JP2023171977A - Electrode catalyst, manufacturing method thereof, and fuel battery - Google Patents

Abstract

To provide an electrode catalyst which can exhibit a satisfactory performance when being used in a fuel battery.SOLUTION: An electrode catalyst comprises: a catalyst component including a first transition metal M1 and a second transition metal M2 as constituent elements; and a conductive material. The electrode catalyst is in the form of a particle containing the first transition metal M1, the second transition metal M2, carbon, hydrogen, nitrogen and sulfur as constituent elements, of which the hydrogen and nitrogen contents are both smaller than 1%. On the surface of the particle, sulfide of the first transition metal M1 and the second transition metal M2 in the form of metal are observed.SELECTED DRAWING: Figure 5

Description

The present invention relates to an electrode catalyst, a method for producing the same, and a fuel cell obtained thereby.

Conventionally, platinum catalysts have generally been widely used as electrode catalysts for fuel cells for both anodes and cathodes, but since platinum catalysts are expensive and a depletable resource, the development of alternative catalysts has been actively researched. It's here.

In order to reduce the amount of metal catalyst such as platinum, it has been considered to maximize the catalytic activity per unit metal, and for this purpose, the use of organometallic complexes has been considered (Patent Document 1). Furthermore, metal sulfides containing sulfur have been reported as excellent catalysts for both anode and cathode catalysts (Patent Document 2, Non-Patent Documents 1 and 2). The catalytic activity of metal sulfides varies depending on the type of metal and the ratio of metal to sulfur. From this point of view, catalysts containing two or more different metals and sulfur have also been widely studied (Non-Patent Documents 3-5).

Furthermore, it is known that a nitrogen-containing carbon alloy obtained by firing a precursor selected from inorganic metal salts and organic metal complexes can be used as a fuel cell catalyst (Patent Document 3). The structures of a series of carbon alloys obtained in this way have been studied in detail. For example, Non-Patent Document 6 describes a carbon alloy catalyst obtained by firing a precursor made of iron phthalocyanine and a phenol resin, and the results of synchrotron radiation analysis thereof.

International Publication No. 2010/143663 Japanese Patent Application Publication No. 2007-87827 International Publication No. 2016/035705

International J. of Hydrogen Energy, 2017, 42, 14253-14263 J. Electrochem. Soc. , 2015, 162, F455-F462. J. Appl. Electrochem, 2016, 46, 497-503 J. Power. Source, 2016, 334, 112-119 Electrochica Acta, 2000, 45, 4237-4250 Surface Science, Vol. 32, No. 11, pp. 716-722, 2011

Conventional electrode catalysts for fuel cells using organometallic complexes and metal sulfides still do not have sufficient performance for use as fuel cells, and further improvement in performance is required. Therefore, an object of the present invention is to provide an electrode catalyst that can exhibit sufficient performance when used as a fuel cell.

As a result of studying the above-mentioned problems, the present inventors found that by applying a type of heat treatment technique called carbonization to a metal complex in which two different metal ions were cross-linked with sulfur, two types of metals and sulfur remained. It was found that a heterogeneous catalyst (carbonization catalyst) was produced. Furthermore, among the carbonization catalysts, those whose hydrogen and nitrogen contents are within a certain range have significantly improved catalytic performance compared to metal complexes that provide the carbonization catalysts, and that the catalysts can be used in hydrogen-oxygen fuel cells. The present invention was completed by confirming that it functions as an electrode catalyst for both the anode and cathode.

That is, the present invention relates to the following [1] to [15].
[1]
An electrode catalyst comprising a catalyst component containing a first transition metal M1 and a second transition metal M2 as constituent elements and a conductive material,
Particles containing a first transition metal M1, a second transition metal M2, carbon, hydrogen, nitrogen and sulfur as constituent elements, and in which the hydrogen content and nitrogen content are both less than 1% by weight,
An electrode catalyst in which a sulfide of a first transition metal and a second transition metal in a metallic state are observed on the surface of the particles.

[2]
The first transition metal M1 is one selected from the group consisting of Ni, Mn, Fe, Co, Cu, and Zn,
The electrode catalyst according to [1] above, wherein the second transition metal M2 is any one selected from the group consisting of Ru, Rh, Pd, Ag, Ir, and Pt.

[3]
the first transition metal M1 is Ni,
The electrode catalyst according to [1] above, wherein the second transition metal M2 is any one selected from the group consisting of Ru, Rh, and Ir.

[4]
The conductive material is acetylene black, Vulcan, Ketjen black, black pearl, graphitized acetylene black, graphitized Vulcan, graphitized Ketjen black, graphitized black pearl, carbon nanotube, carbon nanofiber, carbon nanohorn, and carbon. The electrode catalyst according to any one of [1] to [3] above, which is selected from the group consisting of fibrils.

[5]
A method for producing an electrode catalyst, including the following steps 1a and 2a:
Step 1a: Formula (1) below

（式（１）において、Ｍは、Ｒｕ^II、Ｒｈ^IIIまたはＩｒ^IIIである。Ｌはヘキサメチルベンゼン基またはペンタメチルシクロペンタジエニル基を表す。Ｘは、ハロゲン原子または水素原子、ヒドリドイオンを表し、Ｘが水素原子、ヒドリドイオンの場合、ＸはＮｉ^IIとブリッジを形成していても良い。Ｙは、ハロゲン原子またはＨ₂Ｏを表す。ｌ、ｍおよびｎは、それぞれ独立して２～４の整数である。Ｒはそれぞれ独立して、炭素数１～５のアルキル基である。ｚは錯体の電荷を表し、０または２＋である。）で表される金属錯体を導電性材料と混合し、混合物を得る工程；並びに、
工程２ａ：前記工程１ａで得られた混合物を乾留させる工程。

(In formula (1), M is Ru ^II , Rh ^III or Ir ^III . L represents a hexamethylbenzene group or a pentamethylcyclopentadienyl group. X represents a halogen atom, a hydrogen atom, or a hydride ion. and when X is a hydrogen atom or a hydride ion, X may form a bridge with Ni ^II . Y represents a halogen atom or H ₂ O. l, m and n each independently represent 2 An integer of ~4.R is each independently an alkyl group having 1 to 5 carbon atoms.z represents the charge of the complex and is 0 or 2+. and obtaining a mixture; and
Step 2a: A step of carbonizing the mixture obtained in step 1a.

[6]
The manufacturing method according to [5] above, wherein the step 2a is performed under vacuum at a temperature of 100 to 800°C.

[7]
The manufacturing method according to item [6] above, wherein the temperature is within a range of 300 to 800°C.
[8]
The manufacturing method according to [6] or [7], wherein the vacuum has a degree of vacuum of 10 to 20 Pa.

[9]
The conductive material is acetylene black, Vulcan, Ketjen black, black pearl, graphitized acetylene black, graphitized Vulcan, graphitized Ketjen black, graphitized black pearl, carbon nanotube, carbon nanofiber, carbon nanohorn, and carbon. The manufacturing method according to any one of [5] to [8] above, wherein the method is one selected from the group consisting of fibrils.

[10]
An electrode catalyst obtained by the production method described in [8] above.
[11]
A fuel cell electrode comprising the electrode catalyst according to any one of [1] to [4] and [10].

[12]
A membrane electrode assembly comprising a cathode, an anode, and a proton conductive membrane disposed between the cathode and the anode, wherein at least one selected from the group consisting of the cathode and the anode is the [11 ] A membrane electrode assembly which is an electrode for a fuel cell.

[13]
A fuel cell comprising the membrane electrode assembly according to [12] above.
[14]
A fuel cell comprising the fuel cell electrode according to [11] above as a cathode, an anode, or both a cathode and an anode.

[15]
The fuel cell according to [13] or [14] above, which is a hydrogen-oxygen fuel cell.

According to the present invention, it is possible to provide an electrode catalyst that can exhibit sufficient performance when used as a fuel cell and can be used for both an anode and a cathode. Furthermore, by using the catalyst of the present invention, catalytic reactions using hydrogen and oxygen can be controlled over a wide range.

FIG. 1 shows a TG-DSC curve of a mixture of [Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ] and carbon black, which was simultaneously measured by differential thermogravimetry. FIG. 2 shows a mixture of [Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ] and its carbon black and Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ]. The X-ray photoelectron spectroscopy (XPS) spectrum of the carbonization catalyst synthesized from FIG. 3 shows [Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ], its carbon black mixture and Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ]. The X-ray diffraction (XRD) pattern of the carbon black and carbon black synthesized from FIG. 4 shows a mixture of [Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ] and its carbon black and Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ]. The results of elemental analysis and thermogravimetric analysis (TG) of the carbonization catalyst synthesized from FIG. 5 shows a mixture of [Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ] and its carbon black and Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ]. The results of (scanning) transmission electron microscopy ((S)TEM) observation and energy dispersive X-ray spectroscopy (EDS) mapping of the carbonization catalyst synthesized from FIG. 6 shows the configuration of a fuel cell used for hydrogen-oxygen fuel cell evaluation. Figure 7 shows the results of a hydrogen-oxygen fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst prepared at 600°C as an anode electrode catalyst. Figure 8 shows the results of a hydrogen-oxygen fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst prepared at 600°C as a cathode electrode catalyst. FIG. 9 shows the carbonization temperature dependence results of a hydrogen-oxygen fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst as an anode electrode catalyst. FIG. 10 shows the carbonization temperature dependence results of a hydrogen-oxygen fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst as a cathode electrode catalyst. FIG. 11 shows the results of a hydrogen-oxygen fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst prepared at 600° C. as both the anode and cathode electrode catalysts. FIG. 12 shows the results of a Tafel plot of a hydrogen-oxygen fuel cell using a mixture of [Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ] and its carbon black as an anode electrode catalyst. FIG. 13 shows the Tafel plot results of a hydrogen-oxygen fuel cell using a nickel-rhodium carbonization catalyst prepared at 600° C. as an anode electrode catalyst. FIG. 14 shows the results of a Tafel plot of a hydrogen-oxygen fuel cell using a mixture of [Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ] and its carbon black as a cathode electrode catalyst. FIG. 15 shows the Tafel plot results of a hydrogen-oxygen fuel cell using a nickel-rhodium carbonization catalyst prepared at 600° C. as a cathode electrode catalyst. FIG. 16 shows the impedance spectrum of a hydrogen-oxygen fuel cell using a mixture of [Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ] and its carbon black as an anode electrode catalyst. FIG. 17 shows the impedance spectrum of a hydrogen-oxygen fuel cell using a nickel-rhodium carbonization catalyst prepared at 600° C. as an anode electrode catalyst. FIG. 18 shows the impedance spectrum of a hydrogen-oxygen fuel cell using a mixture of [Ni ^II Cl(N ₂ S ₂ )Rh ^III Clη ⁵ -C ₅ Me ₅ ] and its carbon black as a cathode electrode catalyst. FIG. 19 shows the impedance spectrum of a hydrogen-oxygen fuel cell using a nickel-rhodium carbonization catalyst prepared at 600° C. as a cathode electrode catalyst.

[Electrode catalyst]
The electrode catalyst according to the present invention is
An electrode catalyst comprising a catalyst component containing a first transition metal M1 and a second transition metal M2 as constituent elements and a conductive material,
These particles include a first transition metal M1, a second transition metal M2, carbon, hydrogen, nitrogen, and sulfur as constituent elements.

In a preferred embodiment of the present invention, the first transition metal M1 is one selected from the group consisting of Ni, Mn, Fe, Co, Cu, and Zn. Here, in a particularly preferred embodiment of the present invention, the first transition metal M1 is Ni.

On the other hand, the second transition metal M2 is usually a transition metal different from the first transition metal M1, and in a preferred embodiment of the present invention, the second transition metal M2 is composed of Ru, Rh, Pd, Ag, Ir, and Pt. Any one selected from the group. Here, in a particularly preferred embodiment of the present invention, the second transition metal M2 is one selected from the group consisting of Ru, Rh, and Ir.

In the present invention, both the hydrogen content and the nitrogen content in the particles are less than 1% by weight. This means that even if the particles contain the first transition metal M1, the second transition metal M2, carbon, hydrogen, nitrogen, and sulfur as constituent elements, both the hydrogen content and the nitrogen content are less than 1% by weight. This is based on the findings of the present inventors that, when used as an electrode catalyst for a fuel cell, particles having the following properties had a significantly higher power density than other particles. Here, the hydrogen content is preferably 0.90% by weight or less, more preferably 0.50% by weight or less, and 0.30% by weight from the viewpoint of obtaining higher power density. The following is particularly preferable. The lower limit of the hydrogen content is not particularly limited as long as the effects of the present invention can be exhibited, but it is preferably 0.01% by weight or more, and more preferably 0.10% by weight or more. On the other hand, the nitrogen content is preferably 0.30% by weight or less, more preferably 0.25% by weight or less, and 0.22% by weight or less, from the viewpoint of obtaining higher power density. It is particularly preferable that The lower limit of the nitrogen content is not particularly limited as long as the effects of the present invention can be exhibited, but it is preferably 0.01% by weight or more, and more preferably 0.10% by weight or more. Note that the content of each element constituting the particles can be determined by elemental analysis.

Further, on the surface of the particles, sulfides of the first transition metal M1, a metallic second transition metal M2, and sulfides of the second transition metal M2 are observed. Here, "metal state" means that the valence of the target metal is zero. The presence of sulfide of the first transition metal M1 can be confirmed by XRD and XPS. Further, the presence of the second transition metal M2 in a metallic state can be confirmed by XRD and XPS. Further, the presence of sulfide of the second transition metal M2 can be confirmed by XRD.

Such an electrode catalyst can also be viewed as a composite catalyst including a catalyst component containing a first transition metal M1, a second transition metal M2, carbon, hydrogen, nitrogen, and sulfur as constituent elements, and a conductive material. . In one of the preferred embodiments of the present invention, the catalyst component includes a first transition metal M1 having an organic ligand containing hydrogen and nitrogen as constituent atoms, a second transition metal M2, and the first transition metal M2. This is a heat-treated product obtained by carbonizing an organometallic complex containing a sulfur atom linking the transition metal M1 and the second transition metal M2.

On the other hand, the electrode catalyst of the present invention also contains a conductive material. Examples of the conductive materials constituting the electrode catalyst of the present invention include acetylene black, Vulcan, Ketjen black, black pearl, graphitized acetylene black, graphitized Vulcan, graphitized Ketjen black, graphitized black pearl, and carbon nanotubes. , carbon nanofibers, carbon nanohorns, and carbon fibrils. The conductive materials used in the present invention may be used alone or in combination of two or more.

The content of the conductive material in the electrode catalyst of the present invention is not particularly limited as long as the effects of the present invention can be obtained, but is usually 1% by weight or more and 99% by weight or less based on the total amount of the electrode catalyst. However, when the electrode catalyst of the present invention is obtained by production method A described below, the content of the conductive material in the obtained electrode catalyst is considered to be higher than the content of the conductive material in the mixture obtained in Step 1 described later. For example, when the same amount of the conductive material and the metal complex represented by the following formula (A) are used in Step 1, the amount of the conductive material in the resulting electrode catalyst is the same as that obtained from the metal complex. It is expected that the amount is greater than the amount of the catalyst component containing the first transition metal M1 and the second transition metal M2 as constituent elements. Therefore, in one of the preferred and exemplary embodiments of the present invention, the lower limit of the content of the conductive material in the electrode catalyst of the present invention is preferably 30% by weight or more, more preferably 50% by weight or more. The upper limit is preferably 80% by weight or less, more preferably 70% by weight or less.

[Method for producing electrode catalyst]
The electrode catalyst according to the present invention is, for example,
A first transition metal M1 having an organic ligand containing hydrogen and nitrogen as constituent atoms, a second transition metal M2, and sulfur linking the first transition metal M1 and the second transition metal M2. a step of mixing an organometallic complex containing atoms with a conductive material to obtain a mixture;
It can be obtained by a manufacturing method including a step of carbonizing the mixture.

Here, the sulfur atom is preferably contained in the organic ligand. That is, the organic ligand contains hydrogen, nitrogen, and sulfur as constituent atoms, and the sulfur constituting the organic ligand binds the first transition metal M1 and the second transition metal M2. Preferably linked. Examples of molecules constituting such organic ligands include amines having two or more ω-mercaptoalkyl groups, alkylene diamines having two or more ω-mercaptoalkyl groups, and polyalkyleneimines having two or more ω-mercaptoalkyl groups. Examples include. It is preferable that the nitrogen atoms constituting the amine, the alkylene diamine, and the polyalkylene imine are each independently bonded to an alkyl group such as a methyl group. In a preferred embodiment of the present invention, the polyalkylene imine having two or more ω-mercaptoalkyl groups is a linear polyalkylene imine in which one ω-mercaptoalkyl group is bonded to each nitrogen atom at both ends. , an example of which is N,N'-dimethyl-3,7-diazanonane-1,9-dithiol.

Further, the first transition metal M1 and the second transition metal M2 constituting the organometallic complex are the same as those described above in the "electrode catalyst" section.
When using the above production method, it tends to be easy to control the catalytic ability of the resulting electrode catalyst by changing the metal species and ligands constituting the organometallic complex. For example, by changing the combination of the first transition metal M1 and the second transition metal M2, it is possible to change the catalytic ability of the resulting electrode catalyst.

（式（Ａ）において、Ｍ１は、前記第１の遷移金属Ｍ１であり、Ｍ２は前記第２の遷移金属Ｍ２である。Ｌ、ＸおよびＹは、適当な配位子を表し、Ｘは、Ｍ１とブリッジを形成していても良い。ｌ、ｍおよびｎは、それぞれ独立して２～４の整数である。Ｒはそれぞれ独立して、炭素数１～５のアルキル基である。ｚは錯体の電荷を表し、０または２＋である。）で表される金属錯体を導電性材料と混合し、混合物を得る工程；並びに、
工程２：前記工程１で得られた混合物を乾留させる工程。 Here, in a preferred and exemplary embodiment of the present invention, the manufacturing method is Manufacturing Method A, which includes the following steps 1 and 2:
Step 1: Formula (A) below

(In formula (A), M1 is the first transition metal M1, M2 is the second transition metal M2, L, X and Y represent appropriate ligands, and X is It may form a bridge with M1. l, m and n are each independently an integer of 2 to 4. R is each independently an alkyl group having 1 to 5 carbon atoms. z is A step of mixing a metal complex represented by (representing the charge of the complex and being 0 or 2+) with a conductive material to obtain a mixture; and
Step 2: A step of carbonizing the mixture obtained in Step 1.

（式（１）において、Ｍは、Ｒｕ^II、Ｒｈ^IIIまたはＩｒ^IIIである。Ｌはヘキサメチルベンゼン基またはペンタメチルシクロペンタジエニル基を表す。Ｘは、ハロゲン原子または水素原子、ヒドリドイオンを表し、Ｘが水素原子、ヒドリドイオンの場合、ＸはＮｉ^IIとブリッジを形成していても良い。Ｙは、ハロゲン原子またはＨ₂Ｏを表す。ｌ、ｍおよびｎは、それぞれ独立して２～４の整数である。Ｒはそれぞれ独立して、炭素数１～５のアルキル基である。ｚは錯体の電荷を表し、０または２＋である。）で表される金属錯体を導電性材料と混合し、混合物を得る工程；並びに、
工程２ａ：前記工程１ａで得られた混合物を乾留させる工程。 Here, in one of the typical and preferred aspects of the present invention, the manufacturing method A is manufacturing method A1 including the following steps 1a and 2a:
Step 1a: Formula (1) below

(In formula (1), M is Ru ^II , Rh ^III or Ir ^III . L represents a hexamethylbenzene group or a pentamethylcyclopentadienyl group. X represents a halogen atom, a hydrogen atom, or a hydride ion. and when X is a hydrogen atom or a hydride ion, X may form a bridge with Ni ^II . Y represents a halogen atom or H ₂ O. l, m and n each independently represent 2 An integer of ~4.R is each independently an alkyl group having 1 to 5 carbon atoms.z represents the charge of the complex and is 0 or 2+. and obtaining a mixture; and
Step 2a: A step of carbonizing the mixture obtained in step 1a.

Here, in a particularly preferred embodiment of the present invention, the metal complex of (1) above has N,N'-dimethyl-3,7-diazanonane-1,9- as an organic ligand coordinated to the Ni atom. Dithiolate ligand (corresponds to the case where the above l and n are 2, the above m is 3, and R is a methyl group. In this specification, it may be referred to as "N ₂ S ₂ ".) Each of the above L has a pentamethylcyclopentadienyl group.

Further, the halogen atom that can constitute the above-mentioned X and Y is preferably a chlorine atom.
Moreover, said M is preferably Rh ^III .
The metal complex (1) above can be obtained using a conventionally known method, for example, Inorg. Chem. , 1990, 4779-4788, Inorg. Chem. 1990, 29, 2023-2025, Org. Lett. 2004, 6, 2785-2788, Science 2007, 316, 585-587, Angew. Chem. Int. Ed. It can be obtained with reference to the methods described in 2013, 56, 9723-9726, JP 2017-132671, and the like.

The step of obtaining the mixture can be performed by a conventionally known method, including step 1 in the manufacturing method A and step 1a in the manufacturing method A1. Here, the conductive material that is blended together with the metal complex represented by the above formula (A) or the above formula (1) and is included in the mixture is the conductive material described above in the "electrode catalyst" section. The same is true.

On the other hand, the step of carbonizing the mixture, including step 2 in the manufacturing method A and step 2a in the manufacturing method A1, is performed as a step of heat-treating the mixture. This carbonization causes thermal decomposition of the organometallic complex contained in the mixture, and volatile components containing hydrogen as a constituent element and volatile components containing nitrogen as a constituent element are eliminated. For example, in the case of the metal complex represented by the above formula (1), such thermal decomposition may start at around 220°C. On the other hand, sulfur-containing components derived from organometallic complexes tend to be relatively difficult to desorb even under temperature conditions where volatile components containing hydrogen or nitrogen as a constituent element desorb. . As a result, a chemical species containing the first transition metal M1 and the second transition metal M2 as constituent elements is generated, which has a low hydrogen and nitrogen content but a relatively high sulfur content, It is assumed that this functions as a carbonization catalyst.

Here, the carbonization can usually be performed under vacuum or under an atmosphere of nitrogen, argon, or the like, and is preferably performed under vacuum from the viewpoint of removing decomposition products. Here, the degree of vacuum is usually 10 to 20 Pa.

The temperature at which the carbonization is performed is not particularly limited as long as the catalyst obtained by the carbonization (hereinafter referred to as "carbonization catalyst") can exhibit the effects of the present invention. However, the higher the temperature at which the carbonization is performed, the lower the hydrogen content and nitrogen content in the obtained carbonization catalyst tend to be. As confirmed in the examples described below, a carbonization catalyst with a certain low hydrogen content and nitrogen content can obtain high power density when used as an electrocatalyst for a fuel cell, which is advantageous. It is. Based on these considerations, the temperature at which the carbonization is performed is usually 100 to 800°C.

For example, in step 2a of the production method A1, the temperature at which the carbonization is performed is typically 300 to 800°C, preferably 400 to 800°C. By performing carbonization at such a temperature, it is possible to obtain an electrocatalyst that satisfies the requirements described above in the section of "electrocatalyst".
The carbonization catalyst obtained by the above production method can be used as an electrode catalyst.

〔electrode〕
The above-described electrode catalyst according to the present invention can be used for a fuel cell electrode. That is, the fuel cell electrode according to the present invention includes the above electrode catalyst.

Here, the fuel cell electrode according to the present invention may be composed only of the above electrode catalyst as long as it can maintain a certain shape, but may include components other than the above electrode catalyst (hereinafter referred to as "other components") as necessary. ) may also be included. Examples of such "other components" include catalyst supports such as Vulcan (manufactured by Cabot), carbon black, acetylene black, furnace black, graphite, carbon nanotubes, carbon nanofibers, black smoke, carbon fibers, and activated carbon; Examples include conductive polymers such as polyacetylene, polypyrrole, polythiol, polyimidazole, polypyridine, polyaniline, and polythiophene. When the amount of the above-mentioned electrode catalyst is 100 parts by weight, the amount of "other components" in the catalyst carrier is preferably 0 parts by weight or more and 50 parts by weight or less, and in the above-mentioned conductive polymer. is preferably from 0 parts by weight to 50 parts by weight.

Further, the fuel cell electrode according to the present invention is a stacked layer including a layer made of a conductive material having gas diffusivity (hereinafter referred to as a "gas diffusion layer") and a layer made of the above-mentioned electrode catalyst (hereinafter referred to as a "catalyst layer"). It may be the body. This gas diffusion layer also has the role of supporting the catalyst layer. The gas diffusion layer may be anything as long as it has electron conductivity, high gas diffusivity, and high corrosion resistance, but carbon-based porous materials such as carbon paper and carbon cloth are generally used. material is used. Such fuel cell electrodes are formed by, for example, adding a suitable medium to the electrode catalyst to form a solution, suspension, slurry, paste, etc., applying this to the gas diffusion layer, and drying it. Ru. Here, the medium for forming the electrode catalyst into a solution, suspension, slurry, paste, etc. is not particularly limited, and may be appropriately selected from conventionally known media. The coating amount is preferably 0.1 to 10 mg/cm ² , more preferably 0.5 to 5 mg/cm ² .

On the other hand, the catalyst layer may contain, in addition to the electrode catalyst, the catalyst carrier, a conductive polymer, an ionomer, or the like, if necessary. The catalyst carrier, conductive polymer, ionomer, etc. may be added to the solution, suspension, slurry, paste, etc. of the electrode catalyst, or may be added to the solution, suspension, slurry, paste, etc. of the electrode catalyst. Alternatively, it may be applied as a solution, suspension, solution, slurry or paste before, simultaneously with, or after applying the catalyst layer.

In a fuel cell, an oxidation reaction of fuel occurs at the anode (also referred to as a negative electrode or fuel electrode), and a reduction of an oxidant occurs at the cathode (also referred to as a positive electrode or air electrode). The fuel cell electrode according to the present invention may be an anode or a cathode. Further, it may be both an anode and a cathode. In a particularly preferred embodiment of the present invention, the fuel cell electrode is a cathode.

[Membrane electrode assembly]
The membrane electrode assembly according to the present invention is a membrane electrode assembly comprising a cathode, an anode, and a proton conductive membrane disposed between the cathode and the anode, and is selected from the group consisting of the cathode and the anode. Any one or more of the selected electrodes is the fuel cell electrode of the present invention described above. At this time, as the electrode that does not employ the fuel cell electrode of the present invention, a conventionally known fuel cell electrode, for example, a fuel cell electrode containing a platinum-based catalyst such as platinum-supported carbon, can be used. An example of a particularly preferred embodiment of the membrane electrode assembly of the present invention is one in which the cathode is the fuel cell electrode of the present invention and the anode is a conventionally known fuel cell electrode.

Here, when the fuel cell electrode of the present invention has a gas diffusion layer, in the membrane electrode assembly of the present invention, this gas diffusion layer is arranged on the opposite side of the layer consisting of the electrode catalyst when viewed from the proton conductive membrane. be done.

As the proton conductive membrane, for example, an electrolyte membrane using perfluorosulfonic acid or a hydrocarbon electrolyte membrane is generally used. Specific examples of proton conductive membranes include proton conductive polymer electrolytes such as Nafion (registered trademark), Flemion (registered trademark), and Aciplex (registered trademark).
The membrane electrode assembly of the present invention can be appropriately formed using a conventionally known method.

〔Fuel cell〕
The fuel cell of the present invention includes the membrane electrode assembly of the present invention described above. Here, in a typical embodiment of the present invention, the fuel cell of the present invention further includes two current collectors sandwiching the membrane electrode assembly.

The fuel cell of the present invention has the above-described fuel cell electrode of the present invention as a cathode, an anode, or both a cathode and an anode. Here, in a particularly preferred embodiment of the present invention, the fuel cell electrode is a cathode. A fuel cell having the fuel cell electrode of the present invention as a cathode and a conventionally known fuel cell electrode as an anode is particularly preferable in that a high power density can be obtained. On the other hand, from the viewpoint of being able to reduce the use of expensive pure platinum or platinum alloys and making it easier to control the catalytic ability, it is possible to use the fuel cell electrode of the present invention as described above. It is preferable to have it as both a cathode and an anode.

Further, the current collector may be of a conventionally known type that is generally adopted for fuel cells, for example, as shown in FIG. 6, it may be in the shape of a current collector plate with a built-in flow path. be able to.
Anode gas introduced from outside the fuel cell is supplied to the anode through a current collector placed on the anode side, and cathode gas introduced from outside the fuel cell is supplied to the cathode through a current collector placed on the cathode side. supplied to The anode gas is a gas that serves as a fuel, and is typically hydrogen. When the anode gas is hydrogen, this hydrogen may be obtained by reforming gasoline, methanol, diethyl ether, hydrocarbons, or the like. Furthermore, the cathode gas may be methanol, diethyl ether, or the like.

On the other hand, the cathode gas introduced from the outside of the fuel cell is a gas that serves as an oxidizing agent, and may be oxygen or air.
In a preferred embodiment of the invention, the anode gas is hydrogen and the cathode gas is oxygen. In this embodiment, the fuel cell of the present invention will be used as a hydrogen-oxygen fuel cell.

〔Power generation method〕
In relation to the electrode catalyst and fuel cell according to the present invention described above, the present invention can also be said to provide a power generation method. This is based on the fact that the electrode catalyst of the present invention is inexpensive and the catalytic ability can be easily controlled when used as an electrode for a fuel cell.

The power generation method according to the present invention includes a step of performing an oxidation reaction of fuel using the above electrode catalyst, and/or a step of performing a reduction reaction of an oxidant using the above electrode catalyst. That is, the power generation method according to the present invention may include both a step of performing an oxidation reaction of a fuel using the above-mentioned electrode catalyst and a step of performing a reduction reaction of an oxidant using the above-mentioned electrode catalyst. However, it may also contain either one of them.

More specifically, for example, the power generation method according to the present invention includes a step of emitting electrons from hydrogen molecules to generate hydrogen ions using the above fuel cell electrode catalyst, and/or a step of using the above fuel cell electrode catalyst. The process involves reacting oxygen molecules, hydrogen ions, and electrons to produce water.

The power generation method according to the present invention may be performed by a conventionally known method and is not particularly limited, but to explain one example, hydrogen gas is supplied to the anode side of a fuel cell, and oxygen is supplied to the cathode side. At this time, hydrogen gas and oxygen may be humidified through a bubbler.

When hydrogen gas is supplied from the anode side, the hydrogen gas releases electrons from hydrogen molecules by the action of the fuel cell electrode catalyst and becomes hydrogen ions. These hydrogen ions pass through the electrolyte membrane and move to the opposing cathode. At the cathode, the hydrogen ions that have moved react with the oxygen molecules supplied to the cathode to generate water due to the action of the fuel cell electrode catalyst. At this time, the flow of electrons generated in the wire is extracted as a direct current.

Examples of the present invention will be specifically described below, but the present invention is not limited thereto.
(material and method)
All experiments were performed under _N2 or Ar atmosphere by using standard Schlenk techniques and a glove box.

・Preparation of various metal complexes Ni ^II (N ₂ S ₂ ) was prepared by the method described in the literature ⁽ Inorg. Chem., ₁₉₉₀ , 4779-4788 ₎ . (N ₂ S ₂ =N,N'-dimethyl-3,7-diazanone-1,9-dithiolato).

[Ir ^III (η ⁵ -C ₅ Me ₅ )Cl ₂ ] ₂ was converted to [Ir ^III (η ⁵ -C ₅ Me ₅ )Cl by the method described in the literature (Inorg. Chem. 1990, 29, 2023-2025). ₂ ] (η ⁵ -C _{5 Me 5} =1,2,3,4,5-pentamethylcyclopentadienyl).

[Rh ^III (η ⁵ -C ₅ Me ₅ )Cl ₂ ] ₂ was converted to [Ir ^III (η ⁵ -C ₅ Me ₅ )Cl by the method described in the literature (Org. Lett. 2004, 6, 2785-2788). ₂ ] Prepared by the method described in ₂ .

[Ni ^II (H ₂ O) (N ₂ S ₂ ) (μ-H) Ru ^II (η ⁶ -C ₆ Me ₆ )] (NO ₃ ) is described in the literature (Science 2007, 316, 585-587). It was prepared by the method of

[Ni ^II Cl(N ₂ S ₂ )Ir ^III Cl(η ⁵ -C ₅ Me ₅ )] is described in the method described in the literature (Angew. Chem. Int. Ed. 2013, 56, 9723-9726). It was prepared by the method described below.

[Ni ^II Cl(N ₂ S ₂ )Rh ^III Cl(η ⁵ -C ₅ Me ₅ )] was prepared by the method described in the literature (JP 2017-132671 A).

- Gas and solvent H ₂ gas and O ₂ gas were purchased from Taiyo Toyo Sanso Co., Ltd. H ₂ O was purchased from Wako Pure Chemical Industries, Ltd.
These were used without further purification.

- Ultraviolet-visible spectrum The ultraviolet-visible spectrum was measured with a JASCO V-670 UV-Visible-NIR spectrometer (cell length 0.1 cm) at 25°C.

・Gas chromatography-mass spectrometry (GC-MS)
Gas chromatography-mass spectrometry (GC-MS) data were obtained by SHIMADZU GCMS-QP 2010.

・Simultaneous differential thermal and thermogravimetric measurement (TG-DSC)
Differential thermal-thermogravimetric (TG-DSC) data were obtained on a NETZCCH STA 449 F1 Jupiter analyzer.

・X-ray photoelectron spectroscopy (XPS)
X-ray photoelectron spectroscopy (XPS) spectra were obtained on a ULVAC PHI 5000 VersaProbe II system equipped with an Al anode X-ray source. The binding energy was corrected by the Au 4f7/2 peak of elemental gold in the gold powder mixed with the sample.

- X-ray diffraction (XRD) method X-ray diffraction (XRD) patterns were generated using a Rigaku SmartLab equipped with Cu-Kα radiation emitted at 45 kV and 200 mA {scan speed 0.02 ^o min ^-1 (2θ = 20- 90 ^o ).

- Elemental analysis data Elemental analysis data were obtained with a Yanaco CHN-coder MT-5 and a PerkinElmer 2400 II series CHNS/O analyzer.

・(Scanning type) Transmission electron microscopy ((S)TEM) observation and energy dispersive X-ray spectroscopy (EDS) mapping (Scanning type) Transmission electron microscopy ((S)TEM) observation and Energy dispersive X-ray spectroscopy JEOL JEM-ARM 200F equipped with a JEOL silicon drift detector (SDD) and a JEOL JED-2300T system.

I. Synthesis of carbonization catalyst [Example 1-1] Synthesis of nickel-rhodium carbonization catalyst using nickel-rhodium chloro complex [Ni ^II Cl (N ₂ S ₂ ) Rh ^III Cl (η ⁵ -C ₅ Me ₅ )] Nickel・Rhodium chloro complex [Ni ^II Cl (N ₂ S ₂ ) Rh ^III Cl (η ⁵ -C ₅ Me ₅ )] (hereinafter sometimes referred to as "nickel rhodium chloro complex" or "NiRh complex") (5 mg ) was mixed with carbon black (5 mg) and introduced into a quartz tube (hereinafter referred to as the "apparatus") equipped with an electric furnace. The pressure inside the apparatus was reduced to about 20 Pa using a vacuum pump. The samples were then heated under reduced pressure (15-20 Pa) for 1 hour. Heating starts by raising the temperature from room temperature, and after reaching the target temperature (hereinafter referred to as "carbonization temperature") (the time required to reach the carbonization temperature from room temperature is about 5 minutes), at this temperature 1. This was done by holding the time. After heating, the sample was taken out from the apparatus after releasing the vacuum inside the apparatus, cooled to room temperature in the atmosphere outside the apparatus, and then taken out from the apparatus. The obtained sample was used as a nickel-rhodium carbonization catalyst in the following examples.
Similar synthesis was repeated while changing the carbonization temperature within the range of 100-800°C.

[Example 1-2] Synthesis of nickel-iridium carbonization catalyst using nickel-iridium chloro complex [Ni ^II Cl (N ₂ S ₂ ) Ir ^III Cl (η ⁵ -C ₅ Me ₅ )] Nickel-rhodium chloro complex Instead, a nickel-iridium chloro complex [Ni ^II Cl (N ₂ S ₂ ) Ir ^III Cl (η ⁵ -C ₅ Me ₅ )] (hereinafter sometimes referred to as "nickel-iridium chloro complex" or "NiIr complex") A carbonization catalyst synthesis experiment was conducted in the same manner as in Example 1-1, except that .) was used.

[Example 1-3] Using nickel-ruthenium hydride complex [Ni ^II (H ₂ O) (N ₂ S ₂ ) (μ-H) Ru ^II (η ⁶ -C ₆ Me ₆ )] (NO ₃ ) Synthesis of nickel-ruthenium carbonization catalyst Nickel-ruthenium hydride complex [Ni ^II (H ₂ O) (N ₂ S ₂ ) (μ-H) Ru ^II (η ⁶ -C ₆ Me ₆ ) was used instead of the nickel-rhodium chloro complex. ] (NO ₃ ) (hereinafter sometimes referred to as "nickel-ruthenium hydride complex" or "NiRu complex"), a carbonization catalyst synthesis experiment was carried out in the same manner as in Example 1-1, except for using .

II. Thermal analysis of nickel-rhodium chloro complex [Ni ^II Cl(N ₂ S ₂ )Rh ^III Cl(η ⁵ -C ₅ Me ₅ )] Nickel-rhodium chloro complex [Ni ^II Cl(N ₂ S ₂ )Rh ^III Cl( Simultaneous differential thermal-thermogravimetry (TG-DSC) measurement was performed using a sample of a mixture of η ⁵ -C ₅ Me ₅ )] (5 mg) and carbon black (5 mg). Here, the TG-DSC measurement was performed under nitrogen (flow rate 100 mL/min), and the temperature increase rate was 5° C./min. Figure 1 shows the results of TG-DSC measurement. From the TG-DSC curve shown in FIG. 1, a weight loss of the sample accompanied by an endothermic reaction was observed from around 220° C., and it became clear that the decomposition of the nickel-rhodium chloro complex started at the above temperature.

III. Identification of carbonization catalyst (1) Analysis of nickel-rhodium carbonization catalyst by XPS Nickel-rhodium carbonization catalyst synthesized at various carbonization temperatures (300°C, 450°C, 600°C, and 800°C) in Example 1-1, and , nickel rhodium chloro complex [Ni ^II Cl (N ₂ S ₂ )Rh ^III Cl (η ⁵ -C ₅ Me ₅ )]. Here, the XPS measurement was performed using a mixture of a nickel-rhodium dry distillation catalyst or a nickel-rhodium chloro complex (5 mg) and carbon black (5 mg) as a sample. Figure 2 shows the XPS results. In FIG. 2, "1" represents a nickel-rhodium chloro complex.

(2) XRD analysis of nickel-rhodium carbonization catalyst Synthesized at various carbonization temperatures (100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C) in Example 1-1 XRD measurements were performed on each of the nickel-rhodium dry distillation catalyst and the nickel-rhodium chloro complex [Ni ^II Cl (N ₂ S ₂ )Rh ^III Cl (η ⁵ -C ₅ Me ₅ )]. Here, the XRD measurement was performed using a mixture of a nickel-rhodium dry distillation catalyst or a nickel-rhodium chloro complex (5 mg) and carbon black (5 mg) as a sample. FIG. 3 shows the XRD results.

Regarding the results shown in FIG. 3, the present inventor speculates as follows.
In the carbonization catalyst obtained by carbonization at 200° C. or lower, a portion of the nickel-rhodium chloro complex remains unreacted. The portions of this carbonization catalyst other than the unreacted nickel-rhodium chloro complex are considered to be in an amorphous state.

The carbonized catalyst obtained by carbonizing at 300 to 400°C has a peak that is somewhat similar to Ni ₃ S ₂ but has not been completely identified. From this, it is considered that some unidentified solid exists in this carbonization catalyst.

It is thought that a solid similar to Rh ₁₇ S ₁₅ has begun to form in the carbonized catalyst obtained by carbonizing at 500°C.
The carbonization catalyst obtained by carbonization at 600°C is considered to be a mixture of the solids found in the carbonization catalyst obtained by carbonization at 300°C and solids similar to Rh ₁₇ S ₁₅ .

In a carbonized catalyst obtained by carbonizing at 700° C., the peak intensity of a solid similar to Rh ₁₇ S ₁₅ becomes weak.
It is thought that a solid similar to a sulfur-doped RhNi alloy or sulfur-doped Rh is produced in the carbonization catalyst obtained by carbonization at 800°C.

(3) Elemental analysis of nickel-rhodium carbonization catalyst In Example 1-1, the nickel-rhodium carbonization catalyst synthesized at various carbonization temperatures (200 °C, 300 °C, 450 °C, 600 °C, 800 °C) and nickel - Elemental analysis was conducted for each of the rhodium chloro complexes [Ni ^II Cl (N ₂ S ₂ ) Rh ^III Cl (η ⁵ -C ₅ Me ₅ )]. Here, elemental analysis was performed using a mixture of a nickel-rhodium dry distillation catalyst or a nickel-rhodium chloro complex (5 mg) and carbon black (5 mg) as a sample, and the elements C, H, N, and S were quantified. Table 1 shows the results of elemental analysis. Further, in FIG. 4, the results of elemental analysis are shown superimposed on the results of TG.

(4) Analysis using (scanning) transmission electron microscopy ((S)TEM) observation of nickel-rhodium carbonization catalyst and energy dispersive X-ray spectroscopy (EDS) mapping data In Example 1-1, various carbonization temperatures ( ⁽ _{S _} ^{_ _} _{_ _} ) TEM observation and EDS mapping were performed to analyze the nanoparticles. Here, (S)TEM observation and EDS mapping were performed using 1 mg of a mixture of a nickel-rhodium dry distillation catalyst or a nickel-rhodium chloro complex (5 mg) and carbon black (5 mg) as a sample. FIG. 5 shows the results of (S)TEM observation and EDS mapping obtained for the nickel-rhodium carbonization catalyst synthesized at 600°C.

IV. Oxidation/reduction reaction experiment [Example 2-1] H ₂ oxidation reaction experiment using a nickel-rhodium carbonization catalyst <H ₂ oxidation reaction experiment using methylene blue as an electron acceptor>
The nickel-rhodium carbonization catalyst synthesized in Example 1-1 with a carbonization temperature of 600°C and 30 equivalents of methylene blue were mixed in water (pH 5), and the mixture was heated at 30°C under an H ₂ atmosphere (0.1-0.8 MPa). Stirred for 6 hours. The reduced form of methylene blue (leucomethylene blue) produced was quantified by UV-vis spectroscopy, and the turnover number (TON) was calculated. Under these conditions, TON [(number of moles of leucomethylene blue)/(number of moles of carbonization catalyst)] was 17 as shown in Table 2.

[Comparative Example 2-c1] H ₂ oxidation reaction experiment using a heterogeneous dinuclear complex [NM] <H ₂ oxidation reaction experiment using methylene blue as an electron acceptor>
In order to confirm the effect of the presence or absence of carbonization, an experiment similar to Example 2-1 was conducted, except that a nickel-rhodium chloro complex was used in place of the nickel-rhodium carbonization catalyst.

That is, [Ni ^II Cl(N ₂ S ₂ )Rh ^III Cl(η ⁵ -C ₅ Me ₅ )] and 30 equivalents of methylene blue were mixed in water (pH 7) and mixed in an H ₂ atmosphere (0.1-0. 8 MPa) and stirred at 30° C. for 6 hours. The reduced form of methylene blue (leucomethylene blue) produced was quantified by UV-vis spectroscopy, and the turnover number (TON) was calculated. The TON under this condition was 4 as shown in Table 2.

[Example 3-1] O ₂ reduction reaction experiment using a nickel-rhodium carbonization catalyst H ₂ was bubbled for 20 minutes. ¹⁸ O ₂ (2.0 mL) was injected into the reaction solution, and the mixture was stirred at 25° C. for 5 hours. The catalyst was removed by passing the reaction solution through a short silica gel column. The amount of H ₂ ¹⁸ O produced in the reaction solution was determined by GC-MS, and the turnover number (TON) was calculated. As shown in Table 2, TON [{(number of moles of H ₂ ¹⁸ O)/(number of moles of carbonization catalyst)}/2] was determined to be 1.7 based on the carbonization catalyst.

[Comparative Example 3-c1] O ₂ reduction reaction experiment using a heterogeneous dinuclear complex [NM] In order to confirm the effect of the presence or absence of carbonization, a nickel-rhodium chloro complex was used in place of the nickel-rhodium carbonization catalyst. Except for this, an experiment similar to Example 3-1 was conducted.

That is, H ₂ was bubbled into a phosphate buffer solution (pH 7) of [Ni ^II Cl (N ₂ S ₂ ) Rh ^III Cl (η ⁵ -C ₅ Me ₅ )] for 20 minutes. ¹⁸ O ₂ (2.0 mL) was injected into the reaction solution, and the mixture was stirred at 25° C. for 5 hours. The complex was removed by passing the reaction solution through a short silica gel column. The amount of H ₂ ¹⁸ O produced in the reaction solution was determined by GC-MS, and the turnover number (TON) was calculated. As shown in Table 2, TON [{(number of moles of H ₂ ¹⁸ O)/(number of moles of complex)}/2] was determined to be 0.5 based on the NiRh complex.

V. Hydrogen-oxygen fuel cell evaluation for fuel cells having metal complexes or carbonization complexes as electrode catalysts V-1A. Hydrogen-oxygen fuel cell evaluation of a fuel cell having a nickel-rhodium chloro complex or a nickel-rhodium carbonization catalyst as an anode catalyst [Comparative Example 4A-c0] Fuel cell evaluation experiment using a nickel-rhodium chloro complex as an anode catalyst Nickel rhodium chloro complex [Ni ^II Cl (N ₂ S ₂ ) Rh ^III Cl (η ⁵ -C ₅ Me ₅ )] (5.0 mg) and carbon black (5.0 mg) were mixed, and the resulting mixture was An anode electrode (hereinafter referred to as "anode electrode NiRhc0") containing a nickel-rhodium chloro complex as an anode catalyst was created by coating it on water-resistant carbon cloth (5 cm ² ).

On the other hand, Pt/C (11 mg) was added to Nafion (trademark) solution (59 mg: Nafion/carbon ratio = 2 (wt/wt)) and the suspension obtained by ultrasonication for 1 hour was mixed with water-resistant carbon cloth. (5 cm ² ) to create a cathode electrode (hereinafter referred to as "cathode electrode Pt") containing Pt/C as a cathode catalyst.

Further, the Nafion (trademark) membrane 212 was pretreated by boiling it in 3% hydrogen peroxide solution for 1 hour, in 1.0 M sulfuric acid solution for 1 hour, and in deionized water for 1 hour.
The pretreated Nafion (trademark) membrane 212 was sandwiched between the anode electrode NiRhc0 and the cathode electrode Pt to obtain a membrane electrode assembly (MEA). This MEA has a layer made of carbon cloth, a layer containing an anode catalyst, a layer made of Nafion (trademark) membrane 212, a layer containing a cathode catalyst, and a layer made of carbon cloth in this order. . In this MEA, the Nafion™ membrane 212 functions as a proton conductive membrane. By incorporating this MEA into a fuel cell (5 cm ² ), a fuel cell having the configuration shown in FIG. 6 was obtained. This fuel cell has a pair of current collector plates with built-in flow channels on both sides of the MEA. Here, anode gas introduced from outside the fuel cell is supplied to the anode through a current collector plate placed on the anode side, and cathode gas introduced from outside the fuel cell is supplied to the anode through a current collector plate placed on the cathode side. It is supplied to the cathode through the plate.

The obtained fuel cell was evaluated at 60° C. using hydrogen as an anode gas and oxygen as a cathode gas. Here, the fuel cell evaluation was performed by measuring the current-potential characteristics of the fuel cell using linear sweep voltammetry, and calculating the maximum power density from the obtained current-voltage characteristic curve. As a result, as shown in FIG. 9 and Table 3, it functioned as a battery.

[Comparative Example 4A-c1] Fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 100°C as an anode catalyst A nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 100°C in Example 1-1 ( An anode electrode (hereinafter referred to as "anode electrode NiRhc1") containing NiRh carbonization catalyst 100 as an anode catalyst was created by applying "NiRh carbonization catalyst 100" (5.0 mg) on a water-resistant carbon cloth (5 cm ² ). did.

Then, a membrane electrode assembly (MEA) and a fuel cell were prepared and the fuel cell was evaluated in the same manner as in Comparative Example 4A-c0, except that this anode electrode NiRhc1 was used in place of the anode electrode NiRhc0. . As a result, as shown in FIG. 9 and Table 3, it functioned as a battery.

[Comparative Example 4A-c2] Fuel cell evaluation experiment when a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 200°C was used as an anode catalyst Instead of the NiRh carbonization catalyst 100, a carbonization temperature of 200°C in Example 1-1 was used. An anode electrode (hereinafter referred to as "anode electrode NiRhc2") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 4A-c1, except that a synthesized nickel-rhodium carbonization catalyst (hereinafter referred to as "NiRh carbonization catalyst 200") was used. We also created a fuel cell and evaluated the fuel cell. As a result, as shown in FIG. 9 and Table 3, it functioned as a battery.

[Example 4A-1] Fuel cell evaluation experiment when a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 300°C was used as an anode catalyst Instead of the NiRh carbonization catalyst 100, in Example 1-1 at a carbonization temperature of 300°C. An anode electrode (hereinafter referred to as "anode electrode NiRh1") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 4A-c1, except that a synthesized nickel-rhodium carbonized catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 300") was used. We also created a fuel cell and evaluated the fuel cell. As a result, as shown in FIG. 9 and Table 3, it functioned as a battery.

[Example 4A-2] Fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 400°C as an anode catalyst Instead of the NiRh carbonization catalyst 100, in Example 1-1, a carbonization temperature of 400°C was used. An anode electrode (hereinafter referred to as "anode electrode NiRh2") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 4A-c1, except that a synthesized nickel-rhodium carbonized catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 400") was used. We also created a fuel cell and evaluated the fuel cell. As a result, as shown in FIG. 9 and Table 3, it functioned as a battery.

[Example 4A-3] Fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 500°C as an anode catalyst Instead of the NiRh carbonization catalyst 100, in Example 1-1, a carbonization temperature of 500°C was used. An anode electrode (hereinafter referred to as "anode electrode NiRh3") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 4A-c1, except that a synthesized nickel-rhodium carbonized catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 500") was used. We also created a fuel cell and evaluated the fuel cell. As a result, as shown in FIG. 9 and Table 3, it functioned as a battery.

[Example 4A-4] Fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 600°C as an anode catalyst Instead of the NiRh carbonization catalyst 100, in Example 1-1, a carbonization temperature of 600°C was used. An anode electrode (hereinafter referred to as "anode electrode NiRh4") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 4A-c1, except that a synthesized nickel-rhodium carbonized catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 600") was used. We also created a fuel cell and evaluated the fuel cell. As a result, as shown in FIG. 9 and Table 3, it functioned as a battery. Further, FIG. 7 shows a chart showing the relationship between cell voltage and output density with respect to current density obtained by fuel cell evaluation.

[Example 4A-5] Fuel cell evaluation experiment when a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 700°C was used as an anode catalyst Instead of the NiRh carbonization catalyst 100, in Example 1-1, a carbonization temperature of 700°C was used. An anode electrode (hereinafter referred to as "anode electrode NiRh5") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 4A-c1, except that a synthesized nickel-rhodium carbonized catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 700") was used. We also created a fuel cell and evaluated the fuel cell. As a result, as shown in FIG. 9 and Table 3, it functioned as a battery.

[Example 4A-6] Fuel cell evaluation experiment when a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 800°C was used as an anode catalyst Instead of the NiRh carbonization catalyst 100, in Example 1-1, a carbonization temperature of 800°C was used. An anode electrode (hereinafter referred to as "anode electrode NiRh6") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 4A-c1, except that a synthesized nickel-rhodium carbonized catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 800") was used. We also created a fuel cell and evaluated the fuel cell. As a result, as shown in FIG. 9 and Table 3, it functioned as a battery.

V-1B. Hydrogen-oxygen fuel cell evaluation of a fuel cell having a nickel-iridium carbonization catalyst as an anode catalyst [Example 4B-1] Fuel cell evaluation when a nickel-iridium carbonization catalyst synthesized at a carbonization temperature of 600°C is used as an anode catalyst Experiment By applying the nickel-iridium carbonization catalyst (hereinafter referred to as "NiIr carbonization catalyst 600") (5.0 mg) synthesized at a carbonization temperature of 600°C in Example 1-2 on a water-resistant carbon cloth (5 cm ² ), the anode An electrode (hereinafter referred to as "anode electrode NiIr1") was created.

Then, a membrane electrode assembly (MEA) and a fuel cell were prepared and the fuel cell was evaluated in the same manner as in Comparative Example 4A-c0, except that this anode electrode NiIr1 was used in place of the anode electrode NiRhc0. . As a result, as shown in Table 3, it functioned as a battery.

V-1C. Hydrogen-oxygen fuel cell evaluation of a fuel cell having a nickel-ruthenium carbonization catalyst as an anode catalyst [Example 4C-1] Fuel cell evaluation experiment conducted using a nickel-ruthenium carbonization catalyst as an anode catalyst at a carbonization temperature of 600°C By applying the nickel-ruthenium carbonization catalyst (hereinafter referred to as "NiRu carbonization catalyst 600") (5.0mg) synthesized at a carbonization temperature of 600°C in Example 1-3 onto carbon cloth (5cm ² ), the nickel-ruthenium carbonization catalyst was synthesized at a carbonization temperature of 600°C in Example 1-3. An anode electrode (hereinafter referred to as "anode electrode NiRu1") containing a ruthenium carbonization catalyst 600 was created.

Then, a membrane electrode assembly (MEA) and a fuel cell were prepared and the fuel cell was evaluated in the same manner as in Comparative Example 4A-c0, except that this anode electrode NiRu1 was used in place of the anode electrode NiRhc0. . As a result, as shown in Table 3, it functioned as a battery.

V-2A. Hydrogen-oxygen fuel cell evaluation of a fuel cell having a nickel-rhodium chloro complex or a nickel-rhodium carbonization catalyst as a cathode catalyst [Comparative Example 5A-c0] Fuel cell evaluation experiment using a nickel-rhodium chloro complex as a cathode catalyst Nickel rhodium chloro complex [Ni ^II Cl (N ₂ S ₂ ) Rh ^III Cl (η ⁵ -C ₅ Me ₅ )] (5.0 mg) and carbon black (5.0 mg) were mixed, and the resulting mixture was A cathode electrode (hereinafter referred to as "cathode electrode NiRhc0") containing a nickel-rhodium chloro complex as a cathode catalyst was created by coating it on water-resistant carbon cloth (5 cm ² ).

On the other hand, Pt/C (11 mg) was added to Nafion (trademark) solution (59 mg: Nafion/carbon ratio = 2 (wt/wt)) and the suspension obtained by ultrasonication for 1 hour was mixed with water-resistant carbon cloth. (5 cm ² ) to create an anode electrode (hereinafter referred to as "anode electrode Pt") containing Pt/C as an anode catalyst.

Further, the Nafion (trademark) membrane 212 was pretreated by boiling it in 3% hydrogen peroxide solution for 1 hour, in 1.0 M sulfuric acid solution for 1 hour, and in deionized water for 1 hour.
The pretreated Nafion (trademark) membrane 212 was sandwiched between the cathode electrode NiRhc0 and the anode electrode Pt to obtain a membrane electrode assembly (MEA). This MEA has a layer made of carbon cloth, a layer containing an anode catalyst, a layer made of Nafion (trademark) membrane 212, a layer containing a cathode catalyst, and a layer made of carbon cloth in this order. . A fuel cell was prepared by incorporating this MEA into a fuel cell (5 cm ² ).

The obtained fuel cell was evaluated at 60° C. using hydrogen as an anode gas and oxygen as a cathode gas. Here, the fuel cell evaluation was performed by measuring the current-potential characteristics of the fuel cell using linear sweep voltammetry, and calculating the maximum power density from the obtained current-voltage characteristic curve. As a result, as shown in Table 4, it functioned as a battery.

[Comparative Example 5A-c1] Fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 100°C as a cathode catalyst A nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 100°C in Example 1-1 ( A cathode electrode (hereinafter referred to as "cathode electrode NiRhc1") containing NiRh carbonization catalyst 100 as a cathode catalyst was created by applying "NiRh carbonization catalyst 100" (5.0 mg) on a water-resistant carbon cloth (5 cm ² ). did.

Then, a membrane electrode assembly (MEA) and a fuel cell were prepared and the fuel cell was evaluated in the same manner as in Comparative Example 5A-c0, except that this cathode electrode NiRhc1 was used instead of the cathode electrode NiRhc0. . As a result, it functioned as a battery as shown in FIG. 10 and Table 4.

[Comparative Example 5A-c2] Fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 200°C as a cathode catalyst Instead of the NiRh carbonization catalyst 100, a carbonization catalyst synthesized at a carbonization temperature of 200°C in Example 1-1 was used. A cathode electrode (hereinafter referred to as "cathode electrode NiRhc2") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 5A-c1, except that a synthesized nickel-rhodium carbonization catalyst (hereinafter referred to as "NiRh carbonization catalyst 200") was used. We also created a fuel cell and evaluated the fuel cell. As a result, it functioned as a battery as shown in FIG. 10 and Table 4.

[Example 5A-1] Fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 300°C as a cathode catalyst Instead of the NiRh carbonization catalyst 100, in Example 1-1, a carbonization temperature of 300°C was used. A cathode electrode (hereinafter referred to as "cathode electrode NiRh1") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 5A-c1, except that the prepared nickel rhodium carbonized distillation catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 300") was used. We also created a fuel cell and evaluated the fuel cell. As a result, it functioned as a battery as shown in FIG. 10 and Table 4.

[Example 5A-2] Fuel cell evaluation experiment when using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 400°C as a cathode catalyst Instead of the NiRh carbonization catalyst 100, in Example 1-1 at a carbonization temperature of 400°C A cathode electrode (hereinafter referred to as "cathode electrode NiRh2") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 5A-c1, except that a synthesized nickel-rhodium carbonized catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 400") was used. We also created a fuel cell and evaluated the fuel cell. As a result, it functioned as a battery as shown in FIG. 10 and Table 4.

[Example 5A-3] Fuel cell evaluation experiment when a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 500°C was used as a cathode catalyst Instead of the NiRh carbonization catalyst 100, a carbonization temperature of 500°C in Example 1-1 was used. A cathode electrode (hereinafter referred to as "cathode electrode NiRh3") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 5A-c1, except that a synthesized nickel-rhodium carbonized catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 500") was used. We also created a fuel cell and evaluated the fuel cell. As a result, it functioned as a battery as shown in FIG. 10 and Table 4.

[Example 5A-4] Fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 600°C as a cathode catalyst Instead of the NiRh carbonization catalyst 100, a carbonization temperature of 600°C in Example 1-1 A cathode electrode (hereinafter referred to as "cathode electrode NiRh4") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 5A-c1, except that a synthesized nickel-rhodium carbonized catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 600") was used. We also created a fuel cell and evaluated the fuel cell. As a result, it functioned as a battery as shown in FIG. 10 and Table 4. Further, FIG. 8 shows a chart showing the relationship between cell voltage and output density with respect to current density obtained by fuel cell evaluation.

[Example 5A-5] Fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 700°C as a cathode catalyst Instead of the NiRh carbonization catalyst 100, in Example 1-1, a carbonization temperature of 700°C was used. A cathode electrode (hereinafter referred to as "cathode electrode NiRh5") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 5A-c1, except that a synthesized nickel-rhodium carbonized catalyst (hereinafter referred to as "NiRh carbonized distillation catalyst 700") was used. We also created a fuel cell and evaluated the fuel cell. As a result, it functioned as a battery as shown in FIG. 10 and Table 4.

[Example 5A-6] Fuel cell evaluation experiment using a nickel-rhodium carbonization catalyst synthesized at a carbonization temperature of 800°C as a cathode catalyst Instead of the NiRh carbonization catalyst 100, in Example 1-1, a carbonization temperature of 800°C was used. A cathode electrode (hereinafter referred to as "cathode electrode NiRh6") and a membrane electrode assembly (MEA) were prepared in the same manner as in Comparative Example 5A-c1, except that a synthesized nickel-rhodium carbonization catalyst (hereinafter referred to as "NiRh carbonization catalyst 800") was used. We also created a fuel cell and evaluated the fuel cell. As a result, it functioned as a battery as shown in FIG. 10 and Table 4.

V-2B. Hydrogen-oxygen fuel cell evaluation of a fuel cell having a nickel-iridium carbonization catalyst as a cathode catalyst [Example 5B-1] Fuel cell evaluation when a nickel-iridium carbonization catalyst synthesized at a carbonization temperature of 600°C is used as a cathode catalyst Experiment By applying the nickel-iridium carbonization catalyst (hereinafter referred to as "NiIr carbonization catalyst 600") (5.0 mg) synthesized at a carbonization temperature of 600°C in Example 1-2 onto a water-resistant carbon cloth (5 cm ² ), the cathode An electrode (hereinafter referred to as "cathode electrode NiIr1") was created.

Then, a membrane electrode assembly (MEA) and a fuel cell were prepared and the fuel cell was evaluated in the same manner as in Comparative Example 5A-c0, except that this cathode electrode NiIr1 was used in place of the cathode electrode NiRhc0. . As a result, as shown in Table 4, it functioned as a battery.

V-2C. Hydrogen-oxygen fuel cell evaluation of a fuel cell having a nickel-ruthenium carbonization catalyst as a cathode catalyst [Example 5C-1] Fuel cell evaluation when a nickel-ruthenium carbonization catalyst synthesized at a carbonization temperature of 600°C is used as a cathode catalyst Experiment By applying the nickel-ruthenium carbonization catalyst (hereinafter referred to as "NiRu carbonization catalyst 600") (5.0 mg) synthesized at a carbonization temperature of 600°C in Example 1-3 onto a water-resistant carbon cloth (5 cm ² ), the cathode An electrode (hereinafter referred to as "cathode electrode NiRu1") was created.

Then, a membrane electrode assembly (MEA) and a fuel cell were prepared and the fuel cell was evaluated in the same manner as in Comparative Example 5A-c0, except that this cathode electrode NiRu1 was used in place of the cathode electrode NiRhc0. . As a result, as shown in Table 4, it functioned as a battery.

V-3A. Hydrogen-oxygen fuel cell evaluation for fuel cells having nickel-rhodium chloro complex or nickel-rhodium carbonization catalyst as anode catalyst and cathode catalyst [Comparative Example 6A-c0] Nickel-rhodium chloro complex as both anode catalyst and cathode catalyst Evaluation of hydrogen-oxygen fuel cell when using nickel-rhodium chloro complex [Ni ^II Cl (N ₂ S ₂ ) Rh ^III Cl (η ⁵ -C ₅ Me ₅ )] (5.0 mg) and carbon black (5.0 mg) ) and the resulting mixture was coated on a water-resistant carbon cloth (5 cm ² ) to create an anode electrode (hereinafter referred to as "anode electrode NiRhc0") and a cathode electrode (hereinafter referred to as "cathode electrode NiRhc0").

Further, the Nafion (trademark) membrane 212 was pretreated by boiling it in 3% hydrogen peroxide solution for 1 hour, in 1.0 M sulfuric acid solution for 1 hour, and in deionized water for 1 hour.
The pretreated Nafion (trademark) membrane 212 was sandwiched between the cathode electrode NiRhc0 and the anode electrode NiRhc0 to obtain a membrane electrode assembly (MEA). This MEA has a layer made of carbon cloth, a layer containing an anode catalyst, a layer made of Nafion (trademark) membrane 212, a layer containing a cathode catalyst, and a layer made of carbon cloth in this order. . A fuel cell was prepared by incorporating this MEA into a fuel cell (5 cm ² ).

Fuel cell evaluation was performed on the obtained fuel cell. Here, the fuel cell evaluation was performed by measuring the current-potential characteristics of the fuel cell using linear sweep voltammetry, and calculating the maximum power density from the obtained current-voltage characteristic curve. As a result, as shown in Table 5, it functioned as a battery.

[Example 6A-1] Evaluation of a hydrogen-oxygen fuel cell using a nickel-rhodium carbonization catalyst as both anode and cathode catalysts A nickel-rhodium carbonization catalyst (hereinafter referred to as "NiRh") prepared at a carbonization temperature of 600°C in Example 1-1 An anode electrode (hereinafter referred to as ``anode electrode NiRh1'') and a cathode electrode ( <sup>hereinafter</sup> referred to as ``cathode electrode NiRh1'') were created by applying carbonized catalyst 100'' (5.0 mg) onto a water-resistant carbon cloth (5 cm 2 ). .

Then, the membrane electrode assembly (MEA) and A fuel cell was created and the fuel cell was evaluated. As a result, it functioned as a battery as shown in FIG. 11 and Table 5.

VI. Electrocatalytic performance evaluation for fuel cells having metal complexes or carbonized complexes as electrode catalysts [Comparative Example 7-c1] Tafel of hydrogen-oxygen fuel cells using nickel-rhodium chloro complexes as anode electrode catalysts and platinum as cathode electrode catalysts Evaluation of electrode catalytic performance by plotting and impedance measurement A fuel cell was prepared in the same manner as Comparative Example 4A-c0 except that a reversible hydrogen electrode was used as the reference electrode. A Tafel plot and an impedance spectrum at 60° C. were obtained using oxygen as the sample.

Here, both the Tafel plot and the impedance measurement were performed using a fuel cell evaluation device APM-09 manufactured by Toyo Technica Co., Ltd., Solartron Model 1287A Potentiostat/Galvanostat, and 1255B Frequency Response Analyzer. using a nickel-rhodium chloro complex The measurements were carried out using platinum as the cathode, a reversible hydrogen electrode as the reference electrode, and a measurement temperature of 60°C.

The obtained Tafel plot is shown in FIG. 12. Here, in FIG. 12, the dotted line represents an approximate straight line obtained from a plot in a relatively high IR free overvoltage region, and the value at 0 of IR free overvoltage when this approximate straight line is extrapolated to a low IR free overvoltage region. The exchange current density was determined from

The obtained impedance spectrum is shown in FIG. 16.
The exchange current density of the hydrogen oxidation reaction by the nickel-rhodium complex determined from the Tafel plot and impedance measurement was 0.0286 mA cm ^-2 as shown in Table 6.

[Example 7-1] Electrocatalyst performance evaluation by Tafel plot and impedance measurement of a hydrogen-oxygen fuel cell using a nickel-rhodium carbonization catalyst as an anode electrode catalyst and platinum as a cathode electrode. Configuration with a reversible hydrogen electrode as a reference electrode. A fuel cell was produced in the same manner as in Example 4A-4, except that hydrogen was used as the anode gas, oxygen was used as the cathode gas, and Tafel was heated at 60°C in the same manner as in Comparative Example 7-c1. Plots and impedance spectra were obtained. This Tafel plot and impedance measurement were performed using a nickel-rhodium carbonization catalyst (NiRh carbonization catalyst 600) as an anode, platinum as a cathode, and a reversible hydrogen electrode as a reference electrode. The obtained Tafel plot and impedance spectrum are shown in FIG. 13 and FIG. 17, respectively.

The exchange current density of the hydrogen oxidation reaction using the carbonization catalyst determined from the Tafel plot and impedance measurement was 13.9 mA cm ^-2 as shown in Table 6, which was 486 times higher than that of the nickel-rhodium complex.

[Comparative Example 8-c1] Electrocatalytic performance evaluation by Tafel plot and impedance measurement of a hydrogen-oxygen fuel cell using a nickel-rhodium chloro complex as a cathode electrode catalyst and platinum as an anode electrode catalyst Configuration with a reversible hydrogen electrode as a reference electrode A fuel cell was produced in the same manner as in Comparative Example 5A-c0, except that hydrogen was used as the anode gas, oxygen was used as the cathode gas, and Tafel was heated at 60°C in the same manner as in Comparative Example 7-c1. Plots and impedance spectra were obtained. This Tafel plot and impedance measurement were performed using platinum as an anode, a nickel rhodium chloro complex as a cathode, and a reversible hydrogen electrode as a reference electrode. The obtained Tafel plot and impedance spectrum are shown in FIG. 14 and FIG. 18, respectively.

The exchange current density of the oxygen reduction reaction by the nickel-rhodium complex determined from the Tafel plot and impedance measurement was 0.0161 mA cm ^-2 as shown in Table 6.

[Example 8-1] Electrocatalyst performance evaluation by Tafel plot and impedance measurement of a hydrogen-oxygen fuel cell using a nickel-rhodium dry distillation catalyst as a cathode electrode catalyst and platinum as an anode electrode catalyst Configuration with a reversible hydrogen electrode as a reference electrode A fuel cell was produced in the same manner as in Example 5A-4, except that hydrogen was used as the anode gas, oxygen was used as the cathode gas, and Tafel was heated at 60°C in the same manner as in Comparative Example 7-c1. Plots and impedance spectra were obtained. This Tafel plot and impedance measurement were performed using platinum as an anode, a nickel-rhodium carbonization catalyst (NiRh carbonization catalyst 600) as a cathode, and a reversible hydrogen electrode as a reference electrode. The obtained Tafel plot and impedance spectrum are shown in FIG. 15 and FIG. 19, respectively.

The exchange current density of the oxygen reduction reaction using the carbonization catalyst determined from the Tafel plot and impedance measurement was 10.5 mA cm ^-2 as shown in Table 6, which was 652 times higher than that of the nickel-rhodium complex.

Claims (15)

An electrode catalyst comprising a catalyst component containing a first transition metal M1 and a second transition metal M2 as constituent elements and a conductive material,
Particles containing a first transition metal M1, a second transition metal M2, carbon, hydrogen, nitrogen and sulfur as constituent elements, and in which the hydrogen content and nitrogen content are both less than 1% by weight,
An electrode catalyst in which a sulfide of a first transition metal M1 and a second transition metal M2 in a metallic state are observed on the surface of the particles. The first transition metal M1 is one selected from the group consisting of Ni, Mn, Fe, Co, Cu, and Zn,
The electrode catalyst according to claim 1, wherein the second transition metal M2 is any one selected from the group consisting of Ru, Rh, Pd, Ag, Ir, and Pt. the first transition metal M1 is Ni,
The electrode catalyst according to claim 1, wherein the second transition metal M2 is one selected from the group consisting of Ru, Rh, and Ir. The conductive material is acetylene black, Vulcan, Ketjen black, black pearl, graphitized acetylene black, graphitized Vulcan, graphitized Ketjen black, graphitized black pearl, carbon nanotube, carbon nanofiber, carbon nanohorn, and carbon. The electrode catalyst according to any one of claims 1 to 3, which is selected from the group consisting of fibrils. A method for producing an electrode catalyst, including the following steps 1a and 2a:
Step 1a: Formula (1) below

(In formula (1), M is Ru ^II , Rh ^III or Ir ^III . L represents a hexamethylbenzene group or a pentamethylcyclopentadienyl group. X represents a halogen atom, a hydrogen atom, or a hydride ion. and when X is a hydrogen atom or a hydride ion, X may form a bridge with Ni ^II . Y represents a halogen atom or H ₂ O. l, m and n each independently represent 2 An integer of ~4.R is each independently an alkyl group having 1 to 5 carbon atoms.z represents the charge of the complex and is 0 or 2+. and obtaining a mixture; and
Step 2a: A step of carbonizing the mixture obtained in step 1a. The manufacturing method according to claim 5, wherein the step 2a is performed under vacuum and at a temperature of 100 to 800°C. The manufacturing method according to claim 6, wherein the temperature is within a range of 300 to 800°C. The manufacturing method according to claim 6 or 7, wherein the vacuum has a degree of vacuum of 10 to 20 Pa. The conductive material is acetylene black, Vulcan, Ketjen black, black pearl, graphitized acetylene black, graphitized Vulcan, graphitized Ketjen black, graphitized black pearl, carbon nanotube, carbon nanofiber, carbon nanohorn, and carbon. The manufacturing method according to any one of claims 5 to 8, wherein the manufacturing method is one selected from the group consisting of fibrils. An electrode catalyst obtained by the production method according to claim 8. A fuel cell electrode comprising the electrode catalyst according to any one of claims 1 to 4 and 10. 11. A membrane electrode assembly comprising a cathode, an anode, and a proton conductive membrane disposed between the cathode and the anode, the membrane electrode assembly comprising at least one selected from the group consisting of the cathode and the anode. A membrane electrode assembly which is an electrode for a fuel cell according to . A fuel cell comprising the membrane electrode assembly according to claim 12. A fuel cell comprising the fuel cell electrode according to claim 11 as a cathode, an anode, or both a cathode and an anode. The fuel cell according to claim 13 or 14, which is a hydrogen-oxygen fuel cell.

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