JP2008258150A - Electrode catalyst for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst of high activity which is suitable as an electrode catalyst for fuel cells. <P>SOLUTION: The electrode catalyst for a fuel cell uses multinuclear complex where 5-15 units of ligand comprising one or more kinds of coordinating atoms, selected from among nitrogen atom and oxygen atom in a molecule are coordinated into two to four transition metal atoms characterized as bridged by oxygen atoms of at least one kind of alkoxide or phenoxide, the transition metal atoms being selected from among vanadium, chromium, iron, manganese, cobalt, nickel, and copper. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell electrode catalyst.

Currently, platinum is used as an electrode catalyst in a polymer electrolyte fuel cell that is being developed for practical use. However, there is a problem that the cost of platinum is high, the reserves are limited, and resources will be depleted in the future. Patent Document 1 discloses an electrode catalyst using palladium, and Patent Document 2 discloses an electrode catalyst using protein as a raw material.
However, palladium is a noble metal like platinum, and it is expected that it will be difficult to secure a stable supply in the future. In addition, when using protein as a raw material, care must be taken in handling, for example, the raw material must be refrigerated.

  Non-Patent Document 1 discloses an electrode catalyst using a cobalt mononuclear complex. However, since the complex is a mononuclear complex having only one metal atom, it is not suitable for a multi-electron transfer reaction, and hydrogen peroxide is easily generated.

  For example, Non-Patent Document 2 reports a catalyst obtained by heat-treating a polynuclear complex having bipyridine as a ligand.

  However, the catalytic activity of a metal complex having a low molecular weight organic compound such as bipyridine as a ligand is still insufficient for practical use, and further improvement of the catalytic activity has been desired.

JP 2006-260909 A JP 2004-217507 A Tatsuhiro Okada, et. al. Electrochimica Acta, 45, 4419 (2000). “Development of Fuel Cell Electrode Catalyst Using Organometallic Complex” Catalytic Society of Tsukuba area lecture (December 10, 2004), National Institute of Advanced Industrial Science and Technology Tatsuhiro Okada

  An object of the present invention is to provide a highly active catalyst suitable as a fuel cell electrode catalyst.

The above object of the present invention has been achieved by the following means.
[1] An electrode catalyst for a fuel cell comprising a polynuclear complex in which a ligand having 5 to 15 coordination atoms in the molecule is coordinated to 2 to 4 transition metal atoms.
[2] The fuel cell according to [1], wherein the transition metal atom of the polynuclear complex is at least one selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, nickel, and copper. Electrode catalyst.
[3] The electrode catalyst for a fuel cell according to [1] or [2], wherein the coordination atom of the polynuclear complex is at least one selected from a nitrogen atom and an oxygen atom.
[4] The fuel cell electrode catalyst according to any one of [1] to [3], wherein the transition metal atom of the polynuclear complex is bridged by an oxygen atom of alkoxide or phenoxide.
[5] The fuel cell according to any one of [1] to [4], wherein in the polynuclear complex, at least one of the interatomic distances of the transition metal selected arbitrarily is 3.6 mm or less. Electrode catalyst.
[6] The fuel cell according to any one of [1] to [5], wherein the ligand is a ligand represented by the following general formula (I) or general formula (II): Electrode catalyst.

(Wherein Q ¹ and Q ² are each a divalent organic group having at least two C═N bonds, and T ¹ is a monovalent organic group having at least one C═N bond, R ¹ and R ² are each independently a hydrogen atom or a substituent, two R ¹ or R ² may be linked to each other, and a plurality of R ¹ and R ² are the same as each other The plurality of Q ¹ may be the same or different, and the plurality of T ¹ may be the same or different.)
[7] A fuel cell electrode catalyst obtained by heating the polynuclear complex according to any one of [1] to [6] at a temperature of 250 ° C. or higher and 1500 ° C. or lower.
[8] A fuel cell electrode catalyst comprising a multinuclear complex mixture containing the multinuclear complex according to any one of [1] to [6] above and a carbon support and / or a conductive polymer.
Furthermore, the present invention provides
[9] A polynuclear complex mixture containing the polynuclear complex according to any one of [1] to [6] above and a carbon support and / or a conductive polymer is heated at a temperature of 250 ° C. or higher and 1500 ° C. or lower. The electrode catalyst for fuel cells obtained by this is provided.

  In the present invention, by using a polynuclear complex, it becomes possible to arrange metal atoms at a distance suitable for electrode reaction, and further, by using a ligand having 5 to 15 coordination atoms, Can also retain a multinuclear structure. Such a polynuclear complex exhibits excellent catalytic activity (for example, mass activity) as an electrode catalyst for a fuel cell.

  In the catalyst of the present invention, a ligand having 5 to 15 coordination atoms in the molecule is coordinated to 2 to 4 transition metal atoms. Here, the coordination atom means that electrons are donated to the vacant orbit of metal atoms, as described in Ryogo Kubo et al., “Iwanami Rikagaku Dictionary 4th Edition” (issued January 10, 1991, Iwanami Shoten), page 966. An atom having an unshared electron pair and bonded to a metal atom through a coordinate bond.

  Moreover, in the polynuclear complex applied to the catalyst of the present invention, the transition metal atom to which the coordination atom is coordinated may be an uncharged or charged metal ion.

Examples of the transition metal atom include transition metals belonging to the fourth to sixth periods of the periodic table of elements.
Specifically, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, lanthanum, cerium, praseodymium, neodymium, samarium, europium And a metal atom selected from the group consisting of gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum and gold.
Among these, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, yttrium, zirconium, niobium, molybdenum, silver, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium One or more metal atoms selected from the group consisting of dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum and tungsten, more preferably scandium, titanium, vanadium, chromium, manganese, iron, cobalt, One or more metal atoms selected from the group consisting of nickel, copper, zirconium, niobium, molybdenum, tantalum and tungsten.
Among these, in particular, one or more metal atoms selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, nickel, and copper are preferable, and a group consisting of manganese, iron, cobalt, nickel, and copper is particularly preferable. One or more metal atoms selected from

  Moreover, although the catalyst of this invention has 2-4 transition metal atoms, Preferably it is 2-3 pieces, More preferably, it is two pieces.

  Furthermore, when the catalyst of the present invention contains at least one cobalt atom as a transition metal atom, it is particularly preferable in view of the performance of the catalyst.

  The ligand constituting the polynuclear complex in the catalyst has 5 to 15 coordination atoms that can be bonded to the transition metal atom. The total number of coordinating atoms in the ligand is preferably 5 to 12, more preferably 6 to 10, and particularly preferably 6 to 8. The coordinating atom may be electrically neutral or a charged ion.

  The coordination atom is preferably one or more selected from a nitrogen atom, an oxygen atom, a phosphorus atom, and a sulfur atom, and a plurality of coordination atoms may be the same as or different from each other. More preferably, they are 1 or more types chosen from a nitrogen atom, an oxygen atom, and a sulfur atom, Most preferably, they are 1 or more types chosen from a nitrogen atom and an oxygen atom.

  The polynuclear complex of the present invention is preferable because the transition metal atom is bridged by an oxygen atom of alkoxide or phenoxide, and the effect of arranging the transition metal atom at a distance suitable for the electrode reaction is enhanced.

The alkoxide is one in which a hydroxy group (OH) of an alcohol (R ^α OH) releases a proton, and R ^α indicates an alkyl group. Specifically, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, nonyl group, dodecyl group, pentadecyl group, Octadecyl group, docosyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclononyl group, cyclododecyl group, norbornyl group, adamantyl group, phenylmethyl group, 1-phenylethyl group, 2-phenylethyl group, 1-phenyl-1-propyl group, 1-phenyl-2-propyl group, 2-phenyl-2-propyl group, 3-phenyl-1-propyl group, 4-phenyl-1-butyl group, 5-phenyl-1 -Pentyl group, 6-phenyl-1-hexyl group and the like.

Phenoxide is obtained by releasing a proton from a hydroxy group (OH) of phenol (R ^β OH), and R ^β indicates a monovalent aryl group. Specifically, for example, phenyl group, 1-naphthyl group, 2-naphthyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-propylphenyl group, 4-isopropylphenyl group, 4-butylphenyl group, 4-tert-butylphenyl group, 4-hexylphenyl group, 4-cyclohexylphenyl group, 4-adamantylphenyl group, 4-phenylphenyl group and the like.

Moreover, in the polynuclear complex of the present invention, when at least one of the distances between atoms of the transition metal selected arbitrarily is 3.6 mm or less, the interaction between the transition metal atom and the hydrogen molecule or oxygen molecule is strengthened. The effect of higher catalytic activity is expected. The distance between the transition metal atoms is more preferably 3.4 mm or less, particularly preferably 3.2 mm or less, and particularly preferably 3.0 mm or less. On the other hand, if the interatomic distance of the transition metal is too close, the repulsion between the transition metal atoms becomes strong and the catalyst becomes unstable. Therefore, the interatomic distance of the transition metal is preferably 1.8 mm or more, more preferably 2 0.0Å or more, particularly preferably 2.2Å or more. The interatomic distance of the transition metal can be determined by X-ray crystal structure analysis, but the values reported in the literature can also be used. Or it can also obtain | require by the structure optimization calculation based on a density functional method. Materials Studio DMol ³ version 4.2 (made by accelrys) is used for the structural optimization calculation based on the density functional theory.

  In the catalyst of the present invention, the ligand of the polynuclear complex is required to have 5 to 15 coordinating atoms, more preferably a ligand represented by the following general formula (I), or A ligand represented by the formula (II) can be exemplified.

(Wherein Q ¹ and Q ² are each a divalent organic group having at least two C═N bonds, and T ¹ is a monovalent organic group having at least one C═N bond, R ¹ and R ² are each independently a hydrogen atom or a substituent, two R ¹ or R ² may be linked to each other, and a plurality of R ¹ and R ² are the same as each other May be different.)

  The hydroxy group (OH) in the general formula (I) or (II) becomes a phenoxy group from which a proton has been released, and may be coordinated with a metal atom.

When R ¹ and R ^{2 in the} general formula (I) or (II) are substituents, examples thereof include a hydroxyl group, amino group, nitro group, cyano group, carboxyl group, formyl group, hydroxysulfonyl group, halogen atom, Substituted by two monovalent hydrocarbon groups which may be substituted, hydrocarbyloxy groups which may be substituted (hydrocarbonoxy groups which may be substituted), two unsubstituted or substituted monovalent hydrocarbon groups Amino groups (that is, optionally substituted hydrocarbon disubstituted amino groups), optionally substituted hydrocarbyl mercapto groups (optionally substituted hydrocarbon mercapto groups), optionally substituted hydrocarbyls Carbonyl group (optionally substituted hydrocarbon carbonyl group), optionally substituted hydrocarbyloxycarbonyl group (optionally substituted) Hydrocarbon oxycarbonyl group), an aminocarbonyl group substituted with two unsubstituted or substituted monovalent hydrocarbon groups (ie, an optionally substituted hydrocarbon disubstituted aminocarbonyl group), or substituted A hydrocarbyloxysulfonyl group which may be substituted (an optionally substituted hydrocarbonsulfonyl group), a monovalent hydrocarbon group which may be substituted, a hydrocarbyloxy group which may be substituted, an unsubstituted or substituted group Preferred are an amino group substituted with two monovalent hydrocarbon groups, an optionally substituted hydrocarbyl mercapto group, an optionally substituted hydrocarbylcarbonyl group, and an optionally substituted hydrocarbyloxycarbonyl group. Monovalent hydrocarbon group which may be substituted, hydrocarbyloxy group which may be substituted, unsubstituted or substituted Monovalent more preferably an amino group substituted with a hydrocarbon group two, 1 may be substituted monovalent hydrocarbon group, an optionally substituted hydrocarbyloxy group is more preferred. In these groups, the nitrogen atom to which a hydrogen atom is bonded is preferably substituted with a monovalent hydrocarbon group. In addition, when the group represented by R ¹ has a plurality of substituents, the two substituents may be linked to form a ring.

Examples of the monovalent hydrocarbon group represented by R ¹ include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, and hexyl. Group, nonyl group, dodecyl group, pentadecyl group, octadecyl group, docosyl group, etc., an alkyl group having 1 to 50 carbon atoms (preferably an alkyl group having 1 to 20 carbon atoms); cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclo Hexyl group, cyclononyl group, cyclododecyl group, norbornyl group, adamantyl group and other cyclic saturated hydrocarbon groups having 3 to 50 carbon atoms (preferably cyclic saturated hydrocarbon groups having 3 to 20 carbon atoms); ethenyl group and propenyl group 3-butenyl group, 2-butenyl group, 2-pentenyl group, 2-hexenyl group, 2-nonenyl group, 2-dodecenyl group An alkenyl group having 2 to 50 carbon atoms (preferably an alkenyl group having 2 to 20 carbon atoms) such as phenyl group, 1-naphthyl group, 2-naphthyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl Group, 4-ethylphenyl group, 4-propylphenyl group, 4-isopropylphenyl group, 4-butylphenyl group, 4-tert-butylphenyl group, 4-hexylphenyl group, 4-cyclohexylphenyl group, 4-adamantylphenyl Group, an aryl group having 6 to 50 carbon atoms such as 4-phenylphenyl group (preferably an aryl group having 6 to 20 carbon atoms); phenylmethyl group, 1-phenylethyl group, 2-phenylethyl group, 1-phenyl-1- Propyl group, 1-phenyl-2-propyl group, 2-phenyl-2-propyl group, 3-phenyl-1-propyl group, 4-phenyl group Examples thereof include an aralkyl group having 7 to 50 carbon atoms (preferably an aralkyl group having 7 to 20) such as an phenyl-1-butyl group, a 5-phenyl-1-pentyl group, and a 6-phenyl-1-hexyl group.

The monovalent hydrocarbon group represented by R ¹ preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, more preferably 2 to 12 carbon atoms, and 1 carbon atom. To 10 carbon atoms are more preferable, those having 3 to 10 carbon atoms are more preferable, alkyl groups having 1 to 10 carbon atoms are more preferable, and alkyl groups having 3 to 10 carbon atoms are particularly preferable.

The hydrocarbyloxy group, hydrocarbyl mercapto group, hydrocarbylcarbonyl group, hydrocarbyloxycarbonyl group, and hydrocarbylsulfonyl group represented by R ¹ are each an oxy group, a mercapto group, a carbonyl group, an oxycarbonyl group, and a sulfonyl group. This is a group formed by bonding one valent hydrocarbon group.

“Amino group substituted with two unsubstituted or substituted monovalent hydrocarbon groups” represented by R ¹ , “aminocarbonyl group substituted with two unsubstituted or substituted monovalent hydrocarbon groups” Are groups in which two hydrogen atoms in an amino group and an aminocarbonyl group (that is, —C (═O) —NH ₂ ) are substituted with the monovalent hydrocarbon group. Specific examples and preferred examples of the monovalent hydrocarbon group contained in these are the same as the monovalent hydrocarbon group represented by R ¹ described above.

The monovalent hydrocarbon group represented by R ¹ , hydrocarbyloxy group, hydrocarbyl mercapto group, hydrocarbylcarbonyl group, hydrocarbyloxycarbonyl group, and hydrocarbylsulfonyl group have a part or all of the hydrogen atoms contained in these groups, Halogen atom, hydroxyl group, amino group, nitro group, cyano group, monovalent hydrocarbon group which may be substituted, hydrocarbyloxy group which may be substituted, hydrocarbyl mercapto group which may be substituted, substituted It may be substituted with an optionally substituted hydrocarbylcarbonyl group, an optionally substituted hydrocarbyloxycarbonyl group, an optionally substituted hydrocarbylsulfonyl group, and the like.

Among the above R ¹ , hydrogen atom, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, phenyl group, methylphenyl group, naphthyl group, pyridyl are particularly preferable. It is a group.

In the general formula (I) or (II), Q ¹ and Q ² are divalent organic groups having at least two C═N bonds. These divalent organic groups are preferably those represented by the following formulas (III-a) and (III-b).

(Wherein, R ³ is R ¹ of the general formula (I) or (II), have the same meanings as R ^2, plural R ³ is good .Z ¹ be the same or different from one another, a divalent P1 and P2 are organic groups, and are an atomic group necessary for forming an aromatic heterocyclic ring which may be bonded and bonded together with one C═N—C, and P1 and P2 are bonded to each other. may form a ring Te, the P1 and P2, may .Y ¹ be the same or different from each other, a single bond, a double bond or a linking group.)

Z ¹ in the formula (III-a) represents a divalent organic group, and examples thereof include an optionally substituted alkylene group and an optionally substituted aromatic group.

Examples of the alkylene group in Z ¹ include a methylene group, an ethylene group, a 1,1-propylene group, a 1,2-propylene group, a 1,3-propylene group, a 2,4-butylene group, and 2,4-dimethyl. A linear chain having 1 to 20 carbon atoms, preferably 1 to 10, more preferably 2 to 10, such as a -2,4-butylene group, 1,2-cyclopentylene group, 1,2-cyclohexylene group, etc. A branched or cyclic alkylene group is mentioned. The alkylene group may be substituted with the substituent of R ¹ or R ² .

The aromatic group which may be substituted in Z ¹ is a divalent group generated by removing two hydrogen atoms from an aromatic compound. Examples of the aromatic compound herein include 6 to 60 carbon atoms in total such as benzene, naphthalene, anthracene, tetracene, biphenyl, dibenzofuran, thiophene, benzothiophene, dibenzothiophene, pyridine, pyrazine, phenol, naphthol, binaphthyl, phenanthrene, and the like. An aromatic compound having about 4 to 60 is preferable.
The aromatic group may be substituted with the substituent of R ¹ or R ² .

  The divalent organic group represented by the formula (III-a) is preferably a compound exemplified by the following formulas (III-a-1) to (III-a-9), more preferably (III -A-1) to (III-a-6).

(In the formula, R ⁴ has the same meaning as R ¹ and R ^{2 in} formula (I) or (II), and a plurality of R ⁴ may be the same as or different from each other.)

Specific examples of the optionally substituted aromatic heterocyclic ring formed by combining P1 and P2 of the formula (III-b) with C—N═C include pyridine, pyrazine, pyrimidine, thiazole, imidazole, oxazole, Examples include triazole, benzimidazole, isoquinoline, and quinazoline, which may be substituted with the substituent of R ¹ . Pyridine, pyrazine, pyrimidine, thiazole, imidazole, oxazole, triazole, and benzimidazole are preferable, and pyridine, thiazole, imidazole, and oxazole are more preferable.
The aromatic heterocycles may be bonded to each other to form a new ring, and those having the following structures (IV-1) to (IV-6) are preferred. Preferably, it has a structure of (IV-1)-(IV-3).

(Wherein, R ⁵ in general formula (I) or (II) have the same meanings as R ^1, R ^2, and plurality of R ⁵ may be the same as each other, it may be different .R ⁶ is hydrogen atom or A monovalent hydrocarbon group having 1 to 30 carbon atoms, and a plurality of R ⁶ may be the same or different.

T ^{1 in the} general formula (II) is a monovalent organic group having at least one C═N bond, and the monovalent organic group is represented by the following formula (Va) or (Vb): The monovalent organic group represented can be illustrated.

(In the formula, R ⁷ has the same meaning as R ¹ and R ^{2 in} formulas (I) and (II), and P 3 represents an aromatic heterocyclic group which may be substituted with one C═N—C. A group of atoms necessary for forming a plurality of R ⁷ may be the same or different from each other.

Specific examples of the optionally substituted aromatic heterocycle formed by P3 in the formula (Vb) include pyridine, pyrazine, pyrimidine, thiazole, imidazole, oxazole, triazole, benzimidazole, quinoline, isoquinoline, cinnoline. , Phthalazine, quinazoline, quinoxaline, and benzodiazine, preferably pyridine, pyrazine, pyrimidine, thiazole, imidazole, oxazole, triazole, and benzimidazole, and more preferably pyridine, thiazole, imidazole, and oxazole. These may be substituted with the substituent shown as R ¹ .
As described in, for example, Journal of Organic Chemistry, 69, 5419 (2004), a ligand of the compound represented by the general formula (I) includes a phenol compound having an aldehyde group, a compound having an amino group, Can be synthesized in a solvent such as alcohol. Further, as described in the Australian Journal of Chemistry, 23, 2225 (1970), a target metal complex can be directly synthesized by adding a metal salt during the reaction.
The ligand represented by the general formula (II) undergoes addition reaction and oxidation of an organometallic reagent to a heterocyclic compound as described in non-patent literature Tetrahedron., 1999, 55, 8377. , A halogenation reaction, and then a cross-coupling reaction using a transition metal catalyst. Moreover, it is also possible to synthesize stepwise by a cross-coupling reaction using a halide having a heterocyclic ring.

Here, ligands represented by the following formulas (VI-1) to (VI-14) are exemplified as the ligands represented by the general formula (I) or (II). Among these, ligands represented by formulas (VI-1) to (VI-8) are preferable. In the following formulas, Me is methyl, ^t Bu represents tert- butyl, the.

As the polynuclear complex used as the catalyst of the present invention, the compound represented by the general formula (I) or the general formula (II) and a reagent for imparting a metal atom (hereinafter referred to as “metal imparting agent”) are appropriately used. It can be synthesized by mixing in a reaction solvent. As the metal-imparting agent, the transition metal acetates, chlorides, sulfates, carbonates and the like exemplified as specific examples can be used. A polynuclear complex having a compound represented by the general formula (I) as a ligand can also be synthesized by adding a metal-imparting agent to a phenol compound having an aldehyde and a compound having an amino group as described above. can do. As a reaction solvent, water, acetic acid, oxalic acid, aqueous ammonia, methanol, ethanol, n-propanol, isopropyl alcohol, 2-methoxyethanol, 1-butanol, 1,1-dimethylethanol, ethylene glycol, diethyl ether, 1,2-dimethoxyethane, methyl ethyl ether, 1,4-dioxane, tetrahydrofuran, benzene, toluene, xylene, mesitylene, durene, decalin, dichloromethane, chloroform, carbon tetrachloride, chlorobenzene, 1,2-dichlorobenzene, N, N′-dimethylformamide, N, N′-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, acetone, acetonitrile, benzonitrile, triethylamine, pyridine are included, and two or more of these are mixed. It may be used comprising reaction solvent, but is preferably one ligand and the metal-providing agent is soluble. The reaction temperature is usually −10 to 200 ° C., preferably 0 to 150 ° C., particularly preferably 0 to 100 ° C., and the reaction time is usually 1 minute to 1 week, preferably 5 minutes to 24 hours, particularly preferably. Can be carried out in 1 to 12 hours. The reaction temperature and reaction time can also be optimized as appropriate depending on the type of ligand and metal-providing agent.
As a means for isolating and purifying the produced polynuclear complex from the reaction solution after the reaction, an optimum means can be appropriately selected from known recrystallization methods, reprecipitation methods or chromatography methods, and these means can be used. May be combined.
Depending on the type of the reaction solvent, the produced multinuclear complex may be precipitated, and the precipitated multinuclear complex may be separated by a solid-liquid separation means such as filtration, and washed and dried as necessary. A polynuclear complex can also be isolated and purified.

  The catalyst of the present invention comprises a multinuclear complex in which a ligand having 5 to 15 coordination atoms is coordinated to 2 to 4 metal atoms in the molecule. In addition, you may have another ligand. Such other ligands may be ionic or electrically neutral compounds, and when there are a plurality of such other ligands, these other ligands may be the same or different from each other. Also good.

Examples of the multinuclear complex having the ligand represented by the general formula (I) or (II) include multinuclear complexes represented by the following formulas (VII-1) to (VII-14). M ¹ , M ² , M ³ and M ⁴ in the formula represent transition metal atoms, and specific examples include the transition atoms. M ¹ , M ² , M ³ and M ⁴ may be the same as or different from each other. Me represents methyl, and ^t Bu represents tert-butyl. In the formula, the charge of the polynuclear complex is omitted.

Examples of the other ligands include electrically neutral compounds such as ammonia, pyridine, pyrrole, pyridazine, pyrimidine, pyrazine, 1,2,4-triazine, pyrazole, imidazole, 1,2,3-triazole. , Oxazole, isoxazole, 1,3,4-oxadiazole, thiazole, isothiazole, indole, indazole, quinoline, isoquinoline, phenanthridine, cinnoline, phthalazine, quinazoline, quinoxaline, 1,8-naphthyridine, acridine, 2 , 2′-bipyridine, 4,4′-bipyridine, 1,10-phenanthroline, ethylenediamine, propylenediamine, phenylenediamine, cyclohexanediamine, pyridine N-oxide, 2,2′-bipyridine N, N′-dioxide, oxamide, The Nitrogen atom-containing compounds such as tilglyoxime and o-aminophenol; water, methanol, ethanol, 1-propanol, 2-propanol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, 2-methoxy Ethanol, phenol, oxalic acid, catechol, salicylic acid, phthalic acid, 2,4-pentanedione, 1,1,1-trifluoro-2,4-pentanedione, hexafluoropentanedione, 1,3-diphenyl-1,3 -Oxygen-containing compounds such as propanedione and 2,2'-binaphthol; sulfur-containing compounds such as dimethyl sulfoxide and urea; 1,2-bis (dimethylphosphino) ethane, 1,2-phenylenebis (dimethylphosphine) and the like Examples include phosphorus-containing compounds.
Among these, ammonia, pyridine, pyrrole, pyridazine, pyrimidine, pyrazine, 1,2,4-triazine, pyrazole, imidazole, 1,2,3-triazole, oxazole, isoxazole, 1,3,4-oxa Diazole, indole, indazole, quinoline, isoquinoline, phenanthridine, cinnoline, phthalazine, quinazoline, quinoxaline, 1,8-naphthyridine, acridine, 2,2'-bipyridine, 4,4'-bipyridine, 1,10-phenanthroline , Ethylenediamine, propylenediamine, phenylenediamine, cyclohexanediamine, pyridine N-oxide, 2,2′-bipyridine N, N′-dioxide, oxamide, dimethylglyoxime, o-aminophenol, water, phenol, Uric acid, catechol, salicylic acid, phthalic acid, 2,4-pentanedione, 1,1,1-trifluoro-2,4-pentanedione, hexafluoropentanedione, 1,3-diphenyl-1,3-propanedione 2,2′-binaphthol, more preferably ammonia, pyridine, pyrrole, pyridazine, pyrimidine, pyrazine, 1,2,4-triazine, pyrazole, imidazole, 1,2,3-triazole, oxazole, isoxazole, 1,3,4-oxadiazole, indole, indazole, quinoline, isoquinoline, phenanthridine, cinnoline, phthalazine, quinazoline, quinoxaline, 1,8-naphthyridine, acridine, 2,2'-bipyridine, 4,4'- Bipyridine, 1,10-phenanthroline, ethylenedi Min, propylenediamine, phenylenediamine, cyclohexanediamine, pyridine N-oxide, 2,2'-bipyridine N, N'-dioxide, o-aminophenol, phenol, catechol, salicylic acid, phthalic acid, 1,3-diphenyl-1, Examples include 3-propanedione and 2,2′-binaphthol.
Among these, pyridine, pyrrole, pyridazine, pyrimidine, pyrazine, pyrazole, imidazole, oxazole, indole, quinoline, isoquinoline, acridine, 2,2′-bipyridine, 4,4′-bipyridine, 1,10-phenanthroline, phenylenediamine Further, pyridine N-oxide, 2,2′-bipyridine N, N′-dioxide, o-aminophenol, and phenol are more preferable.

Examples of the anionic ligand include hydroxide ions, peroxides, superoxides, cyanide ions, thiocyanate ions, fluoride ions, chloride ions, bromide ions, iodide ions and the like, Sulfate ion, nitrate ion, carbonate ion, perchlorate ion, tetrafluoroborate ion, tetraarylborate ion such as tetraphenylborate ion, hexafluorophosphate ion, methanesulfonate ion, trifluoromethanesulfonate ion, p-toluene Sulfonate ion, benzenesulfonate ion, phosphate ion, phosphite ion, acetate ion, trifluoroacetate ion, propionate ion, benzoate ion, metal oxide ion, methoxide ion, ethoxide ion, etc. And the like.
Preferably, hydroxide ion, sulfate ion, nitrate ion, carbonate ion, perchlorate ion, tetrafluoroborate ion, tetraphenylborate ion, hexafluorophosphate ion, methanesulfonate ion, trifluoromethanesulfonate ion, p -Toluene sulfonate ion, benzene sulfonate ion, phosphate ion, acetate ion, trifluoroacetate ion are exemplified, among which hydroxide ion, sulfate ion, nitrate ion, carbonate ion, tetraphenylborate ion, trifluoro ion Lomethanesulfonic acid ions, p-toluenesulfonic acid ions, acetate ions, and trifluoroacetic acid ions are more preferable.

  Furthermore, the ions exemplified as the ligand having an anionic property may have as a counter ion for electrically neutralizing the multinuclear complex itself of the present invention.

The polynuclear complex may have a counter ion having a cationic property that maintains electrical neutrality. Examples of the counter ion having a cationic property include alkali metal ions, alkaline earth metal ions, tetraalkylammonium ions such as tetra (n-butyl) ammonium ion and tetraethylammonium ion, and tetraarylphosphonium ions such as tetraphenylphosphonium ion. Specifically, lithium ion, sodium ion, potassium ion, rubidium ion, cesium ion, magnesium ion, calcium ion, strontium ion, barium ion, tetra (n-butyl) ammonium ion, tetraethylammonium ion, tetraphenyl Phosphonium ion, more preferably tetra (n-butyl) ammonium ion, tetraethylammonium ion, tetraphenylphosphonium Ion, and the like.
Among these, tetra (n-butyl) ammonium ions and tetraethylammonium ions are preferable as the counter ion having a cationic property.

In one preferred embodiment of the present invention, the polynuclear complex can be used as a catalyst as it is, or a heat-treated one of the polynuclear complex can be used as a catalyst. What heat-processed the polynuclear complex is preferable.
Next, the heat treatment of the polynuclear complex in the present invention will be described in detail.
As the polynuclear complex used for the heat treatment, only one kind of multinuclear complex may be used, or two or more kinds of polynuclear complexes may be used.
The multinuclear complex is particularly preferably dried for 6 hours or more under a reduced pressure of 1533 ° C. (10 Torr) or less at a temperature of 15 ° C. or more and 200 ° C. or less as a pretreatment for heat treatment. As the pretreatment, a vacuum dryer or the like can be used.

The atmosphere used for the heat treatment of the polynuclear complex is a reducing atmosphere such as hydrogen or carbon monoxide, an oxidizing atmosphere such as oxygen, carbon dioxide or water vapor, or an inert gas such as nitrogen, helium, neon, argon, krypton, or xenon. It is preferably in the presence of an atmosphere, a gas or vapor of a nitrogen-containing compound such as ammonia or acetonitrile, and a mixed gas thereof. More preferably, in a reducing atmosphere, hydrogen and a mixed atmosphere of hydrogen and the inert gas, in an oxidizing atmosphere, oxygen, a mixed atmosphere of oxygen and the inert gas, or an inert gas atmosphere If so, it is a mixed atmosphere of nitrogen, neon, argon, and these gases.
Moreover, the pressure which concerns on heat processing is although it does not specifically limit, It is preferable in the normal pressure vicinity of about 0.5-1.5 atmospheres.

  The temperature at which the polynuclear complex is heat-treated is preferably 250 ° C. or higher, more preferably 300 ° C. or higher, still more preferably 400 ° C. or higher, and particularly preferably 500 ° C. or higher. Moreover, the temperature concerning heat processing becomes like this. Preferably it is 1500 degrees C or less, More preferably, it is 1200 degrees C or less, Most preferably, it is 1000 degrees C or less.

  The processing time required for the heat treatment can be appropriately set depending on the gas used, the temperature, etc. In the sealed or vented state of the gas, the temperature is gradually raised from room temperature and the temperature is lowered immediately after reaching the target temperature. Also good. Among them, it is preferable to gradually heat the polynuclear complex by maintaining the temperature after reaching the target temperature because durability can be further improved. The holding time after reaching the target temperature is preferably 1 to 100 hours, more preferably 1 to 40 hours, further preferably 2 hours to 10 hours, and particularly preferably 2 to 3 hours. .

  An apparatus for performing the heat treatment is not particularly limited, and examples thereof include a tubular furnace, an oven, a furnace, and an IH hot plate.

Next, another embodiment of the fuel cell electrode catalyst of the present invention will be described.
As described above, the fuel cell electrode catalyst may be composed of a polynuclear complex mixture containing the polynuclear complex and a carbon support and / or a conductive polymer. This is useful from the viewpoint of increasing the stability of the catalyst and improving the catalytic activity.

  The mixing ratio of the polynuclear complex, the carbon carrier and the conductive polymer in the polynuclear complex mixture is such that the content of the polynuclear complex is 1 to 70% by mass with respect to the total mass of the multinuclear complex, the carbon carrier and the conductive polymer. It is preferable to set so. The content of the polynuclear complex is more preferably 2 to 60% by mass, and particularly preferably 3 to 50% by weight.

  Examples of the carbon support include Norrit (manufactured by NORIT), Ketjen black (manufactured by Lion), Vulcan (manufactured by Cabot), black pearl (manufactured by Cabot), acetylene black (manufactured by Chevron) (all products) Name), fullerenes such as C60 and C70, carbon nanotubes, carbon nanohorns, and carbon fibers.

  Such a multinuclear complex mixture may be heat-treated to form a fuel cell electrode catalyst, and the conditions for the heat treatment are the same as the conditions for heat-treating the multinuclear complex.

  Examples of the conductive polymer include polyacetylene, polyaniline, and polypyrrole. In addition, the said polynuclear complex, a carbon support | carrier, and a conductive polymer may be used individually by 1 type, or may use 2 or more types together.

  The electrode catalyst for a fuel cell of the present invention can be used as a catalyst for a fuel electrode and an air electrode of a fuel cell, and may be used as a catalyst for both a fuel electrode and an air electrode, or either a fuel electrode or an air electrode. It can also be used as one catalyst.

  The fuel cell using the fuel cell electrode catalyst of the present invention can be used, for example, as a small power source for mobile devices such as an automobile power source, a household power source, a mobile phone, and a portable personal computer.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not restrict | limited to a following example. In addition, the interatomic distance of the transition metal atom of the polynuclear complex described as the calculated value in this example is a value calculated by the calculation program Materials Studio DMol ³ version 4.2, and the calculation includes GGA / PW91 functional and The DNP basis function was used, and DFT Semi-local Pseudopotential (DSPP) was used for the inner electrons of transition metal atoms.

Synthesis example 1 of polynuclear complex [Synthesis of polynuclear complex (A)]
According to the following reaction formula (1), the polynuclear complex (A) is converted to Australian.
It was synthesized with reference to the method described in Journal of Chemistry, 23, 2225 (1970).

First, a 50 ml methanol solution containing 1.9 g of cobalt chloride hexahydrate and 1.31 g of 4-methyl-2,6-diformylphenol was placed in a 100 ml eggplant flask under a nitrogen atmosphere and stirred at room temperature. did. A solution prepared by dissolving 0.59 g of 1,3-propanediamine in 20 ml of methanol was gradually added to this solution. The mixture was refluxed for 3 hours to produce a brown precipitate. The precipitate was collected by filtration and dried to obtain a polynuclear complex (A) (yield 1.75 g: yield 74%). As described in Inorganica Chimica Acta, 16, 121 (1976), at least one of the transition metal atoms had an atomic distance of 3.137 cm. In the above reaction formula, “Cl ₂ ” means that 2 equivalents of chlorine ions are present as counter ions, and “2MeOH” means that 2 equivalents of methanol molecules are coordinated other than macrocyclic ligands. Indicates that it exists as a child.
Elemental analysis (%): Calculated as C ₂₆ H ₃₄ Cl ₂ Co ₂ N ₄ O ₄ : C, 47.65; H, 5.23; N, 8.55. Found: C, 46.64; H, 5.02; N, 8.58.

Synthesis Example 2 [Synthesis of polynuclear complex (B)]
A polynuclear complex (B) was synthesized by the following method according to the following reaction formula (2).

Under a nitrogen atmosphere, 10 ml ethanol solution containing 0.476 g cobalt chloride hexahydrate and 0.412 g 4-tert-butyl-2,6-diformylphenol was placed in a 50 ml eggplant flask and stirred at room temperature. . A solution prepared by dissolving 0.216 g of o-phenylenediamine in 5 ml of ethanol was gradually added to this solution. The mixture was refluxed for 2 hours to produce a brown precipitate. This precipitate was collected by filtration and dried to obtain a polynuclear complex (B) (yield 0.465 g: yield 63%). When the interatomic distance between the transition metal atoms was determined by the above calculation method, at least one of the distances was 2.882 cm. In the above reaction formula, “Cl ₂ ” indicates that 2 equivalents of chlorine ions are present as counter ions, and “2H ₂ O” indicates that 2 equivalents of water molecules are present as other ligands. Indicates to do.
Elemental analysis value (%): C ₃₆ H ₃₈ Cl ₂ Co ₂ N ₄ O ₄ , calculated value: C, 55.47; H, 4.91; N, 7.19. Found: C, 56.34; H, 4.83; N, 7.23.

Synthesis Example 3 [Synthesis of polynuclear complex (C)]
The polynuclear complex (C) is converted into Bulletin according to the following reaction formula (3)
It was synthesized with reference to the method described in of Chemical Society of Japan, 68, 1105 (1995).

10 ml of methanol containing 0.33 g of 4-methyl-2,6-diformylphenol and 0.49 g of manganese acetate tetrahydrate was placed in a 50 ml eggplant flask and stirred at room temperature. A solution prepared by dissolving 0.15 g of 1,3-propanediamine in 5 ml of methanol was gradually added to this solution. After stirring the above mixture for 1 hour, a yellow precipitate was formed. The precipitate was collected by filtration, washed with methanol, and vacuum dried to obtain a polynuclear complex (C) (yield 0.25 g: yield 39%). As described in Bulletin of Chemical Society of Japan, 68, 1105 (1995), at least one of the transition metal atoms had an atomic distance of 3.367 mm. In the above reaction formula, “(OAc) ₂ ” indicates that 2 equivalents of acetate ion is present as a counter ion.
Elemental analysis (%): Calculated as C ₂₈ H ₃₂ Mn ₂ N ₄ O ₆ : C, 53.34; H, 5.12; N, 8.89. Found: C, 53.07; H, 5.12; N, 8.72.

Synthesis Example 4 [Synthesis of polynuclear complex (D)]
A polynuclear complex (D) was synthesized according to the following reaction formula (4) according to the method described in Australian Journal of Chemistry, 23, 2225 (1970).

Under a nitrogen atmosphere, 20 ml of a methanol solution containing 0.4 g of iron chloride tetrahydrate and 0.33 g of 4-methyl-2,6-diformylphenol was placed in a 50 ml eggplant flask and stirred at room temperature. A solution prepared by dissolving 0.15 g of 1,3-propanediamine in 10 ml of methanol was gradually added to this solution. After stirring the mixture for 3 hours, a reddish brown precipitate formed. The precipitate was collected by filtration and dried to obtain a polynuclear complex (D) (yield 0.50 g: yield 85%). As described in Journal of Chemical Crystallography, 34, 83 (2004), at least one of the transition metal atoms had an atomic distance of 3.108 cm. In the above reaction formula, “Cl ₂ ” indicates that 2 equivalents of chlorine ions are present as counter ions.
Elemental analysis value (%): C ₂₄ H ₂₆ Cl ₂ Fe ₂ N ₄ O ₂ , calculated value: C, 49.27; H, 4.48; N, 9.58. Found: C, 44.92; H, 4.94; N, 10.86.

Synthesis Example 5 [Synthesis of polynuclear complex (E)]
According to the following reaction formula (5), the polynuclear complex (E) was synthesized according to the method described in Chemische Berichte, 127, 465 (1994).

To a 50 ml naphth flask containing 10 ml of methanol solution containing 1.9 g of copper (II) tetrafluoroborate, 4 ml of methanol solution containing 0.86 g of 1,2-phenylenediamine was added with stirring. Subsequently, 8 ml of methanol containing 1.65 g of 4-t-butyl-2,6-diformylphenol was gradually added, followed by refluxing for 3 hours.
After concentrating the solution with an evaporator and cooling in a refrigerator, a brown precipitate was generated. The resulting precipitate was collected by filtration and dried to obtain a polynuclear complex (E) (yield 2.63 g: yield 55%). As described in Chemische Berichte, 127, 465 (1994), at least one of the transition metal atoms had an atomic distance of 2.928 cm. In the above reaction formula, “(BF ₄ ) ₂ ” indicates that 2 equivalents of tetrafluoroborate ion exist as a counter ion.
Elemental analysis value (%): C ₅₅ H ₆₀ Cu ₂ N ₆ O ₆ B ₂ F ₈ , calculated value: C, 50.55; H, 4.01; N, 6.55. Found: C, 51.64; H, 4.53; N, 6.83.

Synthesis Example 6 [Synthesis of polynuclear complex (F)]
According to the following reaction formula (6), the polynuclear complex (F) was synthesized with reference to the method described in Journal of Chemical Society, Dalton Transactions, 1223 (1996).

Under a nitrogen atmosphere, a 30 ml methanol solution containing 1.63 g vanadium oxysulfate hydrate and 1.63 g 2,6-diacetylpyridine was placed in a 100 ml eggplant flask and heated to 80 ° C. with stirring. To this solution, 0.90 g of 1,3-diaminopropane dissolved in 20 ml of methanol was added dropwise over 30 minutes. The mixed solution was refluxed for 8 hours to form a deep blue-violet precipitate. The precipitate was collected by filtration and dried to obtain a polynuclear complex (F) (yield 3.1 g: yield 45%). As described in Journal of Chemical Society, Chemical Communications, 64 (1990), at least one of the transition metal atoms had an atomic distance of 3.275 cm. In the above reaction formula, “(SO ₄ ) ₂ ” indicates that 2 equivalents of sulfate ion is used as a counter ion, and “4MeOH” indicates that 4 equivalents of methanol molecules exist as other ligands. Indicates to do.
Elemental analysis value (%): C ₂₈ H ₄₄ V ₂ N ₆ O ₁₄ S ₂ , calculated value: C, 39.35; H, 5.19; N, 9.83. Found: C, 39.73; H, 5.44; N, 10.42.

Synthesis Example 7 [Synthesis of polynuclear complex (G)]
A polynuclear complex (G) was synthesized according to the following reaction formula (7).

In addition, the said ligand used as the raw material of a complex was synthesize | combined by the method as described in Tetrahedron, 55,8377 (1999). In a nitrogen atmosphere, a 200 ml solution of 2-methoxyethanol containing 1.388 g of ligand and 1.245 g of cobalt acetate tetrahydrate was placed in a 500 ml eggplant flask and stirred for 2 hours while heating to 80 ° C. A brown solid was formed. This solid was collected by filtration, further washed with 20 ml of 2-methoxyethanol and dried to obtain a polynuclear complex (G) (yield 1.532 g: yield 74%). When the interatomic distance between the transition metal atoms was determined by the above calculation method, at least one of the distances was 2.822 mm. In the above reaction formula, “(OAc) ₂ ” indicates that 2 equivalents of acetate ion is used as a counter ion, and “MeOEtOH” includes 1 equivalent of 2-methoxyethanol. Is shown.
Elemental analysis (%): as _{C 49 H 50 Co 2 N 4} O 8, Calculated: C, 62.56; H, 5.36 ; N, 5.96; Co, 12.53. Found: C, 62.12; H, 5.07; N, 6.03; Co, 12.74.

Synthesis Example 8 [Synthesis of polynuclear complex (H)]
A polynuclear complex (H) was synthesized according to the following reaction formula (8).

In addition, the ligand synthesize | combined in the synthesis example 7 was used for the said ligand used as the raw material of a complex. In a nitrogen atmosphere, 10 ml of ethanol containing 0.126 g of ligand and 5 ml of methanol containing 0.078 g of iron acetate were placed in a 50 ml eggplant flask and stirred for 3 hours while heating to 80 ° C. A brown solid precipitated out. The solid was collected by filtration, further washed with methanol, and dried to obtain a polynuclear complex (H) (yield 0.075 g: yield 41%). When the interatomic distance between the transition metal atoms was determined by the above-described calculation method, at least one was 2.824 cm. In the above reaction formula, “(OAc) ₂ ” indicates that 2 equivalents of acetate ions are present as a counter ion, and “MeOH” indicates that 2 equivalents of methanol molecules are contained. ing. Elemental analysis value (%): C ₄₈ H ₅₀ Fe ₂ N ₄ O ₈ , calculated value: C, 62.49; H, 5.46; N, 6.07. Found: C, 59.93; H, 5.29; N, 5.70.

Synthesis Example 9 [Synthesis of polynuclear complex (I)]
The polynuclear complex (I) was synthesized according to the following reaction formula (9).

In addition, the ligand synthesize | combined in the synthesis example 7 was used for the said ligand used as the raw material of a complex. In a nitrogen atmosphere, 2 ml of chloroform containing 0.126 g of ligand and 6 ml of ethanol containing 0.089 g of manganese chloride tetrahydrate were placed in a 25 ml eggplant flask and heated to 80 ° C. while heating. When stirred for a period of time, a yellow solid precipitated. The solid was collected by filtration, further washed with chloroform and ethanol, and dried to obtain a polynuclear complex (I) (yield 0.092 g: yield%). When the interatomic distance between the transition metal atoms was determined by the above calculation method, at least one was 2.672 Å. In the above reaction formula, “Cl ₂ ” means that 2 equivalents of chloride ions are present as a counter ion, and “2H ₂ O” means that 2 equivalents of water molecules are contained. Show. Elemental analysis (%): as _{C 42 H 40 Mn 2 N 4} O 4, calcd: C, 59.66; H, 4.77 ; N, 6.63. Found: C, 58.26; H, 4.58; N, 6.33.

Synthesis Example 10 [Synthesis of polynuclear complex (J)]
A polynuclear complex (J) was synthesized according to the following reaction formula.

Under a nitrogen atmosphere, a 5 ml ethanol solution containing 0.238 g of cobalt chloride hexahydrate and 0.192 g of 4-methyl-2,6-diacetylphenol was placed in a 50 ml eggplant flask and stirred at room temperature. To this solution was slowly added a 10 ml ethanol solution containing 0.108 g o-phenylenediamine. The mixture was refluxed for 3 hours to produce a brown precipitate. The precipitate was collected by filtration and dried to obtain a polynuclear complex (J) (yield 0.129 g: yield 36%). When the interatomic distance between the transition metal atoms was determined by the above calculation method, at least one was 2.849 cm. Elemental analysis _{(%): Calcd for C 34} H 34 Cl 2 Co 2 N 4 O 4; C, 54.34; H, 4.56; N, 7.46. Found: C, 53.57; H, 4.49; N, 7.00. In the above reaction formula, “Cl ₂ ” indicates that 2 equivalents of chloride ions are used as a counter ion, and “2H ₂ O” indicates that 2 equivalents of water molecules constitute the polynuclear complex (J). It is included as

Synthesis Example 11 [Synthesis of polynuclear complex (K)]
A polynuclear complex (K) was synthesized according to the following reaction formula.

Under a nitrogen atmosphere, a 25 ml methanol solution containing 0.476 g cobalt chloride hexahydrate and 0.328 g 4-methyl-2,6-diformylphenol was placed in a 100 ml eggplant flask and stirred at room temperature. To this solution was slowly added a 5 ml methanol solution containing 0.216 g o-phenylenediamine. The resulting mixture was stirred at room temperature for 2 hours to produce a black brown precipitate. The precipitate was collected by filtration and dried to obtain a polynuclear complex (K) (yield 0.368 g: yield 56%). When the interatomic distance between the transition metal atoms was determined by the above calculation method, at least one was 2.892 cm. Elemental analysis _{(%): Calcd for C 30} H 26 Cl 2 Co 2 N 4 O 4; C, 51.82; H, 3.77; N, 8.06. Found: C, 52.41; H, 3.95; N, 8.20. In the above reaction formula, “Cl ₂ ” indicates that 2 equivalents of chloride ions are present as a counter ion, and “2H ₂ O” indicates that 2 equivalents of water molecules constitute the polynuclear complex (K). It is included as

Synthesis Example 12 [Synthesis of polynuclear complex (L)]
A polynuclear complex (L) was synthesized according to the following reaction formula.

Under a nitrogen atmosphere, a 10 ml methanol solution containing 0.476 g cobalt chloride hexahydrate and 0.328 g 4-methyl-2,6-diformylphenol was placed in a 50 ml eggplant flask and stirred at room temperature. To this solution was slowly added a 5 ml methanol solution containing 0.228 g of trans-1,2-cyclohexanediamine. The mixture was refluxed for 2 hours to produce a brown precipitate. The precipitate was collected by filtration and dried to obtain a polynuclear complex (M) (yield 0.141 g: yield 21%). When the interatomic distance between the transition metal atoms was determined by the above calculation method, at least one of the distances was 2.870cm. Elemental analysis _{(%): Calcd for C 30} H 38 Cl 2 Co 2 N 4 O 4; C, 50.93; H, 5.41; N, 7.92. Found: C, 49.60; H, 5.47; N, 8.04. In the above reaction formula, “Cl ₂ ” indicates that 2 equivalents of chloride ions are present as counter ions, and “2H ₂ O” indicates that 2 equivalents of water molecules constitute the polynuclear complex (L). It is included as

Synthesis Example 13 [Synthesis of polynuclear complex (M)]
A polynuclear complex (M) was synthesized according to the following reaction formula.

[Synthesis of Compound (A)]

The raw material 2,9-bis (3′-bromo-5′-tert-butyl-2′-methoxyphenyl) -1,10-phenanthroline was synthesized by the method described in the literature Tetrahedron., 1999, 55, 8377. 3.945 g 2,9-bis (3'-bromo-5'-tert-butyl-2'-methoxyphenyl) -1,10-phenanthroline, 3.165 g 1-N-Boc-pyrrole- under argon atmosphere 2-boronic acid, 0.138 g tris (benzylideneacetone) dipalladium, 0.247 g 2-dicyclohexylphosphino-2 ', 6'-dimethoxybiphenyl, 5.527 g potassium phosphate mixed with 200 mL dioxane and 20 mL water It melt | dissolved in the solvent and stirred at 60 degreeC for 6 hours. After completion of the reaction, the mixture was allowed to cool, distilled water and chloroform were added, and the organic layer was extracted. The resulting organic layer was concentrated to give a black residue. This was refine | purified using the silica gel column, and the compound (A) was obtained. ¹ H-NMR (300 MHz, CDCl ₃ ) δ 1.34 (s, 18H), 1.37 (s, 18H), 3.30 (s, 6H), 6.21 (m, 2H), 6.27 (m, 2H), 7.37 (m , 2H), 7.41 (s, 2H), 7.82 (s, 2H), 8.00 (s, 2H), 8.19 (d, J = 8.6Hz, 2H), 8.27 (d, J = 8.6Hz, 2H).

[Synthesis of Compound (B)]

Under a nitrogen atmosphere, 0.904 g of compound (A) is dissolved in 10 mL of anhydrous dichloromethane. While cooling the dichloromethane solution to −78 ° C., 8.8 mL of boron tribromide (1.0 M dichloromethane solution) was slowly added dropwise. After dropping, the mixture was allowed to stir for 10 minutes and then allowed to stand while stirring to room temperature. After 3 hours, the reaction solution was cooled to 0 ° C., saturated aqueous NaHCO ₃ solution was added, chloroform was added for extraction, and the organic layer was concentrated. The resulting brown residue was purified with a silica gel column to obtain compound (B). ¹ H-NMR (300 MHz, CDCl ₃ ) δ 1.40 (s, 18H), 6.25 (m, 2H), 6.44 (m, 2H), 6.74 (m, 2H), 7.84 (s, 2H), 7.89 (s , 2H), 7.92 (s, 2H), 8.35 (d, J = 8.4Hz, 2H), 8.46 (d, J = 8.4Hz, 2H), 10.61 (s, 2H), 15.88 (s, 2H).

  2 mol equivalent cobalt acetate was added with respect to the obtained compound (B), and the polynuclear complex (M) was prepared by stirring in methanol. When the interatomic distance between the transition metal atoms was determined by the above calculation method, at least one was 2.881 cm.

Synthesis Example 14 [Synthesis of polynuclear complex (N)]
A polynuclear complex (N) was synthesized according to the following reaction formula.

In addition, the ligand synthesize | combined in the synthesis example 7 was used for the said ligand used as the raw material of a complex. In a nitrogen atmosphere, an ethanol 30 ml solution containing 0.200 g of ligand and 0.250 g of nickel acetate tetrahydrate was stirred in a 50 mL eggplant flask while heating to 100 ° C. for 2 hours. Precipitated. The solid was collected by filtration, washed with ethanol and diethyl ether, and dried to obtain a polynuclear complex (N) (yield 0.276 g: yield 81%). When the interatomic distance between the transition metal atoms was determined by the above calculation method, at least one of the distances was 2.804 cm. In the above reaction formula, “(OAc) ₂ ” indicates that 2 equivalents of acetate ion is present as a counter ion. Elemental analysis _(%): as _{C 46 H 42 N 4 Ni 2} O 6, Calculated: C, 63.93; H, 4.90 ; N, 6.07. Found: C, 63.22; H, 5.02; N, 6.43.

Synthesis Example 15 [Synthesis of polynuclear complex (O)]
A polynuclear complex (O) was synthesized according to the following reaction formula.

Ni complexes used as raw materials for polynuclear complexes are described in Z. Anorg. Allg. Chem., 626, 1934 (2000). Was synthesized according to the method described in 1. Under a nitrogen atmosphere, a methanol 10 ml solution containing 0.200 g of Ni complex and 0.080 g of iron chloride tetrahydrate was stirred for 2 hours while heating to 80 ° C. in a 50 mL eggplant flask. After cooling to room temperature, 5 ml of a methanol solution containing 0.090 g of 1,2-phenylenediamine was added with stirring, and the mixture was further stirred for 2 hours while being heated to 80 ° C. As a result, an orange solid was obtained. This solid was collected by filtration, washed with diethyl ether and dried to obtain a polynuclear complex (O) (yield 0.127 g: yield 46%). When the interatomic distance between the transition metal atoms was determined by the above calculation method, at least one of the distances was 2.877 mm. In the above reaction formula, “(Cl) ₂ ” indicates that 2 equivalents of acetate ion is present as a counter ion. “H ₂ O” indicates that one equivalent of water molecules is contained. Elemental analysis (%): Calculated as C ₃₆ H ₃₆ Cl ₂ FeN ₄ NiO ₃ : C, 57.03; H, 4.79; N, 7.39. Found: C, 56.84; H, 4.97; N, 7.25.

Synthesis Example 16 [Synthesis of Mononuclear Complex (P)]
The mononuclear complex (P) shown in the following reaction formula is described in the document Tatsuhiro Okada, et. al. It was synthesized with reference to the method described in Electrochimica Acta, 45, 4419 (2000).

Example 1 (Evaluation of oxygen reduction ability)
[Preparation of electrode catalyst]
The polynuclear complex (A) and the carbon support (Ketjen Black EC300J, Lion) were mixed at a weight ratio of 1: 4, and the mixture was stirred in ethanol at room temperature and then at a reduced pressure of 1.5 Torr at room temperature. The electrode catalyst was prepared by drying for 12 hours.
[Production of electrodes]
As the electrode, a ring disk electrode in which the disk part is glassy carbon (6.0 mmφ) and the ring part is Pt (ring inner diameter 7.3 mm, ring outer diameter 9.3 mm) was used. After adding 0.5 ml of a fluorinated ionomer solution having a sulfonic acid group diluted to 1/50 with methanol (Aldrich, 5% by mass Nafion solution) to a sample bottle containing 1 mg of the electrode catalyst, ultrasonic waves were added. And distributed processing. 10 μL of the obtained suspension was dropped on the disk part of the electrode, and then dried at room temperature for 30 minutes to obtain a measurement electrode.
[Evaluation of oxygen reduction ability by rotating ring disk electrode]
By rotating the electrode produced above, the current value of the oxygen reduction reaction at that time was evaluated. The measurement is performed at room temperature in a nitrogen atmosphere and an oxygen atmosphere, and the current value obtained by measurement in the nitrogen atmosphere is subtracted from the current value obtained in the measurement in the oxygen atmosphere. It was. The measurement apparatus and measurement conditions are as follows.

Measuring device Rotating ring disk electrode device: Day thickness measurement RRDE-1
Dual potentio galvanostat: thickness measurement model DPGS-1
Function generator: Toho Giken model FG-02
Measurement conditions Test solution: 0.05 mol / L sulfuric acid aqueous solution Reference electrode: Reversible hydrogen electrode (RHE)
Counter electrode: Platinum wire Disk potential sweep speed: 5 mV / s
Ring potential: 1.4V vs RHE
Electrode rotation speed: 600 rpm

Using the values of the disk current and ring current obtained from the measurement, the 4-electron reduction rate of oxygen by the electrode catalyst was determined. The 4-electron reduction rate (% H ₂ O) was calculated based on the following formula.

Here, i _D represents the disk current, i _R represents the ring current, and N _{r / d} represents the capture rate of the disk reaction product at the ring electrode. The complementation rate was measured using a redox system of [Fe (CN) ₆ ] ^{3- / 4-} and was 0.38 for the electrodes used in the examples.
By using the capture rate, the 4-electron reduction rate of oxygen by the electrode catalyst was determined. Table 1 shows the 4-electron reduction rate and mass activity of oxygen. Here, the mass activity is a value obtained by dividing the current density at a potential of 0.6 V with respect to the reversible hydrogen electrode by the amount of metal supported per electrode unit area.

  The electrode was exactly the same except that the polynuclear complex (A) in the above operation was changed to a polynuclear complex (B), a polynuclear complex (C), a polynuclear complex (D), a polynuclear complex (E), and a polynuclear complex (F). The oxygen reduction ability was evaluated. The results are shown in Table 1.

Comparative Example 1
A mononuclear complex (P) and graphite powder (Wako Pure Chemicals; 45 μm) were mixed in ethanol at a weight ratio of 1: 4 and then vacuum dried to obtain an electrode catalyst. The electrode catalyst was evaluated according to the method described in Example 1. The results are shown in Table 1.

Example 2 (Evaluation of oxygen reduction ability)
[Preparation of electrode catalyst]
The polynuclear complex (A) and the carbon support (Ketjen Black EC300J, Lion) were mixed at a weight ratio of 1: 4, and the mixture was stirred in ethanol at room temperature for 15 minutes and then decompressed at 1.5 Torr at room temperature. Dry under 12 hours. The treated mixture was heat-treated at a target temperature for 2 hours under a nitrogen stream of 200 ml / min using a tubular furnace to prepare an electrode catalyst, and the electrode catalyst was evaluated according to the method described in Example 1. went. Table 2 shows the heat treatment temperature and the evaluation results.

  In the above operation, the polynuclear complex (A) is converted into a polynuclear complex (B), a polynuclear complex (G), a polynuclear complex (H), a polynuclear complex (I), a polynuclear complex (J), a polynuclear complex (K), a polynuclear complex, respectively. (L) The electrode catalyst was prepared in the same manner except that the polynuclear complex (M) was changed, and the oxygen reduction ability was evaluated. The temperature during the heat treatment is as shown in Table 2.

Comparative Example 2
Mononuclear complex (P) and graphite powder (manufactured by Wako Pure Chemical Industries, Ltd .; particle size 45 μm) were mixed at a weight ratio of 1: 4, and the mixture was heat-treated for 2 hours in a nitrogen stream using a tubular furnace. . The oxygen reduction ability of the heat-treated product was evaluated according to the method described above.

Example 3 (Evaluation of hydrogen oxidation ability)
[Preparation of electrode catalyst]
A polynuclear complex (N) and a carbon support (Ketjen Black EC300J, manufactured by Lion Corporation) were mixed at a mass ratio of 1: 4 to prepare an electrode catalyst. A part of the mixture was heat-treated for 2 hours in a tube furnace under a nitrogen stream of 200 ml / min. The heat treatment temperature is as shown in Table 3.
[Production of electrodes]
As the electrode, a ring disk electrode in which the disk part is glassy carbon (6.0 mmφ) and the ring part is Pt (ring inner diameter 7.3 mm, ring outer diameter 9.3 mm) was used. 0.5 ml of a fully fluorinated ionomer solution having a sulfonic acid group diluted to 1/50 with methanol (Aldrich, 5% by mass Nafion solution) was added to a sample bottle containing 1 mg of an electrode catalyst, followed by ultrasonication. Distributed processing was performed. After applying 10 μL of the obtained suspension to the disk part of the electrode, the electrode for measurement was obtained by drying at room temperature for 30 minutes.
[Evaluation of hydrogen oxidation ability by rotating ring disk electrode]
Measurement is performed at room temperature in a nitrogen atmosphere and a hydrogen atmosphere, and a value obtained by subtracting a current value obtained by measurement in a nitrogen atmosphere from a current value obtained by measurement in a hydrogen atmosphere at 0.1 V is subjected to hydrogen oxidation. Current value. The apparatus and measurement conditions are as follows. The results are shown in Table 3. Here, the mass activity is a value obtained by dividing the current value at a potential of 0.1 V with respect to the reversible hydrogen electrode by the electrode area and then dividing by the amount of metal supported per electrode unit area. A hyphen (-) in Table 3 indicates that no heat treatment was performed.

Measuring device Rotating ring disk electrode device: Day thickness measurement RRDE-1
Dual Potentiogalvanostat: Day thickness measurement DPGS-1
Function generator: Toho Giken model FG-02
Measurement method Linear sweep voltammetry Measurement conditions Test solution: 0.10 mol / L perchloric acid aqueous solution Reference electrode: Reversible hydrogen electrode (RHE)
Counter electrode: Platinum wire Disk potential sweep speed: 5 mV / s

Example 4 (Evaluation of hydrogen oxidation ability)
The polynuclear complex (N) of Example 3 was changed to a polynuclear complex (B), a polynuclear complex (G), a polynuclear complex (M), and a polynuclear complex (O), and the hydrogen oxidation ability was evaluated. The temperature during the heat treatment is as shown in Table 4. The results are shown in Table 4. This measurement was performed by rotating the disk electrode at 300 rpm.

Claims (9)

  An electrode catalyst for a fuel cell using a polynuclear complex in which a ligand having 5 to 15 coordination atoms in a molecule is coordinated to 2 to 4 transition metal atoms.   2. The fuel cell electrode catalyst according to claim 1, wherein the transition metal atom of the polynuclear complex is at least one selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, nickel, and copper.   3. The fuel cell electrode catalyst according to claim 1, wherein the coordinating atom of the polynuclear complex is at least one selected from a nitrogen atom and an oxygen atom. 4.   The fuel cell electrode catalyst according to any one of claims 1 to 3, wherein the transition metal atom of the polynuclear complex is bridged by an oxygen atom of an alkoxide or phenoxide.   5. The fuel cell electrode catalyst according to claim 1, wherein in the polynuclear complex, at least one of the interatomic distances of transition metal atoms arbitrarily selected is 3.6 cm or less. The said ligand is a ligand shown by the following general formula (I) or general formula (II), The electrode catalyst for fuel cells in any one of Claims 1-5 characterized by the above-mentioned.

(Wherein Q ¹ and Q ² are each a divalent organic group having at least two C═N bonds, and T ¹ is a monovalent organic group having at least one C═N bond, R ¹ and R ² are each independently a hydrogen atom or a substituent, two R ¹ or R ² may be linked to each other, and a plurality of R ¹ and R ² are the same as each other The plurality of Q ¹ may be the same or different, and the plurality of T ¹ may be the same or different.)   The electrode catalyst for fuel cells obtained by heating the polynuclear complex in any one of Claims 1-6 at the temperature of 250 degreeC or more and 1500 degrees C or less.   A fuel cell electrode catalyst comprising a multinuclear complex mixture comprising the multinuclear complex according to any one of claims 1 to 6 and a carbon support and / or a conductive polymer.   7. A fuel cell obtained by heating a polynuclear complex mixture containing the polynuclear complex according to claim 1 and a carbon support and / or a conductive polymer at a temperature of 250 ° C. or higher and 1500 ° C. or lower. Electrocatalyst.