JP2007099551A - Carbon-based composite material and its manufacturing method, electrode for solid polymer type fuel cell and solid polymer type fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new manufacturing method of a carbon-based composite material which has a large surface area and can control the characteristics such as gas permeability, liquid permeability and a pore distribution or the like. <P>SOLUTION: The manufacturing method of a carbon-based composite material comprises a step for supporting a catalyst 2 on a carbonaceous porous material support 1, and a step for producing a carbon nanofiber 3 on the carbonaceous porous material support 1 by bringing a carbon-containing compound under a high temperature into contact with the carbonaceous porous material support 1 supported with the catalyst 2, or comprises a step for producing a fibril-like polymer on a carbonaceous porous material support 1 by polymerizing an aromatic compound on the carbonaceous porous material support 1, a step for producing a three dimensional continuous carbon fiber by firing the fibril-like polymer, a step for supporting a catalyst 2 on the three dimensional continuous carbon fiber, and a step for producing a carbon nanofiber 3 on the three dimensional continuous carbon fiber by bringing a carbon-containing compound under a high temperature into contact with the three dimensional continuous carbon fiber supported with the catalyst 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a carbon-based composite material, a carbon-based composite material produced by the method, and an electrode for a polymer electrolyte fuel cell and a polymer electrolyte fuel cell using the carbon-based composite material, In particular, the present invention relates to a novel method for producing a carbon-based composite material having a large surface area and capable of controlling various properties such as gas permeability, liquid permeability, and pore distribution.

  In recent years, fuel cells have attracted attention as a battery having high power generation efficiency and a low environmental load, and extensive research and development has been conducted. Among fuel cells, solid polymer fuel cells with high power density and low operating temperature are easier to reduce in size and cost than other types of fuel cells. It is expected to spread widely as a household cogeneration system.

  Generally, a polymer electrolyte fuel cell has a structure in which a catalyst layer containing a noble metal catalyst is disposed on both sides of a solid polymer electrolyte membrane, and carbon paper or the like is disposed as a gas diffusion layer outside the catalyst layer. It has a body (MEA). Furthermore, a conductive separator having a gas flow path is disposed on both outer sides of the gas diffusion layer. The separator allows the fuel gas and the oxidant gas to pass therethrough and at the same time from the gas diffusion layer. It plays a role of transmitting electric current to the outside and extracting electric energy (see Non-Patent Documents 1 and 2).

The Chemical Society of Japan, “Chemical Review No. 49, Material Chemistry of New Batteries”, Academic Publishing Center, 2001, p. 180-182 “Polymer fuel cell <2001 edition>”, Technical Information Association, 2001, p. 14-15

  By the way, carbon paper, which is a carbon-based porous material suitable as a gas diffusion layer of the polymer electrolyte fuel cell, is generally obtained by dispersing a carbon fiber chip having a specific fiber diameter in a binder liquid and extracting it. It is manufactured by hot pressing a sheet. However, with this method, it is difficult to arrange the carbon fiber by controlling the fiber diameter in the thickness direction of the carbon paper, and various properties such as gas permeability, liquid permeability, and pore distribution of the obtained carbon paper are obtained. It is also difficult to control.

  When carbon paper is used as a gas diffusion layer of a polymer electrolyte fuel cell, the fuel gas and oxidant gas permeability and water vapor permeability of the carbon paper are considered to greatly affect the performance of the polymer electrolyte fuel cell. However, since the above-mentioned permeability of the carbon paper cannot be controlled, the present condition is that the thickness of the carbon paper and the amount of Nafion applied when forming the catalyst layer are adjusted. However, with this method, it is difficult to precisely control the permeability of fuel gas and oxidant gas, and further, the permeability of water vapor, and there is a possibility of changing the thickness of the membrane electrode assembly (MEA) itself. In addition, the performance of the polymer electrolyte fuel cell may be greatly deteriorated.

  Further, when carbon paper is used as a catalyst carrier for various catalysts, there is a problem that it is difficult to secure a sufficiently large surface area with carbon paper made of carbon fibers having a single fiber diameter.

  Therefore, an object of the present invention is to provide a novel method for producing a carbon-based composite material having a large surface area and capable of controlling various properties such as gas permeability, liquid permeability, and pore distribution. Another object of the present invention is to provide a carbon-based composite material produced by such a method, and a polymer electrolyte fuel cell electrode and solid polymer fuel cell using the carbon-based composite material. It is in.

  As a result of intensive studies to achieve the above object, the present inventors have produced carbon nanofibers directly on a carbon-based porous support such as carbon paper, or three-dimensional continuous on a carbon-based porous support. The carbon nanofibers are formed on the three-dimensional continuous carbon fibers after forming the carbon-like carbon fibers, so that the surface area is large and suitable as a support for the gas diffusion layer and the catalyst layer of the solid polymer fuel cell. It has been found that a carbon-based composite material can be obtained, and further, by controlling the production conditions of the carbon nanofibers, various properties such as gas permeability, liquid permeability, and pore distribution of the obtained carbon-based composite material can be controlled. The present invention has been completed.

That is, the first method for producing a carbon-based composite material of the present invention is:
(A) a step of supporting a catalyst on a carbon-based porous support;
(B) contacting the carbon-based porous support on which the catalyst is supported with a carbon-containing compound at a high temperature to form carbon nanofibers on the carbon-based porous support, and A carbon-based composite material including a carbon-based porous support and carbon nanofibers can be manufactured.

  In the first method for producing a carbon-based composite material of the present invention, the carbon-based porous support used in the step (A) is preferably carbon paper, and the catalyst supported in the step (A) is Fe. Ni and Co are preferred. Moreover, it is preferable to carry | support the catalyst in the said (A) process by an electroplating method or a sputtering method, and it is preferable to perform the said (B) process in non-oxidizing atmosphere.

In addition, the method for producing the second carbon-based composite material of the present invention includes:
(A) polymerizing an aromatic compound on a carbon-based porous support to form a fibrillated polymer on the carbon-based porous support;
(B) firing the fibrillated polymer to form a three-dimensional continuous carbon fiber;
(C) supporting a catalyst on the three-dimensional continuous carbon fiber;
(D) contacting the three-dimensional continuous carbon fiber carrying the catalyst with a carbon-containing compound at a high temperature to form carbon nanofibers on the three-dimensional continuous carbon fiber, A carbon-based composite material including a carbon-based porous support, a three-dimensional continuous carbon fiber, and a carbon nanofiber can be manufactured.

  In the second method for producing a carbon-based composite material of the present invention, the carbon-based porous support used in the step (a) is preferably carbon paper, and the polymerization in the step (a) is electrolytic oxidation polymerization. The aromatic compound used in the step (a) is preferably an aromatic amine compound or a heterocyclic compound, and more preferably aniline, pyrrole, thiophene or a derivative thereof.

  In the second method for producing a carbon-based composite material of the present invention, the step (b) is preferably performed in a non-oxidizing atmosphere, and the catalyst is supported in the step (c) by electroplating or sputtering. Preferably, the step (d) is performed in a non-oxidizing atmosphere. The catalyst supported in the step (c) is preferably Fe, Ni and Co.

  The carbon-based composite material of the present invention is manufactured by the above method, and the solid polymer fuel cell electrode of the present invention comprises a metal supported on the carbon-based composite material. The solid polymer fuel cell is provided with the electrode.

  According to the present invention, a novel method for producing a carbon-based composite material having a large surface area and capable of controlling various characteristics such as gas permeability, liquid permeability, and pore distribution can be provided. In addition, it is possible to provide a carbon-based composite material produced by such a method, a polymer electrolyte fuel cell electrode and a polymer electrolyte fuel cell using the carbon-based composite material. Since the carbon composite material has a large surface area, it is useful as a support for various catalysts, and is particularly useful as a support for a catalyst layer and a gas diffusion layer of a polymer electrolyte fuel cell.

<Method for producing carbon-based composite material>
Below, the manufacturing method of the carbon type composite material of this invention is demonstrated in detail. As shown in FIG. 1, the first method for producing a carbon-based composite material of the present invention includes (A) a step of supporting a catalyst 2 on a carbon-based porous support 1, and (B) a step of supporting the catalyst 2. The carbon-based porous support 1 comprising the step of bringing the carbon-containing porous support 1 into contact with a carbon-containing compound at a high temperature to form a carbon nanofiber 3 on the carbon-based porous support 1. A carbon-based composite material including the body 1 and the carbon nanofiber 3 can be manufactured. In addition, after the step (B), the catalyst 2 remaining in the carbon-based composite material may be removed according to the use of the carbon-based composite material.

  In addition, as shown in FIG. 2, the second method for producing a carbon-based composite material according to the present invention includes: (a) polymerizing an aromatic compound on the carbon-based porous support 1 to obtain a carbon-based porous support. A step of generating a fibril-like polymer 4 on 1, (b) a step of firing the fibril-like polymer 4 to generate a three-dimensional continuous carbon fiber 5, and (c) the three-dimensional continuous carbon fiber 5. A step of supporting the catalyst 2, and (d) contacting the carbon-containing compound at a high temperature with the three-dimensional continuous carbon fiber 5 on which the catalyst 2 is supported, so that the carbon nanofiber 3 is placed on the three-dimensional continuous carbon fiber 5. A carbon-based composite material including the carbon-based porous support 1, the three-dimensional continuous carbon fiber 5, and the carbon nanofiber 3 can be manufactured. In addition, after the step (d), the catalyst 2 remaining in the carbon-based composite material may be removed according to the use of the carbon-based composite material.

  In the method for producing a carbon-based composite material according to the present invention, the carbon nanofiber 3 is generated directly on the carbon-based porous support 1 or the three-dimensional continuous carbon fiber 5 is generated on the carbon-based porous support 1. After that, carbon nanofibers 3 are formed on the three-dimensional continuous carbon fibers 5. Here, since the carbon nanofiber 3 to be produced has a very small diameter and a very large surface area than the carbon-based porous support 1, the resulting carbon-based composite material has a very large surface area. Therefore, the carbon-based composite material produced by the method of the present invention is useful as a support for various catalysts, and is particularly useful as a support for a catalyst layer and a gas diffusion layer of a polymer electrolyte fuel cell. In the second method for producing a carbon-based composite material of the present invention, a three-dimensional continuous carbon fiber 5 is generated on the carbon-based porous support 1, and the three-dimensional continuous carbon fiber 5 is also a carbon-based material. Since the diameter is smaller than the porous support 1 and the surface area is large, the carbon-based composite material obtained by the second carbon-based composite material manufacturing method of the present invention has a very large surface area.

  Further, in the method for producing a carbon-based composite material according to the present invention, various properties such as gas permeability, liquid permeability, and pore distribution of the obtained carbon-based composite material are selected by selecting the generation conditions of the carbon nanofiber 3. Can be controlled. Further, in the second method for producing a carbon-based composite material of the present invention, the carbon-based composite material obtained by selecting the production conditions for the three-dimensional continuous carbon fiber 5 in addition to the production conditions for the carbon nanofibers 3 Various properties such as gas permeability, liquid permeability and pore distribution can be controlled.

  In the first production method of the present invention, a catalyst is supported on a carbon-based porous support in the step (A). Here, examples of the carbon-based porous support used include carbon paper, carbon non-woven fabric, carbon cloth, carbon net, and mesh-like carbon, and among these, carbon paper is preferable. A commercially available product can be used as the carbon-based porous support.

  The method for supporting the catalyst in the step (A) is not particularly limited, and examples thereof include an electroplating method, an electroless plating method, a sputtering method, and an impregnation method. Among these, the electroplating method and the sputtering method are exemplified. preferable. The supported catalyst may be any catalyst as long as it has a catalytic action for the formation reaction of carbon nanofibers, and examples thereof include metals such as Fe, Ni and Co. It may be more than seeds. The amount of catalyst supported is not particularly limited, and is preferably in the range of 0.001 μg to 0.1 mg with respect to 1 g of the carbon-based porous support.

  In the first production method of the present invention, in the step (B), the carbon-containing porous material is brought into contact with the carbon-based porous support on which the catalyst is supported at a high temperature by a thermal CVD method. Carbon nanofibers are generated on the support. Here, the step (B) is preferably performed in a non-oxidizing atmosphere. For example, a carbon-based porous support on which the catalyst is supported is charged into a reactor, and a mixed gas of a carbon-containing compound serving as a carbon source and a non-oxidizing carrier gas at a high temperature, preferably at about 500 to 1000 ° C. May be circulated through the reactor. Here, examples of the carbon-containing compound include gaseous carbon sources such as methane, ethylene, and acetylene, and liquid carbon sources such as alcohols and liquid hydrocarbons. Carrier gases include helium gas, argon gas, and nitrogen. Non-oxidizing gas such as gas can be used.

  In the second production method of the present invention, in the step (a), an aromatic compound is polymerized on the carbon-based porous support to produce a fibrillated polymer on the carbon-based porous support. Here, examples of the carbon-based porous support used include carbon paper, carbon non-woven fabric, carbon cloth, carbon net, and mesh-like carbon, and among these, carbon paper is preferable.

  The polymerization method of the aromatic compound is preferably an oxidative polymerization method, and examples of the oxidative polymerization method include an electrolytic oxidative polymerization method and a chemical oxidative polymerization method, and the electrolytic oxidative polymerization method is particularly preferable. Here, examples of the aromatic compound include an aromatic amine compound and a heterocyclic compound. As the aromatic amine compound, specifically, aniline and aniline derivatives are preferable, and as the heterocyclic compound, specific examples are given. Specifically, pyrrole, thiophene, and derivatives thereof are preferable. These aromatic compounds may be used alone or in a mixture of two or more.

For example, when the fibrillated polymer is produced by an electrolytic oxidation polymerization method, it is preferable to mix an acid together with the starting aromatic compound. In this case, the negative ion of the acid is taken into the fibril polymer synthesized as a dopant, and a fibril polymer with excellent conductivity is obtained. By using this fibril polymer, the conductivity of the produced carbon fiber is increased. Can be improved. The acid mixed in the polymerization is not particularly limited, and examples thereof include HBF ₄ , H ₂ SO ₄ , HCl, HClO ₄ , and the concentration of the acid is 0.1 to 3 mol / The range of L is preferable, and the range of 0.5 to 2.5 mol / L is more preferable.

In the case of obtaining a fibrillated polymer by electrolytic oxidation polymerization, the carbon-based porous support is immersed as a working electrode in a solution containing an aromatic compound, the counter electrode is immersed, and the aromatic compound is sandwiched between both electrodes. It is sufficient to apply a voltage equal to or higher than the oxidation potential, or to pass an electric current under such a condition that a voltage sufficient to polymerize the aromatic compound can be secured. A fibrillar polymer is formed. As the counter electrode, a plate made of a highly conductive material such as stainless steel, platinum, or carbon, a porous material, or the like can be used. Also, the current density in the electrolytic oxidation polymerization is preferably in the range of 0.1~1000mA / cm ^2, more preferably in the range of 0.2~100mA / cm ^2, the concentration of the electrolytic solution of the aromatic compound, the 0.05 to 3 mol / L The range is preferable, and the range of 0.25 to 1.5 mol / L is more preferable. In addition to the above components, a soluble salt or the like may be appropriately added to the electrolytic solution in order to adjust the pH.

  In the second production method of the present invention, it is preferable that the fibrillated polymer obtained as described above is washed with a solvent such as water or an organic solvent, dried and used in the next step. Here, the drying method is not particularly limited, and examples thereof include a method using a fluidized bed drying device, an air dryer, a spray dryer, etc., in addition to air drying and vacuum drying.

  The fibril-like polymer produced in the step (a) usually has a diameter of 30 nm to several hundreds of nm, preferably 40 nm to 500 nm, and a length of 0.5 μm to 100 mm, preferably 1 μm to 10 mm.

  In the second production method of the present invention, in the step (b), the fibrillated polymer is baked to produce a three-dimensional continuous carbon fiber. Here, the firing of the fibrillated polymer is preferably performed in a non-oxidizing atmosphere. Examples of the non-oxidizing atmosphere include a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere. In some cases, a hydrogen atmosphere can also be used. The non-oxidizing atmosphere may contain a small amount of oxygen as long as the fibrillated polymer is not completely lost. The firing conditions are not particularly limited, and may be set as appropriate according to the purpose. For example, firing is preferably performed at a temperature of 500 to 3000 ° C., preferably 600 to 2800 ° C. for 0.5 to 6 hours. .

The carbon fiber produced in the step (b) has a diameter of 30 nm to several hundreds of nm, preferably 40 nm to 500 nm, a length of 0.5 μm to 100 mm, preferably 1 μm to 10 mm, and a surface resistance of 10 ⁶ to 10 ⁻² Ω, preferably 10 ⁴ to 10 ⁻² Ω. The carbon fiber has a residual carbon ratio of 95 to 30%, preferably 90 to 40%. The carbon fiber obtained in the step (b) has a network structure in which the entire carbon is three-dimensionally continuous, and is excellent in conductivity.

  In the second production method of the present invention, a catalyst is supported on the three-dimensional continuous carbon fiber in the step (c). Here, the method for supporting the catalyst is not particularly limited, and examples thereof include an impregnation method, an electroplating method, an electroless plating method, and a sputter film forming method. Sputtering is preferred. Further, the supported catalyst may be any catalyst that has a catalytic action on the formation reaction of carbon nanofibers, and examples thereof include metals such as Fe, Ni, and Co. The amount of catalyst supported is not particularly limited, and is preferably in the range of 0.001 μg to 0.1 mg per 1 g of three-dimensional continuous carbon fiber.

  In the second production method of the present invention, in the step (d), a carbon-containing compound is brought into contact with the three-dimensional continuous carbon fiber carrying the catalyst at a high temperature by a thermal CVD method at a high temperature. Carbon nanofibers are generated on carbon fibers. Here, the step (d) is preferably performed in a non-oxidizing atmosphere. For example, a three-dimensional continuous carbon fiber carrying the above catalyst is charged into a reactor together with a carbon-based porous support, and at a high temperature, preferably at about 500 to 1000 ° C., a carbon-containing compound serving as a carbon source and a non-oxidizing property What is necessary is just to distribute | circulate the mixed gas with other carrier gas to a reactor. Here, examples of the carbon-containing compound include gaseous carbon sources such as methane, ethylene, and acetylene, and liquid carbon sources such as alcohols and liquid hydrocarbons. Carrier gases include helium gas, argon gas, and nitrogen. Non-oxidizing gas such as gas can be used.

  The carbon nanofiber formed on the carbon-based porous support or the three-dimensional continuous carbon fiber as described above is a fibrous carbon containing SWNT and MWNT, and the diameter of the carbon nanofiber is particularly limited. Usually, it is in the range of 0.7 nm to 300 nm.

  In the method for producing a carbon-based composite material of the present invention, a catalyst removal step may be performed after the carbon nanofiber generation step (that is, step (B) and step (d)). Here, the method for removing the catalyst is not particularly limited, and can be appropriately selected depending on the supported catalyst. For example, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, hydrofluoric acid, chromic acid, excess Acids such as hydrogen oxide, perchloric acid, chloric acid, chlorous acid, hypochlorous acid, citric acid, oxalic acid, and hydrogen bromide, and alkalis such as sodium hydroxide and potassium hydroxide can be used.

<Electrode for polymer electrolyte fuel cell>
The electrode for a polymer electrolyte fuel cell of the present invention is formed by supporting fine particles of metal, preferably noble metal, on the carbon-based composite material produced by the above-described method. In the present invention, it is preferable to support a metal on the carbon nanofiber of the carbon-based composite material. Here, Pt is particularly preferable as the metal supported on the carbon-based composite material. In the present invention, Pt may be used alone or as an alloy with another metal such as Ru. By using Pt as the metal to be supported, hydrogen can be oxidized with high efficiency even at a low temperature of 100 ° C. or lower. Further, by using an alloy such as Pt and Ru, it is possible to prevent poisoning of Pt by CO and prevent a decrease in the activity of the catalyst. When the supported metal is in the form of fine particles, the particle size of the metal is preferably in the range of 0.5 to 100 nm, and more preferably in the range of 1 to 50 nm. The metal may be in the form of a fiber, a wire, or a thin film. The supporting rate of the metal is preferably in the range of 0.05 to 5 g with respect to 1 g of carbon nanofibers of the carbon-based composite material. Here, the method for supporting the metal on the carbon-based composite material is not particularly limited, and examples thereof include an impregnation method, an electroplating method (electrolytic reduction method), an electroless plating method, and a sputtering method. It is done.

  In the polymer electrolyte fuel cell electrode of the present invention, after the metal is supported on the carbon-based composite material, a part of the supported metal may be dissolved to increase the surface area. Here, for dissolution of the supported metal, for example, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, hydrofluoric acid, chromic acid, hydrogen peroxide, perchloric acid, chloric acid, chlorous acid, hypochlorous acid, Acids such as citric acid, oxalic acid, and hydrogen bromide, and alkalis such as sodium hydroxide and potassium hydroxide can be used.

  In the polymer electrolyte fuel cell electrode of the present invention, the carbon-based porous support of the carbon-based composite material mainly corresponds to a gas diffusion layer, and a carbon nanofiber and a three-dimensional continuous carbon fiber on which a metal is supported. Corresponds mainly to the catalyst layer. The gas diffusion layer is a layer for supplying a fuel gas such as hydrogen or an oxidant gas such as oxygen or air to the catalyst layer and transferring the generated electrons, and functions as a gas diffusion layer. It functions as a current collector.

The catalyst layer is preferably impregnated with a polymer electrolyte, and an ion conductive polymer can be used as the polymer electrolyte. Examples of the ion conductive polymer include polymers having ion exchange groups such as sulfonic acid, carboxylic acid, phosphonic acid, and phosphonous acid, and the polymer may or may not contain fluorine. Specifically, the ion conductive polymer is preferably a perfluorocarbon sulfonic acid polymer such as Nafion (registered trademark). The amount of impregnation of the polymer electrolyte is preferably in the range of 10 to 500 parts by mass with respect to 100 parts by mass of the carbon nanofibers in the catalyst layer or 100 parts by mass in total of the carbon nanofibers and the three-dimensional continuous carbon fibers. . The thickness of the catalyst layer is not particularly limited, but is preferably in the range of 0.1 to 100 μm. Further, the metal loading amount of the catalyst layer is determined by the loading ratio and the thickness of the catalyst layer, and is preferably in the range of 0.001 to 0.8 mg / cm ² .

<Solid polymer fuel cell>
The polymer electrolyte fuel cell of the present invention comprises the above-mentioned electrode for a polymer electrolyte fuel cell. For example, as shown in FIG. 3, the polymer electrolyte fuel cell of the present invention includes a membrane electrode assembly (MEA) 11 and separators 12 positioned on both sides thereof. The membrane electrode assembly (MEA) 11 includes a solid polymer electrolyte membrane 13 and a fuel electrode 14A and an air electrode 14B located on both sides thereof. In the fuel electrode 14A, for example, a reaction represented by 2H ₂ → 4H ⁺ + 4e ⁻ occurs, and the generated H ⁺ passes through the solid polymer electrolyte membrane 13 to the air electrode 14B, and the generated e ⁻ It is taken out and becomes an electric current. On the other hand, in the air electrode 14B, a reaction represented by O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O occurs, and water is generated. Here, at least one of the fuel electrode 14A and the air electrode 14B is the above-described electrode for a polymer electrolyte fuel cell of the present invention. The fuel electrode 14 </ b> A and the air electrode 14 </ b> B are each composed of a catalyst layer 15 and a gas diffusion layer 16, and are arranged so that the catalyst layer 15 contacts the solid polymer electrolyte membrane 13.

  As the solid polymer electrolyte membrane 13, an ion conductive polymer can be used. As the ion conductive polymer, those exemplified as the polymer electrolyte that can be impregnated in the catalyst layer are used. Can be used. Moreover, as the separator 12, the normal separator by which flow paths (not shown), such as a fuel, air, and produced | generated water, were formed in the surface can be used.

  In the polymer electrolyte fuel cell of the present invention, at least one of the fuel electrode 14A and the air electrode 14B has a high surface area, high electron conductivity, carbon-based composite material excellent in gas permeability and liquid permeability, and metal. Since the electrode for the polymer electrolyte fuel cell of the present invention is used, the mass transfer of the fuel gas and the oxidant gas at the electrode is performed smoothly, and the water produced by the reaction is also discharged smoothly. It is possible to prevent the output of the fuel cell from being lowered.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

1. Carbon nanofibers were directly formed on carbon paper. A Ni thin film having a thickness of about 10 nm was formed on carbon paper [manufactured by Toray Industries, Inc.] by DC sputtering.

  Carbon paper on which a Ni thin film was formed was placed in a reaction tube of a thermal CVD apparatus, and nitrogen was introduced at a flow rate of 300 sccm. In this state, the temperature of the reaction tube was raised to 450 ° C. When the temperature reached 450 ° C., ethanol was introduced into the reaction tube at a flow rate of 1 ml / min. Nitrogen was stopped, and the temperature of the reaction tube was further raised in this state to raise the reaction temperature to 650 ° C. The reaction was carried out at 650 ° C. for 30 minutes. The ethanol was stopped and the sample was taken out when it was allowed to cool to room temperature. When the formed product was observed by SEM, it was confirmed that a carbon fiber having a fiber diameter of approximately 10 to 100 nm was generated.

2. Directly generate carbon nanofibers after preparing fibril carbon on carbon paper Install a working electrode made of carbon paper [manufactured by Toray] in an acidic aqueous solution containing 0.5 mol / L aniline monomer and 1.0 mol / L HBF ₄ A platinum plate was used, and electropolymerization was performed at a constant current of 15 mA / cm ² at room temperature for 3 minutes to deposit polyaniline on the working electrode. The obtained polyaniline was washed with ion-exchanged water, vacuum-dried for 24 hours, then heated with carbon paper to 950 ° C at a rate of 3 ° C / min in an Ar atmosphere, and then held at 950 ° C for 1 hour for firing. Processed. When the obtained fired product was observed by SEM, it was confirmed that fibril-like and three-dimensional continuous carbon fibers having a diameter of 50 to 300 nm were formed on the carbon paper.

  Next, a Ni thin film having a thickness of about 10 nm was formed on carbon paper with fibril carbon by DC sputtering.

  Carbon paper with fibril carbon on which a Ni thin film was formed was placed in a reaction tube of a thermal CVD apparatus, and nitrogen was introduced at a flow rate of 300 sccm. In this state, the temperature of the reaction tube was raised to 450 ° C. When the temperature reached 450 ° C., ethanol was introduced into the reaction tube at a flow rate of 1 ml / min. Nitrogen was stopped, and the temperature of the reaction tube was further raised in this state to raise the reaction temperature to 650 ° C. The reaction was carried out at 650 ° C. for 30 minutes. The ethanol was stopped and the sample was taken out when it was allowed to cool to room temperature. When the formed product was observed by SEM, it was confirmed that a carbon fiber having a fiber diameter of approximately 10 to 100 nm was generated.

3. Fuel cell evaluation (Example 1 (when 2 above is used))
A carbon paper with the above carbon fiber on the surface is installed as a working electrode in a 3% by mass chloroplatinic acid aqueous solution, a platinum plate is used as the counter electrode, and electroplating (electrolytic reduction) at a constant current of 30 mA / cm ² at room temperature. ) For 25 seconds to deposit platinum on the carbon fiber to form a catalyst structure with a platinum loading of 0.4 mg / cm ² on the carbon paper. Here, the working electrode and the platinum plate were arranged such that the surface of the carbon paper to which the carbon fibers were added faced the platinum plate.

A 5 mass% Nafion (registered trademark) solution was applied to the catalyst structure formed on the carbon paper, and then dried to form a catalyst layer on the carbon paper. Next, carbon paper with a catalyst layer is arranged so that the catalyst layer is in contact with both surfaces of a solid polymer electrolyte membrane (film thickness: 175 μm) made of Nafion (registered trademark), and the membrane electrode assembly ( MEA) was prepared. The membrane electrode assembly was incorporated into a test cell (EFC25-01SP) manufactured by Electrochem to produce a fuel cell. The voltage-current characteristics of the fuel cell were measured under the conditions of an H ₂ flow rate of 300 cm ³ / min, an O ₂ flow rate of 300 cm ³ / min, a cell temperature of 80 ° C., and a humidification temperature of 80 ° C. The results are shown in FIG.

(Comparative Example 1)
Example except that MEA manufactured by Electrochemical Co. (solid polymer electrolyte membrane: Nafion membrane, film thickness: 130 μm, carrier: granular carbon, platinum loading 20 mass%, platinum loading: 1 mg / cm ² ) In the same manner as in Example 1, a polymer electrolyte fuel cell was produced and its voltage-current characteristics were measured. The results are shown in FIG.

  FIG. 4 shows that the polymer electrolyte fuel cell of the present invention shows equivalent cell performance and greatly improved platinum utilization efficiency even when the amount of platinum supported is greatly reduced compared to the conventional one. I understand. In particular, the polymer electrolyte fuel cell of the present invention is considered to have a small activation polarization and a small voltage drop due to a chemical reaction in the catalyst layer because the cell voltage on the low current side is high.

It is process drawing of the manufacturing method of the 1st carbon type composite material of this invention. It is process drawing of the manufacturing method of the 2nd carbon type composite material of this invention. It is sectional drawing of an example of the polymer electrolyte fuel cell of this invention. The voltage-current curve of the polymer electrolyte fuel cell of Example 1 and Comparative Example 1 is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carbon type porous support body 2 Catalyst 3 Carbon nanofiber 4 Fibrous polymer 5 Three-dimensional continuous carbon fiber 11 Membrane electrode assembly (MEA)
12 Separator 13 Solid polymer electrolyte membrane 14A Fuel electrode 14B Air electrode 15 Catalyst layer 16 Gas diffusion layer

Claims (17)

(A) a step of supporting a catalyst on a carbon-based porous support;
(B) contacting a carbon-containing porous support on which the catalyst is supported with a carbon-containing compound at a high temperature to produce carbon nanofibers on the carbon-based porous support. A method for producing a carbon-based composite material comprising a porous support and carbon nanofibers.   2. The method for producing a carbon-based composite material according to claim 1, wherein the carbon-based porous support used in the step (A) is carbon paper.   The method for producing a carbon-based composite material according to claim 1, wherein the catalyst supported in the step (A) is at least one metal selected from the group consisting of Fe, Ni, and Co.   The method for producing a carbon-based composite material according to claim 1, wherein the catalyst is supported in the step (A) by electroplating or sputtering.   The method for producing a carbon-based composite material according to claim 1, wherein the step (B) is performed in a non-oxidizing atmosphere. (A) polymerizing an aromatic compound on a carbon-based porous support to form a fibrillated polymer on the carbon-based porous support;
(B) firing the fibrillated polymer to form a three-dimensional continuous carbon fiber;
(C) supporting a catalyst on the three-dimensional continuous carbon fiber;
(D) a step of bringing a carbon-containing compound into contact with a three-dimensional continuous carbon fiber carrying the catalyst at a high temperature to form a carbon nanofiber on the three-dimensional continuous carbon fiber. A method for producing a carbon-based composite material comprising a porous support, a three-dimensional continuous carbon fiber, and a carbon nanofiber.   The method for producing a carbon-based composite material according to claim 6, wherein the carbon-based porous support used in the step (a) is carbon paper.   The method for producing a carbon-based composite material according to claim 6, wherein the polymerization in the step (a) is electrolytic oxidation polymerization.   The method for producing a carbon-based composite material according to claim 6, wherein the aromatic compound used in the step (a) is at least one selected from the group consisting of an aromatic amine compound and a heterocyclic compound. .   The method for producing a carbon-based composite material according to claim 9, wherein the aromatic compound used in the step (a) is at least one selected from the group consisting of aniline, pyrrole, thiophene, and derivatives thereof. .   The method for producing a carbon-based composite material according to claim 6, wherein the step (b) is performed in a non-oxidizing atmosphere.   The method for producing a carbon-based composite material according to claim 6, wherein the catalyst supported in the step (c) is at least one metal selected from the group consisting of Fe, Ni, and Co.   The method for producing a carbon-based composite material according to claim 6, wherein the catalyst is supported in the step (c) by electroplating or sputtering.   The method for producing a carbon-based composite material according to claim 6, wherein the step (d) is performed in a non-oxidizing atmosphere.   The carbon-type composite material manufactured by the method in any one of Claims 1-14.   The electrode for solid polymer fuel cells formed by carrying | supporting a metal on the carbon type composite material of Claim 15.   A polymer electrolyte fuel cell comprising the electrode according to claim 16.

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