel cell, comprising: preparing a catalyst ink containing graphitized carbon having an ionomer; and drying a coating film made of the catalyst ink. Hereinafter, it demonstrates in detail in order of a process.

  First, a hydrophilic functional group that disappears during operation of the fuel cell is added to the surface of graphitized carbon carrying the catalyst metal. Since the catalyst metal and graphitized carbon used are as described above, description thereof is omitted here. The hydrophilic functional group to be added is a functional group that can improve the hydrophilicity of the graphitized carbon by adhering to the surface of the graphitized carbon. Specific examples of the hydrophilic functional group include, but are not limited to, a carboxyl group, a phenolic hydroxyl group, a hydroxyl group, a carbonyl group, a nitro group, a sulfonic acid group, and an amino group. Two or more hydrophilic functional groups may be added.

  A technique for adding a hydrophilic functional group to the surface of the graphitized carbon carrying the catalyst metal is not particularly limited, and a technique for treating the graphitized carbon with an acid may be mentioned. That is, by treating the graphitized carbon carrying the catalyst metal with an acid, a hydrophilic functional group that disappears during operation of the fuel cell is added to the surface of the graphitized carbon.

  Examples of the acid used for adding a hydrophilic functional group to graphitized carbon include a mixed solution of nitric acid and sulfuric acid, potassium permanganate, nitric acid, chlorosulfonic acid, and the like. By adjusting the type and concentration of the acid, the type and amount of the hydrophilic functional group to be added can be controlled. For example, when a mixed solution of nitric acid and sulfuric acid is used as the acid, carboxyl groups, carbonyl groups, and ether groups are easily introduced. When potassium permanganate is used as the acid, phenolic hydroxyl groups and hydroxyl groups are introduced. It is easy to introduce, when nitric acid is used as the acid, amino groups and nitro groups are easily introduced, and when chlorosulfonic acid is used as the acid, sulfonic acid groups are easily introduced.

  Next, a catalyst ink containing graphitized carbon having a hydrophilic functional group on the surface and an ionomer is prepared. Other components such as isopropyl alcohol may be included as necessary. The catalyst ink may be for the cathode or for the anode. In some cases, one catalyst ink can be applied to both the cathode and anode.

There are no particular limitations on the type, blending amount, catalyst ink preparation means, and the like of the ionomer. It may be prepared as appropriate based on the knowledge already obtained, or newly obtained knowledge may be applied. For example, as the ionomer, an ionomer having proton conductivity such as a perfluorosulfonic acid type polymer represented by Nafion ^TM or a polymer in which a sulfonic acid group is introduced into a non-fluorinated aromatic ring-containing polymer is used.

  Thereafter, the coating film made of the catalyst ink is dried to form a catalyst layer. The catalyst layer may be formed on a sheet such as polytetrafluoroethylene and then transferred to a necessary place. Or you may form a catalyst layer by apply | coating a catalyst ink directly to a required location. For example, when producing a polymer electrolyte fuel cell, the catalyst layer may be formed by directly applying a catalyst ink to the polymer electrolyte membrane.

  When using a method of adding hydrophilic functional groups to the surface of graphitized carbon, the hydrophilic functional groups remain on the surface of the graphitized carbon at this stage, but disappear with the operation of the fuel cell. The surface of activated carbon returns to hydrophobic. Such an action prevents flooding in the catalyst layer.

  The 4th of this invention is related with the manufacturing method of the catalyst layer of a fuel cell using the method of making a hydrophilic compound adhere to the surface of graphitized carbon. Specifically, the fourth aspect of the present invention is the step of adding a hydrophilic compound that can be removed by chemical treatment to the surface of the graphitized carbon carrying the catalyst metal, and the graphitized carbon having the hydrophilic compound on the surface. And a step of preparing a catalyst ink containing an ionomer, a step of drying a coating film made of the catalyst ink, and a chemical treatment of the coating film after the coating film has been dried. And a step of removing the catalyst layer. Hereinafter, it demonstrates in detail in order of a process.

  First, a hydrophilic compound that can be removed by chemical treatment is added to the surface of graphitized carbon carrying the catalyst metal. Since the catalyst metal and graphitized carbon used are as described above, description thereof is omitted here. The hydrophilic compound to be added is a compound that can improve the hydrophilicity of graphitized carbon by adhering to the surface of graphitized carbon. Specific examples of the hydrophilic compound include, but are not limited to, metal oxidation of a metal selected from the group consisting of silicon, magnesium, tin, aluminum, niobium, ruthenium, tantalum, titanium, zinc, zirconium, and mixtures thereof. Products, metal hydroxides, or metal oxyhydroxides. Two or more hydrophilic compounds may be added.

  The technique for adding the hydrophilic compound to the surface of the graphitized carbon supporting the catalyst metal is not particularly limited, and a technique for supporting the hydrophilic compound on the graphitized carbon may be mentioned. That is, a hydrophilic compound that can be removed by chemical treatment and graphitized carbon supporting the catalyst metal are mixed in a liquid, and then the mixture of the hydrophilic compound and the catalyst metal is dried to make the hydrophilic compound surface. The graphitized carbon supported on the surface is obtained. For example, graphitized carbon carrying a catalyst metal and a desired hydrophilic compound are mixed in water, and the resulting mixture is dried to volatilize water to obtain graphitized carbon having the hydrophilic compound attached to the surface. The amount of the hydrophilic compound added to the surface of the graphitized carbon can be controlled.

  Next, a catalyst ink containing graphitized carbon having a hydrophilic compound on the surface and an ionomer is prepared. The preparation of the catalyst ink is the same as that described for the third aspect of the present invention, and thus the description thereof is omitted here.

  Thereafter, the coating film made of the catalyst ink is dried to obtain a film acting as a catalyst layer. The catalyst layer may be formed on a sheet such as polytetrafluoroethylene and then transferred to a necessary place. Or you may form a catalyst layer by apply | coating a catalyst ink directly to a required location. For example, when producing a polymer electrolyte fuel cell, the catalyst layer may be formed by directly applying a catalyst ink to the polymer electrolyte membrane.

  When a method of adding a hydrophilic compound to the surface of graphitized carbon is used, the hydrophilic compound remains on the surface of the graphitized carbon at this stage. The hydrophilic compound is removed by chemically treating the coating film after drying the coating film made of the catalyst ink made of graphitized carbon and ionomer.

  A technique for removing the hydrophilic compound by chemically treating the coating film is not particularly limited, and a technique for removing the hydrophilic compound by bringing the coating film into contact with an acid aqueous solution may be mentioned. That is, the hydrophilic compound is dissolved with an acid aqueous solution to remove the hydrophilic compound from the surface of the graphitized carbon. Such an action prevents flooding in the catalyst layer.

  As the acid aqueous solution, for example, an aqueous solution containing an acid such as sulfuric acid, nitric acid, hydrofluoric acid, and acetic acid is preferably used. From the viewpoint of uniformly forming the catalyst layer, the acid aqueous solution is preferably a sulfuric acid aqueous solution. The concentration of the acid aqueous solution is not particularly limited, but is preferably about 0.1 to 3M.

  The temperature during the chemical treatment of the coating film with the acid aqueous solution is not particularly limited. Considering energy efficiency, it is preferable to perform at normal temperature. Further, the chemical treatment time of the coating film with the acid aqueous solution is not particularly limited. Although it depends on the type and concentration of the acid aqueous solution, it is usually possible to remove the hydrophilic compound by treating for about 30 minutes.

<Comparative Example 1>
1. Preparation of catalyst ink Platinum-supported graphitized carbon, 5% by weight Nafion ^TM solution manufactured by Du Pont Co., Ltd., water, and isopropyl alcohol (IPA) as an ionomer were mixed at a ratio of 1: 0.5: 2.5: 1. The mixture was stirred and pulverized with a homogenizer for fine pulverization to obtain a catalyst ink.

2. Preparation of Catalyst Layer The prepared catalyst ink was applied onto a 0.2 mm thick polytetrafluoroethylene sheet using a screen printer and dried to form a sheet-like catalyst layer. The amount of platinum was 0.4 mg / cm ² .

3. Production of Membrane / Electrode Assembly An electrolyte membrane was sandwiched between two produced sheet-like catalyst layers, and hot pressing was performed at 130 ° C. for 10 minutes to obtain a membrane / electrode assembly. Nafion ^TM 111 manufactured by Du Pont Co., Ltd. was used as the electrolyte membrane.

4). Performance Evaluation Using the produced membrane / electrode assembly, an electrochemically active surface area (ECA) was evaluated by cyclic voltammetry at a cell temperature of 70 ° C., and the ECA was 50 m ² / g-Pt.

<Example 1>
1. Addition of hydrophilic functional group Platinum-supported graphitized carbon was placed in a 0.4 mol / l potassium permanganate aqueous solution and reacted at 70 ° C. for 4 hours. The platinum-supported graphitized carbon powder after the reaction was filtered. The powder is sufficiently washed with distilled water at about 70 ° C. and dried at 110 ° C., and a phenolic hydroxyl group that is a hydrophilic functional group that disappears during operation of the fuel cell and graphitized carbon having a hydroxyl group added to the surface, and graphite A fuel cell catalyst having platinum as a catalyst metal supported on activated carbon was obtained.

2. Preparation of cathode catalyst ink The prepared fuel cell catalyst, 5% by weight Nafion ^TM solution made by Du Pont Co., Ltd., water, and IPA as an ionomer were mixed at a ratio of 1: 0.5: 2.5: 1 and pulverized. The mixture was stirred and pulverized with a homogenizer for use to obtain a cathode catalyst ink.

3. Preparation of anode catalyst ink Platinum-supported graphitized carbon, 5% by weight Nafion ^TM solution made by Du Pont Co., Ltd., water, and IPA as an ionomer were mixed at a ratio of 1: 0.5: 2.5: 1 for fine grinding. Agitation and pulverization were performed with a homogenizer to obtain an anode catalyst ink.

4). Preparation of Catalyst Layer The prepared cathode catalyst ink and anode catalyst ink were applied onto a 0.2 mm-thick polytetrafluoroethylene sheet using a screen printer and dried to form a sheet-like catalyst layer. The amount of platinum was 0.4 mg / cm ² .

5. Production of Membrane / Electrode Assembly An electrolyte membrane was sandwiched between two produced sheet-like catalyst layers, and hot pressing was performed at 130 ° C. for 10 minutes to obtain a membrane / electrode assembly. Nafion ^TM 111 manufactured by Du Pont Co., Ltd. was used as the electrolyte membrane.

6). Performance Evaluation Using the produced membrane / electrode assembly, an ECA evaluation was performed by cyclic voltammetry at a cell temperature of 70 ° C. As a result, the ECA was improved by 10% as compared with the case where no hydrophilic functional group was added.

<Example 2>
1. Hydrophilic Compound Addition Platinum-supported graphitized carbon and a colloidal solution containing titanium oxide as a hydrophilic compound that can be removed by chemical treatment were mixed. The mixed liquid was held for 2 hours with stirring, and titanium oxide was supported on the platinum-supporting graphitized carbon. Thereafter, the mixed solution is filtered, sufficiently washed with distilled water at about 70 ° C., and further dried at 110 ° C., and the titanium oxide as a hydrophilic compound adheres to the surface of the platinum-supported graphitized carbon. A catalyst was obtained.

2. Preparation of cathode catalyst ink The prepared fuel cell catalyst, 5% by weight Nafion ^TM solution made by Du Pont Co., Ltd., water, and IPA as an ionomer were mixed at a ratio of 1: 0.5: 2.5: 1 and pulverized. The mixture was stirred and pulverized with a homogenizer for use to obtain a cathode catalyst ink.

3. Preparation of anode catalyst ink Platinum-supported graphitized carbon, 5% by weight Nafion ^TM solution made by Du Pont Co., Ltd., water, and IPA as an ionomer were mixed at a ratio of 1: 0.5: 2.5: 1 for fine grinding. Agitation and pulverization were performed with a homogenizer to obtain an anode catalyst ink.

4). Preparation of Catalyst Layer The prepared cathode catalyst ink and anode catalyst ink were applied onto a 0.2 mm-thick polytetrafluoroethylene sheet using a screen printer and dried to form a sheet-like catalyst layer. The amount of platinum was 0.4 mg / cm ² .

5. Production of Membrane / Electrode Assembly An electrolyte membrane was sandwiched between two produced sheet-like catalyst layers, and hot pressing was performed at 130 ° C. for 10 minutes to obtain a membrane / electrode assembly. Nafion ^TM 111 manufactured by Du Pont Co., Ltd. was used as the electrolyte membrane.

6). Removal of hydrophilic compound The obtained membrane-electrode assembly was immersed in a 1 mol / l sulfuric acid aqueous solution for 1 hour to dissolve and remove the titanium oxide adhering to the carbon surface.

7). Performance Evaluation ECA evaluation by cyclic voltammetry was performed at a cell temperature of 70 ° C. using a membrane / electrode assembly that had been subjected to chemical treatment with an acid aqueous solution. As a result, ECA was improved by 13% compared to the case where no hydrophilic compound was added. .

<Evaluation>
As shown in Example 1 and Example 2, when the fuel cell catalyst of the present invention is used, the affinity between graphitized carbon as a carrier and ionomer is exerted by the action of a hydrophilic functional group or a hydrophilic compound. And ECA is improved.

  The catalyst of the present invention is applied to a fuel cell using graphitized carbon carrying a metal catalyst. For example, the catalyst of this invention is arrange | positioned at the catalyst layer of the electrode of a polymer electrolyte fuel cell.

It is a schematic diagram explaining affinity of graphitized carbon and ionomer in graphitized carbon in which a hydrophilic functional group is arranged on the surface. It is a schematic diagram explaining the affinity of graphitized carbon and ionomer in graphitized carbon with which the hydrophilic compound is arrange | positioned on the surface.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Graphitized carbon, 20 ... Catalytic metal, 30 ... Hydrophilic functional group, 40 ... Hydrophilic compound.

Claims (11)

Graphitized carbon having a hydrophilic functional group that disappears during operation of the fuel cell or a hydrophilic compound that can be removed by chemical treatment on the surface;
A fuel cell catalyst comprising a catalyst metal supported on the graphitized carbon.   2. The fuel cell catalyst according to claim 1, wherein the hydrophilic functional group is selected from the group consisting of a carboxyl group, a phenolic hydroxyl group, a hydroxyl group, a carbonyl group, a nitro group, a sulfonic acid group, and an amino group.   The hydrophilic compound is a metal oxide, metal hydroxide, or metal selected from the group consisting of silicon, magnesium, tin, aluminum, niobium, ruthenium, tantalum, titanium, zinc, zirconium, and mixtures thereof, or The fuel cell catalyst according to claim 1, which is a metal oxyhydroxide.   A fuel cell comprising the catalyst for a fuel cell according to any one of claims 1 to 3 and a proton conductive ionomer arranged in a catalyst layer. Adding a hydrophilic functional group that disappears during operation of the fuel cell to the surface of graphitized carbon carrying the catalyst metal;
Preparing a catalyst ink comprising graphitized carbon having a hydrophilic functional group on its surface and an ionomer;
Drying the coating film comprising the catalyst ink;
The manufacturing method of the catalyst layer of a fuel cell containing this. The step of adding a hydrophilic functional group that disappears during operation of the fuel cell to the surface of graphitized carbon carrying the catalyst metal is as follows:
6. The production according to claim 5, wherein the graphitized carbon supporting the catalyst metal is treated with an acid to add a hydrophilic functional group that disappears during operation of the fuel cell to the surface of the graphitized carbon. Method.   The hydrophilic functional group added to the surface of the graphitized carbon is selected from the group consisting of a carboxyl group, a phenolic hydroxyl group, a hydroxyl group, a carbonyl group, a nitro group, a sulfonic acid group, and an amino group. 6. The production method according to 6. Adding a hydrophilic compound that can be removed by chemical treatment to the surface of graphitized carbon carrying the catalytic metal;
Preparing a catalyst ink comprising graphitized carbon having the hydrophilic compound on its surface and an ionomer;
Drying the coating film comprising the catalyst ink;
Removing the hydrophilic compound by chemically treating the coating film after drying the coating film;
The manufacturing method of the catalyst layer of a fuel cell containing this. The step of adding a hydrophilic compound that can be removed by chemical treatment to the surface of graphitized carbon carrying the catalyst metal is as follows:
Mixing the hydrophilic compound that can be removed by chemical treatment and graphitized carbon carrying the catalyst metal in a liquid; and drying the mixture of the hydrophilic compound and the catalyst metal to obtain the hydrophilic compound The method according to claim 8, further comprising obtaining the graphitized carbon supported on a surface.   The hydrophilic compound added to the surface of the graphitized carbon is a metal selected from the group consisting of silicon, magnesium, tin, aluminum, niobium, ruthenium, tantalum, titanium, zinc, zirconium, and mixtures thereof. The manufacturing method of Claim 8 or 9 which is an oxide, a metal hydroxide, or a metal oxyhydroxide. After the coating film is dried, the step of removing the hydrophilic compound by chemically treating the coating film comprises the steps of:
The manufacturing method according to any one of claims 8 to 10, wherein the hydrophilic compound is removed by bringing the coating film into contact with an acid aqueous solution after the coating film is dried.