Electrode material and method for manufacturing the same, electrode, membrane electrode assembly, and solid polymer fuel cell using the same

Abstract

An electrode material is provided that provides an electrode for a fuel cell with excellent electrode performance and durability. The electrode material is any one of the following electrode materials (A) or (B): Electrode material (A): comprising a porous composite support and electrode catalyst particles supported on the porous composite support, the porous composite support comprising: a carbon support composed of mesoporous carbon; and an electronically conductive oxide fixed to at least the inner surface and outer surface of the micropores of the mesoporous carbon, wherein a portion or all of the electrode catalyst particles are supported within the micropores of the mesoporous carbon via the electronically conductive oxide. Electrode material (B): comprising a carbon support composed of mesoporous carbon; and an electrode catalyst composite fixed to at least the inner surface and outer surface of the micropores of the mesoporous carbon, wherein the electrode catalyst composite comprises electrode catalyst particles and an electronically conductive oxide, the electronically conductive oxide being present in a manner that fills the spaces between the electrode catalyst particles.

Description

Technical Field

[0001] (Reference to relevant applications)

[0002] This application claims the interest and priority of Japanese Patent Application No. 2022-1995 (filed January 10, 2022) and Japanese Patent Application No. 2022-39083 (filed March 14, 2022). Priority to the aforementioned patent applications is expressly claimed, and the entire disclosure of those applications is incorporated herein by reference for various purposes. The entire contents of these Japanese patent applications are incorporated herein by reference.

[0003] This invention relates to an electrode material suitable for an electrode in a solid polymer fuel cell, an electrode, a membrane electrode assembly using the electrode material, and a solid polymer fuel cell. Background Technology

[0004] Regarding solid polymer fuel cells (PEFCs), fuel cell vehicles (FCVs) powered by PEFCs are already on the market, with the expectation of expanding and popularizing their applications in trucks, buses, and ships. PEFCs typically have the following structure: a membrane electrode assembly (MEA) consisting of a pair of electrodes positioned on both sides of a solid polymer electrolyte membrane, held together by spacers forming gas flow paths. The electrodes for fuel cells (especially PEFC electrodes) typically consist of an electrode catalyst layer and a gas diffusion layer that combines gas permeability and electron conductivity. The electrode catalyst layer contains electrode materials with electrode catalytic activity and a polymer electrolyte.

[0005] As a commonly used electrode material for PEFCs, electrode materials are made by dispersing and supporting electrode catalyst particles (typically Pt or Pt alloy particles) on a carbon-based support. In addition, in recent years, electrode materials using mesoporous carbon as the catalyst support framework and supporting Pt particles within the fine pores (mesopores) of the mesoporous carbon have attracted attention (e.g., Patent Documents 1 and 2). Mesoporous carbon has excellent electrical conductivity, facilitates gas diffusion, and has a high surface area; therefore, if used as a support for the electrode catalyst in solid polymer fuel cells, electrodes with excellent power generation performance can be obtained.

[0006] On the other hand, the electrolyte membrane of a PEFC is acidic (pH = 0–3), therefore the electrode materials of a PEFC are used in an acidic atmosphere. Furthermore, it is known that the battery voltage during normal operation is 0.4–1.0V, rising to 1.5V during start-up and shutdown. Under these operating conditions, the cathode and anode are in a region where the carbon-based material serving as the support decomposes into carbon dioxide (CO2). Therefore, in the cathode, a reaction occurs where the carbon support is electrochemically oxidized and decomposed into CO2. As a result, the carbon support is corroded (carbon corrosion), causing aggregation / detachment of Pt particles, the catalytically active component, which becomes a major cause of performance degradation in the fuel cell. Moreover, not only in the cathode but also in the anode, if the fuel gas is insufficient during the initial stages of operation, the voltage in that area may decrease, or concentration polarization may occur, locally creating a potential opposite to the normal value, leading to the electrochemical oxidation and decomposition of carbon.

[0007] Regarding the aforementioned corrosion problem of carbon supports, reports have been made of titanium dioxide (TiO2), a thermodynamically stable electronically conductive oxide under PEFC operating conditions (strong acidity, high potential), as an electrode material used as a support. For example, Patent Document 3 reports an electrode material for fuel cells that simultaneously generates Pt and electronically conductive oxide (TiO2) by using a hydrophobic acetylacetone coordination compound as a raw material, suppressing the particle growth of both Pt and TiO2, and generating an electrode catalyst composite containing nanoscale particles, which is then supported on a carbon support.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent No. 6969996

[0011] Patent Document 2: Japanese Patent No. 6931808

[0012] Patent Document 3: Japanese Patent Application Publication No. 2020-161272 Summary of the Invention

[0013] The problem the invention aims to solve

[0014] The electrode materials disclosed in Patent Documents 1 and 2, which are made by carrying Pt particles in the pores (mesopores) of mesoporous carbon, are considered to be less prone to Pt particle aggregation. However, since the Pt particles are in direct contact with and carried on the pore walls of the mesoporous carbon, the following problems exist: carbon corrosion cannot be avoided, and if power generation is carried out for a long time, it is impossible to prevent the aggregation / detachment of Pt particles caused by carbon corrosion.

[0015] Furthermore, in the electrode material of Patent Document 3, TiO2 constituting the electrode catalyst composite supported on a carbon support exhibits excellent durability under PEFC operating conditions. On the other hand, its electronic conductivity is not very high. Therefore, the electronic conductivity of the electrode catalyst composite containing TiO2 is insufficient, leaving room for improvement in order to obtain practical electrode performance.

[0016] In this context, the object of the present invention is to provide an electrode material, an electrode using the electrode material, a membrane electrode assembly, and a solid polymer fuel cell, wherein the electrode material provides an electrode with excellent electrode performance.

[0017] Technical solution

[0018] In order to solve the above problems, the inventors have repeatedly conducted in-depth research and found that the following invention meets the above objectives, thus completing the present invention.

[0019] That is, the present invention is as follows.

[0020] <1A> An electrode material comprising: a porous composite support and electrode catalyst particles supported on the porous composite support, wherein the porous composite support comprises: a carbon support composed of mesoporous carbon; and an electronically conductive oxide fixed to at least the inner surface of the micropores and the outer surface of the micropores of the mesoporous carbon, wherein a portion or all of the electrode catalyst particles are supported in the micropores of the mesoporous carbon via the electronically conductive oxide.

[0021] <2A> According to the electrode material of <1A>, wherein the mesoporous carbon has: a connecting hole in which part or all of the pores in the mesoporous region are interconnected with the pores in the adjacent mesoporous region.

[0022] <3A> The electrode material according to <1A> or <2A>, wherein the pore diameter of the mesoporous carbon is 3 nm or more and 40 nm or less.

[0023] <4A> The electrode material according to any one of <1A> to <3A>, wherein the electronically conductive oxide is an electronically conductive oxide mainly composed of tin oxide.

[0024] <5A> The electrode material according to any one of <1A> to <4A>, wherein the electronically conductive oxide comprises niobium-doped tin oxide.

[0025] <6A> The electrode material according to any one of <1A> to <5A>, wherein the particle size of the electronically conductive oxide fixed to the inner surface of the fine pores of the mesoporous carbon is 0.5 nm or more and 3 nm or less.

[0026] <7A> The electrode material according to any one of <1A> to <6A>, wherein the electrode catalyst particles are particles composed of Pt or an alloy containing Pt.

[0027] <8A> An electrode characterized in that it comprises an electrode material as described in any one of <1A> to <7A> and a proton-conducting electrolyte material.

[0028] <9A> A membrane electrode assembly comprising: a solid polymer electrolyte membrane; a cathode bonded to one side of the solid polymer electrolyte membrane; and an anode bonded to the other side of the solid polymer electrolyte membrane, wherein either or both of the anode or cathode are electrodes as described in <8A>.

[0029] <10A> A solid polymer fuel cell having a membrane electrode assembly as described in <9A>.

[0030] <11A> A method for manufacturing an electrode material, which is the method for manufacturing an electrode material as described in <1A>, includes the following steps (1A) to (4A).

[0031] Step (1A): A step in which mesoporous carbon, which serves as a carbon support, is mixed with an alkoxide compound that is an electronically conductive oxide precursor in a non-aqueous organic solvent until homogeneous, and then the solvent is removed by distillation and the mixture is dried.

[0032] Process (2A): The process involves treating the dried material obtained in process (1A) with steam to decompose the electronically conductive oxide precursor, followed by heat treatment, thereby obtaining a porous composite carrier with an electronically conductive oxide bonded to its surface.

[0033] Step (3A): The solution containing the porous composite support and electrode catalyst precursor obtained in step (2A) is mixed until homogeneous, and the solvent is removed by distillation to obtain the dried product.

[0034] Process (4A): The process of heat-treating the dried material obtained in process (3A) in an inert gas atmosphere.

[0035] <1B> An electrode material comprising: a carbon support composed of mesoporous carbon; and an electrode catalyst composite fixed to at least the inner surface of the micropores and the outer surface of the micropores of the mesoporous carbon, wherein the electrode catalyst composite comprises electrode catalyst particles and an electronically conductive oxide, the electronically conductive oxide being present in a manner that fills the spaces between the electrode catalyst particles.

[0036] <2B>According to the electrode material of <1B>, wherein the mesoporous carbon has: a connecting hole in which part or all of the pores in the mesoporous region are interconnected with the pores in the adjacent mesoporous region.

[0037] <3B> The electrode material according to <1B> or <2B>, wherein the pore diameter of the mesoporous carbon is 3 nm or more and 40 nm or less.

[0038] <4B> The electrode material according to any one of <1B> to <3B>, wherein the electronically conductive oxide is an electronically conductive oxide mainly composed of tin oxide.

[0039] <5B> The electrode material according to any one of <1B> to <4B>, wherein the electronically conductive oxide comprises niobium-doped tin oxide.

[0040] <6B> The electrode material according to any one of <1B> to <5B>, wherein the electrode catalyst particles constituting the electrode catalyst composite are particles with a particle size of 1 nm or more and 10 nm or less.

[0041] <7B> The electrode material according to <1B> to <6B>, wherein part or all of the electronically conductive oxide constituting the electrode catalyst complex is crystalline.

[0042] <8B> The electrode material according to any one of <1B> to <7B>, wherein the electrode catalyst particles are particles composed of Pt or an alloy containing Pt.

[0043] <9B> An electrode characterized in that it comprises an electrode material as described in any one of <1B> to <8B> and a proton-conducting electrolyte material.

[0044] <10B> A membrane electrode assembly comprising: a solid polymer electrolyte membrane; a cathode bonded to one side of the solid polymer electrolyte membrane; and an anode bonded to the other side of the solid polymer electrolyte membrane, wherein either or both of the anode or cathode are electrodes as described in <9B>.

[0045] <11B> A solid polymer fuel cell having a membrane electrode assembly as described in <10B>.

[0046] <12B> A method for manufacturing an electrode material, which is the method for manufacturing an electrode material as described in <1B>, includes the following steps (1B) to (2B).

[0047] Step (1B): Dissolving the acetylacetone coordination compound of the electrode catalyst metal precursor and the acetylacetone coordination compound of the electronically conductive oxide precursor in a dispersion prepared by dispersing the mesoporous carbon as a carbon support in a hydrophobic organic solvent, stirring and removing the solvent by distillation, thereby obtaining mesoporous carbon on which the electrode catalyst metal precursor and the electronically conductive oxide precursor are supported.

[0048] Step (2B): The mesoporous carbon supported on the electrode catalyst metal precursor and the electronically conductive oxide precursor obtained in step (1B) is heat-treated in an inert gas atmosphere to form an electrode catalyst composite.

[0049] <1C> An electrode material comprising: a carbon support; and an electrode catalyst composite supported on the surface of the carbon support via an electronically conductive oxide layer, the carbon support being mesoporous carbon or particle-shaped solid carbon, the electrode catalyst composite comprising electrode catalyst particles and an electronically conductive oxide, the electronically conductive oxide being present in a manner that fills the spaces between the electrode catalyst particles.

[0050] <2C> According to the electrode material described in <1C>, the electronically conductive oxide layer is composed of an electronically conductive oxide mainly composed of an oxide of a metal element selected from tin (Sn), molybdenum (Mo), niobium (Nb), tantalum (Ta), titanium (Ti), and tungsten (W).

[0051] <3C> The electrode material according to <2C>, wherein the electronically conductive oxide layer comprises niobium-doped tin oxide.

[0052] <4C> The electrode material according to any one of <1C> to <3C>, wherein the electrode catalyst particles constituting the electrode catalyst composite are composed of Pt or an alloy containing Pt.

[0053] <5C> The electrode material according to any one of <1C> to <4C>, wherein the electrode catalyst particles constituting the electrode catalyst composite are particles with a particle size of 1 nm or more and 10 nm or less.

[0054] <6C> The electrode material according to any one of <1C> to <5C>, wherein the electronically conductive oxide constituting the electrode catalyst complex is an electronically conductive oxide mainly composed of tin oxide.

[0055] <7C> According to the electrode material of <6C>, wherein the electronically conductive oxide constituting the electrode catalyst complex comprises niobium-doped tin oxide.

[0056] <8C> The electrode material according to any one of <1C> to <7C>, wherein part or all of the electronically conductive oxide constituting the electrode catalyst complex is crystalline.

[0057] <9C> An electrode comprising: an electrode material as described in any one of <1C> to <8C> and a proton-conducting electrolyte material.

[0058] <10C> A membrane electrode assembly comprising: a solid polymer electrolyte membrane; a cathode bonded to one side of the solid polymer electrolyte membrane; and an anode bonded to the other side of the solid polymer electrolyte membrane, wherein either or both of the anode or cathode are electrodes as described in <9C>.

[0059] <11C> A solid polymer fuel cell having a membrane electrode assembly as described in <10C>.

[0060] <12C> A method for manufacturing an electrode material, which is the method for manufacturing an electrode material as described in <1C>, comprising the following steps (1C) to (3C).

[0061] Process (1C): The process of forming an electronically conductive oxide layer on a carbon support.

[0062] Step (2C): The acetylacetone coordination compound of the electrode catalyst metal precursor and the acetylacetone coordination compound of the electronically conductive oxide precursor are dissolved in a dispersion obtained by dispersing the carbon support with the electronically conductive oxide layer obtained in step (1C) in a hydrophobic organic solvent. The mixture is stirred and the solvent is removed by distillation, thereby obtaining a carbon support on which the electrode catalyst metal precursor and the electronically conductive oxide precursor are supported.

[0063] Step (3C): The carbon support containing the electrode catalyst metal precursor and the electronically conductive oxide precursor obtained in step (2C) is heat-treated in an inert gas atmosphere to form the electrode catalyst composite.

[0064] Beneficial effects

[0065] According to the present invention, an electrode material is provided, as well as an electrode, a membrane electrode assembly and a solid polymer fuel cell using the electrode material, wherein the electrode material provides an electrode with excellent electrode performance. Attached Figure Description

[0066] Figure 1A (a) is a conceptual schematic diagram of the electrode material (A) of the present invention. Figure 1A (b) is an enlarged schematic diagram of the vicinity of the pores (electron-conducting oxide dispersion fixation). Figure 1A (c) is an enlarged schematic diagram of the vicinity of the pore (electron-conducting oxide continuous bonding (coating)).

[0067] Figure 1B (a) is a conceptual schematic diagram of the electrode material (B) of the present invention. Figure 1B (b) is an enlarged schematic diagram of the vicinity of the pore.

[0068] Figure 1C (a) is a conceptual schematic diagram of the electrode material (C) of the present invention. Figure 1C (b) is an enlarged schematic diagram of the surface. Figure 1C (c) is an enlarged schematic diagram of the vicinity of the pore.

[0069] Figure 2 This is a cross-sectional schematic diagram of the membrane electrode assembly of the present invention.

[0070] Figure 3 This is a conceptual diagram illustrating a representative structure of the solid polymer fuel cell of the present invention.

[0071] Figure 4 This is a flowchart of the preparation steps for the electrode material (without supporting electrode catalyst) in the embodiment.

[0072] Figure 5 The electrode material of Example 1A (without supported electrode catalyst, "Sn") 0.9 Nb 0.1 FESEM image (left) and STEM image (right) of O2 / MC”.

[0073] Figure 6 (a) is an FESEM image (high magnification) of the electrode material (without supported electrode catalyst) of Example 2A. Figure 6 (b) is Figure 6 A magnified photograph of the area (inside the fine hole (medium hole)) of the dashed line portion in (a).

[0074] Figure 7 This is a schematic diagram showing the electron-conducting oxides within the pores (mesopores) of mesoporous carbon.

[0075] Figure 8 The electrode material (Pt / Sn) of Example 1A 0.9 Nb 0.1 FESEM image (left) and STEM image (right) of O2 / MC.

[0076] Figure 9 These are FESEM images (left) and STEM images (right) of the electrode material (Pt / MC) of Comparative Example 1.

[0077] Figure 10The electrode material of Example 2A (supported by Pt, "Pt / Sn") 0.98 Nb 0.02 STEM images of O2 / MC”), Figure 10 (a) is the outer surface. Figure 10 (b) is the interior of the central hole.

[0078] Figure 11 The electrode material (Pt / Sn) of Example 1A 0.9 Nb 0.1 Cyclic voltammograms (CV) of the electrode material (O2 / MC) and Comparative Example 1 (Pt / MC).

[0079] Figure 12 The image shows a linear scan voltammetry (1600 rpm) of the electrode materials of Example 1A and Comparative Example 1.

[0080] Figure 13 This is a diagram showing the conditions for starting and stopping a cyclic test.

[0081] Figure 14 This is a graph showing the ECSA changes (relative values) of the electrode materials of Example 1A and Comparative Example 1 during the start-stop cycle test.

[0082] Figure 15 The images are FESEM (top) and STEM (bottom) images of the electrode material (Pt / MC) of Comparative Example 1 before and after the start-stop cycle test (20,000 cycles).

[0083] Figure 16 The electrode material (Pt / Sn) of Example 1A 0.9 Nb 0.1 FESEM images (top) and STEM images (bottom) before and after the start-stop cycle test of O2 / MC (60,000 cycles).

[0084] Figure 17 This is a flowchart of the electrode material fabrication steps for Experiment 1B and Experiment 2B.

[0085] Figure 18 These are the heat treatment conditions used in the fabrication of the electrode materials for the experimental example.

[0086] Figure 19 The X-ray diffraction (XRD) patterns of the electrode materials in the experimental examples are shown in Experiment 1B: Pt-SnO2 / MC and Experiment A2: Pt-SnO2 / CB (Vulcan).

[0087] Figure 20 These are scanning transmission electron microscopy (STEM) images and EDS mappings of the electrode material (Pt-SnO2 / CB(Vulcan)) in Experimental Example 2B.

[0088] Figure 21 This is a high-angle scattering dark-field scanning transmission electron microscope (HAADF-STEM) image of the electrode material in Experiment Example 2B.

[0089] Figure 22 These are STEM images and EDS mappings of the electrode material (Pt-SnO2 / MC) in Experimental Example 1B.

[0090] Figure 23 This is a HAADF-STEM image of the electrode material in Experiment Example 1B.

[0091] Figure 24 This is a STEM image of the electrode material (Pt-SnO2 / MC) in Experimental Example 1B. Figure 24 (a) is the front side of MC (0nm). Figure 24 (b) is the interior of the mesopore (-170nm). Figure 24 (c) is the interior of the mesopore (-290nm). Figure 24 (d) is the back side of MC (-414nm) (the focal length in parentheses is the focal length when the front side of MC is set to 0nm).

[0092] Figure 25 These are cyclic voltammograms (CV) of the electrode material (Pt-SnO2 / MC) in Experimental Example 1B and the electrode material (Pt-SnO2 / CB(Vulcan)) in Experimental Example 2B.

[0093] Figure 26 These are linear sweep voltammetry (LSV, 1600 rpm) plots of the electrode materials for Experimental Example 1B and Experimental Example 2B.

[0094] Figure 27 The LSV (1600 rpm) of the electrode materials of Experimental Example 1B and Comparative Example 1 before and after the start-stop cycle test (Experimental Example 1B: Pt-SnO2 / MC, Comparative Example 1: Pt / MC).

[0095] Figure 28 This is a diagram showing the conditions of a load variation cyclic test.

[0096] Figure 29 The LSV (1600 rpm) of the electrode materials of Experimental Example 1B and Comparative Example 1 before and after the load variation cycle test (Experimental Example 1B: Pt-SnO2 / MC, Comparative Example 1: Pt / MC).

[0097] Figure 30The XRD patterns of the electrode materials in the experimental examples are shown in Experimental Example 1C: Pt-SnO2 / Sn(Nb)O2 / GCB, Experimental Example 2C: Pt-SnO2 / Sn(Nb)O2 / CB(Vulcan)).

[0098] Figure 31 This is a field emission scanning electron microscope (FESEM) image of the electrode material (Pt-SnO2 / Sn(Nb)O2 / GCB) of Experimental Example 1C.

[0099] Figure 32 This is an FESEM image of the electrode material (Pt-SnO2 / Sn(Nb)O2 / CB(Vulcan)) of Experimental Example 2C.

[0100] Figure 33 This is a graph showing the ECSA changes of the electrode materials in Experimental Example 1C and Comparative Example 2 during the start-stop cycle test (Experimental Example 1C: Pt-SnO2 / Sn(Nb)O2 / GCB, Comparative Example 2: Pt / C (Made by Tanaka Precious Metals Industry Co., Ltd., TEC10E50E)).

[0101] Explanation of reference numerals in the attached figures

[0102] 1A, 1B, 1C: Electrode materials;

[0103] 2: Carbon support (mesoporous carbon);

[0104] 2A: Carbon carrier (solid carbon);

[0105] 2a: Inner surface of the fine pore;

[0106] 2b: Outer surface of the pore;

[0107] 2c: Electron-conducting oxide layer;

[0108] 3: Electrode catalyst complex;

[0109] 3a: Electron-conducting oxide;

[0110] 3b: Electrode catalyst particles;

[0111] 4: Electrode (cathode);

[0112] 4a: Electrode catalyst layer (cathode);

[0113] 4b: Gas diffusion layer;

[0114] 5: Electrode (Anode);

[0115] 5a: Electrode catalyst layer (anode);

[0116] 5b: Gas diffusion layer;

[0117] 6: Solid polymer electrolyte membrane;

[0118] 10: Membrane electrode assembly (MEA);

[0119] 20: Solid polymer fuel cells;

[0120] 21: External circuitry;

[0121] P: Fine pore (medium pore). Detailed Implementation

[0122] The present invention will now be described in detail with examples. It should be noted that the present invention is not limited to the embodiments described below, and can be implemented in any way without departing from the spirit of the invention. The dimensions, materials, and other specific values ​​shown in the embodiments are merely examples for easy understanding of the invention and are not intended to limit the invention, unless specifically stated otherwise.

[0123] Furthermore, throughout all the accompanying drawings, the same reference numerals are used to denote the same constituent elements, and descriptions are appropriately omitted. Additionally, when the symbol “~” is used in this specification, it is used to indicate the numerical values ​​preceding and following it.

[0124] (Definitions of terms, etc.)

[0125] In this specification, "carbon support" refers to porous carbon material that forms the framework (base) of the electrode material.

[0126] In this specification, "fine pore" refers to, for example, pores with a diameter of 150 nm or less (especially pores with a diameter of 100 nm or less). "Fine pores in the mesopore region" refers to fine pores with a diameter of 2 nm to 50 nm. Furthermore, in this specification, "fine pores in the micropore region" refers to fine pores with a diameter of less than 2 nm, and "fine pores in the macropore region" refers to fine pores with a diameter greater than 50 nm but less than 150 nm.

[0127] Furthermore, in this specification, when referred to as "M oxide" (where M is a metallic element), the form of M oxide is not limited to crystals; the concept includes any of the following: crystals, amorphous substances, and mixtures of crystals and amorphous substances. For example, Sn oxides include SnO2 crystals, oxygen non-stoichiometric oxides (denoted as "SnOx"), and mixtures thereof.

[0128] Furthermore, in this specification, the cathode conditions of a solid polymer fuel cell (PEFC) refer to the cathode conditions during normal operation of the PEFC, which are conditions where the temperature is approximately room temperature to 150°C and an oxygen-containing gas such as air is supplied (oxidizing atmosphere). The anode conditions refer to the anode conditions during normal operation of the PEFC, which are conditions where the temperature is approximately room temperature to 150°C and a hydrogen-containing fuel gas is supplied (reducing atmosphere).

[0129] <1. Electrode Materials>

[0130] The present invention relates to the following electrode materials (A) and (B).

[0131] Electrode material (A):

[0132] The invention comprises: a porous composite support and electrode catalyst particles supported on the porous composite support, wherein the porous composite support comprises: a carbon support composed of mesoporous carbon; and an electronically conductive oxide fixed to at least the inner surface of the micropores and the outer surface of the micropores of the mesoporous carbon, wherein a portion or all of the electrode catalyst particles are supported in the micropores of the mesoporous carbon via the electronically conductive oxide.

[0133] Electrode material (B):

[0134] The invention comprises: a carbon support composed of mesoporous carbon; and an electrode catalyst composite fixed to at least the inner surface of the micropores and the outer surface of the micropores of the mesoporous carbon, wherein the electrode catalyst composite comprises electrode catalyst particles and an electronically conductive oxide, the electronically conductive oxide being present in such a way that it fills the spaces between the electrode catalyst particles.

[0135] Here, "fixed" means that the electronically conductive oxide (in the case of electrode catalyst (A)) or the electrode catalyst complex (in the case of electrode catalyst (B)) is fixed to the inner and outer surfaces of the pores of the carbon support to a degree that makes it difficult to detach (peel off).

[0136] In electrode material (A), an electronically conductive oxide is fixed in a manner that coats part or all of the inner surface of the micropores in the mesoporous region of the mesoporous carbon, and electrode catalyst particles are supported on this electronically conductive oxide. That is, the electrode catalyst particles are supported within the micropores of the mesoporous region of the mesoporous carbon via the electronically conductive oxide. It should be noted that in electrode material (A), the electrode catalyst particles can not only be supported inside the micropores of the mesoporous region, but also on the micropores outside the micropores of the mesoporous region, or on the outer surface, via the electronically conductive oxide.

[0137] The morphology of the electron-conducting oxides after bonding can be any shape, such as particle-like, island-like, or thin-film, as long as it does not impair the purpose of this invention. "Island-like" refers to a state in which several particle-like electron-conducting oxides are packed together and separated, while "film-like" refers to a state in which electron-conducting oxides are continuously connected to form a thin film.

[0138] In electrode material (B), the electrode catalyst composite comprising electrode catalyst particles and electronically conductive oxides is fixed in a manner that covers part or all of the inner surface of the micropores in the mesoporous region of the mesoporous carbon. It should be noted that in electrode material (B), the electrode catalyst composite can be fixed not only inside the micropores of the mesoporous region, but also outside the micropores or on the outer surface of the mesoporous region.

[0139] The morphology of the bonded electrode catalyst composite can be any shape, such as particle-like, island-like, or film-like, as long as it does not impair the purpose of this invention. "Island-like" refers to a state in which several particle-like electrode catalyst composites are formed into a block and are separated, while "film-like" refers to a state in which the electrode catalyst composites are continuously connected to form a thin film.

[0140] The first embodiment (electrode material (A)) and the second embodiment (electrode material (B)) of the present invention share the following characteristics: "Mesoporous carbon is used as the carbon support for the skeleton of the electrode material, and electrode catalyst particles and electronically conductive oxides are present in the pores of the mesoporous carbon."

[0141] Furthermore, they differ in the following aspects: in electrode material (A), "part or all of the electrode catalyst particles are supported in the pores of mesoporous carbon via electronically conductive oxides," while in electrode material (B), "part or all of the electrode catalyst particles are fixed in the pores of mesoporous carbon in the form of an electrode catalyst complex."

[0142] Furthermore, the present invention relates to the following electrode material (C).

[0143] Electrode material (C):

[0144] The invention comprises: a carbon support; and an electrode catalyst composite supported on the surface of the carbon support via an electronically conductive oxide layer, the carbon support being mesoporous carbon or solid carbon in particle form, the electrode catalyst composite comprising electrode catalyst particles and an electronically conductive oxide, the electronically conductive oxide being present in such a way that it fills the spaces between the electrode catalyst particles.

[0145] The electrode material (C) has the following characteristics: an electronically conductive oxide layer is present on the surface (inner surface of the pores, outer surface of the pores) of the carbon support, and the electrode catalyst composite is fixed to the carbon support via this electronically conductive oxide layer.

[0146] It should be noted that in electrode material (C), when the carbon support is mesoporous carbon, it has the same characteristics as electrode material (A) and electrode material (B) as described above in the following aspects: "The carbon support that serves as the framework of the electrode material is mesoporous carbon, and electrode catalyst particles and electronically conductive oxides are present in the pores of the mesoporous carbon."

[0147] In the following description, electrode material (A) is sometimes referred to as the electrode material of the present invention (first embodiment), electrode material (B) is sometimes referred to as the electrode material of the present invention (second embodiment), and electrode material (C) is sometimes referred to as the electrode material of the present invention (third embodiment). In addition, they are sometimes collectively referred to as "electrode material of the present invention".

[0148] The electrode materials of the present invention (electrode materials (A) to (C)) all have the following common characteristic effects: suppressing the expansion caused by the aggregation of electrode catalyst particles, and possessing both the excellent durability against electrochemical oxidation brought by electronically conductive oxides and the excellent electronic conductivity brought by carbon materials.

[0149] The electrode material of the present invention is suitable as an electrode material for use in solid polymer fuel cells, but can also be used for other applications (e.g., electrodes for solid polymer water electrolysis).

[0150] Hereinafter, suitable embodiments of the present invention will be described in detail based on the accompanying drawings. It should be noted that the following description assumes that the electrode material of the present invention is used as an electrode for a solid polymer fuel cell (PEFC).

[0151] <Electrode Material (A)>

[0152] Hereinafter, the electrode material (A) of the first embodiment of the electrode material of the present invention will be described.

[0153] As described above, electrode material (A) is an electrode material comprising: a porous composite support and electrode catalyst particles supported on the porous composite support, wherein the porous composite support comprises: a carbon support composed of mesoporous carbon; and an electronically conductive oxide fixed to at least the inner surface of the micropores and the outer surface of the micropores of the mesoporous carbon, wherein a portion or all of the electrode catalyst particles are supported in the micropores of the mesoporous carbon via the electronically conductive oxide.

[0154] Figure 1A (a) is a schematic diagram showing a representative structure of electrode material (A). Figure 1A (b) and Figure 1A (c) is an enlarged schematic diagram of the vicinity of the pore.

[0155] like Figure 1A As shown in (a), the electrode material 1A of the present invention is composed of a porous composite support and electrode catalyst particles 3b supported on an electronically conductive oxide 3a. The porous composite support includes: mesoporous carbon 2 as a carbon support; and particle-shaped electronically conductive oxide 3a, which is fixed to the mesoporous carbon 2 (the inner surface 2a and the outer surface 2b of the pores).

[0156] It should be noted that, Figure 1A The electrode material 1A shown in (a) also has an electronically conductive oxide 3a and electrode catalyst particles 3b dispersed on the outer surface 2b, but the electronically conductive oxide 3a and electrode catalyst particles 3b may also exist only on the inner surface 2a of the pores.

[0157] The mesoporous carbon 2 (hereinafter, sometimes referred to as "the mesoporous carbon of the present invention") that serves as the framework of electrode material 1A is a porous carbon with fine pores having many mesoporous regions.

[0158] Porous carbon with fine pores having a mesopore region (2-50 nm) can be used as mesopore carbon 2, preferably with a pore diameter of 3 nm or more and 40 nm or less. If it is within this range, even if an electron-conducting oxide or electrode catalyst is fixed (supported) on the inner wall of the pore, the diffusion of substances into the pore will not be significantly hindered and will proceed smoothly.

[0159] Furthermore, when fabricating the electrode for a fuel cell as described below, the electrode material of the present invention is mixed with a proton-conductive electrolyte material (ionomer). The proton-conductive electrolyte material (ionomer) is tens of nm in size, and therefore cannot penetrate into the mesopores with small pore diameters. Thus, poisoning of the electrode catalyst metal, which originates from the ionomer, by means of the electron-conductive oxide supported in the pores of the mesoporous carbon can be suppressed.

[0160] The mesoporous carbon of the present invention may also include regions other than the fine pores in the mesoporous region (2nm to 50nm) (micropore region, macropores), but preferably the mesoporous region has a higher proportion of fine pores.

[0161] The structure of the micropores in mesoporous carbon (pore diameter, shape, etc.) can be confirmed by observation using an electron microscope. Examples of electron microscopes include field emission scanning electron microscopy (FESEM) and scanning transmission electron microscopy (STEM).

[0162] In addition to being individual pores independent of other micropores, the micropores in the mesoporous carbon 2 also have interconnecting pores, where part or all of the micropores in the mesoporous region are interconnected with the micropores in adjacent mesoporous regions, preferably having a three-dimensional mesh structure. The presence of these interconnecting pores promotes the diffusion of substances within the micropores of the mesoporous carbon.

[0163] The size and shape of electrode material 1A depend on the size and shape of the mesoporous carbon that forms its framework. The size and shape of the mesoporous carbon are determined within a range that allows the electrode materials to be in continuous contact when forming the electrode for a fuel cell, and to create a space that allows for the smooth diffusion of gases such as hydrogen and oxygen and the removal of water (vapor) within the electrode for a fuel cell.

[0164] The mesoporous carbon used in the electrode material for the fuel cell of the present invention can be synthesized appropriately or commercially available products can be used. Examples of commercially available products include, for instance, the CNovel series manufactured by Toyo Carbon Co., Ltd. (designed mesoporous diameter: 5–150 nm), which uses MgO as a mold for mesoporous carbon.

[0165] (Electron-conducting oxides)

[0166] like Figure 1A As shown, in the electrode material 1A of this embodiment, the electronically conductive oxide 3a is fixed to the inner surface 2a of the fine pores in the mesoporous region of the mesoporous carbon 2. Furthermore, in the electrode material 1A of this embodiment, the electronically conductive oxide 3a is also fixed to the outer surface of the mesoporous carbon 2, but the electronically conductive oxide on the outer surface is not mandatory.

[0167] The optimal amount of electron-conducting oxides varies depending on the physical properties of the electron-conducting oxides, such as particle size (film thickness in the case of thin films) and surface area, as well as the manufacturing method of the electron-conducting oxides. Therefore, it should be appropriately determined within the range that can support a sufficient amount of electrode catalyst particles.

[0168] The size of the electron-conducting oxide within the micropores is determined within a range that does not clog the micropores of the mesoporous carbon 2 and does not impede the movement of substances such as gases. Although it also depends on the micropore diameter of the mesoporous carbon 2, the size of the electron-conducting oxide fixed to the inner surface of the micropores is preferably 0.5 nm or more and 3 nm or less.

[0169] The electronically conductive oxide 3a on the outer surface does not substantially participate in the blockage of the mesopores, and therefore can be larger than the electronically conductive oxide inside the fine pores. However, to reduce resistance, it is preferable to have a small particle size within a range that can disperse the electrode catalyst particles 3b. In the case of an electronically conductive oxide with an outer surface, its size is preferably 0.5 nm or more and 10 nm or less.

[0170] It should be noted that the "average particle size of particulate electronically conductive oxides" can be obtained from the average particle size of any 20 particulate electronically conductive oxides investigated by electron microscopy images.

[0171] It should be noted that, in Figure 1AIn (a) and (b), the electronically conductive oxide 3a is a particle-shaped electronically conductive oxide dispersed and fixed in mesoporous carbon 2, but it is not limited to this; the electronically conductive oxide 3a only needs to be fixed in mesoporous carbon 2. For example, it can also be as follows: Figure 1A As in (c), the electronically conductive oxide 3a is fixed in a way that it is non-dispersed and continuously coated on the surface of the mesoporous carbon 2 (especially the inner surface of the micropores).

[0172] That is, in the electrode material (A) of the first embodiment of the electrode material of the present invention, the morphology of the electron-conducting oxide after fixation can be any morphology such as particle, island, or thin film, as long as it does not impair the purpose of the present invention.

[0173] As an electronically conductive oxide constituting the electronically conductive oxide 3a, it is sufficient to have both adequate durability and electronic conductivity under at least one of the anode and cathode conditions of a fuel cell (especially a solid polymer fuel cell).

[0174] Specifically, electronically conductive oxides that are predominantly composed of a parent oxide can be listed as such: selected from tin oxide, molybdenum oxide, niobium oxide, tantalum oxide, titanium oxide, and tungsten oxide. Here, in this invention, "predominantly composed of a parent oxide" refers to (A) an electronically conductive oxide consisting solely of a parent oxide; and (B) an electronically conductive oxide doped with other elements and containing 80 mol% or more of the parent oxide.

[0175] Specifically, doping elements include: Sn, Ti, Sb, Nb, Ta, W, In, V, Cr, Mn, Mo, etc. (where Sb is an element different from the parent oxide). The doping element is an element with a higher valence than the parent oxide. For example, if the parent oxide is titanium oxide, then among the doping elements mentioned above, elements other than Ti (such as Nb) are selected.

[0176] Among them, the electronically conductive oxide 3a is preferably an oxide mainly composed of tin oxide. Here, "mainly composed of oxide" means an oxide containing 50 mol% or more of the desired oxide.

[0177] In this case, when the electron-conducting oxide is an oxide mainly composed of tin oxide, it is preferable to use the electrode for fuel cells of the present invention as a cathode.

[0178] Tin (Sn) as an element is thermodynamically stable as an oxide (SnO2) under the cathode conditions of a PEFC, and does not undergo oxidative decomposition. Furthermore, tin oxide possesses sufficient electronic conductivity, making it a suitable support for highly dispersed electrode catalyst particles (especially noble metal particles).

[0179] It should be noted that when the electrode for fuel cells of the present invention is used as the anode, the oxide, which is mainly composed of tin oxide, is reduced to metallic Sn under the anodic conditions of PEFC, which is therefore not preferred.

[0180] Among oxides with tin oxide as the main component, niobium-doped tin oxide with 0.1 to 20 mol% niobium (Nb) is particularly preferred in terms of forming electrodes for fuel cells with superior electrode performance.

[0181] (Electrode catalyst particles)

[0182] Electrode catalyst particles 3b are selectively dispersed and supported on electron-conducting oxide 3a. Here, "selectively dispersed and supported on electron-conducting oxide" means that at least 80%, preferably 90%, and more preferably 95% or more (including 100%) of all electrode catalyst particles are supported on electron-conducting oxide. The proportion of electrode catalyst particles supported on electron-conducting oxide can be evaluated by observing the fuel cell electrode material to be evaluated using an electron microscope, selecting any observed electrode catalyst particles (100 or more), and counting the number of particles supported on electron-conducting oxide and the number supported on mesoporous carbon.

[0183] The electrode catalyst particles 3b can be any type of catalyst, either noble metal-based or non-noble metal-based, as long as they possess electrochemical catalytic activity for oxygen reduction (and hydrogen oxidation). Preferably, they are selected from noble metals such as Pt, Ru, Ir, Pd, Rh, Os, Au, and Ag, and alloys containing these noble metals. It should be noted that "alloys containing noble metals" includes: "alloys composed solely of the aforementioned noble metals" and "alloys composed of the aforementioned noble metals and metals other than the aforementioned noble metals, containing 10% by mass or more of the aforementioned noble metals." The "metals other than the aforementioned noble metals" alloyed with noble metals are not particularly limited; examples include Co, Ni, W, Ta, Nb, and Sn, and one or more of these can be used. Furthermore, two or more of the aforementioned noble metals and alloys containing noble metals can be used in a phase-separated state. It should be noted that in this specification, the aforementioned noble metals and alloys containing these noble metals are sometimes referred to as "electrode catalyst metals."

[0184] Among electrode catalyst metals, Pt and Pt-containing alloys exhibit high electrochemical catalytic activity for oxygen reduction (and hydrogen oxidation) in the temperature range of around 80°C, which is the operating temperature of solid polymer fuel cells, and are therefore particularly preferred.

[0185] The shape of the electrode catalyst particle 3b is not particularly limited and can be the same as that of known electrode catalyst particles. Specific shapes include spherical, elliptical, polyhedral, core-shell structure, etc. Furthermore, the structure of the electrode catalyst particle 3b is not limited to crystals; it can be amorphous or a mixture of crystalline and amorphous materials.

[0186] The smaller the size of the electrode catalyst particles 3b, the greater the effective surface area for electrochemical reactions, thus tending to increase electrochemical catalytic activity. However, if the size of the electrode catalyst particles 3b is too small, the electrochemical reaction activity decreases. Therefore, the size of the electrode catalyst particles 3b, in terms of average particle size, is preferably 0.5–4 nm.

[0187] It should be noted that the "average particle size of the electrode catalyst particles" in this invention can be obtained from the average particle size of 20 electrode catalyst particles investigated by electron microscope images. When calculating the average particle size using electron microscope images, if the shape of the particle is not spherical, the length in the direction representing the maximum length of the particle is taken as its particle size.

[0188] The loading of electrode catalyst particles should be appropriately determined considering factors such as the type of catalyst and the size (thickness) of the electronically conductive oxide supporting it. If the catalyst loading is too low, the electrode performance may be insufficient; if the catalyst loading is too high, the electrode catalyst particles may aggregate, resulting in reduced performance.

[0189] If the loading of electrode catalyst particles relative to the total weight of electrode material is preferably 0.1 to 60% by mass, more preferably 0.5 to 20% by mass, then the catalytic activity per unit mass is excellent, and the desired electrode reaction activity corresponding to the loading can be obtained.

[0190] Furthermore, the loading of electrode catalyst particles is typically 3–40% by mass relative to the electron-conducting oxide. Within this range, excellent catalytic activity per unit mass is achieved, yielding the desired electrochemical catalytic activity corresponding to the loading.

[0191] When the loading is less than 3% by mass, insufficient electrode reactivity occurs. When the loading is greater than 40% by mass, agglomeration of electrode catalyst particles easily occurs, reducing the effective surface area for the electrochemical reactions of oxygen and hydrogen. It should be noted that the loading of electrode catalyst particles can be investigated, for example, by inductively coupled plasma light emission analysis (ICP).

[0192] (Manufacturing method of electrode material (A))

[0193] The manufacturing method of the electrode material (A) of the present invention described above is not particularly limited. As long as an appropriate and preferred method is selected according to the type of mesoporous carbon, electronically conductive oxide, and electrode catalyst particles constituting the electrode material (A), the method of loading the electronically conductive oxide onto the mesoporous carbon and then loading the electrode catalyst particles onto the electronically conductive oxide is generally adopted.

[0194] A preferred example of the manufacturing method of the electrode material (A) of the present invention (hereinafter, sometimes referred to as "the manufacturing method (A) of the present invention") is a manufacturing method including the steps (1A) to (4A) described below.

[0195] Step (1A): A step in which mesoporous carbon, which serves as a carbon support, is mixed with an alkoxide compound that is an electronically conductive oxide precursor in a non-aqueous organic solvent until homogeneous, and then the solvent is removed by distillation and the mixture is dried.

[0196] Process (2A): The process involves treating the dried material obtained in process (1A) with steam to decompose the electronically conductive oxide precursor, followed by heat treatment, thereby obtaining a porous composite carrier with an electronically conductive oxide bonded to its surface.

[0197] Step (3A): The solution containing the porous composite support and electrode catalyst precursor obtained in step (2A) is mixed until homogeneous, and the solvent is removed by distillation to obtain the dried product.

[0198] Process (4A): The process of heat-treating the dried material obtained in process (3A) in an inert gas atmosphere.

[0199] The manufacturing method (A) of the present invention will now be described in detail.

[0200] In step (1A), the mesoporous carbon, which serves as a carbon support, is mixed with an alkoxide compound that is an electronically conductive oxide precursor in a non-aqueous organic solvent until homogeneous, and then the solvent is removed by distillation and the mixture is dried.

[0201] As described above, mesoporous carbon as a carbon carrier has fine pores (diameter of 2nm to 50nm) in the mesoporous region. Aqueous solvents do not easily penetrate into these fine pores, but by using non-aqueous organic solvents, alkoxide compounds can be penetrated into the fine pores.

[0202] Therefore, by using alkoxide compounds as electronically conductive oxide precursors, dissolving them together with mesoporous carbon in a non-aqueous organic solvent and mixing them, and then removing the non-aqueous organic solvent by distillation, the alkoxide compounds can be dried while adsorbed on the surface of the mesoporous carbon (especially the inner surface of the pores).

[0203] As a precursor for an electronically conductive oxide, an alkoxide compound containing a metal corresponding to the target electronically conductive oxide can be used.

[0204] For example, when the electron-conducting oxide is a Sn oxide, tin ethoxide, tin propoxide, tin butoxide, tin methoxyethoxide, and tin ethoxyethoxide can be used as alkoxide compounds. Among these, tin ethoxide is preferred.

[0205] For example, if the target electronically conductive oxide is a Sn oxide containing niobium oxide, the niobium alkoxide compound can be used in conjunction with the aforementioned tin alkoxide compound.

[0206] Niobium alkoxide compounds such as niobium methoxide, niobium ethanol, niobium propoxide, niobium butoxide, niobium methoxyethanol, and niobium ethoxyethanol can be used. Among them, niobium ethanol is preferred.

[0207] Non-aqueous organic solvents are acceptable as long as they do not react with alkoxides. Examples include acetone, acetylacetone, toluene, xylene, and kerosene.

[0208] Non-aqueous organic solvents are preferably substantially free of water. Here, "substantially free of water" means that trace amounts of water, including impurities such as hydrophilic solvents, are not excluded, but also includes situations where the proportion of water in the solvent has been minimized through the usual industrial efforts made by those skilled in the art.

[0209] The concentrations of mesoporous carbon and electronically conductive oxide precursors can be appropriately determined within the range that allows for the fabrication of electrode material (A).

[0210] The method of removing the solvent by distillation is arbitrary as long as it does not impair the purpose of the present invention, but distillation by reduced pressure is preferred.

[0211] In step (2A), firstly, the electronically conductive oxide precursors (alkoxide compounds) adsorbed on the surface (inner surface of the pores, outer surface of the pores) of the dried material obtained in step (1A) are hydrolyzed by steam treatment. Here, "steam treatment" refers to the reaction occurring through contact with a gas containing water vapor.

[0212] The gas used for steam treatment is an inert gas such as nitrogen, helium, or argon, with nitrogen being the most common.

[0213] The gas used for steam treatment preferably contains 0.5% to 90% (preferably 1% to 20%) of water vapor.

[0214] After hydrolysis using steam treatment, heat treatment is carried out to convert the hydrolysate of alkoxide compounds (mainly hydroxides) into the target electronically conductive oxide.

[0215] The heat treatment temperature can be any temperature above that at which the hydrolysate of the alkoxide is converted into an oxide. The appropriate temperature should be selected by taking into account factors such as the electron conductivity of the oxide and the type of its precursor.

[0216] In the case of Sn oxide, the heat treatment temperature is 350°C or higher, preferably 400°C or higher, and more preferably 500°C or higher. The upper limit temperature is 700°C or lower, preferably 650°C or lower.

[0217] The atmosphere at the heat treatment temperature should be one in which the hydrolysate of alkoxides is converted into oxides, without affecting the electron-conducting oxides or carbon support. Typically, inert gas atmospheres such as nitrogen, helium, and argon are used.

[0218] In step (3A), the solution containing the porous composite support and electrode catalyst precursor obtained in step (2A) is mixed until homogeneous, and the solvent is removed by distillation to obtain a dried product. Through step (3A), the electrode catalyst particle precursor is supported on the electronically conductive oxide in the porous composite support (mesoporous carbon with electronically conductive oxides fixed on its surface).

[0219] There are no restrictions on the electrode catalyst precursor in step (3A) as long as it does not impair the purpose of the present invention. However, depending on the electrode catalyst precursor, the purpose of the present invention may not be achieved in some cases, considering the particle size and dispersibility of the electrode metal particles.

[0220] As an electrode catalyst precursor that yields highly dispersed electrode catalyst particles with small particle sizes, an acetylacetone coordination compound is preferred. By supporting the acetylacetone coordination compound, which serves as the electrode catalyst precursor, on a porous composite support, the electrode catalyst precursor is directly converted into electrode catalyst particles. In this method, the electrode catalyst precursor is free of residual impurities, thus an improvement in catalytic activity can be anticipated.

[0221] In the acetylacetone coordination method, the electrode catalyst precursor can be supported by dispersing a porous composite support in a solution in which the acetylacetone coordination compound of the electrode catalyst is dissolved in a suitable solvent such as dichloromethane, followed by stirring and solvent removal. This method avoids the introduction of impurities such as chlorine and sulfur, and enables the highly dispersed support of electrode catalyst particles with a uniform nanoscale size distribution. Furthermore, strong oxidants and reducing agents are not used in the solution, thus offering advantages such as preventing the degradation of electronically conductive oxides constituting the porous composite support and the mesoporous carbon serving as the carbon support.

[0222] Acetylacetone coordination compounds used as electrode catalysts include acetylacetone coordination compounds of noble metals such as Pt, Ru, Ir, Pd, Rh, Os, Au, and Ag. One or more of these compounds can be used. The solvent can be any organic solvent capable of dispersing the noble metal acetylacetone coordination compound; dichloromethane and acetylacetone are representative examples.

[0223] If a method for supporting electrode catalyst particles using the acetylacetone coordination method is proposed, the following method can be listed: add a conductive auxiliary material loaded with an electronically conductive oxide and a noble metal acetylacetone coordination compound into a specified container, and stir with an ultrasonic stirrer until the solvent is completely evaporated while cooling.

[0224] In step (4A), the dried material obtained in step (3A) is heat-treated in an inert gas atmosphere.

[0225] Regarding the dried product obtained in step (3A), the electrode catalyst particles supported on the porous composite support sometimes contain non-stoichiometric metal oxides in step (4A), which have low activity when kept in this state. Therefore, by heat treatment in an inert atmosphere such as nitrogen or argon or a reducing atmosphere containing hydrogen, the electrochemical catalytic effect of the metal that becomes the electrode catalyst is activated.

[0226] The heat treatment conditions are appropriately selected based on the type of electronically conductive oxide, the metal that serves as the electrode catalyst, and the precursor. For example, in the case of electronically conductive oxides such as tin oxide that are unstable in a reducing atmosphere, and when the electrode catalyst is Pt or a Pt alloy, the temperature is typically 180–400°C, preferably 200–250°C. If the temperature is too low, the metal serving as the electrode catalyst may not be sufficiently activated; if the temperature is too high, the electrode catalyst particles may aggregate, resulting in a small effective reaction surface area. Water vapor may also be added to the atmosphere as needed.

[0227] (Electrode material (B) and electrode material (C))

[0228] Hereinafter, electrode material (B) as the second embodiment of the electrode material of the present invention and electrode material (C) as the third embodiment will be described.

[0229] As described above, electrode material (B) is an electrode material comprising: a carbon support composed of mesoporous carbon; and an electrode catalyst composite fixed to at least the inner surface of the micropores and the outer surface of the micropores of the mesoporous carbon, wherein the electrode catalyst composite comprises electrode catalyst particles and an electronically conductive oxide, the electronically conductive oxide being present in such a way that it fills the spaces between the electrode catalyst particles.

[0230] Figure 1B (a) is a conceptual schematic diagram showing a representative structure of the electrode material (second embodiment) of the present invention. Figure 1B (b) is an enlarged schematic diagram of the vicinity of the pore.

[0231] like Figure 1B As shown in (a), the electrode material 1B (second embodiment) of the present invention is composed of mesoporous carbon as a carbon support 2 and an electrode catalyst composite 3 supported (fixed) on the mesoporous carbon (inner surface 2a of the micropores and inner and outer surfaces 2b of the micropores). It should be noted that... Figure 1B The electrode material 1B shown in (a) also has an electrode catalyst complex 3 on its outer surface 2b, but the electrode catalyst complex 3 may also exist only on the inner surface 2a of the pores.

[0232] That is, in the electrode material (B) of the present invention, the electrode catalyst composite 3 is supported on part or all of the micropore inner surface of the mesoporous region in the mesoporous carbon.

[0233] In the electrode material (B) of the present invention, the electrode catalyst composite 3 can be supported not only inside the pores of the mesopore region, but also on the pores outside the mesopore region and on the outer surface.

[0234] The electrode catalyst composite 3 comprises electrode catalyst particles and electronically conductive oxides present between the electrode catalyst particles. By having the electronically conductive oxides fill the gaps between the electrode catalyst particles, the agglomeration and expansion of the electrode catalyst metal can be suppressed. The electrode catalyst composite 3 is dispersed and supported on a carbon support 2 (mesoporous carbon), with a portion of the surface of the carbon support 2 (mesoporous carbon) exposed. Therefore, when using this electrode material to construct an electrode, the carbon supports 2 are in contact with each other, forming a low-resistance conductive path, resulting in an electrode with excellent electronic conductivity.

[0235] It should be noted that, in Figure 1B In this process, the electronically conductive oxides existing between the electrode catalyst particles are in the form of particles. However, the form of the electronically conductive oxides is not limited to particles as long as they exist in a way that fills the spaces between the electrode catalyst particles; they can also be irregularly shaped. Furthermore, the electronically conductive oxides can be crystalline or amorphous, but it is preferable that a portion of them is crystalline (i.e., a mixture of crystalline and amorphous materials), and more preferably that they are entirely crystalline.

[0236] Electrode material (C) is an electrode material comprising: a carbon support; and an electrode catalyst composite supported via an electronically conductive oxide layer on at least the inner surface of the micropores and the outer surface of the micropores of the carbon support, wherein the carbon support is mesoporous carbon or particle-shaped solid carbon, and the electrode catalyst composite comprises electrode catalyst particles and an electronically conductive oxide, wherein the electronically conductive oxide is present in a manner that fills the spaces between the electrode catalyst particles.

[0237] Figure 1C (a) is a conceptual schematic diagram showing a representative structure of the electrode material (C) (third embodiment) of the present invention. Figure 1C (b) is an enlarged schematic diagram of the vicinity of the surface. Figure 1C (c) is an enlarged schematic diagram of the vicinity of the pore.

[0238] The electrode material of the present invention (third embodiment) is characterized in that it has an electronically conductive oxide layer on the surface of the carbon support.

[0239] The electrode material 1C (third embodiment) of the present invention comprises: a particulate carbon support 2A having an electronically conductive oxide layer on its surface; and an electrode catalyst composite 3 supported on the carbon support 2A.

[0240] The electrode catalyst composite 3 comprises: electrode catalyst particles (typically microparticles) and an electronically conductive oxide present between the electrode catalyst particles (the same as the electrode catalyst composite 3 of electrode material 1B (second embodiment) of the present invention). It should be noted that... Figure 1C The carbon support 2A in (a) shows particle-shaped solid carbon, but the carbon support is not limited to this, and mesoporous carbon can also be used as the electrode material (C).

[0241] By having an electronically conductive oxide in such a way that it fills the gaps between electrode catalyst particles, the aggregation and expansion of electrode catalyst particles can be suppressed.

[0242] The electrode catalyst composite 3 is dispersed and supported on the carbon support 2A via an electronically conductive oxide layer 2c. When the electrode is constructed using this electrode material, even if the carbon supports 2A are in contact with each other through the electronically conductive oxide layer 2c, a low-resistance conductive path is formed because the electronically conductive oxide layer 2c is a thin layer (e.g., 1-10 nm), thus becoming an electrode with excellent electronic conductivity.

[0243] It should be noted that, in Figure 1C In this process, the electronically conductive oxide layer 2c is formed over the entire surface of the carbon support 2A, but it may also be formed only on a portion of it. In this case, an electrode catalyst composite 3 may also be included, which is supported on the carbon support 2A without passing through the electronically conductive oxide layer 2c.

[0244] It should be noted that, in Figure 1C In this process, the electronically conductive oxide (preferably Sn oxide) existing between the electrode catalyst particles is in the form of particles, but the form of the electronically conductive oxide is not limited to particles as long as it exists in a way that fills the spaces between the electrode catalyst particles; it can also be an irregular shape. Furthermore, the electronically conductive oxide can be crystalline or amorphous, but it is preferred that a portion of it is crystalline (i.e., a mixture of crystalline and amorphous materials), and more preferably that it is entirely crystalline.

[0245] In the electrode material (C), the carbon support having an electronically conductive oxide layer serves as the electrode framework, thus reducing the particle size of the electrode catalyst complex. Therefore, in the electrode formed using the electrode material of the present invention, the resistance caused by the electronically conductive oxide contained in the electrode catalyst complex can be reduced.

[0246] Thus, the electrode materials (B) and (C) of the present invention suppress the aggregation of electrode catalyst particles through the presence of electronically conductive oxides (preferably Sn oxides) between the electrode catalyst particles, exhibiting excellent durability against electrochemical oxidation due to the electronically conductive oxides (preferably Sn oxides) and also possessing excellent electronic conductivity due to the carbon support. Therefore, the electrode formed from this electrode material exhibits excellent electrode performance and high durability, enabling long-term power generation.

[0247] The constituent elements of electrode materials (B) and (C) of the present invention will now be described in detail. It should be noted that the following description assumes that the electrode materials of the present invention are used in a solid polymer fuel cell (PEFC) electrode, but the electrode materials of the present invention are not limited to this application.

[0248] [Carbon carrier]

[0249] In the electrode material of the present invention, the carbon support is included in the electrode material of the present invention, which has the function of improving electronic conductivity when forming an electrode, and also serves as the skeleton of the electrode.

[0250] The carbon support in electrode material (B) is mesoporous carbon.

[0251] Porous carbon with mesopore regions (2–50 nm) can be used as mesopore carbon, preferably with a pore diameter of 3 nm or more and 40 nm or less. If it is within this range, even if an electron-conducting oxide or electrode catalyst is fixed (supported) on the inner wall of the pore, the diffusion of substances into the pore will not be significantly hindered and will proceed smoothly.

[0252] Furthermore, when the electrode for a fuel cell is fabricated as described below, the electrode material of the present invention is mixed with a proton-conductive electrolyte material (ionomer). The proton-conductive electrolyte material (ionomer) is tens of nm in size, and therefore cannot penetrate into the mesopores with small pore diameters. Thus, poisoning of the electrode catalyst particles, which originate from the ionomer, by means of the electron-conductive oxide supported in the pores of the mesoporous carbon can be suppressed.

[0253] The mesoporous carbon of the present invention may also include regions other than the fine pores in the mesoporous region (2nm to 50nm) (micropore region, macropores), but preferably the mesoporous region has a higher proportion of fine pores.

[0254] The structure of the micropores in mesoporous carbon (pore diameter, shape, etc.) can be confirmed by observation using an electron microscope. Examples of electron microscopes include field emission scanning electron microscopy (FESEM) and scanning transmission electron microscopy (STEM).

[0255] In addition to being individual pores independent of other pores, the micropores in the mesoporous regions of mesoporous carbon also have interconnecting pores, where part or all of the micropores in the mesoporous regions are interconnected with the micropores in adjacent mesoporous regions, preferably having a three-dimensional mesh structure. The presence of these interconnecting pores promotes the diffusion of substances within the micropores of the mesoporous carbon.

[0256] The size and shape of the electrode material depend on the size and shape of the mesoporous carbon that forms its framework. The size and shape of the mesoporous carbon are determined within a range that allows the electrode materials to maintain continuous contact when forming the electrode for a fuel cell, and to create a space that facilitates the smooth diffusion of gases such as hydrogen and oxygen and the removal of water (vapor) within the electrode.

[0257] The mesoporous carbon used in the electrode material of the present invention can be synthesized appropriately or commercially available products can be used. Examples of commercially available products include, for instance, the CNovel series manufactured by Toyo Carbon Co., Ltd. (designed mesoporous diameter: 5–150 nm), which uses MgO as a mold for mesoporous carbon.

[0258] The carbon support in the electrode material (C) is a carbon support with an electronically conductive oxide layer on its surface.

[0259] The carbon support in electrode material (C) (third embodiment) can be any carbon support used in secondary batteries and fuel cells. Its shape and size can be appropriately selected considering the intended use of the electrode, but in applications such as gas diffusion electrodes for fuel cells, both conductivity and gas diffusion within the electrode during formation are required. Therefore, to balance conductivity and gas diffusion, when the carbon support is in particulate form, the particle size is 0.03–500 μm; when the carbon support is in fibrous form, a diameter of 2 nm–20 μm and a total length of approximately 0.03–500 μm are preferred.

[0260] The carbon support is at least one of mesoporous carbon and particulate solid carbon (third option). Mesoporous carbon is described above, therefore its description is omitted. Carbon black (CB) or graphitized carbon black (GCB), obtained by graphitizing (crystallizing) CB, can preferably be used as the solid carbon. The particulate solid carbon preferably has a secondary particle size of 0.03–500 μm (primary particle size of approximately 10 nm–100 nm).

[0261] Solid carbon can be made from either homemade or commercially available materials. Examples include: CABOT's "Vulcan" series (model: XC-72, etc.), CABOT's "GCB" series (model: GCB200, etc.), and Tokai Carbon's "TOKABLACK" series (model: TOKABLACK#3800, etc.).

[0262] The carbon support can be one type, or two or more carbon materials of different sizes (particle size, fiber diameter, and fiber length), crystallinity, etc., can be used in any proportion.

[0263] The electronically conductive oxide layer on the surface of the carbon support can be any electronically conductive oxide that is stable under the cathode conditions of a PEFC. Examples of electronically conductive oxides with oxides of the following metal elements as the main component are those selected from tin (Sn), molybdenum (Mo), niobium (Nb), tantalum (Ta), titanium (Ti), and tungsten (W). It should be noted that, in this specification, "electronically conductive oxide with the main component as the main component" refers to (A) an electronically conductive oxide composed solely of a parent oxide; and (B) an electronically conductive oxide doped with other elements and containing more than 80 mol% of the parent oxide.

[0264] Among them, tin oxide as the main body is preferred as an electronically conductive oxide. Considering that it can further improve electronic conductivity, niobium-doped tin oxide with 0.1 to 20 mol% niobium (Nb) is particularly preferred.

[0265] The thickness of the electronically conductive oxide layer also depends on the type and amount of electronically conductive oxide, but is preferably 1 to 10 nm. In addition, the electronically conductive oxide layer preferably covers the entire surface of the carbon support, but may also cover only a portion of the surface.

[0266] [Electrode Catalyst Complex]

[0267] The electrode catalyst composite of the present invention is characterized by comprising electrode catalyst particles and an electronically conductive oxide, the electronically conductive oxide being present in a manner that fills the spaces between the electrode catalyst particles. By having such a structure, the electrode material of the present invention can suppress the swelling caused by the aggregation of electrode catalyst particles, while possessing both the excellent durability against electrochemical oxidation provided by the electronically conductive oxide and the excellent electronic conductivity provided by the carbon material.

[0268] The morphology of the electrode catalyst complex supported on the carbon support can be any form as long as it does not impair the purpose of the present invention. Examples include: particulate, island, and film-like structures.

[0269] From the viewpoint of conductivity during electrode formation, it is preferable that the electrode catalyst complex is particulate and that the particulate electrode catalyst complex does not completely cover the surface of the carbon support, with a portion of the surface of the carbon support exposed, so as to disperse the loading to a degree that does not hinder direct contact between the carbon support and other carbon supports.

[0270] Regarding the size of the electrode catalyst complex, the "size of the electrode catalyst complex" can be obtained by averaging the sizes of any 20 electrode catalyst complexes surveyed by electron microscopy images. In cases where the shape of the electrode catalyst complex is not spherical, the length in the direction representing the maximum length is taken as the size of the electrode catalyst complex.

[0271] The size of the electrode catalyst complex, when supported on the surface of a carbon support, is typically an average particle size of 10–500 nm. The “average particle size of the electrode catalyst complex” can be obtained from the average particle size of any 20 electrode catalyst complexes investigated by electron microscopy images.

[0272] Furthermore, when the carbon support is mesoporous carbon, part or all of the electrode catalyst complex can also exist within the pores of the mesoporous carbon. In this case, the size of the electrode catalyst complex needs to be smaller than the diameter of the mesoporous carbon pores, corresponding to a size of 2 to 30 nm, which is equivalent to the diameter of the mesoporous carbon pores (e.g., 3–40 nm).

[0273] The proportion of electrode catalyst complex within the pores of the mesoporous carbon is preferably 50% or more, more preferably 80% or more, and even more preferably 90% or more (including 100%) when the total number of electrode catalyst complexes (the sum of electrode catalyst complexes outside and inside the pores) is set to 100%.

[0274] The number of electrode catalyst complexes within the pores of mesoporous carbon can be confirmed using high-angle scattering dark-field scanning transmission electron microscopy (HAADF-STEM).

[0275] Furthermore, the loading of the electrode catalyst composite is appropriately determined within a range that includes a sufficient amount of electrode catalyst particles as electrodes. The activity of the electrode catalyst particles depends on the type, crystallinity, and particle size of the electrode catalyst metal, as well as the type, crystallinity, and particle size of the Sn oxide to be composited; therefore, these factors are taken into account when determining the loading of the electrode catalyst composite.

[0276] The loading of the electrode catalyst composite is typically 5 to 50% by weight, preferably 10 to 40% by weight, when the total weight of the carbon support and the electrode catalyst composite is set to 100% by weight.

[0277] The electrode catalyst particles and electron-conducting oxides constituting the electrode catalyst complex are described in detail below.

[0278] (Electrode catalyst particles)

[0279] Electrode catalyst particles are particles of electrode catalyst metal. The electrode catalyst metal can be any type of catalyst, either noble metal-based or non-noble metal-based, as long as it possesses electrochemical catalytic activity for oxygen reduction (and hydrogen oxidation). Preferably, it is selected from noble metals such as Pt, Ru, Ir, Pd, Rh, Os, Au, and Ag, and alloys containing these noble metals. It should be noted that "alloys containing noble metals" includes: "alloys composed solely of the aforementioned noble metals" and "alloys composed of the aforementioned noble metals and metals other than the aforementioned noble metals, and containing 10% by mass or more of the aforementioned noble metals." The "metals other than the aforementioned noble metals" alloyed with noble metals are not particularly limited; examples include Co, Ni, W, Ta, Nb, and Sn, and one or more of these can be used. Furthermore, two or more of the aforementioned noble metals and alloys containing noble metals can be used in a phase-separated state.

[0280] Among electrode catalyst metals, Pt and Pt-containing alloys exhibit high electrochemical catalytic activity for oxygen reduction (and hydrogen oxidation) in the temperature range of around 80°C, which is the operating temperature of solid polymer fuel cells, and are therefore particularly preferred.

[0281] The shape of the electrode catalyst particles 3b is not particularly limited as long as it does not impair the purpose of the present invention, and can be of various shapes. Specific shapes include spheres, ellipses, polyhedra, etc. Furthermore, the structure of the electrode catalyst particles 3b is not limited to crystals; it can be amorphous or a mixture of crystalline and amorphous materials.

[0282] Smaller electrode catalyst particles result in a larger effective surface area for electrochemical reactions, thus tending to increase electrochemical catalytic activity. However, if the electrode catalyst particles are too small, the electrochemical reaction activity decreases. Therefore, the preferred size of the electrode catalyst particles, based on the average particle size, is 1–10 nm, more preferably 1.5–5 nm.

[0283] It should be noted that the "average particle size of the electrode catalyst particles" in this invention can be obtained from the average particle size of 20 electrode catalyst particles investigated by electron microscope images. When calculating the average particle size using electron microscope images, if the shape of the particle is not spherical, the length in the direction representing the maximum length of the particle is taken as its particle size.

[0284] That is, in one preferred embodiment of the electrode catalyst particles in the electrode material of the present invention, the electrode catalyst particles are particles composed of noble metals (preferably Pt and alloys containing Pt) with an average particle size of 1 to 10 nm.

[0285] The amount of electrode catalyst particles is determined by considering the catalytic activity of the target electrode and the dopant species and amounts of the electron-conducting oxide to be composited. It should be noted that the loading of electrode catalyst particles can be investigated, for example, by inductively coupled plasma luminescence analysis (ICP).

[0286] From the viewpoint of electrode catalytic activity, if the catalytic activity per unit mass is preferably 0.1 to 60% by mass, more preferably 0.5 to 30% by mass, relative to the total weight of the electrode material, then the catalytic activity per unit mass is excellent, and the desired electrode reaction activity corresponding to the loading can be obtained.

[0287] (Electron-conducting oxides)

[0288] The electronically conductive oxides constituting the electrode catalyst complex possess both sufficient durability and electronic conductivity under PEFC cathode conditions.

[0289] The morphology of the electronically conductive oxide can be any form as long as it does not impair the purpose of the present invention. Examples include particle-like, island-like, and film-like forms, with particle-like forms being preferred. Furthermore, the electronically conductive oxide is not limited to crystals; it can be amorphous or a mixture of crystals and amorphous materials. To improve the electronic conductivity, the electronically conductive oxide is preferably crystalline.

[0290] As an electronically conductive oxide constituting an electrode catalyst complex, examples of electronically conductive oxides are those whose main body is an oxide of a metal element selected from tin (Sn), molybdenum (Mo), niobium (Nb), tantalum (Ta), titanium (Ti), and tungsten (W).

[0291] Among them, tin oxide as the main component is preferred, which is an electronically conductive oxide (Sn oxide).

[0292] Sn oxides are electronically conductive oxides with tin oxide (SnO2) as the main component. Here, in this invention, "electronically conductive oxides with tin oxide as the main component" refers to (A) electronically conductive oxides consisting solely of tin oxide (SnO2) as the parent oxide; and (B) electronically conductive oxides doped with other elements and containing 80 mol% or more of tin oxide (SnO2) as the parent oxide.

[0293] Specifically, doping elements include: Ti, Sb, Nb, Ta, W, In, V, Cr, Mn, Mo, etc. (where is an element different from the parent oxide). The doping element is one with a higher valence than the parent oxide. Among the above doping species, elements other than Sn are selected (e.g., Sb, Nb, Ta, W, In, V, Cr, Mn, Mo, etc.). Niobium-doped tin oxide, with 0.1–20 mol% niobium (Nb), can also be used, especially considering its ability to significantly improve the electronic conductivity of tin oxide.

[0294] As described above, in the electrode catalyst composite of the present invention, the electronically conductive oxides prevent the aggregation of the electrode catalyst particles by existing in a manner that fills the spaces between the electrode catalyst particles. The electronically conductive oxides need only be contained in a form that achieves this purpose.

[0295] The proportion of electron-conducting oxides in the electrode catalyst composite is appropriately determined based on the type, size, and crystallinity of the electron-conducting oxides, as well as the type, amount, and size of the electrode catalyst metal to be composited. For example, when the electrode catalyst metal is Pt, the molar ratio of Pt:Sn is 0.1 to 10:1.

[0296] It should be noted that in electrode materials (B) and (C), the electronically conductive oxide fills the spaces between the electrode catalyst particles in the electrode catalyst composite, thereby reducing the amount of electronically conductive oxide and thus reducing the resulting resistance. Therefore, the electronically conductive oxide can be either crystalline or amorphous. However, to further reduce resistance, it is preferable that at least a portion of the electronically conductive oxide is crystalline, and preferably all of it is crystalline.

[0297] <Method for manufacturing electrode material (B) or electrode material (C)>

[0298] The manufacturing methods for the electrode materials (B) and (C) described above are not particularly limited; any appropriate and preferred method may be selected based on the type of carbon support, electronically conductive oxide, and electrode catalyst metal constituting the electrode material. A preferred example of the manufacturing method for the electrode material (B) or electrode material (C) of the present invention is the manufacturing method described below.

[0299] The manufacturing method of the electrode material (B) of the present invention includes the following steps (1B) to (2B).

[0300] Step (1B): Dissolving the acetylacetone coordination compound of the electrode catalyst metal precursor and the acetylacetone coordination compound of the electronically conductive oxide precursor in a dispersion prepared by dispersing the mesoporous carbon as a carbon support in a hydrophobic organic solvent, stirring and removing the solvent by distillation, thereby obtaining mesoporous carbon on which the electrode catalyst metal precursor and the electronically conductive oxide precursor are supported.

[0301] Step (2B): The mesoporous carbon supported on the electrode catalyst metal precursor and the electronically conductive oxide precursor obtained in step (1B) is heat-treated in an inert gas atmosphere to form an electrode catalyst composite.

[0302] A specific example of the method for manufacturing the electrode material (B) of the present invention is the method described in the embodiments described later.

[0303] The method for manufacturing the electrode material (B) of the present invention is characterized in that, in step (1B), a hydrophobic organic solvent is used, and acetylacetone coordination compounds, which are precursor compounds of the electrode catalyst metal and the electronically conductive oxide, are supported on a carbon support (mesoporous carbon) in one step, thereby obtaining an electrode catalyst composite precursor formed by the composite (nanocomposite) of the electrode catalyst metal and the electronically conductive oxide. Furthermore, the acetylacetone coordination compounds have the advantage of not containing impurities such as chlorine and sulfur, which are among the causes of performance degradation in electrode catalysts.

[0304] In step (2B), the carbon support containing the electrode catalyst metal precursor and the electronically conductive oxide precursor obtained in step (1B) is heat-treated in an inert gas atmosphere to form an electrode catalyst composite.

[0305] In process (2B), the electrode catalyst complex precursor, which includes the electrode catalyst precursor and the electronically conductive oxide precursor, is decomposed by heat treatment in an inert atmosphere such as nitrogen or argon. This activates the electrochemical catalytic effect of the metal that becomes the electrode catalyst, improves the crystallinity of the electronically conductive oxide, and enhances its electronic conductivity.

[0306] In the manufacturing method of the present invention, the heat treatment temperature in step (2B) is appropriately determined taking into account the decomposition temperature of the acetylacetone coordination compound used as a raw material. In this case, it is preferable to perform the heat treatment in two stages at different temperatures.

[0307] When the electron-conducting oxide is Sn oxide, the heat treatment temperature is typically 180–400 °C, preferably 200–250 °C, when the electrode catalyst is Pt or a Pt alloy. If the temperature is too low, the metal that serves as the electrode catalyst will not be sufficiently activated; if the temperature is too high, the electrode catalyst metal will agglomerate, resulting in a small effective reaction surface area.

[0308] Furthermore, in step (2B), a heat treatment process under the presence of water vapor is preferably included. Through heat treatment under the presence of water vapor (humidified atmosphere), the electronically conductive oxide precursor is sufficiently decomposed / oxidized, thus tending to improve electrode performance.

[0309] The manufacturing method of the electrode material (C) of the present invention includes the following steps (1C) to (3C).

[0310] Process (1C): The process of forming an electronically conductive oxide layer on a carbon support containing mesoporous carbon or particle-shaped solid carbon.

[0311] Step (2C): The acetylacetone coordination compound of the electrode catalyst metal precursor and the acetylacetone coordination compound of the electronically conductive oxide precursor are dissolved in a dispersion obtained by dispersing the carbon support with the electronically conductive oxide layer obtained in step (1C) in a hydrophobic organic solvent. The mixture is stirred and the solvent is removed by distillation, thereby obtaining a carbon support on which the electrode catalyst metal precursor and the electronically conductive oxide precursor are supported.

[0312] Step (3C): The carbon support containing the electrode catalyst metal precursor and the electronically conductive oxide precursor obtained in step (2C) is heat-treated in an inert gas atmosphere to form the electrode catalyst composite.

[0313] A specific example of the method for manufacturing the electrode material (C) of the present invention is the method described in the embodiments described later.

[0314] The method for manufacturing the electrode material (C) of the present invention is characterized in that an electronically conductive oxide layer is pre-formed on the carbon support for the electrode catalyst composite precursor (composite electrode catalyst particles and electronically conductive oxide) that supports (fixes) the electrode material (B), as described in step (1C).

[0315] As described above, the electronically conductive oxides that constitute the electronically conductive oxide layer are not limited to any precursor compound as long as they can produce the target electronically conductive oxide layer; for example, chlorides and alkoxides can be listed.

[0316] In step (1C), an electronically conductive oxide layer is formed on a carbon support containing mesoporous carbon or granular solid carbon. A preferred embodiment is the following method: the carbon support is dispersed in a solvent (e.g., anhydrous ethanol), and ammonia is added dropwise while stirring and adding a precursor compound for the electronically conductive oxide layer.

[0317] Furthermore, the formation of the electronically conductive oxide layer can also be based on the steps (1A) and (2A) in the above-mentioned method for manufacturing electrode material (A), and the following steps (1-1C) and (1-2C) can be used.

[0318] Process (1-1C): The process of mixing the carbon support and the alkoxide compound of the electronically conductive oxide precursor in a non-aqueous organic solvent until homogeneous, then removing the solvent by distillation and drying.

[0319] Process (1-2C): The dried material obtained in process (1-1C) is subjected to steam treatment to decompose the electronically conductive oxide precursor, followed by heat treatment, thereby obtaining a porous composite carrier with an electronically conductive oxide layer formed on its surface.

[0320] It should be noted that the conditions for processes (1-1C) and (1-2C) are essentially the same as those for processes (1A) and (2A), so the explanation is omitted.

[0321] Furthermore, the subsequent steps (2C) (supporting the electrode catalyst composite precursor onto the carbon support) and (3C) (forming the electrode catalyst composite) are substantially the same as steps (1B) and (2B) of the method for manufacturing the electrode material (B) of the present invention, and therefore are omitted from the description.

[0322] <2. Electrodes>

[0323] The electrode of the present invention comprises the electrode materials (electrode materials (A) to (C)) described above and a proton-conducting electrolyte material. In the electrode of the present invention, the electrode materials are in contact with each other to form a conductive path.

[0324] The following describes an electrode for a fuel cell formed using the electrode material of the present invention. Specifically, an example of using the above-described electrode material as an electrode in a PEFC will be described. It should be noted that the electrode material of the present invention can also be used as an electrode other than that used in fuel cells (e.g., an electrode for a solid polymer water electrolysis device).

[0325] The electrode of the present invention may also be composed solely of the electrode material described above, but typically includes a proton-conducting electrolyte material (hereinafter sometimes referred to as "proton-conducting electrolyte material" or simply "electrolyte material") for use in fuel cells. The electrolyte material included in the electrode of the fuel cell along with the electrode material may be the same as or different from the electrolyte material used in the electrolyte membrane for fuel cells. From the viewpoint of improving the adhesion between the electrode and the electrolyte membrane for fuel cells, it is preferable to use the same electrolyte material.

[0326] Proton-conducting electrolyte materials can be cited as examples of electrolyte materials used in electrodes and electrolyte membranes for PEFCs. These proton-conducting electrolyte materials are broadly classified into fluorine-based electrolyte materials, whose polymer backbone contains all or part of fluorine atoms, and hydrocarbon-based electrolyte materials, whose polymer backbone does not contain fluorine atoms. Both of these can be used as electrolyte materials.

[0327] As fluorinated electrolyte materials, examples of preferred choices include Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), and FLEMION (registered trademark, manufactured by Asahi Glass Co., Ltd.).

[0328] Specifically, examples of hydrocarbon-based electrolyte materials include polymers such as polysulfonic acid, polystyrene sulfonic acid, polyaryletherketone sulfonic acid, polybenzene sulfonic acid, polybenzimidazole sulfonic acid, polybenzimidazole phosphonic acid, and polyimide sulfonic acid; polymers having alkyl or other side chains are preferred examples among them.

[0329] The mass ratio of the electrode material to the electrolyte material mixed with it can be appropriately determined to impart good proton conductivity to the electrode formed using these materials and to facilitate smooth gas diffusion and water vapor removal within the electrode. However, if the amount of electrolyte material mixed with the electrode material is too large, the proton conductivity improves, but the gas diffusivity decreases. Conversely, if the amount of electrolyte material mixed is too small, the gas diffusivity improves, but the proton conductivity decreases. Therefore, the mass ratio of the electrolyte material to the electrode material is preferably in the range of 10 to 50% by mass. When this mass ratio is less than 10% by mass, the continuity of the proton-conductive material deteriorates, and sufficient proton conductivity cannot be ensured as an electrode for a fuel cell. Conversely, when this mass ratio is greater than 50% by mass, the continuity of the electrode material deteriorates, and sometimes sufficient electronic conductivity cannot be achieved as an electrode for a fuel cell. Moreover, sometimes the diffusivity of gases (oxygen, hydrogen, water vapor) inside the electrode decreases.

[0330] The electrode for the fuel cell of the present invention may also contain components other than the electrode material and proton-conducting material described above, without prejudice to the purpose of the present invention.

[0331] For example, it may also include conductive materials other than the carbon support contained in the electrode material described above (hereinafter referred to as "other conductive materials"). By including other conductive materials, the conductive pathways connecting the electrode material are increased, and sometimes the overall conductivity of the electrode is improved.

[0332] Other conductive materials can be used as well as those known for use in fuel cell electrodes. Typically, carbon-based conductive materials include, for example, particulate carbon such as carbon black and activated carbon (including chain-linked carbon particles), carbon fibers, and fibrous carbon such as carbon nanotubes (CNTs). Alternatively, unsupported mesoporous carbon can also be used as other conductive materials.

[0333] It should be noted that, as an electrode for a fuel cell incorporating the electrode material of the present invention, an electrode for PEFC has been described, but it can also be used as an electrode in various fuel cells such as alkaline fuel cells and phosphoric acid fuel cells, in addition to PEFC. Furthermore, it is also preferably used as an electrode in a water electrolysis device that uses the same polymer electrolyte membrane as PEFC.

[0334] It should be noted that the electrode for fuel cells incorporating the electrode material of the present invention exhibits excellent electrochemical catalytic activity for oxygen reduction and hydrogen oxidation, and therefore can be used as both a cathode and anode. In particular, its excellent electrochemical catalytic activity for oxygen reduction prevents electrochemical oxidative decomposition of the conductive material serving as the support under fuel cell operating conditions, making it especially preferred as a cathode.

[0335] Furthermore, the electrode for fuel cells of the present invention can be used not only in PEFCs, but also in various other fuel cells such as alkaline fuel cells and phosphoric acid fuel cells. Additionally, it is preferably used as an electrode in water electrolysis devices that utilize the same solid polymer electrolyte membrane as PEFCs.

[0336] <3. Membrane Electrode Assembly (MEA)>

[0337] The membrane electrode assembly of the present invention is characterized by comprising: a solid polymer electrolyte membrane; a cathode bonded to one side of the solid polymer electrolyte membrane; and an anode bonded to the other side of the solid polymer electrolyte membrane, wherein either or both of the cathode and the anode are electrodes of the present invention.

[0338] As a preferred embodiment of the present invention, a membrane electrode assembly in which an electrode for a fuel cell comprising the electrode material of the present invention is used as a cathode will be described.

[0339] Figure 2 This is a schematic cross-sectional view illustrating an embodiment of the membrane electrode assembly of the present invention. Figure 2 As shown, the membrane electrode assembly 10 has a structure in which the cathode 4 and anode 5 are arranged facing the solid polymer electrolyte membrane 6.

[0340] The cathode 4 consists of an electrode catalyst layer 4a and a gas diffusion layer 4b.

[0341] As the gas diffusion layer 4b, conventionally known gas diffusion layers can be used. Examples include conductive carbon-based sheet members with a pore diameter distribution of approximately 100 nm to 90 μm, which are commonly used as gas diffusion layers in conventional PEFCs. Preferably, hydrophobic treated carbon cloth, carbon paper, or carbon nonwoven fabric can be used. Alternatively, sheet members other than carbon-based materials such as stainless steel can also be used. The thickness of such a gas diffusion layer 4b is not particularly limited, typically ranging from approximately 50 μm to 1 mm. Furthermore, the gas diffusion layer 4b may also have a microporous layer on one side composed of an aggregate of carbon particles with an average particle size of approximately 10 to 100 nm and a hydrophobic material.

[0342] The anode 5 is composed of an electrode catalyst layer 5a and a gas diffusion layer 5b. Besides the fuel cell electrode of the present invention, other known anodes can also be used as the anode 5. For example, an electrode in which an electrode catalyst layer 5a is formed on the gas diffusion layer 5b can be described. This electrode catalyst layer 5a is manufactured by coating / drying a dispersion of electrode material carrying noble metal particles as catalyst and electrolyte material of a fuel cell onto the surface of a conductive support made of carbon-based materials such as graphite, carbon black, activated carbon, carbon nanotubes, or glassy carbon. The gas diffusion layer 5b of the anode 5 can be the same as the gas diffusion layer 4b described in the cathode 4.

[0343] As for the solid polymer electrolyte membrane 6, as long as it possesses proton conductivity, chemical stability, and thermal stability, a known electrolyte membrane for PEFCs can be used. It should be noted that... Figure 3 The thickness is emphasized in the illustration, but in order to reduce resistance, the thickness of the solid polymer electrolyte membrane 6 is usually around 0.007 to 0.05 mm.

[0344] As electrolyte materials constituting the solid polymer electrolyte membrane 6, fluorinated electrolyte materials and hydrocarbon electrolyte materials can be listed. In particular, electrolyte membranes formed from fluorinated electrolyte materials have excellent heat resistance and chemical stability, and are therefore preferred. Specifically, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), and FLEMION (registered trademark, manufactured by Asahi Glass Co., Ltd.) are among the preferred examples.

[0345] The embodiments of the MEA of the present invention have been described above with reference to the accompanying drawings, but these are examples of the present invention, and various structures other than those described above may also be adopted.

[0346] <4. Solid Polymer Fuel Cells>

[0347] The solid polymer fuel cell (single cell) of the present invention has the membrane electrode assembly of the present invention, and generally has a structure in which the membrane electrode assembly is held by a spacer having a gas flow path.

[0348] Figure 3 This is a conceptual diagram illustrating a representative structure of the solid polymer fuel cell of the present invention. (Example) Figure 3 As shown, in the solid polymer fuel cell 20, hydrogen is supplied to the anode 5, and through (reaction 1) 2H2→4H + +4e - The generated protons (H + Electrons generated are supplied to the cathode 4 via a solid polymer electrolyte membrane 6. Additionally, the generated electrons are supplied to the cathode via an external circuit 21, through (reaction 2) O₂ + 4H₂O.+ +4e - →2H2O, reacts with oxygen to produce water.

[0349] A potential difference is generated between the two electrodes through the electrochemical reaction between the anode and cathode. In the solid polymer fuel cell of the present invention, the constituent elements other than the membrane electrode assembly are the same as those in known solid polymer fuel cells, therefore detailed descriptions are omitted.

[0350] In practice, the fuel cell stack formed by stacking the solid polymer fuel cell (single cell) of the present invention in a base number corresponding to the power generation performance is used by assembling other auxiliary devices such as gas supply devices and cooling devices.

[0351] Example

[0352] The following examples illustrate the invention in further detail, but the invention is not limited thereto. It should be noted that, in the following, mesoporous carbon is sometimes referred to as "MC", carbon black as "CB", and highly graphitized carbon black as "GCB".

[0353] "Electrode Material (A)"

[0354] A1. Fabrication of Electrode Material (A)

[0355] The electrode materials of Examples 1A and 2A were manufactured as electrode materials (A) of Examples.

[0356] The carbon support, electrode catalyst precursor, and electronically conductive oxide used are described below.

[0357] <Carbon carrier>

[0358] The following mesoporous carbon (MC) (manufactured by Toyo Carbon Co., Ltd., "Porous Carbon CNovel MJ(4)010 (grade name)") was used as the carbon carrier.

[0359] Designed aperture diameter: 10nm.

[0360] Specific surface area: 1100m² 2 / g.

[0361] Total micropore volume: 2.0 mL / g.

[0362] Micropore volume: 0.4 mL / g.

[0363] Particle size: Passes through 100 mesh (for use after pulverization).

[0364] <Electronic-conducting oxide precursor compounds>

[0365] Tin ethanol (Sn(OC2H5)4) (Strem chemicals INC) was used as the Sn raw material compound, and niobium ethanol (Nb(OC2H5)5) (Sigma Aldrich) was used as the Nb raw material compound.

[0366] <Electrode Catalyst Precursors>

[0367] Acetylacetone Pt (Pt(C5H7O2)2, platinum(II) acetylacetone, 97%, Sigma Aldrich) was used as the electrode catalyst precursor. It should be noted that, in the following, acetylacetone Pt is sometimes referred to as the Pt precursor (Pt(acac)2).

[0368] <Example 1A>

[0369] like Figure 4 The flowchart shown illustrates the preparation of the electrode material (without supported electrode catalyst) for the embodiment via steam hydrolysis.

[0370] First, as step (1A), 200 mg of the aforementioned mesoporous carbon (MC), which serves as the carbon carrier, was pulverized to a particle size of approximately 1 μm using a ball mill and then dispersed in an organic solvent (a mixture of acetylacetone and toluene in a volume ratio of 2:1) to obtain a dispersion containing MC. Next, a metal ethanol salt reagent (750 mg of tin ethanol and 128 mg of niobium ethanol) was prepared by dissolving a metal ethanol salt solution in a mixed organic solvent at a Sn:Nb ratio of 90:10 (mol ratio). This metal ethanol salt solution was added to the dispersion containing MC, and the total solvent volume was 45 mL. The organic solvent was evaporated under reduced pressure while being ultrasonically stirred, thereby obtaining a dry powder in which the metal ethanol salt reagent was uniformly adsorbed on the front side (inner and outer surfaces of the micropores) of MC.

[0371] After the obtained dry powder is pulverized, as in step (2A), it is subjected to steam hydrolysis of the metal ethanol salt reagent by holding it in a steam atmosphere (3% humidified N2 atmosphere) at 150°C for 3 hours. Then, the temperature is raised to 300°C and held for another 3 hours to induce niobium-doped tin oxide (Sn). 0.9 Nb 0.1 O2) crystallization (confirmed by XRD). Then, it was restored to room temperature by natural cooling, thereby obtaining the electrode material of Example 1A (without supported electrode catalyst, "Sn"). 0.9 Nb 0.1 O2 / MC”).

[0372] Next, as steps (3A) and (4A), Pt catalyst particles, serving as electrode catalyst particles, were supported on the electrode material (without supported electrode catalyst) of Example 1A by the platinum acetylacetone method. The amount of Pt precursor (Pt(acac)2) was set to 20 wt%.

[0373] The electrode material (without electrode catalyst) of Example 1A containing MC supported on niobium-doped tin oxide and the Pt precursor were added to a flask, and dichloromethane was added to dissolve it. Then, while the flask was chilled, the mixture was stirred with an ultrasonic stirrer until all the solvent evaporated, resulting in a dry powder (step (3A)).

[0374] Next, the obtained dry powder was subjected to reduction treatment at 210°C for 3 hours under a N2 atmosphere, and then at 240°C for 3 hours (step (4A)), thereby obtaining the electrode material (Pt / Sn) of Example 1A. 0.9 Nb 0.1 O2 / MC).

[0375] <Example 2A>

[0376] A metal ethanol salt solution was prepared in a Sn:Nb ratio of 98:2 (mol ratio). The heating temperature of the dry powder adsorbed with the metal ethanol salt reagent was set to 400°C (Example 1A: 300°C). Otherwise, the electrode material of Example 2A (supported by Pt, "Pt / Sn") was obtained in the same manner as in Example 1A. 0.98 Nb 0.02 O2 / MC”). It should be noted that in the electrode material of Example 2A, niobium-doped tin oxide (Sn) crystals were formed. 0.98 Nb 0.02 O2 (confirmed by XRD).

[0377] <Comparative Example 1>

[0378] As a comparative example, no metal ethanol salt solution was used, but the electrode material (Pt / MC) of Comparative Example 1 was obtained in the same manner as in Example 1A.

[0379] A2. Physical Property Evaluation

[0380] A2-1. Observation of fine structure

[0381] (1) Electrode material (without supported electrode catalyst)

[0382] Figure 5 The image shows FESEM and STEM (top view) images of the electrode material (without supported electrode catalyst) of Example 1A. Furthermore, Figure 6Image (a) shows an FESEM image (top view) of the electrode material (without supported electrode catalyst) of Example 2A. Figure 6 (b) shows Figure 6 A magnified photograph of the area (equivalent to the central hole) of the dashed section in (a).

[0383] like Figure 5 , Figure 6 As shown in (a), regarding the electrode materials of Example 1A and Example 2A, it was confirmed that 2-5 nm particle-shaped Sn(Nb)O2 was fixed on the outer surface of MC.

[0384] In addition, when Figure 6 When the area marked by the dashed line in (a) is magnified and the inside of the mesopore is observed, Sn(Nb)O2 with a particle size of about 2nm (less than 3nm) is confirmed on the inner surface of the mesopore. Figure 7 The diagram shows a particle-like Sn(Nb)O2 inside the fine pores (mesopores) of MC.

[0385] (2) Electrode material (supported by Pt)

[0386] Figure 8 The electrode material (Pt / Sn) of Example 1A is shown in the figure. 0.9 Nb 0.1 O2 / MC), Figure 9 The image shows FESEM and STEM (top view) images of the electrode material (Pt / MC) of Comparative Example 1. According to... Figure 8 It was confirmed that in the electrode material of Example 1A, Pt particles were dispersed and supported on MC via Sn(Nb)O2. Furthermore, according to... Figure 9 It was confirmed that in the electrode material of Comparative Example 1, Pt particles were directly supported on MC.

[0387] The electrode material (Pt / Sn) of Example 2A 0.98 Nb 0.02 STEM image (top view) of O2 / MC is shown. Figure 10 (a) and (b).

[0388] exist Figure 10 On the outer surface of the electrode material of Example 2A shown in (a), Pt particles (particle size 2-3 nm) supported on particulate Sn(Nb)O2 were confirmed. Furthermore, in Figure 10 In the electrode material of Example 2A shown in (b), Pt particles were also found to be supported on Sn(Nb)O2 within the mesopores (approximately 10 nm).

[0389] A3. Electrochemical Evaluation (Half-cell)

[0390] A3-1. Evaluation of Cyclic Voltammetry (CV)

[0391] The electrode material of Comparative Example 1 in Example 1A was evaluated using cyclic voltammetry (CV). The electrochemical surface area (ECSA) was calculated based on the amount of hydrogen adsorbed from the CV. It should be noted that the ECSA is equivalent to the effective surface area of ​​Pt contained in the electrode material.

[0392] The fuel cell electrode for evaluation is fabricated according to the following steps.

[0393] First, a mixture of 19 mL of ultrapure water and 6 mL of 2-propanol was added to a sample vial containing electrode material powder. Then, 100 μL of 5% Nafion dispersion was added. The sample vial was then ultrasonically stirred for 30 minutes while immersed in ice water to prepare the electrode material dispersion. It should be noted that when 10 μL of the electrode material dispersion was added to the electrode, the Pt mass per unit area on the electrode was 17.3 μg-Pt·cm³. -2 Using a micropipette, 10 μL of the prepared electrode material dispersion was added dropwise to the Au disk electrode, which was then placed in a thermostat and dried at 60°C for about 15 minutes to form a Nafion membrane, thus fixing the electrode material onto the Au electrode and obtaining the fuel cell electrode (working electrode) for evaluation.

[0394] The CV measurement conditions are as follows. It should be noted that if we assume that each Pt atom adsorbs one H atom, then the result is 210 μC / cm³. 2 The amount of electricity.

[0395] Measurement: Three-electrode cell (working electrode: fuel cell electrode for evaluation, counter electrode: Pt, reference electrode: Ag / AgCl).

[0396] Electrolyte: 0.1M HClO4 (pH: approximately 1).

[0397] Measurement potential range: 0.05~1.2V (based on reversible hydrogen electrode).

[0398] Scanning speed: 50mV / s.

[0399] Hydrogen adsorption capacity: calculated based on the peak area of ​​hydrogen adsorption shown in the range of 0.05 to 0.4V.

[0400] Electrochemical surface area (ECSA): Calculated according to the following formula.

[0401] ECSA = (hydrogen adsorption capacity) [μC] / 210 [μC / cm²] 2 ]

[0402] Figure 11The CVs of the electrode materials of Example 1A and Comparative Example 1 are shown in the figure. Figure 11 As shown, the electrode material (Pt / Sn) of Example 1A was used. 0.9 Nb 0.1 For the O2 / MC electrode, peaks (0.05–0.4 V) originating from hydrogen adsorption and desorption were observed, confirming its function as an electrode for fuel cells.

[0403] Furthermore, the electrode material (Pt / Sn) of Example 1A was confirmed. 0.9 Nb 0.1 Compared to the electrode material (Pt / MC) of Comparative Example 1, which is an oxide without electronic conductivity, O2 / MC has a higher hydrogen adsorption capacity and a larger electrochemical surface area (ECSA) (ECSA: Example 1A: 112m²). 2 / g, Comparative Example 1: 79.5m 2 / g).

[0404] Evaluation of A3-2. ORR activity

[0405] ORR activity was evaluated for the electrode materials of Example 1A and Comparative Example 1.

[0406] ORR activity was determined by linear sweep voltammetry (LSV) using the rotating disk electrode method (RDE method) to obtain the activation dominance current (i). k Based on this, the mass activity (activity per unit mass of Pt) is calculated and used as an indicator.

[0407] Mass activity = i k Pt mass on the electrode

[0408] Regarding the activation governing current (i) k Regarding the current-potential curve obtained by measuring with rotating electrodes, it is constructed at any potential with i -1 and ω -1 / 2 The Koutecky-Levich notation obtained by marking is used to extrapolate the obtained line and calculate the result based on the intercept.

[0409] As a specific procedure, firstly, after bubbling O2 at 50 mL / min for 30 minutes, the volume is increased from 0.2V. RHE Scan the potential towards higher potential at 10mV / s up to 1.20V. RHE The measurements were performed. It should be noted that O2 was purged at a rate of 50 mL / min throughout the measurements. It should also be noted that V... RHE The potential is based on the reversible hydrogen electrode (RHE).

[0410] Figure 12Linear scan voltammograms (1600 rpm) of the electrode materials of Example 1A and Comparative Example 1 are shown. Figure 12 The 0.9V of the electrode material of Example 1A obtained in the ORR measurement RHE The mass activity at that time was 38.2 A / g. Pt .

[0411] A3-3. Start-stop cycle test

[0412] The electrode materials of Example 1A and Comparative Example 1 were subjected to start-up and stop-cycle tests using the method recommended by the Fuel Cell Commercialization Promotion Council (FCCJ) (Proposal on Objectives / Research and Development Issues and Evaluation Methods for Solid Polymer Fuel Cells, issued January 2005). The start-up and stop-cycle test is a cycle test that promotes carbon corrosion; specifically, it involves... Figure 13 The 1.0–1.5V shown RHE The short waveform was applied for 2 seconds per cycle, and the above operation was repeated. The degradation behavior of the electrode catalyst after the cycle test was evaluated as ECSA change.

[0413] Figure 14 The ECSA changes (relative values) of the electrode materials of Example 1A and Comparative Example 1 are shown in the start-stop cycle test (up to 60,000 cycles).

[0414] Depend on Figure 14 It can be seen that the electrode using the electrode material (Pt / MC) of Comparative Example 1 experienced a significant decrease in ECSA immediately after the start-stop cycle test, reaching approximately 50% of its initial value at 10,000 cycles, making it impossible to continue the test to 20,000 cycles (where the ECSA retention rate was approximately 0). In contrast, the electrode using the electrode material (Pt / Sn) of Example 1A... 0.9 Nb 0.1 In the O2 / MC electrode, the reduction of ECSA was confirmed to be slow, maintaining about 30% of the initial value even at 60,000 cycles.

[0415] Figure 15 The image shows FESEM and STEM images of the electrode material (Pt / MC) of Comparative Example 1 before and after the start-stop cycle test (20,000 cycles). Figure 16 The electrode material (Pt / Sn) of Example 1A is shown in the figure. 0.9 Nb 0.1 FESEM and STEM images of O2 / MC before and after the start-stop cycle test (60,000 cycles).

[0416] Based on the above results, it was confirmed that even after cyclic testing, the Pt particles in the electrode material of Example 1A remained highly dispersed and supported on the front side (inner and outer surfaces of the pores) of the MC via an electronically conductive oxide (Sn(Nb)O2). In contrast, in the electrode material (Pt / MC) of Comparative Example 1, which does not have an electronically conductive oxide, Pt particles detached / aggregated as the cyclic testing progressed.

[0417] "Electrode material (B) and electrode material (C)"

[0418] The electrode material of Experimental Example 1B was fabricated as the electrode material (B) of the embodiment. Furthermore, the electrode materials of Experimental Examples 1C and 2C were fabricated as the electrode materials (C) of the embodiment.

[0419] The carbon support, electrode catalyst precursor, and electronically conductive oxide precursor used are described below.

[0420] <Carbon carrier>

[0421] (1) Carbon carrier 1

[0422] Mesoporous carbon (MC) (manufactured by Toyo Carbon Co., Ltd., “Porous Carbon CNovel MJ(4)010 (grade name)”) was used as the carbon carrier 1.

[0423] Designed aperture diameter: 10nm.

[0424] Specific surface area: 1100m² 2 / g.

[0425] Total micropore volume: 2.0 mL / g.

[0426] Micropore volume: 0.4 mL / g.

[0427] Particle size: Passes through 100 mesh (for use after pulverization).

[0428] (2) Carbon carrier 2

[0429] Carbon black (CB) (manufactured by CABOT, “Vulcan XC-72”) was used as the carbon carrier 2.

[0430] (3) Carbon support 3

[0431] Highly graphitized carbon black (GCB) (manufactured by CABOT, “GCB200”) was used as the carbon carrier 3.

[0432] <Electrode Catalyst Precursors>

[0433] Acetylacetone Pt (platinum acetylacetone (II), Sigma Aldrich) (hereinafter sometimes referred to as "Pt(acac)2") was used as an electrode catalyst precursor.

[0434] <Electronic-conductive oxide precursor>

[0435] (1) Sn oxide precursor (for electrode catalyst complex formation)

[0436] Acetylacetone Sn (acetylacetone tin(II), Sigma Aldrich) (hereinafter sometimes referred to as “Sn(acac)2”) was used as a precursor for Sn oxide.

[0437] (2) Precursor for forming electronically conductive oxide layers

[0438] Tin chloride hydrate (SnCl2·2H2O, KISHIDA CHEMICAL Co., Ltd.) was used as the Sn raw material compound, and niobium chloride (NbCl5, FUJIFILM Wako Chemicals Co., Ltd.) was used as the Nb raw material compound.

[0439] <Experimental Example B>

[0440] B1. Fabrication of Electrode Material B (Second Scheme)

[0441] like Figure 17 The flowchart shown illustrates the fabrication of the electrode material for Experimental Example 1B.

[0442] "Experimental Example 1B: Pt-SnO2 / MC"

[0443] Process (1B)

[0444] First, as step (1B), 100 mg of mesoporous carbon (MC) used as carbon carrier 1 was pulverized to a particle size of about 1 μm using a ball mill, and then placed in a flask. Acetylacetone (30 mL) was added to the flask, and the mixture was stirred with an ultrasonic homogenizer to obtain a dispersion of MC.

[0445] Add Pt(acac)2 and Sn(acac)2 to the obtained MC dispersion and stir thoroughly to dissolve them.

[0446] The loading amounts of Pt precursor (Pt(acac)2) and Sn oxide precursor (Sn(acac)2) are set to 42 wt% relative to the total loading of the electrode material of the Pt-SnO2 electrode catalyst composite. It should be noted that at this loading amount, the Pt:SnO2 (volume ratio) is 1:2.

[0447] Next, the eggplant-shaped flask containing the sample was placed in a rotary evaporator with both decompression and rotation functions. While decompressing until all the solvent evaporated, ultrasonic stirring was performed to obtain a powder (MC containing an electrode catalyst composite precursor including Pt precursor and Sn oxide precursor).

[0448] Process (2B)

[0449] The powder obtained in process (1B) is then... Figure 18 The heat treatment was carried out under the heat treatment conditions shown (heating rate of 1℃ / min in N2 atmosphere, holding at 210℃ for 3 hours, holding at 240℃ for 3 hours, and holding in 3% humidified N2 atmosphere for 30 minutes (activation treatment of electrode catalyst complex)), thereby obtaining the electrode material (Pt-SnO2 / MC) of Experimental Example 1B.

[0450] "Experimental Example 2B (Reference Example): Pt-SnO2 / CB (Vulcan)"

[0451] In step (1), carbon support 2 (CB(Vulcan)) was used instead of carbon support 1 (MC), and the loading was set to 32 wt% relative to the total loading of the electrode material of the Pt-SnO2 electrode catalyst composite. Otherwise, the electrode material (Pt-SnO2 / CB(Vulcan)) of Experimental Example 2B was obtained in the same manner as in Experimental Example 1B. It should be noted that the electrode material of Experimental Example 2B is described here as a comparison (reference example) with the electrode material of Experimental Example 1B.

[0452] Table 1 shows the actual loading rates and volume ratios of Pt and SnO2 for the electrode materials of Experimental Example 1B and Experimental Example 2B (Reference Example), calculated based on ICP and TG measurements.

[0453] [Table 1]

[0454] Sample Name Pt actual load factor <![CDATA[Actual loading rate of SnO2]]> <![CDATA[Volume ratio of Pt∶SnO2]]> Experimental Example 1B <![CDATA[Pt-SnO2 / MC]]> 25.7 wt.% 14.6 wt.% 1∶1.75 Experimental Example 2B <![CDATA[Pt-SnO2 / CB(Vulcan)]]> 18.2 wt.% 10.5 wt.% 1∶1.78

[0455] B2. Physical property evaluation

[0456] B2-1. Analysis using X-ray diffraction (XRD)

[0457] The crystal structure of each prepared electrode material was evaluated using XRD. Figure 19 The XRD patterns of the electrode materials in Experimental Example 1B and Experimental Example 2B are shown. It should be noted that the peak at approximately 27° 2θ is due to the carbon support (MC, CB).

[0458] In all electrode materials, Pt peaks were identified, confirming that Pt exists in crystalline form. Furthermore, no distinct peaks for Pt-Sn alloys were identified, nor was a peak shift observed for Pt. Therefore, it was determined that no alloying of Pt and Sn occurred, and the Sn oxide precursor was fully oxidized to SnO2 through heat treatment in a humidified nitrogen atmosphere.

[0459] On the other hand, no SnO2 peak could be detected in any electrode material, so it was determined that Sn exists in the form of very small SnO2 crystals or amorphous Sn oxide (SnOx).

[0460] B2-2. Fine-grained structural evaluation

[0461] The STEM image and EDS mapping of the electrode material (Pt-SnO2 / CB(Vulcan)) of Experimental Example 2B are shown in the figure. Figure 20 HAADF-STEM images are shown in Figure 21 .

[0462] Based on the STEM image of the electrode material in Experiment Example 2B ( Figure 20 (Top left) and HAADF-STEM image ( Figure 21 It was confirmed that a Pt-SnO2 electrode catalyst complex was supported on the surface of a carbon support (CB(Vulcan)).

[0463] In addition, by Figure 20 EDS analysis and Figure 21 It is known that, in the Pt-SnO2 electrode catalyst composite, Sn oxide is distributed in a manner that penetrates into the spaces between Pt particles with a particle size of 1-2 nm, forming a composite structure of Pt and Sn oxide. It is determined that by this penetration of Sn oxide into the spaces between Pt particles, the Sn oxide exists in a way that fills the spaces between Pt particles, which can inhibit Pt particle growth and maintain small Pt particles with a particle size of approximately 1-2 nm.

[0464] Furthermore, as mentioned above, based on the results of XRD measurements ( Figure 19 Since no alloying of Pt and Sn occurred, it was determined that in the electrode material of Experimental Example 2B, electrode catalyst composite particles with a nanocomposite structure of Pt and SnO2 were fixed on the carbon support (CB(Vulcan)).

[0465] The STEM image and EDS mapping of the electrode material (Pt-SnO2 / MC) in Experimental Example 1B are shown below. Figure 22 HAADF-STEM images are shown in Figure 23 .

[0466] Based on the STEM image of the electrode material in Experiment Example 1B ( Figure 22(Top left) and HAADF-STEM image ( Figure 23 It was confirmed that particles with a diameter of 1-2 nm were highly dispersed on the surface of the carbon support (MC).

[0467] In addition, by Figure 22 EDS analysis and Figure 23 It is known that Sn oxide is distributed by entering the spaces between Pt particles with a diameter of 1-2 nm, forming a complex structure of Pt and Sn oxide. It is determined that by entering the spaces between Pt particles in this way, Sn oxide exists in a way that fills the spaces between Pt particles, which can inhibit the growth of Pt particles and maintain the small Pt particles with a diameter of about 1-2 nm.

[0468] Furthermore, as mentioned above, based on the results of XRD measurements ( Figure 19 Since no alloying of Pt and Sn occurred, it was determined that in the electrode material of Experimental Example 1B, electrode catalyst composite particles with a nanocomposite structure of Pt and SnO2 were fixed on the carbon support (MC).

[0469] Furthermore, to confirm whether the Pt-SnO2 electrode catalyst complex could be supported within the mesopores of MC, further observations were conducted using STEM, and the results are presented below. Figure 24 It should be noted that, in Figure 24 In (a) to (d), the part in parentheses is the focal length when the front of MC is set to 0nm.

[0470] like Figure 24 As shown, not only on the surface of MC ( Figure 24 (a) of, back ( Figure 24 (d) confirmed the presence of Pt-SnO2 electrode catalyst composite particles, and in the focused internal ( Figure 24 Pt-SnO2 electrode catalyst composite particles were also confirmed in (b) and (c). That is, it was determined that Pt-SnO2 electrode catalyst composites were also supported inside MC.

[0471] In addition, for Figure 24 The number of particles inside and outside the MC in (a) to (d) were counted, and the ratio of particles inside the MC was calculated. The result was 55.3%, indicating that more than half of the particles were carried inside the pore.

[0472] B3. Electrochemical Evaluation (Half-cell)

[0473] B3-1. Evaluation of Cyclic Voltammetry (CV)

[0474] The electrode materials of Experimental Example 1B and Experimental Example 2B were evaluated using cyclic voltammetry (CV). The electrochemical surface area (ECSA) was calculated based on the amount of hydrogen adsorption obtained from CV. It should be noted that ECSA corresponds to the effective surface area of ​​Pt contained in the electrode material.

[0475] The specific evaluation method is the same as that in "A3-1. Evaluation of Cyclic Voltammetry (CV)," so the explanation here is omitted.

[0476] Figure 25 The CVs of the electrode materials for Experimental Example 1B and Experimental Example 2B are shown in the figure. Figure 25 As shown, for the electrodes using the electrode materials of Experimental Example 1B and Experimental Example 2B, peaks (0.05-0.4V) originating from hydrogen adsorption and desorption were observed, confirming that they function as electrodes for fuel cells.

[0477] Furthermore, it was confirmed that the electrode material of Example 1B, which used MC as the carbon support, had a higher hydrogen adsorption capacity and a larger electrochemical effective surface area (ECSA) compared to the electrode material of Example 2B, which used CB (Vulcan) as the carbon support (ECSA: Example 1B: 48.0 m²). 2 / g, Experimental Example 2B: 39.1m 2 / g). B3-2. Evaluation of Oxygen Reduction Activity (ORR Activity)

[0478] ORR activity was evaluated on the electrode materials of Experimental Example 1B and Experimental Example 2B.

[0479] The specific evaluation method is the same as that in "A3-2. Evaluation of Oxygen Reduction Activity (ORR Activity)," so the explanation here is omitted.

[0480] Figure 26 Linear scan voltammograms (1600 rpm) of the electrode materials for Experimental Example 1B and Experimental Example 2B are shown. Figure 26 The 0.9V electrode materials of Experimental Example 1B and Experimental Example 2B obtained in the ORR determination RHE Regarding the mass activity at that time, Example 1B: 62.3A / g Pt Experimental Example 2B: 44.9 A / g Pt .

[0481] Thus, compared with Experimental Example 2B (Pt-SnO2 / CB(Vulcan)), Experimental Example 1B (Pt-SnO2 / MC) has slightly higher mass activity. Therefore, it can be considered that using mesoporous carbon as a carbon support helps to improve the activity of the Pt-SnO2 electrode catalyst complex.

[0482] B3-3. Start-stop cycle test

[0483] A start-stop cycle test was conducted on the electrode material of Experiment 1B.

[0484] The specific evaluation method is the same as that in "A3-3. Start-up and Stop Cycle Test", so the explanation here is omitted.

[0485] It should be noted that, for comparison purposes, a start-stop cycle test was also conducted on the electrode material (Pt / MC) of Comparative Example 1, which does not have Sn oxide, using the same method as the electrode material in Experimental Example 1B.

[0486] Regarding the ECSA retention rate (relative to the initial value) after the start-stop cycle test (60,000 cycles), the electrode material (Pt / MC) of Comparative Example 1 was approximately 0, while the electrode material (Pt-SnO2 / MC) of Experimental Example 1B was 11.6%.

[0487] Furthermore, linear sweep voltammetry (1600 rpm) of the electrode materials of Experimental Example 1B and Comparative Example 1 before and after the start-stop cycle test (60,000 cycles) is shown below. Figure 27 .

[0488] Depend on Figure 27 The LSV curves show that the negative shift of the oxygen reduction potential before and after the test of the electrode material of Experimental Example 1B is slightly suppressed compared with that of the electrode material of Comparative Example 1. Therefore, the electrode material of Experimental Example 1B (Pt-SnO2 / MC) has high durability compared with the electrode material of Comparative Example 1 (Pt / MC).

[0489] B3-4. Load Variation Cyclic Test

[0490] Load variation cycle durability tests were conducted on the electrode materials of Experimental Example 1B and Comparative Example 1. The load variation cycle tests were conducted by applying simulated load variation potential cycles using the method recommended by the Fuel Cell Commercialization Promotion Council (FCCJ) (Proposal on Objectives / Research and Development Issues and Evaluation Methods for Solid Polymer Fuel Cells, issued in January 2005). Figure 28 The load variation cycle shown is as follows: it promotes degradation accompanied by catalyst dissolution / re-precipitation, etc., by using 0.6–1.0V. RHE The experiment was conducted by applying a short waveform for 3 seconds in each cycle for a total of 6 seconds, and the changes in ECSA and LSV before and after the load variation cycle test were measured.

[0491] It should be noted that the FCCJ recommends 400,000 cycles, but ECSA showed significant changes, so the experiment ended at 100,000 cycles.

[0492] Regarding the ECSA retention rate after load variation cyclic testing (100,000 cycles), the electrode material (Pt / MC) of Comparative Example 1 had a retention rate of 22.1%, while the electrode material (Pt-SnO2 / MC) of Experimental Example 1B had a retention rate of 26.8%.

[0493] The LSV changes of the electrode materials in Experimental Example 1B and Comparative Example 1 before and after the load variation cycle test (100,000 cycles) are shown in the figure. Figure 29 .according to Figure 29 The LSV curve confirms that the electrode material (Pt) in Experimental Example 1B...

[0494] Compared to the electrode material (Pt / MC) of Comparative Example 1, the -SnO2 / MC material suppressed the negative shift of the oxygen reduction potential and improved the durability in terms of activity.

[0495] <Experimental Example C>

[0496] C1. Fabrication of Electrode Material (C) (Third Scheme)

[0497] Electrode materials (without supported electrode catalyst) for Experimental Example 1C and Experimental Example 2C were manufactured as described below.

[0498] "Experimental Example 1C: Pt-SnO2 / Sn(Nb)O2 / GCB"

[0499] Process (1C)

[0500] First, 580 mL of anhydrous ethanol was added to GCB, which served as carbon support 3, and the mixture was stirred using an ultrasonic homogenizer to obtain a dispersion of GCB. Tin chloride hydrate (SnCl2·2H2O, KISHIDA CHEMICAL Co., Ltd.) and niobium chloride (NbCl5, FUJIFILM Wako Chemicals Co., Ltd.) were added to the obtained GCB dispersion. While stirring with a heated stirrer at 50°C, 120 mL of ammonia water was added dropwise using a burette at a rate of 5 cc / min. After all the addition was completed, the mixture was stirred for 1 hour, filtered and washed a total of 4 times, and then dried at 100°C for 10 hours. Then, the mixture was heat-treated in a reduction furnace with a rotary function at 600°C for 2 hours to obtain the powder of Experimental Example 1C (unsupported electrode catalyst, "Sn(Nb)O2 / GCB") containing a carbon support with a Sn oxide layer formed on its surface. It should be noted that in process (1C), Sn(Nb)O2 is prepared with a loading rate of 75 wt% (filling amount).

[0501] Process (2C)

[0502] 100 mg of carbon support (Sn(Nb)O2 / GCB) with a Sn oxide layer on its surface obtained in step (1C) was pulverized to a particle size of about 1 μm using a ball mill. The pulverized carbon support was then placed in a flask, and acetylacetone (30 mL) was added. The mixture was stirred with an ultrasonic homogenizer to obtain a dispersion of the carbon support (with the Sn oxide layer).

[0503] Pt(acac)2 and Sn(acac)2 were added to the dispersion of the obtained carbon support (with a Sn oxide layer) and stirred thoroughly to dissolve it.

[0504] The loading amounts of Pt precursor (Pt(acac)2) and Sn oxide precursor (Sn(acac)2) are set to 22 wt% relative to the total loading of the electrode material of the Pt-SnO2 electrode catalyst composite. It should be noted that at this loading amount, the Pt:SnO2 (volume ratio) is 1:2.

[0505] Next, the eggplant-shaped flask containing the sample was placed in a rotary evaporator with both decompression and rotation functions. While decompressing until all the solvent evaporated, ultrasonic stirring was performed to obtain a powder (a carbon support (containing a Sn oxide layer) of an electrode catalyst composite precursor containing Pt precursor and Sn oxide precursor).

[0506] Process (3C)

[0507] The powder obtained in step (2C) was subjected to heat treatment under the following conditions (heating rate of 1°C / min in N2 atmosphere, holding at 210°C for 3 hours, holding at 240°C for 3 hours, and holding in 3% humidified N2 atmosphere for 30 minutes (activation treatment of electrode catalyst complex)) to obtain the electrode material (Pt-SnO2 / Sn(Nb)O2 / GCB) of Experimental Example 1C.

[0508] "Experimental Example 2C: Pt-SnO2 / Sn(Nb)O2 / CB(Vulcan)"

[0509] In the manufacturing method of the electrode material in Experimental Example 1C, GCB was replaced as carbon support 3, CB (Vulcan) was replaced as carbon support 3, and the heat treatment temperature was changed to 300°C. Otherwise, the electrode material (Pt-SnO2 / Sn(Nb)O2 / CB(Vulcan)) of Experimental Example 2C was obtained in the same way as Experimental Example 1C.

[0510] Table 2 shows the actual loading rates and volume ratios of Pt and SnO2 for the electrode materials of Experimental Example 1C and Experimental Example 2C, calculated based on ICP and TG measurements.

[0511] [Table 2]

[0512] Sample Name Pt actual load factor SnO2 actual loading rate Pt:SnO2 volume ratio Experimental Example 1C Pt-SnO2 / Sn(Nb)O2 / GCB 4.21 wt.% 2.69 wt.% 1∶1.97 Experimental Example 2C Pt-SnO2 / Sn(Nb)O2 / CB(Vulcan) 3.54 wt.% 2.46 wt.% 1∶2.15

[0513] C2. Physical property evaluation

[0514] C2-1. Analysis using X-ray diffraction (XRD)

[0515] The crystal structure of each prepared electrode material was evaluated using XRD. Figure 30 The XRD patterns of the electrode materials in Experimental Examples 1C and 2C are shown. It should be noted that the peak at approximately 27° 2θ is due to the carbon support (GCB, CB).

[0516] Furthermore, the crystallite diameters of Sn(Nb)O2 of the electrode materials in Experimental Example 1C and Experimental Example 2C, determined by the Scherrer method, are shown in Table 3.

[0517] [Table 3]

[0518] Sample Name Average crystallite diameter of Sn(Nb)O2 particles Experimental Example 1C Pt-SnO2 / Sn(Nb)O2 / GCB 9.42nm Experimental Example 2C Pt-SnO2 / Sn(Nb)O2 / CB(Vulcan) 5.02nm

[0519] A distinct SnO2 peak was observed in all electrode materials used in Experimental Examples 1C and 2C. Furthermore, the SnO2 peak was smaller in the electrode material of Experimental Example 2C, which used Vulcan CB, compared to the electrode material of Experimental Example 1C, which used GCB, as shown in Table 3. The average crystallite diameter was also smaller. Therefore, it can be said that small Sn(Nb)O2 particles can be supported by heat treatment at 300°C.

[0520] C2-2. Fine-scale structural evaluation

[0521] Figure 31 The image shown is an FESEM image of the electrode material of Experimental Example 1C. Figure 32 The image shows a FESEM image of the electrode material of Experimental Example 2C. Highly dispersed Pt particles were confirmed to be supported in all catalysts. High-resolution observations (not shown) of the electrode material of Experimental Example 1C using GCB were performed using STEM-EDS and HAADF-STEM. The results showed the lattice distances of Pt and SnO2, indicating that no alloying of Pt and Sn had occurred.

[0522] C3. Electrochemical Evaluation (Half-cell)

[0523] C3-1. Start-stop cycle test

[0524] A start-stop cycle test was conducted on the electrode material of Experimental Example 1C. The evaluation method is as described in "A3-3. Start-stop Cycle Test", therefore, the description is omitted.

[0525] The changes in mass activity before and after the cyclic test are shown in Figure 33 Furthermore, as a comparison, the results of a commercially available platinum-supported carbon black catalyst (Pt / C, manufactured by Tanaka Precious Metals Industry Co., Ltd., TEC10E50E) as Comparative Example 2 are also shown. Figure 33 As shown, the electrode material of Experimental Example 1C with the Sn(Nb)O2 support surface layer was found to have superior start-stop cycle durability compared to the electrode material of Comparative Example 2.

Claims

1. An electrode material, which is any one of the following electrode materials: A or B. Electrode material A: The composite material comprises: a porous composite support and electrode catalyst particles supported on the porous composite support, wherein the porous composite support comprises: a carbon support composed of mesoporous carbon; and an electronically conductive oxide fixed to at least the inner surface of the micropores and the outer surface of the micropores of the mesoporous carbon, wherein... Some or all of the electrode catalyst particles are supported in the pores of the mesoporous carbon via the electronically conductive oxide, and the electrode catalyst particles and the electronically conductive oxide are present in the pores of the mesoporous carbon. Electrode material B: It comprises: a carbon support composed of mesoporous carbon; and an electrode catalyst composite, fixed to at least the inner surface of the micropores and the outer surface of the micropores of the mesoporous carbon, wherein, The electrode catalyst composite comprises electrode catalyst particles and an electronically conductive oxide, the electronically conductive oxide being present in a manner that fills the spaces between the electrode catalyst particles. The electrode catalyst particles and the electronically conductive oxide are present within the fine pores of the mesoporous carbon. The electrode catalyst particles in electrode material A or electrode material B are composed of Pt or Pt-containing alloy particles.

2. The electrode material according to claim 1, wherein, In electrode material A or electrode material B, the mesoporous carbon has: a connecting hole in which part or all of the pores in the mesoporous region are interconnected with the pores in the adjacent mesoporous region.

3. The electrode material according to claim 1 or 2, wherein, In electrode material A or electrode material B, the pore diameter of the mesoporous carbon is greater than 3 nm and less than 40 nm.

4. The electrode material according to claim 1 or 2, wherein, In electrode material A or electrode material B, the electronically conductive oxide is an electronically conductive oxide mainly composed of tin oxide.

5. The electrode material according to claim 4, wherein, In electrode material A or electrode material B, the electronically conductive oxide comprises niobium-doped tin oxide.

6. The electrode material according to claim 1 or 2, wherein, In electrode material A, the particle size of the electronically conductive oxides fixed to the inner surface of the pores of the mesoporous carbon is 0.5 nm or more and 3 nm or less.

7. The electrode material according to claim 1 or 2, wherein, In electrode material B, the electrode catalyst particles constituting the electrode catalyst composite are particles with a particle size of 1 nm or more and 10 nm or less.

8. The electrode material according to claim 7, wherein, In electrode material B, some or all of the electronically conductive oxide constituting the electrode catalyst complex is crystalline.

9. An electrode, characterized in that, It comprises the electrode material and the proton-conducting electrolyte material as described in any one of claims 1 to 8.

10. A membrane electrode assembly comprising: a solid polymer electrolyte membrane; a cathode bonded to one side of the solid polymer electrolyte membrane; and an anode bonded to the other side of the solid polymer electrolyte membrane, wherein, Either or both of the anode or cathode are electrodes as described in claim 9.

11. A solid polymer fuel cell comprising the membrane electrode assembly as described in claim 10.

12. A method for manufacturing electrode material A as described in any one of claims 1 to 6, comprising the following steps 1A to 4A, Step 1A: The process of mixing mesoporous carbon, which serves as a carbon support, with an alkoxide compound that is an electronically conductive oxide precursor in a non-aqueous organic solvent until homogeneous, followed by distillation to remove the solvent and drying. Step 2A: The dried material obtained in Step 1A is subjected to steam treatment to decompose the electronically conductive oxide precursor, followed by heat treatment, thereby obtaining a porous composite carrier with electronically conductive oxides fixed on the surface of mesoporous carbon. Step 3A: The solution containing the porous composite support and electrode catalyst precursor obtained in Step 2A is mixed until homogeneous, and then the solvent is removed by distillation to obtain the dried product. Step 4A: A step of heat-treating the dried material obtained in Step 3A in an inert gas atmosphere.

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