Electrode material, electrode, membrane electrode assembly, and solid polymer fuel cell

Abstract

Provided is an electrode material which is capable of providing an electrode for a fuel cell, said electrode material having both high activity and potential cycle durability, and particularly having excellent load fluctuation cycle characteristics. An electrode material comprising a conductive carrier and a catalyst composite supported on the conductive carrier, the catalyst composite containing a PtTaCo composite comprising platinum (Pt) as a first component, tantalum (Ta) as a second component, and cobalt (Co) as a third component. The catalyst composite obtained by phase separation of the PtTaCo composite in the electrode material contains Pt-rich particles and Ta-rich particles.

Description

TECHNICAL FIELD

[0001] (CITATION LIST) This application claims the benefit of Japanese Patent Application No. 2023-125985 filed on August 2, 2023. The entire disclosure of the above application is hereby incorporated by reference herein in its entirety for all purposes.

[0002] The present application relates to an electrode material suitable for an electrode of a solid polymer fuel cell, and an electrode, a membrane electrode assembly, and a solid polymer fuel cell using the electrode material. BACKGROUND

[0003] As for a solid polymer fuel cell (PEFC), a fuel cell vehicle (FCV) using the same as a power source has been on the market, and expansion and popularization to uses such as trucks, buses, ships, construction machines, and the like are expected. A PEFC generally has a structure in which a pair of electrodes disposed on both surfaces of a solid polymer electrolyte membrane with a separator in which a gas flow path is formed interposed therebetween, that is, a membrane electrode assembly (MEA) is configured. A fuel cell electrode (particularly, a PEFC electrode) is generally composed of an electrode catalyst layer containing an electrode material having electrode catalytic activity and a polymer electrolyte, and a gas diffusion layer having gas permeability and electronic conductivity.

[0004] As a currently popular PEFC electrode material, an electrode material in which electrode catalyst fine particles (typically, Pt or Pt alloy fine particles) are dispersed and supported in a carbon support is used. Such an electrode material using a carbon support has a problem in that, under the operating conditions of a PEFC, Pt is peeled off due to carbon corrosion accompanying start / stop, or the particle size of Pt catalyst increases due to Pt dissolution / precipitation accompanying load fluctuation, and the electrochemical effective surface area (ECSA) of Pt and the oxygen reduction reaction (ORR) activity decrease.

[0005] So far, it has been shown that by using an electron-conductive oxide support such as niobium-doped tin oxide (Nb-SnO2) as an electrode catalyst support, the durability of a catalyst in a start / stop cycle test is improved (see Patent Literature 1). In addition, it is well known that an alloy catalyst of Pt with Co, Ni, or the like can exhibit an activity higher than that of a pure Pt catalyst (for example, Patent Literature 2). Recently, research on ternary or multinary alloy catalysts has also been conducted, and there are reports of achieving high initial ORR activity and durability (for example, Non-Patent Literature 1).

[0006] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 5322110 Patent Document 2: Japanese Patent Application Publication No. 2021-093270 Non-patent literature Non-patent literature 1: H. Chen, C. Guan, and H. Feng, ACS Applied Nano Mater., 5(7), 9810-9817 (2022). Summary of the Invention

[0007] The problem the invention aims to solve However, in the aforementioned conventional electrode materials, there is room for improvement regarding potential cycling durability (especially load variation cycling durability) in order to obtain practical electrode performance.

[0008] In this context, the object of the present invention is to provide an electrode material that can balance high activity and potential cycle durability and provide an electrode for a fuel cell, as well as an electrode, a membrane electrode assembly, and a solid polymer fuel cell using the electrode material.

[0009] Solution for solving the problem In order to solve the above problems, the inventors have repeatedly conducted in-depth research and found that the catalyst complex composed of Pt, Ta and Co can balance high activity and potential cycling durability, especially with excellent loading variation cycling characteristics, thus completing the present invention.

[0010] That is, the present invention relates to the following invention.

[0011] <1> An electrode material comprising a conductive support and a catalyst composite supported on the conductive support, the catalyst composite comprising a PtTaCo composite consisting of platinum (Pt) as a first component, tantalum (Ta) as a second component, and cobalt (Co) as a third component.

[0012] <2> according to <1> The electrode material is formed by separating the PtTaCo complex phase constituting the catalyst complex.

[0013] <3> according to <2> The electrode material, wherein the catalyst composite after phase separation comprises Pt-rich particles and Ta-rich particles.

[0014] <4> according to <3> The electrode material, wherein the Pt-rich particles are a PtCo alloy.

[0015] <5> according to <3> or <4> The electrode material, wherein the Ta-rich particles are Ta oxides.

[0016] <6> according to <1> to <5> In any one of the electrode materials, Pt is 60-80 atomic%, Ta is 10-30 atomic%, and Co is 1-20 atomic% relative to the total of Pt, Ta, and Co (100 atomic%).

[0017] <7> according to <1> to <6> The electrode material described in any one of the following statements, wherein the conductive carrier is a carbon carrier.

[0018] <8> according to <7> The electrode material, wherein the carbon support is highly crystalline carbon.

[0019] <9> An electrode comprising according to <1> to <8> The electrode material and proton-conducting electrolyte material described in any one of the following statements.

[0020] <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 and cathode are based on... <9> The aforementioned electrode.

[0021] <11> A solid polymer fuel cell, the solid polymer fuel cell having according to <10> The aforementioned membrane electrode assembly.

[0022] Invention Effects According to the present invention, an electrode material for a fuel cell electrode that can balance high activity and potential cycle durability, and provides particularly excellent load variation cycle characteristics, is provided, as well as an electrode, a membrane electrode assembly, and a solid polymer fuel cell using the electrode material. Attached Figure Description

[0023] FIG. 1 This is a conceptual schematic diagram of the electrode material of the present invention. FIG. 1 (a) is the first scheme (PtTaCo complex, before phase separation). FIG. 1 (b) is the second scheme (nanocomposite structure, after phase separation).

[0024] FIG. 2 This is an illustrative diagram illustrating the phase separation of the PtTaCo complex in the catalyst complex of the electrode material of the present invention. FIG. 2 (a) is before phase separation. FIG. 2 (b) is after phase separation.

[0025] FIG. 3This is a cross-sectional schematic diagram of the membrane electrode assembly of the present invention.

[0026] FIG. 4 This is a conceptual diagram illustrating a representative configuration of the solid polymer fuel cell of the present invention.

[0027] FIG. 5 This is a flowchart of the fabrication steps of the electrode material (PtTaCo / KB) in this embodiment.

[0028] FIG. 6 This is a diagram illustrating the conditions for a load variation cyclic test.

[0029] FIG. 7 This is a graph showing the relationship between the number of load variation cycles and the electrochemical effective surface area (ECSA) in Example 1.

[0030] FIG. 8 This is a graph showing the relationship between the number of load variation cycles and mass activity (MA) in Example 1.

[0031] FIG. 9 These are the STEM-EDS-based analysis results before (initial: 0 cycles) and after (400,000 cycles) the load variation cycle test in Example 1. Detailed Implementation

[0032] 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.

[0033] Furthermore, in all the accompanying drawings, the same reference numerals are used to label the same constituent elements, and descriptions are omitted where appropriate.

[0034] When the expression “~” is used in this specification, it is used to indicate the numerical values ​​before and after it. Furthermore, in this specification, the expression “A and / or B” includes “A only”, “B only”, and “both A and B”.

[0035] <1. Electrode material> The electrode material of the present invention is as follows: comprising a conductive support and a catalyst composite supported on the conductive support, wherein the catalyst composite comprises a PtTaCo composite consisting of platinum (Pt) as a first component, tantalum (Ta) as a second component and cobalt (Co) as a third component.

[0036] The electrode material of the present invention can be used to separate the PtTaCo composite that constitutes the catalyst composite through phase separation treatment to prepare a catalyst composite with a nanocomposite structure.

[0037] In this specification, "phase separation (of a solid)" refers to the phenomenon in which a solid being studied separates into multiple solid phases.

[0038] Furthermore, in this specification, "nanocomposite structure" refers to a structure in which particles of metals (including alloys) or metal compounds (typically metal oxides) with a size of nm (less than 10 nm) are integrated into a single structure. The particles constituting the nanocomposite structure can be crystalline or amorphous, and their shape and size are arbitrary; they can be the same or different.

[0039] Furthermore, in this specification, the electrode material before phase separation of the catalyst complex (PtTaCo complex) is sometimes described as "electrode material of the present invention (before phase separation)" and the electrode material after phase separation is described as "electrode material of the present invention (after phase separation)".

[0040] FIG. 1 (a) shows a conceptual schematic diagram of the electrode material of the present invention (before phase separation).

[0041] like FIG. 1 As shown in (a), the electrode material 1 of the present invention is composed of a conductive carrier 2 and a catalyst composite 3 supported (adhered) on the surface (inner surface of the pores, outer surface of the pores) of the conductive carrier 2.

[0042] The conductive carrier 2 enhances electronic conductivity during electrode formation and serves as the electrode framework. Typically, carbon carriers are used as conductive carriers, but electronically conductive oxide carriers and metal carriers can also be used.

[0043] The catalyst complex 3 in the electrode material (before phase separation) of the present invention is a PtTaCo complex composed of platinum (Pt) as the first component, tantalum (Ta) as the second component, and cobalt (Co) as the third component.

[0044] The catalyst complex 3 is dispersed and supported on the surface (inner surface of the micropores and outer surface of the micropores) of the conductive support 2. A portion of the surface of the conductive support 2 is exposed. Therefore, when the electrode material is used to construct the electrode, the conductive supports 2 come into contact with each other to form a low-resistance conductive path, thus becoming an electrode with excellent electronic conductivity.

[0045] Furthermore, the electrode material of the present invention (after phase separation) is an electrode material obtained by phase separation of the PtTaCo complex constituting the catalyst complex of the electrode material of the present invention (before phase separation).

[0046] FIG. 1 A conceptual schematic diagram of the electrode material (after phase separation) of the present invention is shown in (b). Furthermore, FIG. 2 The diagram illustrates the phase separation of the PtTaCo complex.

[0047] Regarding the manufacturing method of the electrode material (after phase separation) of the present invention, for example, it can be obtained by performing a phase separation treatment on the electrode material (before phase separation) of the present invention to separate the PtTaCo composite phase. In this manufacturing method, the PtTaCo composite phase in the electrode material of the present invention is separated into Pt-rich particles 3A and Ta-rich particles 3B (details of the Pt-rich particles and Ta-rich particles will be described later). As a result, the electrode material of the present invention (after phase separation) becomes a catalyst composite 3 (nanocomposite structure composite) containing nano-sized Pt-rich particles 3A and Ta-rich particles 3B supported on a conductive carrier 2.

[0048] The electrode material of the present invention balances high activity and potential cycling durability, providing an electrode for fuel cells with particularly excellent load-varying cycling characteristics. Therefore, fuel cells equipped with electrodes formed from the aforementioned electrode material exhibit excellent electrode performance and high durability, enabling long-term power generation.

[0049] The constituent elements of the electrode material of the present invention will be described in detail below. It should be noted that the electrode material of the present invention will be described below as an electrode for a solid polymer fuel cell (PEFC), but the electrode material of the present invention is not limited to this application.

[0050] It should be noted that, in the following, the cathode conditions of PEFC refer to the cathode conditions during normal operation of PEFC, which are conditions where the temperature is around room temperature to about 150°C and the gas supply is oxygen-containing gas such as air (oxidizing atmosphere). The anode conditions refer to the anode conditions during normal operation of PEFC, which are conditions where the temperature is around room temperature to about 150°C and the gas supply is fuel gas containing hydrogen (reducing atmosphere).

[0051] [Conductive carrier] The conductive carrier contained in the electrode material of the present invention has the function of improving conductivity (electronic conductivity) when forming an electrode, and also serves as the skeleton of the electrode.

[0052] As a conductive support, any conductive support capable of supporting the catalyst complex is acceptable. Typically, carbon supports are used, but electronically conductive oxide supports and metal supports can also be used.

[0053] The conductive support is more preferably a conductive support with a large surface area, where the catalyst complex is distributed on the surface at a nanoscale. The BET specific surface area of ​​the support is not limited, for example, it can be 100 m². 2 / g~1500m 2 / g.

[0054] The size and shape of the electrode material of the present invention depend on the size and shape of the conductive carrier that serves as its skeleton material. Therefore, the size and shape of the conductive carrier are determined within a range that allows the electrode materials to be in continuous contact when forming the electrode for a fuel cell, and allows for the smooth diffusion of gases such as hydrogen and oxygen and the discharge of water (vapor) within the electrode for a fuel cell.

[0055] [Carbon carrier] As a preferred example of a conductive carrier, a carbon carrier can be used, and any carbon carrier used in electrode materials can be used as long as it does not impair the purpose of the present invention. Its shape and size can be appropriately selected considering the intended use of the electrode, etc. However, in applications such as gas diffusion electrodes for fuel cells, both conductivity and gas diffusion within the electrode during formation are required. Therefore, in order to balance conductivity and gas diffusion, when the carbon carrier is in particulate form, the particle size is 0.03 to 500 μm; when the carbon carrier is in fibrous form, a diameter of 2 nm to 20 μm and an overall length of approximately 0.03 to 500 μm are preferred.

[0056] As a carbon carrier, carbon materials of any shape and size, such as granular or fibrous, can be used. Examples of carbon materials include: carbon black, acetylene black, Ketjen black, activated carbon, mesoporous carbon, carbon nanotubes, carbon nanoangles, carbon nanorings, carbon nanofibers, carbon nanowires, and fullerenes.

[0057] The carbon support used in this invention can be one type, or two or more carbon materials with different sizes (particle size, fiber diameter, and fiber length), crystallinity, etc., can be used in any proportion.

[0058] The preferred carbon carrier is highly crystalline carbon. "Highly crystalline carbon" refers to carbon that has been graphitized (crystallized) through high-temperature heat treatment, etc., and exhibits superior oxidation resistance compared to amorphous and low-crystallinity carbon. The highly crystalline carbon can be either homemade or commercially available.

[0059] Preferred examples of carbon carriers include particulate solid carbon. Among solid carbons, carbon black (CB) and graphitized carbon black (GCB) obtained by graphitizing (crystallizing) it are preferred.

[0060] The particle-shaped solid carbon is preferably 0.03 to 500 μm in size, based on the secondary particle size (the primary particle size is about 10 nm to 100 nm).

[0061] Solid carbon can be made from either homemade or commercially available materials. Examples of commercially available materials include: LionSpecialty Chemicals' "Ketjen Black" series (model: EC600JD, etc.), 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.).

[0062] Commercially available solid charcoal can also be pulverized and adjusted to the target particle size for use.

[0063] Other preferred examples of carbon supports include mesoporous carbon.

[0064] Mesoporous carbon (hereinafter, sometimes referred to as "MC") is porous carbon with many mesoporous regions. As mesoporous carbon, porous carbon with fine pores having mesoporous regions (2–50 nm) can be used, preferably with a pore diameter of 3 nm or more and 40 nm or less. Within this range, even if electron-conducting oxides or electrode catalysts are adhered to (supported) on the inner wall of the fine pores, the diffusion of substances into the interior of the fine pores will proceed smoothly without being significantly hindered.

[0065] 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 metal, which is derived from the ionomer, by means of the electron-conductive oxide supported in the pores of the mesoporous carbon can be suppressed.

[0066] 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.

[0067] The structure of the pores (pore size, shape, etc.) of mesoporous carbon 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).

[0068] In addition to individual pores independent of other pores, the micropores in the mesoporous region of the mesoporous carbon also have interconnecting pores, some or all of which are connected to 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.

[0069] 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.

[0070] Furthermore, the carbon support can also be a carbon support with an electronically conductive oxide layer on its surface. Here, "having an electronically conductive oxide layer on its surface" means that part or all of the surface of the carbon support is covered by an electronically conductive oxide layer. Unlike carbon materials, the electronically conductive oxide layer does not undergo oxidative decomposition. Therefore, by supporting the above-mentioned catalyst complex on the electronically conductive oxide layer without allowing it to directly contact the carbon support, durability (e.g., durability during start-up and shutdown of a fuel cell under high load) is improved.

[0071] 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 body are 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 body" refers to (A) an electronically conductive oxide composed solely of a parent oxide; and (B) an electronically conductive oxide that is doped with other elements and contains more than 80 mol% of the parent oxide.

[0072] Preferred examples of electronically conductive oxide layers include Ta2O5 layers and Nb2O5 layers. Other elements can be doped into Ta2O5 layers and Nb2O5 layers as needed.

[0073] The thickness of the electronically conductive oxide layer also depends on the type and amount of the 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 a portion of the surface of the carbon support.

[0074] [Catalyst composite] The catalyst complex in the electrode material (before phase separation) of the present invention contains a PtTaCo complex consisting of platinum (Pt) as the first component, tantalum (Ta) as the second component, and cobalt (Co) as the third component.

[0075] The proportions of the first to third components in the PtTaCo complex are determined within the range where phase separation occurs in the PtTaCo complex.

[0076] As a preferred composition example of the PtTaCo complex, relative to the total of Pt, Ta and Co (100 atomic%), Pt is 60-80 atomic%, Ta is 10-30 atomic%, and Co is 1-20 atomic%; or Pt is 65-75 atomic%, Ta is 15-25 atomic%, and Co is 5-15 atomic%.

[0077] It should be noted that the Pt7Ta2Co1 disclosed in the embodiments described later is included within this composition range.

[0078] The PtTaCo complex constituting the catalyst complex is based on the first to third components (Pt, Ta, Co), but may also contain other elements (e.g., Ni) without prejudice to the purpose of the present invention. It should be noted that the amounts of each component in the catalyst complex can be investigated using inductively coupled plasma luminescence analysis (ICP).

[0079] The morphology of the catalyst complex supported on the conductive support can be any shape as long as it does not impair the purpose of the present invention. Examples include: particulate, island-like, film-like, and linear.

[0080] From the viewpoint of conductivity during electrode formation, it is preferable that the catalyst complex is particulate and that the particulate catalyst complex does not completely cover the surface of the conductive support, with a portion of the surface of the conductive support exposed, so as to disperse the loading to a degree that does not impede direct contact between the conductive support and other conductive supports.

[0081] The size of the catalyst complex is typically 1–10 nm in diameter, preferably 2–5 nm. The “size of the catalyst complex” can be obtained from the average particle size of any 20 catalyst complexes examined using electron microscopy images. When calculating the average particle size using electron microscopy images, if the particle shape is not spherical, the length in the direction showing the maximum length of the particle is taken as its particle size.

[0082] Furthermore, the loading of the catalyst complex is appropriately determined within a range that yields sufficient electrode catalytic activity when forming the electrode. Typically, the catalyst complex is 5–60% by mass relative to the total weight of the electrode material, or 0.5–30% by mass based on the amount of Pt. Within this range, excellent catalytic activity per unit mass is achieved, resulting in the desired electrode reaction activity corresponding to the loading.

[0083] The PtTaCo complex that constitutes the catalyst complex of the electrode material (before phase separation) of the present invention can be crystalline, amorphous, or a mixture of crystalline and amorphous.

[0084] As described above, the electrode material (before phase separation) of the present invention can be made into the electrode material (after phase separation) of the present invention having a structure in which the catalyst complex (nanocomposite structure complex) is supported on a conductive carrier in the form of the catalyst complex by phase-separating the catalyst complex (PtTaCo complex) into Pt-rich particles and Ta-rich particles, and the catalyst complex is a nanocomposite structure containing Pt-rich particles and Ta-rich particles.

[0085] The method of the phase separation treatment may be any treatment method that can significantly phase-separate the PtTaCo complex, and examples thereof include heat treatment at a high temperature, chemical treatment, electrochemical treatment (including combinations thereof), and the like.

[0086] "Pt-rich particles" refer to particles formed by phase separation of the PtTaCo complex and having Pt as the main component (Pt 50 atomic% or more).

[0087] The atoms other than Pt that constitute the Pt-rich particles are Co contained in the PtTaCo complex before phase separation, and thus the Pt-rich particles are typically PtCo alloy particles.

[0088] The morphology of the Pt-rich particles is arbitrary as long as the object of the present invention is not impaired. In addition, the Pt-rich particles are not limited to crystalline, and can be amorphous or a mixture of crystalline and amorphous.

[0089] The particle size of the Pt-rich particles depends on the particle size and morphology of the PtTaCo complex before phase separation, but is typically 1 to 5 nm (preferably 1 to 3 nm). The "particle size of the Pt-rich particles" can be obtained from the average value of the particle sizes of any catalyst complex (20) investigated by an electron microscope image. When calculating the average particle size using an electron microscope image, in the case where the shape of the fine particles is other than spherical, the length in the direction showing the maximum length of the particles is taken as its particle size.

[0090] "Ta-rich particles" are particles formed by phase separation of the PtTaCo complex and are composed of Ta oxides.

[0091] In the present specification, "Ta oxides" refers to oxides of tantalum (Ta), and is a concept that includes not only crystals of Ta2O5 (TaOx, x = 2.5) as the most stable oxide, but also crystals of oxides in an oxygen-deficient state (TaOx, 0.1 < x < 2.5).

[0092] The Ta oxides that constitute Ta-rich particles may also contain atoms other than Ta and oxygen. Although it depends on the method and conditions of the phase separation process, the Co component of the Ta-rich particles can be dissolved in the Ta oxides during the phase separation of the PtTaCo complex.

[0093] The morphology of the Ta-rich particles is arbitrary as long as it does not impair the purpose of this invention. Furthermore, the Ta-rich particles are not limited to crystals; they can be amorphous or a mixture of crystals and amorphous materials.

[0094] The particle size of Ta-rich particles depends on the particle size and morphology of the PtTaCo complex before phase separation, but is typically 1–5 nm (preferably 1–3 nm). The "particle size of Ta-rich particles" can be obtained from the average particle size of any catalyst complex (20 particles) investigated by electron microscopy images. When calculating the average particle size using electron microscopy images, if the particle shape is not spherical, the length in the direction showing the maximum length of the particle is taken as its particle size.

[0095] Furthermore, as shown in the embodiments, Ta-rich particles may include Ta-core Pt-shell particles. Ta-core Pt-shell particles comprise a core (approximately 1–3 nm) composed of Ta particles and a fine Pt shell (approximately 0.1–3 nm) present on its surface. In this configuration, the fine Pt particles exist stably, thus contributing to high reactivity.

[0096] <2. Electrode> The electrode of the present invention comprises the electrode material of the present invention described above and a proton-conductive electrolyte material. In the electrode of the present invention, the electrode materials of the present invention are in contact with each other to form a conductive path.

[0097] The electrode of the present invention is preferably used as an electrode for fuel cells. 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).

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.).

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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). Mesoporous carbon can also be used as another conductive material.

[0107] 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.

[0108] It should be noted that the electrode for fuel cells containing the electrode material of the present invention has excellent electrochemical catalytic activity for oxygen reduction and hydrogen oxidation, and therefore can be used as a cathode and anode. In particular, it has excellent electrochemical catalytic activity for oxygen reduction, and no electrochemical oxidative decomposition of the conductive material serving as the support occurs under the operating conditions of the fuel cell, so it is particularly preferred as a cathode.

[0109] 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 use the same solid polymer electrolyte membrane as PEFCs.

[0110] <3. Membrane electrode assembly (MEA)> 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 anode are electrodes of the present invention.

[0111] 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 the cathode will be described.

[0112] FIG. 3 This is a schematic cross-sectional view illustrating an embodiment of the membrane electrode assembly of the present invention. FIG. 3 As shown, the membrane electrode assembly 10 has a structure in which the cathode 4 and the anode 5 are arranged facing the solid polymer electrolyte membrane 6.

[0113] The cathode 4 is composed of an electrode catalyst layer 4a and a gas diffusion layer 4b. The electrode catalyst layer 4a uses the electrode of the present invention.

[0114] As the gas diffusion layer 4b, conventionally known gas diffusion layers can be used. Examples include conductive carbon-based sheet members with a fine pore size distribution of approximately 100 nm to 90 μm, which are commonly used as gas diffusion layers in conventional PEFCs. Preferably, these are carbon paper, carbon cloth, or carbon nonwoven fabric that have undergone hydrophobic treatment. 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, and is typically around 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.

[0115] The anode 5 is composed of an electrode catalyst layer 5a and a gas diffusion layer 5b. As the electrode catalyst layer 5a, other known anode electrode catalyst layers can be used in addition to those of the present invention. For example, an electrode in which the 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 for 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.

[0116] 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... FIG. 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.

[0117] 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.

[0118] The embodiments of the membrane electrode assembly of the present invention have been described above with reference to the accompanying drawings, but these are examples of the present invention and various configurations other than those described above may also be used.

[0119] <4. Solid polymer fuel cell> The solid polymer fuel cell (single cell) of the present invention includes the membrane electrode assembly of the present invention, which typically has a structure in which the membrane electrode assembly is held by a spacer having a gas flow path formed therein.

[0120] FIG. 4 This is a conceptual diagram illustrating a representative configuration of the solid polymer fuel cell of the present invention. (See diagram for example.) FIG. 4 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.

[0121] 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.

[0122] 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.

[0123] Example The following examples illustrate the invention in more detail, but the invention is not limited thereto. It should be noted that, in the following, Ketjenheit is sometimes referred to as "KB".

[0124] A. Electrode material (PtTaCo / KB) A1. Production of electrode material As an example, the electrode material is according to... FIG. 5 The electrode material of Example 1 below was manufactured according to the flowchart shown.

[0125] The conductive support (carbon support) and metal catalyst precursor compound (starting compound) used are described below.

[0126] [Conductive carrier (carbon carrier)] Ketjenblack (KB) (EC600JD, Lion Specialty Chemicals Co., Ltd.) was used as the carbon carrier.

[0127] [Pt raw material compound] Acetylacetone Pt (Acetylacetone Platinum (II), Sigma Aldrich) (hereinafter, sometimes referred to as "Pt(acac)2") was used as the Pt starting compound.

[0128] [Ta raw material compound] Tantalum ethoxide (Ta(OC2H5)5, (Co., High Purity Chemical Research Institute)) was used as the Ta raw material compound.

[0129] [Co raw material compound] Cobalt(II) nitrate hexahydrate (Co(NO3)2·6H2O, Kishida Chemical Co., Ltd.) was used as the Co raw material compound.

[0130] <Example 1: Pt7Ta2Co1 / KB> Process (1) First, as the raw material compounds for Pt, Co, and Ta, Pt(acac)₂ was dissolved in dichloromethane (10 mL), and (Ta(OC₂H₅)₅ and (Co(NO₃)₂·6H₂O) were dissolved in ethanol. It should be noted that the atomic ratio of Pt:Ta:Co is 7:2:1 based on the amount of material. Next, the reagent solutions were added to a dispersion of 125 mg of Ketjen Black (KB) that had been ultrasonically dispersed in an ethanol solution beforehand. Finally, acetone, which accounts for about 20% of the total volume of the solvent, was added to prepare a dispersion (total ethanol: 110 mL, acetone: 30 mL).

[0131] It should be noted that the loading amount of Pt raw material compound (Pt(acac)2), Ta raw material compound (Ta(OC2H5)5) and Co raw material compound (Co(NO3)2·6H2O) is 40wt% based on the loading amount of PtTaCo composite relative to the overall electrode material.

[0132] Next, the eggplant-shaped flask containing the sample was placed in a rotary evaporator with both decompression and rotation functions. Ultrasonic waves were applied while decompression was applied until all the solvent was evaporated. The flask was then rotated and evaporated until the solvent was completely evaporated, thereby obtaining a dry powder of the precursor of the PtTaCo complex adsorbed on the KB surface (both the inner and outer surfaces of the pores).

[0133] Process (2) The powder obtained in step (1) was heated to 210°C in an Ar atmosphere (heating rate 1°C / min) and held for 3 hours, and then further heated to 240°C in an Ar atmosphere (heating rate 1°C / min) and held for 3 hours. After that, it was further heated to 800°C in an Ar atmosphere for 30 minutes and held for 30 minutes to produce the electrode material of Example 1 (Pt7Ta2Co1 / KB) composed of KB carrying the Pt7Ta2Co1 composite.

[0134] <Comparative example 1> A Pt / C catalyst (Tanaka Precious Metals Industry Co., Ltd., TEC10E50E, Pt 46wt%) was used as the electrode material for Comparative Example 1.

[0135] <Comparative example 2> As a comparative example 2, the Pt3Co1 / C catalyst (manufactured by Tanaka Precious Metals Industry Co., Ltd., TEC36E52, Pt 46wt%, Co 5wt%, Pt∶Co (atomic ratio) = 3∶1) A2. Electrochemical evaluation (half cell) The electrodes used for evaluation are fabricated according to the following steps.

[0136] First, a mixture of 19 mL ultrapure water and 6 mL 2-propanol was added to a sample vial containing electrode material powder. Then, 5% Nafion dispersion was added at an I / C ratio of 0.3. 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 a glassy carbon (GC) disk electrode, which was then fixed in a rotating device and dried at room temperature for about 30 minutes at a rotation speed of 300 rpm, thereby forming a Nafion film. This fixed the electrode material onto the GC electrode, resulting in the evaluation electrode (working electrode).

[0137] A2-1. Load variation cycle test The load variation cycle test was 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 May 2023). FIG. 6 The load variation cycle shown promotes degradation associated with catalyst dissolution / re-precipitation, etc., by using 0.6–0.95V.RHE The experiment was conducted by applying a rectangular wave for 3 seconds in each cycle, for a total of 6 seconds.

[0138] For the electrode material of Example 1, the ECSA and 0.9V were measured from 0 (initial) cycles up to 400,000 cycles per 100,000 cycles. RHE MA below.

[0139] Furthermore, for Comparative Example 1 (Pt / C catalyst (TEC10E50E)) and Comparative Example 2 (Pt3Co / C catalyst (TEC36E52)), load variation tests were conducted under the same conditions up to 100,000 cycles, and the ECSA and 0.9V were measured. RHE MA below.

[0140] A2-2. Evaluation by cyclic voltammetry (CV) The electrode materials of Example 1 (Pt7Ta2Co1 / KB), Comparative Example 1 (Pt / C), and Comparative Example 2 (Pt3Co1 / C) were evaluated using cyclic voltammetry (CV). The electrochemical effective surface area (ECSA) was calculated based on the amount of hydrogen adsorbed from the CV. It should be noted that ECSA is equivalent to the effective surface area of ​​Pt contained in the electrode material.

[0141] The CV measurement conditions are as follows. It should be noted that, assuming that each Pt atom adsorbs one H atom, the temperature becomes 210 μC / cm³. 2 The amount of electricity.

[0142] Measurement: Three-electrode cell (working electrode: fuel cell electrode for evaluation, counter electrode: graphite or Pt, reference electrode: Ag / AgCl).

[0143] Electrolyte: 0.1M HClO4 (pH: approximately 1).

[0144] Measurement potential range: 0.05~1.2V (based on reversible hydrogen electrode).

[0145] Scanning speed: 50mV / s.

[0146] Hydrogen adsorption capacity: calculated based on the peak area of ​​hydrogen adsorption in the range of 0.05–0.4 V.

[0147] Electrochemical effective surface area (ECSA): Calculated according to the following formula.

[0148] ECSA = (Hydrogen adsorption capacity) [μC] / 210 [μC / cm²] 2 ] CV evaluation was performed before and after a load variation cycle test on the electrode using the electrode material of Example 1. The results showed that, in the initial state of 0 cycles, a hydrogen adsorption / desorption peak was observed on the low potential side of the CV curve, indicating that oxygen adsorption on the Pt surface began near 0.8VRHE. As the number of cycles increased, the hydrogen adsorption / desorption peak in the CV curve became smaller.

[0149] FIG. 7 The figure shows the relationship between the number of load variation cycles and the electrochemical effective surface area (ECSA) of each electrode material in Example 1 (Pt7Ta2Co1 / KB), Comparative Example 1 (Pt / C), and Comparative Example 2 (Pt3Co1 / C).

[0150] like FIG. 7 As shown, at the beginning of the load variation cycle (0 cycles), Example 1 exhibits an ECSA value comparable to Comparative Example 1 and larger than that of Comparative Example 2. Subsequently, as the number of load variation cycles increases, the ECSA of Comparative Example 1 decreases, while the ECSA of Comparative Example 2 progresses smoothly. In contrast, as the number of load variation cycles increases, the ECSA of Example 1, although decreasing, remains larger than that of Comparative Examples 1 and 2.

[0151] Therefore, from the ECSA's point of view, Example 1 is judged to have superior durability compared to Comparative Example 1 and Comparative Example 2.

[0152] A2-3. Evaluation of ORR activity ORR activity was evaluated for the electrode materials of Example 1 (Pt7Ta2Co1 / KB), Comparative Example 1 (Pt / C), and Comparative Example 2 (Pt3Co1 / C).

[0153] ORR activity was determined by linear sweep voltammetry (LSV) using the rotating disk electrode method (RDE) 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.

[0154] Mass activity = i k Pt mass on the electrode 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.

[0155] As a specific procedure, firstly, after bubbling O2 at 50 mL / min for 30 minutes, the volume is increased from 0.2V.RHE The potential is scanned at 10 mV / s towards the high potential direction up to 1.2 V. 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).

[0156] The results of evaluating the linear sweep voltammograms (LSVs) of the electrode using the electrode material of Example 1 before and after load variation cycling at 1600 rpm showed that the ORR onset potential decreased slightly faster from 0 cycles to 100,000 cycles, and slower at 200,000, 300,000, and 400,000 cycles. This can be inferred to be that during the load variation cycling test, the surface of the Pt7Ta2Co1 composite undergoes dissolution of Co, dissolution / precipitation of Pt, and potential cycling, transforming into a stable catalyst structure consisting of the separation of the PtCo alloy and Ta oxide (TaOx) phases.

[0157] FIG. 8 The figure shows the relationship between the number of load variation cycles and mass activity (MA) of each electrode material in Example 1, Comparative Example 1 and Comparative Example 2.

[0158] like FIG. 8 As shown, at the beginning of the load variation cycle (cycle number 0), Example 1 shows a value that is comparable to that of Comparative Example 1 and smaller than that of Comparative Example 2.

[0159] Subsequently, as the number of load variation cycles increased, the MA of Comparative Example 1 and Comparative Example 2 decreased significantly, but the decrease in MA of Example 1 was more stable compared to Comparative Example 1 and Comparative Example 2. Therefore, from the viewpoint of MA, Example 1 was also judged to have superior durability than Comparative Example 1 and Comparative Example 2.

[0160] A3. Physical property evaluation (microstructure evaluation) FIG. 9 The results of STEM-EDS analysis of the electrode material of Example 1 are shown in the figure.

[0161] FIG. 9 (a) to (c) are the results before the load variation cycle test (initial: 0 cycles), (a) is the STEM image, (b) is the EDS-based mapping image (Pt+Ta+Co), and (c) is the EDS-based line profile (Pt, Ta).

[0162] FIG. 9 (d) to (f) are the results after load variation cyclic test (400,000 cycles). (d) is a STEM image, (e) is a mapping image based on EDS (Pt+Ta+Co), and (f) is a line profile based on EDS (Pt, Ta).

[0163] In the electrode material of Example 1 prior to the load variation cycle test, by FIG. 9 As can be seen from the STEM image of (a), the catalyst particles are uniformly and highly dispersed on the carbon support (KB) with a diameter of 2-5 nm.

[0164] according to FIG. 9 In the mapping image of (b), the elemental distributions of Pt, Ta, and Co largely overlap in most of the catalyst particles, thus indicating that the initial (before the cycle test) catalyst particles existed as a complex of Pt, Ta, and Co. FIG. 9 In the line analysis image of (c), it can be confirmed that there is a slight excess of Ta on the particle surface.

[0165] On the other hand, in the electrode material of Example 1 after load variation cycle testing (400,000 cycles), according to FIG. 9 STEM image of (d) and FIG. 9 The mapping image of (e) shows that the Pt particle size has grown slightly compared to the initial state, confirming large particles with a diameter exceeding 5 nm, and as... FIG. 9 As indicated by the white arrow in (d), a large number of particles that have hardly changed from the initial state were also confirmed.

[0166] Moreover, according to FIG. 9 (e) confirms that after the variable load cycling test (400,000 cycles), a portion of the catalyst complex underwent phase separation, revealing the presence of Pt-rich and Ta-rich particles. Furthermore, according to... Industrial applicability (f) confirmed that Pt is present in a roughly uniform manner within the Pt-rich particles, while the distribution of Ta is concentrated in the center of the particles. Based on this result, it was determined that at least a portion of the catalyst complex after the load variation cycle test (400,000 cycles) has a structure in which Pt-rich particles cover the surrounding Ta-rich particles, a so-called "Ta core Pt shell" structure.

[0167] Based on the comparative analysis of catalyst particles before and after the load variation cycling test of the electrode material in Example 1, it is inferred that the nanocomposite structure containing Pt-rich and Ta-rich particles, formed through phase separation of the PtTaCo composite (catalyst composite), contributes to the improved performance of the electrode material in Example 1. Even after 400,000 load variation cycles, the catalyst composite particles (Pt7Ta2Co1) of Example 1 maintained a high degree of dispersion and loading on the Ketjen Black (KB) surface, indicating that, compared to conventional catalysts, it can prevent the expansion of catalyst particles caused by shedding and dissolution during the load variation cycling test.

[0168] Explanation of reference signs The electrode material of the present invention provides an electrode for fuel cells with excellent catalytic activity, electronic conductivity, gas diffusion, and excellent durability, and is expected to serve as an electrode component for solid polymer fuel cells used in the automotive, power, gas, and home appliance industries. In particular, it is anticipated for use in fuel cell vehicles (passenger cars and commercial vehicles) with drastic load variations.

[0169] ​ 1: Electrode material; 2: Conductive carrier; 3: Catalyst complex; 3A: Rich in Pt particles; 3B: Ta-rich particles; 4: Electrode (cathode) for fuel cells; 4a: Electrode catalyst layer (cathode); 4b: Gas diffusion layer; 5: Electrode (anode) for fuel cells; 5a: Electrode catalyst layer (anode); 5b: Gas diffusion layer; 6: Solid polymer electrolyte membrane; 10: Membrane electrode assembly (MEA); 20: Solid polymer fuel cells; 21: External circuit.

Claims

1. An electrode material, characterized by, a catalyst composite supported on the electrically conductive carrier, the catalyst composite contains a PtTaCo composite composed of platinum (Pt) as a first component, tantalum (Ta) as a second component, and cobalt (Co) as a third component.

2. The electrode material according to claim 1, wherein the electrode material is formed by phase separation of the PtTaCo composite that constitutes the catalyst composite.

3. The electrode material according to claim 2, wherein the catalyst composite after phase separation contains Pt-rich particles and Ta-rich particles.

4. The electrode material according to claim 3, wherein the Pt-rich particles are a PtCo alloy.

5. The electrode material according to claim 3 or 4, wherein the Ta-rich particles are a Ta oxide.

6. The electrode material according to any one of claims 1 to 5, wherein with respect to 100 atomic% of the total of Pt, Ta, and Co, Pt is 60 to 80 atomic%, Ta is 10 to 30 atomic%, and Co is 1 to 20 atomic%.

7. The electrode material according to any one of claims 1 to 6, wherein the electrically conductive carrier is a carbon carrier.

8. The electrode material according to claim 7, wherein the carbon carrier is a highly crystalline carbon.

9. An electrode comprising the electrode material according to any one of claims 1 to 8 and a proton-conducting electrolyte material.

10. A membrane-electrode assembly having: a solid polymer electrolyte membrane; a cathode joined to one face of the solid polymer electrolyte membrane; and an anode joined to the other face of the solid polymer electrolyte membrane, either or both of the anode or the cathode being the electrode according to claim 9.

11. A solid polymer fuel cell provided with the membrane-electrode assembly according to claim 10.

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