JP6560932B2 - Nitrogen-containing carbon material and production method thereof, precursor composition for nitrogen-containing carbon material, and electrode for fuel cell - Google Patents

Description

  The present invention relates to a nitrogen-containing carbon material and a method for producing the same, a precursor composition for a nitrogen-containing carbon material, and a fuel cell electrode.

  The polymer electrolyte fuel cell has advantages such as high power generation efficiency, high output density, rapid start / stop, small size and light weight, portable power, mobile power, small stationary It is expected to be applied to power generators.

  In a polymer electrolyte fuel cell, platinum or a platinum alloy is generally used as a catalyst in order to promote the oxygen reduction reaction occurring at the positive electrode. However, since the amount of platinum resources is extremely small and expensive, it is put to practical use. It has become a big barrier. Therefore, as an electrode catalyst for a fuel cell that does not require a noble metal such as platinum, a carbon material that expresses oxygen reduction activity by containing a transition metal and nitrogen (hereinafter also referred to as “carbon catalyst”) attracts attention. Yes.

  For example, it is known that a nitrogen-containing carbon material containing a large amount of nitrogen can be obtained by paying attention to azurmic acid which is a cyanide polymer and carbonizing the same (see Patent Document 1). Further, it is known that carbon materials useful as an electrode catalyst can be synthesized by carbonizing a precursor obtained by adding a transition metal or a salt thereof (see Patent Documents 2, 3, and 4). .

  In addition, focusing on nitrogen-containing aromatic compounds such as 1,10-phenanthroline, carbon materials useful as electrode catalysts can be synthesized by carbonizing a precursor obtained by adding a transition metal or a salt thereof. Is known (Non-Patent Document 1).

International Publication No. 2007/043311 Pamphlet International Publication No. 2008/123380 Pamphlet JP 2011-256093 A JP2013-043821A

Iron-Based Catalysts with Improved Oxygen Reduction Activity in Polymer Electroly Fuel Cells, Michel Lefere, Electric Profiti, 71

  The oxygen reduction active site of the carbon catalyst containing transition metal and nitrogen is a structure in which the end of the graphene skeleton and defects are doped with nitrogen, or its transition metal complexed with nitrogen, although the details are not clear it is conceivable that. Basically, the transition metal added to azulmic acid functions as a carbonization catalyst, but may also contribute as a reaction active site. In any case, it is important that the transition metal is highly dispersed in the precursor.

  However, there is no solvent that well dissolves both azulmic acid and transition metal salt, and there is a problem that it is difficult to mix them highly. As a result, the carbon material obtained by carbonizing the precursor, which is a mixture of azulmic acid and transition metal, does not have sufficient oxygen reduction activity as an electrode catalyst for a polymer electrolyte fuel cell, and has superior oxygen reduction activity. There is a demand for the development of an electrode catalyst.

  It is also conceivable to use diaminomaleonitrile, which is a hydrocyanic acid tetramer and has solubility in a solvent, instead of azulmic acid. However, the nitrogen-containing carbon material derived from diaminomaleonitrile obtained by carbonizing at a high temperature has a problem that the added transition metal tends to aggregate. At that time, due to the effect of the agglomerated transition metal, the amount of nitrogen in the obtained nitrogen-containing carbon material is reduced, and as a result, there may be a problem that high oxygen reduction activity cannot be obtained.

  On the other hand, when a nitrogen-containing aromatic compound such as 1,10-phenanthroline is used, a nitrogen-containing carbon material can be obtained with a relatively high yield, but the nitrogen content in the precursor is reflected to reflect the low nitrogen content. There is a problem that the nitrogen content in the contained carbon material is low, and as a result, high oxygen reduction activity cannot be obtained.

  Therefore, the present invention has been made in view of the above circumstances, a nitrogen-containing carbon material having high oxygen reduction activity, a method for producing the same, a precursor composition for a nitrogen-containing carbon material that gives the nitrogen-containing carbon material, and the above An object of the present invention is to provide a fuel cell electrode using a nitrogen-containing carbon material.

  As a result of intensive studies to solve the above problems, the present inventors surprisingly have four or more nitrogen atoms in the aromatic ring structure, and are multidentate coordinated by two or more nitrogen atoms. It has been found that the above problem can be solved by using a nitrogen-containing aromatic ring compound having two or more groups as a starting material, and the present invention has been completed.

That is, the present invention is as follows.
[1]
The aromatic ring structure has 4 or more nitrogen atoms, and —N ¹ —C ¹ —C ² —N ² — (where N ¹ and C ¹ are the first aromatic ring). , C ² and N ² represent an atom forming a second aromatic ring), or —N ¹ —C ¹ —C ² —N ² —C ³ —C ⁴ —N ³ — (where N ¹ And C ¹ are the first aromatic rings, C ² , N ² and C ³ are the second aromatic rings, and C ⁴ and N ³ are the atoms forming the third aromatic ring). Nitrogen-containing aromatic ring compounds having two or more pairs of position sites (however, one or both of the ring skeleton constituent atoms at the 3-position and 4-position with respect to the linking group bonded to the aromatic ring structure is a nitrogen atom) and excluding), a first step of obtaining a nitrogen-containing carbon material precursor composition by mixing a transition metal salt, and
Heat-treating the obtained precursor composition for nitrogen-containing carbon material to obtain a nitrogen-containing carbon material, and
A method for producing a nitrogen-containing carbon material.
[2]
The aromatic ring structure has 4 or more nitrogen atoms, and —N ¹ —C ¹ —C ² —N ² — (where N ¹ and C ¹ are the first aromatic ring). , C ² and N ² represent an atom forming a second aromatic ring), or —N ¹ —C ¹ —C ² —N ² —C ³ —C ⁴ —N ³ — (where N ¹ And C ¹ are the first aromatic rings, C ² , N ² and C ³ are the second aromatic rings, and C ⁴ and N ³ are the atoms forming the third aromatic ring). Nitrogen-containing aromatic ring compounds having two or more pairs of position sites (however, one or both of the ring skeleton constituent atoms at the 3-position and 4-position with respect to the linking group bonded to the aromatic ring structure is a nitrogen atom) and excluding), made by carbonizing a nitrogen-containing carbon material precursor composition comprising a transition metal salt, a nitrogen-containing carbon material.
[3]
A fuel cell electrode comprising the nitrogen-containing carbon material according to [2].
[4]
The aromatic ring structure has 4 or more nitrogen atoms, and —N ¹ —C ¹ —C ² —N ² — (where N ¹ and C ¹ are the first aromatic ring). , C ² and N ² represent an atom forming a second aromatic ring), or —N ¹ —C ¹ —C ² —N ² —C ³ —C ⁴ —N ³ — (where N ¹ And C ¹ are the first aromatic rings, C ² , N ² and C ³ are the second aromatic rings, and C ⁴ and N ³ are the atoms forming the third aromatic ring). Nitrogen-containing aromatic ring compounds having two or more pairs of position sites (however, one or both of the ring skeleton constituent atoms at the 3-position and 4-position with respect to the linking group bonded to the aromatic ring structure is a nitrogen atom) and excluding) comprises a transition metal salt, a nitrogen-containing carbon material precursor composition.

  According to the present invention, a nitrogen-containing carbon material that exhibits a high oxygen reduction starting potential and has high oxygen reduction activity, a method for producing the same, a precursor composition for a nitrogen-containing carbon material that provides the nitrogen-containing carbon material, and the nitrogen-containing material A fuel cell electrode using a carbon material can be provided.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The present embodiment is an example for explaining the present invention, and the present invention is not limited only to the embodiment. That is, the present invention can be variously modified without departing from the gist thereof.

[Method for producing nitrogen-containing carbon material]
The method for producing a nitrogen-containing carbon material of the present embodiment includes a nitrogen-containing aromatic ring compound having four or more nitrogen atoms in an aromatic ring structure and two or more pairs of multidentate coordination sites by the two or more nitrogen atoms. A first step of mixing a transition metal salt to obtain a precursor composition for a nitrogen-containing carbon material, a second step of subjecting the obtained precursor composition for a nitrogen-containing carbon material to a heat treatment, Have

[First step]
The first step includes a nitrogen-containing aromatic ring compound having 4 or more nitrogen atoms in the aromatic ring structure and having two or more pairs of multidentate coordination sites by the 2 or more nitrogen atoms, and a transition metal salt. This is a step of mixing to obtain a precursor composition for nitrogen-containing carbon material (hereinafter also simply referred to as “precursor”).

(Precursor composition for nitrogen-containing carbon material)
The precursor composition for a nitrogen-containing carbon material includes a nitrogen-containing aromatic ring compound having 4 or more nitrogen atoms in an aromatic ring structure and having two or more pairs of multidentate coordination sites by the two or more nitrogen atoms, Transition metal salts. By heat-treating such a precursor composition for a nitrogen-containing carbon material, a nitrogen-containing carbon material having a high oxygen reduction starting potential and having a high oxygen reduction activity can be obtained. Note that the nitrogen-containing aromatic ring compound and the transition metal salt may form a complex. Hereinafter, the components contained in the precursor composition for nitrogen-containing carbon material will be described.

(Nitrogen-containing aromatic ring compound)
The nitrogen-containing aromatic ring compound used in the present embodiment is a nitrogen-containing aromatic ring compound having 4 or more nitrogen atoms in the aromatic ring structure and having two or more pairs of multidentate coordination sites by the 2 or more nitrogen atoms. is there.

  “Having 4 or more nitrogen atoms in the aromatic ring structure” means that one molecule of a nitrogen-containing aromatic ring compound has one or more aromatic rings containing nitrogen atoms, and nitrogen contained in the aromatic rings It means that the total number of atoms is 4 or more. Further, “a multidentate coordination site by two or more nitrogen atoms” means that two or more nitrogen atoms (coordinating atoms) contained in an aromatic ring can coordinate to the same metal atom. The site | part comprised was said and it may be comprised so that two or more aromatic rings may form one multidentate coordination site | part. The “multidentate” refers to a bidentate site or a tridentate site. Furthermore, “having two or more pairs of multidentate coordination sites” means that one molecule of a nitrogen-containing aromatic ring compound is configured to be capable of multidentate coordination with respect to two or more metal atoms, For example, it means that the structure of the multidentate coordination site described later has two or more sites in one molecule.

The structure of multidentate coordination site by 2 or more nitrogen atoms is not particularly limited, for ^{example, -N 1 -C 1 -C 2 -N} 2 -, ^or, -N ^{1 -C 1} -C 2 -N ^{2 -C 3 -C 4 -N 3 -} , can be shown with. Here, N ¹ , N ² , and N ³ represent nitrogen atoms, C ¹ , C ² , C ³ , and C ⁴ represent carbon atoms, and these all represent atoms that form an aromatic ring. Specifically, N ¹ and C ¹ may be a first aromatic ring, and C ² and N ² may be a nitrogen-containing aromatic ring compound having two aromatic rings belonging to the second aromatic ring. N ¹ and C ¹ are first aromatic rings, C ² , N ² and C ³ are second aromatic rings, and C ⁴ and N ³ are nitrogen-containing nitrogen rings having three aromatic rings belonging to the third aromatic ring. Aromatic ring compounds can be mentioned.

  Such nitrogen-containing aromatic ring compounds are not particularly limited, but 2,2'-bipyrimidine, 2,3-bis (2-pyridyl) pyrazine, tetra-2-pyridinylpyrazine, 4 ', 4 ""- (1,4-phenylene) bis (2,2 ′: 6 ′, 2 ″ -terpyridine), 6,7-dimethyl-2,3-di (2-pyridyl) quinoxaline, dipyrazino [2,3-f: 2 ', 3'-h] quinoxaline-2,3,6,7,10,11-hexacarbonitrile, etc. Particularly preferably, it is highly soluble in a solvent and easily forms a complex with a transition metal. From the viewpoint of being able to suppress aggregation of the transition metal component in the heat treatment step, and thus obtaining a nitrogen-containing carbon material in which the transition metal is more evenly dispersed and obtaining high oxygen reduction activity, 2,2′-bipyrimidine, 2,3-bis (2-pyridy ) Pyrazine, tetra-2-pyridinylcarbonyl pyrazine, but is particularly preferred. The nitrogen-containing aromatic ring compound, may be used in one kind alone, or in combination of two or more.

  In the nitrogen-containing aromatic ring compound, a characteristic group, a functional group, and a substituent which can be exemplified below may be bonded to a carbon atom in the aromatic ring structure.

The characteristic group is not particularly limited, for example, an alkyl group (aliphatic), halogen (-Cl, -Br, -I, -F), hydroxy (-OH), an amino group _(-NH 2) , Imino group (═NH), N-oxide group (N → O), N-hydroxy group (—NH—OH), nitro group (—NO ₂ ), nitroso group (—NO), azo group (—N═ N-), diazo group (—N + ≡N), azide group (—N ₃ ), oxy group (—O—), oxo group (═O), carbonyl group (—CO—), phenyl group (aromatic compound) ), Phosphino group (phosphorus compound), thio group (—S—), S-oxide group (S → O), and thioxy (═S).

  The functional group is not particularly limited. For example, a hydroxyl group, a peroxy group, a ketone group, an acyl group, an acetyl group, an enol group, an enamine group, an aldehyde group, an acetal group, a hemiacetal group, a carboxyl group (carboxylic acid, acid Anhydride, acid halide, acid hydrazone, acid azide, peracid, ester, thioester, nitrate ester, phosphate ester), amide group, thioamide group, imide group, amidine group, oxime group, thiol group, sulfide group, disulfide Group, sulfonic acid, sulfenic acid, urea group, urethane group, guanidine group, isonitrile group (-NC), allene group (> C = C = C <), ketene group (-C = C = O), diimide group ( -N = C = N-), isocyanate (-N = C = O), thioisocyanate (-N = C = S), carbonyl Examples thereof include a group, an amino group, an imino group, a cyano group, an azo group, an azide group, a thiol group, a sulfo group, a nitro group, an ether bond, an ester bond, an amide bond, and a urethane bond.

  Although it does not specifically limit as a substituent, For example, an alkyl group (vinyl group, allyl group), an aryl group (phenyl group, naphthyl group), an araalkyl group (benzyl group), a cycloalkyl group, an alkoxy group (methoxy group, ethoxy) Group).

(Transition metal salt)
The transition metal salt is not particularly limited, and examples thereof include transition metal cyano complexes, hydroxy complexes, chloro complexes, acetylacetonate complexes, nitrates, sulfates, acetates, carbonates, oxalates, nitrites, Examples include chloride, bromide, iodide, and various organometallic compounds. Of these, cyano complexes, chloro complexes, acetylacetonate complexes, nitrates, chlorides and bromides are preferable, and nitrates, chlorides and bromides are more preferable. Among these, those that are soluble in polar solvents such as water and lower alcohols are more preferable.

  Further, the transition metal is not particularly limited, but for example, Fe, Co, Ni, Cu, Mn, or Cr is preferable, Fe, Co, or Cu is more preferable, Fe or Co is further preferable, and particularly preferable Fe. By using such a transition metal, the oxygen reduction activity of the nitrogen-containing carbon material tends to be further improved. A transition metal may be used individually by 1 type, and may use 2 or more types together. When two or more transition metals are used in combination, one is preferably Fe, and more preferably one or more selected from Fe and Co, Ni, Cu, Mn, or Cr. In addition, when the iron salt and other transition metal salt are used in combination, the content of the iron salt is preferably 50% by weight or more of the total amount, and more preferably 75% by weight or more.

  Specific iron salts are not particularly limited. For example, iron (II) chloride, iron (II) chloride tetrahydrate, iron (III) chloride, iron (III) chloride hexahydrate, iron bromide (II), iron (II) bromide hexahydrate, iron (III) bromide, iron (III) bromide hexahydrate, ammonium hexacyanoferrate (II) trihydrate, iron hexacyanoferrate (II) Potassium acid trihydrate, ammonium hexacyanoferrate (III), potassium hexacyanoiron (III), sodium hexacyanoferrate (II) decahydrate, sodium hexacyanoferrate (III) monohydrate, iron nitrate (II ) Hexahydrate, iron (III) nitrate nonahydrate, iron (III) thiocyanate, iron (II) carbonate, iron (II) carbonate monohydrate, methylammonium hexachloroferrate (III), tetrachloro Tetramethy iron (II) acid Ammonium, potassium pentacyanonitrosyl iron (III) dihydrate, potassium iron (III) hexacyanoferrate (II), sodium pentacyanonitrosyl iron (III) dihydrate, ammine pentacyanoiron ( II) Sodium acid trihydrate, aquapentacyanoiron iron (II) sodium heptahydrate, iron (II) thiocyanate trihydrate, iron acetate, iron (III) oxalate pentahydrate, oxalic acid Iron (II) dihydrate, iron (III) citrate trihydrate, iron (II) iodide, iron (II) iodide tetrahydrate, iron (III) sulfate, iron (III) sulfate nine Hydrates, ammonium tetrachloroferrate (II), iron (II) perchlorate hexahydrate, iron (III) perchlorate hexahydrate, potassium aquapentafluoroiron (III), potassium iron sulfate (III) Twelve water Bis (sulfato) iron (II) diammonium hexahydrate, tris (sulfate) iron (III) sodium trihydrate, iron (III) phosphate dihydrate, iron (II) phosphate eight Hydrates, iron (II) sulfate heptahydrate and the like can be mentioned. Preferably, iron (II) chloride, iron (III) chloride, iron (II) bromide, iron (III) bromide, and iron (III) nitrate nonahydrate are used.

  Specific cobalt salts are not particularly limited. For example, potassium hexacyanocobalt (III) acid, cobalt (II) nitrate hexahydrate, cobalt (II) fluoride, cobalt (II) bromide, cobalt bromide. (II) hexahydrate, cobalt carbonate (II), cobalt thiocyanate (II) trihydrate, cobalt acetate (II) tetrahydrate, cobalt acetate (III), cobalt chloride (II), cobalt chloride ( II) Hexahydrate, cesium tetrachlorocobalt (II), potassium hexafluorocobalt (III), cobalt (II) iodide, cobalt (II) iodide hexahydrate, hexanitrocobalt (III) acid Examples include potassium, cobalt (II) phosphate, cobalt (II) phosphate octahydrate, cobalt (II) sulfate, and cobalt (II) sulfate heptahydrate. It is. Preferably, cobalt (II) chloride, cobalt (II) bromide, and cobalt (II) nitrate hexahydrate are used.

  Specific nickel salts are not particularly limited, and examples thereof include nickel chloride (II), nickel chloride (II) hexahydrate, nickel bromide (II), nickel nitrate (II) hexahydrate and the like. It is done.

  Specific copper salts are not particularly limited, and examples include copper (II) chloride, copper (II) chloride dihydrate, copper (II) bromide, copper nitrate (II) dihydrate, and the like. It is done.

  Specific examples of the manganese salt include, but are not limited to, manganese chloride (II), manganese bromide (II), manganese nitrate (II) tetrahydrate, and the like.

  Specific examples of the chromium salt include, but are not limited to, chromium (III) chloride, chromium (III) bromide, and chromium (III) nitrate nonahydrate.

  The ratio of the mass of the transition metal element in the transition metal salt to the mass of the nitrogen-containing aromatic ring compound is preferably 0.0001 to 10.00, more preferably 0.0005 to 5.00, and 0.001 to 1.00. Is more preferable. When this ratio is 0.0001 or more, the yield of the nitrogen-containing carbon material obtained when the precursor is heat-treated tends to be more excellent. Moreover, when this ratio is 10.00 or less, the oxygen reduction activity tends to be more excellent when a nitrogen-containing carbon material is used.

(Other organic compounds)
In the first step of obtaining a precursor by mixing a nitrogen-containing aromatic ring compound and a transition metal salt, another organic compound may be added.

  As the other organic compounds, organic compounds that volatilize before being carbonized by a heat treatment described later, for example, organic solvents having a boiling point of 250 ° C. or less are excluded because they do not serve as raw materials for nitrogen-containing carbon materials. Other than that, although not particularly limited, an organic compound that is less likely to volatilize by the heat treatment is preferable. The other organic compound may be an aliphatic compound or an aromatic compound. The other organic compound may be nitrogen-containing or non-nitrogen-containing. In particular, a monomer material and a polymer material that are polymerized by the heat treatment are preferable.

  The monomer material is not particularly limited, and examples thereof include diaminomaleonitrile, acrylonitrile, glycine, melamine, and urea. Of these, diaminomaleonitrile is preferable. By using such a monomer material, a nitrogen-containing carbon material having a high oxygen reduction activity tends to be obtained in a high yield.

  Here, diaminomaleonitrile is a tetramer of hydrocyanic acid. Diaminomaleonitrile may be a commercially available product, or may be produced and used based on a known method (for example, see JP-A Nos. 49-126619 and 60-651158). Diaminomaleonitrile may be purified by a method such as recrystallization to increase the purity, or may be unpurified.

  The polymer material is not particularly limited. For example, azulmic acid, polyacrylonitrile, polyaniline, aromatic polyamide, polyimide, polyvinylpyridine, polyvinylpyrrolidone, melamine resin, urea resin, phenol resin, polyvinyl alcohol, polyethylene glycol, polyacrylic acid , Etc. Of these, azulmic acid, polyacrylonitrile, polyimide, and phenol resin are preferable. By using such a polymer material, a nitrogen-containing carbon material having a high oxygen reduction activity tends to be obtained in a high yield.

  When the precursor contains the other organic compound, the mass ratio of the other organic compound to the nitrogen-containing aromatic ring compound is preferably 0.01 to 100, more preferably 0.1 to 10, and 0.5 ~ 5 is more preferred. When this ratio is 0.01 or more, the oxygen reduction activity tends to be more excellent when a nitrogen-containing carbon material is used. Moreover, when this ratio is 100 or less, the yield of the nitrogen-containing carbon material obtained when the precursor is heat-treated tends to be more excellent.

(mixture)
The method for mixing the nitrogen-containing aromatic ring compound and the transition metal salt is not particularly limited. For example, there is a method in which the nitrogen-containing aromatic ring compound and the transition metal salt are dissolved in a solvent and the solvent is evaporated to dryness. preferable. The mixing method is not particularly limited. For example, all the raw materials may be dissolved in one solvent, or the respective solvents may be mixed after dissolving the respective raw materials in different solvents.

  Although it does not specifically limit as a solvent, For example, water, alcohols (methanol, ethanol, propanol, butanol, etc.), ketones (acetone, diethyl ketone, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), chlorinated hydrocarbons (Dichloromethane, chloroform, dichloroethylene, trichloroethylene, carbon tetrachloride, etc.), glycols (ethylene glycol, propylene glycol, etc.), nitriles (acetonitrile, propionitrile, benzonitrile, etc.), amides (N, N-dimethylformamide) , Dimethylacetamide, etc.), lactams (N-methyl-2-pyrrolidone, etc.), dimethyl sulfoxide, aliphatic hydrocarbons (n-pentane, n-hexane, cyclohexane, n-heptane, n-octane, etc.), aroma Hydrocarbons (benzene, toluene, xylene, ethylbenzene, etc.) and the like. Among these, preferred are polar solvents, and more preferred are lower alcohols such as methanol and ethanol, acetonitrile, N, N-dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide and the like. As the solvent, one type of solution may be used alone, or two or more types of solutions may be used in combination. In particular, methanol and acetonitrile are preferable from the viewpoint of the high solubility of the nitrogen-containing aromatic ring compound and the transition metal salt, or the ease of evaporation and drying described later.

  The temperature at the time of mixing a nitrogen-containing aromatic ring compound and a transition metal salt is preferably 0 to 200 ° C, more preferably 10 to 100 ° C, and further preferably 20 to 50 ° C. When the temperature is 0 ° C. or higher, the solubility of the nitrogen-containing aromatic ring compound and the transition metal salt tends to be further improved. Moreover, it exists in the tendency which stability of a nitrogen-containing aromatic ring compound and a transition metal salt improves more because temperature is 200 degrees C or less.

  The pressure when mixing the nitrogen-containing aromatic ring compound and the transition metal salt is preferably 0.05 to 2.0 MPa, more preferably 0.08 to 1.5 MPa, and still more preferably 0.8. 1 to 1.0 MPa. When the pressure is 0.05 MPa or more, the oxygen reduction activity when the nitrogen-containing carbon material is used tends to be further improved. Moreover, when the pressure is 2.0 MPa or less, the runaway reaction can be further suppressed, and the safety during the preparation of the precursor tends to be further improved.

  The time for mixing the nitrogen-containing aromatic ring compound and the transition metal salt is preferably 1 minute to 240 hours, preferably 10 minutes to 120 hours, and more preferably 30 minutes to 60 hours. . When the time is 1 minute or longer, the oxygen reduction activity of the nitrogen-containing carbon material tends to be further improved. Moreover, when time is 240 hours or less, it exists in the tendency for oxygen reduction activity when it is set as a nitrogen containing carbon material to improve more.

  When mixing the nitrogen-containing aromatic ring compound and the transition metal salt, a batch reactor or a flow reactor may be used. The flow reactor may be a complete mixing tank, a tubular reactor, or a combination of a complete mixing tank and a tubular reactor.

  The atmosphere in the reactor may be air, but may be an inert gas such as nitrogen, helium, or argon.

  The method for evaporating and drying is not particularly limited. For example, the solvent may be removed under reduced pressure using a rotary evaporator or the like, or the solvent may be volatilized using a spray dryer or the like. Among these, a method using a spray dryer is preferable from the viewpoint of maintaining a uniform composite state and from the viewpoint of granulation.

[Second step]
The second step is a step of obtaining a nitrogen-containing carbon material by heat-treating the precursor obtained in the first step. The second step may be a one-step heat treatment, but may be a two-step or more heat treatment. Among these, in the second step, it is preferable to perform both the heat treatment in an inert gas atmosphere and the heat treatment in an ammonia-containing gas atmosphere in this order. The heat treatment in an inert gas atmosphere is mainly for the purpose of carbonization, and the heat treatment in an ammonia-containing gas atmosphere is mainly for the purpose of activation, and such a second step is performed. Thus, there is a tendency to obtain a nitrogen-containing carbon material that is superior in oxygen reduction activity.

  Although it does not specifically limit as said inert gas, For example, nitrogen, a noble gas, a vacuum etc. can be used. The heat treatment temperature in an inert gas atmosphere is preferably 600 to 1100 ° C, more preferably 600 to 1000 ° C, and further preferably 600 to 950 ° C. When the heat treatment temperature is 600 ° C. or higher, the carbonization of the precursor tends to proceed sufficiently. Moreover, when the heat treatment temperature is 1100 ° C. or lower, a sufficient yield tends to be obtained.

  The heat treatment time in an inert gas atmosphere is preferably 5 minutes to 50 hours, more preferably 10 minutes to 20 hours, and further preferably 20 minutes to 10 hours. When the heat treatment time is 5 minutes or longer, carbonization of the precursor tends to proceed sufficiently. Moreover, it exists in the tendency for sufficient yield to be acquired because heat processing time is 50 hours or less.

  The appropriate heat treatment temperature and / or heat treatment time varies depending on the type and amount of the transition metal salt used.

  The ammonia-containing gas is not particularly limited. For example, it is preferable to use only ammonia or a gas obtained by diluting ammonia with nitrogen or a rare gas. The heat treatment temperature in the ammonia-containing gas atmosphere is preferably 600 to 1200 ° C, more preferably 700 to 1100 ° C, and further preferably 800 to 1000 ° C. When the heat treatment temperature is 600 ° C. or higher, activation of the precursor is sufficiently advanced, and a nitrogen-containing carbon material excellent in oxygen reduction activity tends to be obtained. Moreover, it exists in the tendency for sufficient yield to be acquired because heat processing temperature is 1200 degrees C or less.

  The heat treatment time in an ammonia-containing gas atmosphere is preferably 5 minutes to 5 hours, more preferably 10 minutes to 3 hours, and even more preferably 15 minutes to 2 hours. When the heat treatment time is 5 minutes or longer, activation of the precursor is sufficiently advanced, and a nitrogen-containing carbon material excellent in oxygen reduction activity tends to be obtained. Moreover, it exists in the tendency for sufficient yield to be acquired because heat processing time is 5 hours or less.

  Before and after the heat treatment in an inert gas atmosphere and / or the heat treatment in an ammonia-containing gas atmosphere, a part of the transition metal may be removed using hydrochloric acid, sulfuric acid, or the like. In particular, when transition metal particles are generated by heat treatment, it is preferable to remove the transition metal particles from the viewpoint of suppressing an increase in crystallinity in a subsequent heat treatment step (heat treatment in an ammonia-containing gas atmosphere). The ease with which transition metal particles can be produced varies depending on the type, concentration, dispersibility, or heat treatment temperature of the transition metal. In order to increase the removal rate of the transition metal particles, it is preferable to divide the heat treatment step under an inert gas atmosphere and / or the heat treatment step under an ammonia-containing gas atmosphere into a plurality of steps, and repeatedly remove the transition metal. .

  More specifically, after the step 2-1a in which the precursor is heat-treated in an inert gas atmosphere, and the step 2-1a in which the precursor is further heat-treated in an inert gas atmosphere. After the step 2a and the step 2-2a, it is preferable to have a step 2-3a in which the precursor is heat-treated in an ammonia-containing gas atmosphere. In addition, the heat processing temperature and heat processing time in this case can be made the same as the above. Further, in addition to the above steps 2-1a to 2-3a, after each of these steps, the precursor after the heat treatment is acid-treated to remove at least part of the metal on the precursor surface. You may have the process of 1b-2-3b. Note that it is not necessary to perform all of the above-mentioned steps 2-1b to 2-3b, and only one or two of them may be performed. Further, in addition to the above-mentioned steps 2-1a to 2-3a, after each of these steps, the precursor after heat treatment is pulverized to reduce the average particle size of the precursor 2-1c. You may have the process of process-2-3c. In addition, it is not necessary to perform all the processes of the said 2-1c process-2-3c, You may perform only one or two processes among them. In addition, the order of the steps 2-1b to 2-3b and the steps 2-1c to 2-3c may be first, but the steps 2-1c to 2-3c may be performed. It is more preferable to carry out the treatment first because the effect of the acid treatment is increased.

[Nitrogen-containing carbon material]
The nitrogen-containing carbon material of the present embodiment includes a nitrogen-containing aromatic ring compound having four or more nitrogen atoms in an aromatic ring structure and two or more pairs of multidentate coordination sites by the two or more nitrogen atoms, and a transition metal A precursor containing a salt is carbonized (heat treated). The nitrogen-containing carbon material according to the present embodiment can be suitably used for a fuel cell electrode or the like, and the fuel cell electrode including the nitrogen-containing carbon material according to the present embodiment has a high oxygen reducing property. A method for obtaining an oxygen reduction electrode, a fuel cell and the like from the oxygen reduction catalyst is not particularly limited, and a general method for producing a polymer electrolyte fuel cell can be used.

[Fuel cell electrode]
The fuel cell electrode of the present embodiment includes the nitrogen-containing carbon material. More specifically, the fuel cell electrode includes at least a current collecting plate and an electrode composition containing the nitrogen-containing carbon material, and if necessary, an electrolyte membrane, a gas diffusion electrode layer, a separator May be laminated.

  Here, the current collector plate may be a porous carbon plate, a metal plate such as aluminum / nickel, or a wire mesh. Moreover, it is preferable that an electrode composition contains 10-300 mass parts of ionomers with respect to 100 mass parts of nitrogen-containing carbon materials, and it is further more preferable that 50-150 mass parts is included. For example, Nafion can be used as the ionomer. The thickness of the layer made of the electrode composition is preferably 100 to 500 μm.

Hereinafter, although an example etc. are given and the present invention is explained still in detail, these are illustrations and the present invention is not limited to these. Accordingly, those skilled in the art can implement the present invention by making various modifications to the examples described below.
First, the measurement method performed in this example will be described.

<Electrochemical measurement>
The measurement method of linear sweep voltammetry by the electrode manufacturing method and the rotating electrode method (using a rotating ring disk electrode device “RRDE-1” manufactured by Nisshi Kogyo) is shown below. First, 5 mg of nitrogen-containing carbon material is weighed into a vial, about 50 mg of glass beads, 50 μL of 5% by mass Nafion (trade name) dispersion (manufactured by Sigma Aldrich Japan), ion-exchanged water and ethanol. 150 μL of each was added, and the mixture was irradiated with ultrasonic waves for 20 minutes to prepare a slurry. 4 μL of this slurry was weighed and applied onto glassy carbon (0.2828 cm ² ) of the rotating electrode, and dried at room temperature of 25 ° C. The dried rotating electrode was the working electrode, the reversible hydrogen electrode (RHE) was the reference electrode, and the carbon electrode was the counter electrode. 0.5M sulfuric acid was used as an electrolyte, and oxygen was bubbled through the electrolyte for 30 minutes, and then the electrochemical measurement was performed by sweeping from 1.1 V to 0 V at a sweep speed of 5 mV / s and a rotation speed of 1500 rpm. Further, the oxygen reduction start potential E ₀ was defined as a potential giving a current of −10 μA / cm ² . As E ₀ indicates a high value, the higher the oxygen reduction activity.

[Example 1]
<Preparation of 2,3-bis (2-pyridyl) pyrazine-iron complex>
In a 0.5 L eggplant-shaped flask, 2.00 g of 2,3-bis (2-pyridyl) pyrazine (manufactured by Sigma-Aldrich), 2.16 g of iron chloride (II) ((manufactured by Sigma-Aldrich)), and 200 g of methanol And stirred at room temperature for 5 hours. Thereafter, the solvent is removed using a rotary evaporator in a water bath at 50 ° C., and dried at 80 ° C. for 2 hours in a vacuum dryer to obtain 2,3-bis (2-pyridyl) pyrazine-iron complex. 10 g was obtained.

<Preparation of precursor>
To a 0.5 L eggplant-shaped flask, 4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex and 200 g of methanol were added and stirred for 12 hours. Then, the solvent was removed using a rotary evaporator in a 50 ° C. water bath, and the precursor was obtained by drying at 80 ° C. for 2 hours using a vacuum dryer.

<Synthesis of nitrogen-containing carbon materials>
Of the prepared precursor, 2.00 g was placed on a quartz boat, which was housed in a quartz tube furnace having an inner diameter of 36 mm, and the furnace was heated from room temperature to 600 over 60 minutes under nitrogen flow at atmospheric pressure and 1 NL / min. The temperature was raised to 0 ° C. and kept at 600 ° C. for 1 hour to obtain a carbide. After cooling to room temperature, this was pulverized and classified with a planetary ball mill (manufactured by Fritsch, trade name “Pulverisete-7”) to adjust the average particle size of the carbide to about 2 μm.

  The total amount of the carbide after pulverization was placed in 500 mL of 36 mass% concentrated hydrochloric acid and stirred at room temperature for 4 hours to dissolve and remove metal species on the surface of the carbide. This was filtered through a membrane filter, washed with pure water, and then vacuum dried at 80 ° C. The entire amount of the carbide after drying was put into the same heating furnace as described above, and the temperature in the furnace was increased from room temperature to 800 ° C. over 20 minutes under nitrogen flow of atmospheric pressure and 1 NL / min, and kept at 800 ° C. for 1 hour.

  The total amount of the carbide after cooling was placed in 500 mL of 36% by mass concentrated hydrochloric acid and stirred at room temperature for 4 hours to dissolve and remove metal species on the surface of the carbide. This was filtered through a membrane filter, washed with pure water, and then vacuum dried at 80 ° C. The dried carbide is put into the same heating furnace as described above, and the temperature in the furnace is increased from room temperature to 900 ° C. over 20 minutes under a mixed gas flow of atmospheric pressure, 1 NL / min ammonia gas / nitrogen = 1/1 (volume ratio). Warm and hold at 900 ° C. for 1 hour. After cooling to room temperature, 0.13 g of a nitrogen-containing carbon material was finally obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.93 V, the current when the potential was 0.5 V was −3.95 mA / cm ² , and the current when the potential was 0.6 V was −3.61 mA / cm ² .

[Example 2]
<Preparation of precursor>
The same as Example 1 except that 4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 0.128 g, and 4.0 g of diaminomaleonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) was added. The precursor was prepared by the method.

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.06 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.94 V, the current when the potential was 0.5 V was −4.29 mA / cm ² , and the current when the potential was 0.6 V was −3.93 mA / cm ² .

[Example 3]
<Preparation of precursor>
The same method as in Example 1 except that 4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 0.128 g and 4.0 g of polyacrylonitrile (manufactured by Sigma-Aldrich) was added. The precursor was prepared with

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.22 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.93 V, the current when the potential was 0.5 V was −4.05 mA / cm ² , and the current when the potential was 0.6 V was −3.73 mA / cm ² .

[Example 4]
<Preparation of precursor>
4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 0.128 g, and 1.3 g of diaminomaleonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) and phenol resin (PSK2320 manufactured by Gunei Chemical Co., Ltd.) 2 A precursor was prepared in the same manner as in Example 1 except that 0.7 g was added.

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.36 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.93 V, the current when the potential was 0.5 V was −4.22 mA / cm ² , and the current when the potential was 0.6 V was −3.83 mA / cm ² .

[Example 5]
<Preparation of precursor>
1. 4.0 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 0.128 g, and 1.3 g of diaminomaleonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) and polyacrylonitrile (manufactured by Sigma-Aldrich) A precursor was prepared in the same manner as in Example 1 except that 7 g was added.

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.23 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.92 V, the current when the potential was 0.5 V was −4.13 mA / cm ² , and the current when the potential was 0.6 V was −3.75 mA / cm ² .

[Example 6]
<Preparation of tetra-2-pyridinylpyrazine-iron complex>
Add 2.00 g of tetra-2-pyridinylpyrazine (manufactured by Sigma-Aldrich), 1.31 g of iron (II) chloride (manufactured by Sigma-Aldrich), and 200 g of methanol to a 0.5 L eggplant-shaped flask. Stir for 5 hours. Then, the solvent was removed using a rotary evaporator in a 50 ° C. water bath, and dried at 80 ° C. for 2 hours using a vacuum dryer to obtain 3.10 g of a tetra-2-pyridinylpyrazine-iron complex. It was.

<Preparation of precursor>
A precursor was prepared in the same manner as in Example 1, except that 4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 3.00 g of tetra-2-pyridinylpyrazine-iron. did.

<Synthesis of nitrogen-containing carbon materials>
Using 2.0 g of the prepared precursor, a nitrogen-containing carbon material was synthesized in the same manner as in Example 1. Finally, 0.42 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.92 V, the current when the potential was 0.5 V was −3.78 mA / cm ² , and the current when the potential was 0.6 V was −3.34 mA / cm ² .

[Example 7]
<Preparation of precursor>
4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 0.194 g of tetra-2-pyridinylpyrazine-iron, and 4.0 g of diaminomaleonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) A precursor was prepared in the same manner as in Example 1 except that it was added.

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.10 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.92 V, the current when the potential was 0.5 V was −4.05 mA / cm ² , and the current when the potential was 0.6 V was −3.66 mA / cm ² .

[Example 8]
<Preparation of tetra-2-pyridinylpyrazine-iron-manganese complex>
Add 2.00 g of tetra-2-pyridinylpyrazine (manufactured by Sigma-Aldrich), 0.13 g of manganese chloride (II) (manufactured by Sigma-Aldrich), and 200 g of methanol to a 0.5 L eggplant-shaped flask. Stir for 1 hour. Further, 1.18 g of iron (II) chloride (manufactured by Sigma-Aldrich) was added and stirred at room temperature for 1 hour. Thereafter, the solvent was removed using a rotary evaporator in a 50 ° C. water bath, dried at 80 ° C. for 2 hours in a vacuum dryer, and 3.10 g of tetra-2-pyridinylpyrazine-iron-manganese complex. Got.

<Preparation of precursor>
4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 0.194 g of tetra-2-pyridinylpyrazine-iron-manganese complex, and diaminomaleonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) 4 A precursor was prepared in the same manner as in Example 1 except that 0.0 g was added.

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.05 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.93 V, the current when the potential was 0.5 V was −4.20 mA / cm ² , and the current when the potential was 0.6 V was −3.77 mA / cm ² .

[Example 9]
<Preparation of tetra-2-pyridinylpyrazine-iron-cobalt complex>
Add 2.00 g of tetra-2-pyridinylpyrazine (manufactured by Sigma-Aldrich), 0.13 g of cobalt (II) chloride (manufactured by Sigma-Aldrich), and 200 g of methanol to a 0.5 L eggplant-shaped flask. Stir for 1 hour. Further, 1.18 g of iron (II) chloride (manufactured by Sigma-Aldrich) was added and stirred at room temperature for 1 hour. Thereafter, the solvent was removed using a rotary evaporator in a 50 ° C. water bath, and dried at 80 ° C. for 2 hours in a vacuum dryer to give 3.10 g of a tetra-2-pyridinylpyrazine-iron-cobalt complex. Got.

<Preparation of precursor>
4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 0.194 g of tetra-2-pyridinylpyrazine-iron-cobalt complex, and diaminomaleonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) 1 The precursor was prepared in the same manner as in Example 1 except that .3 g and 2.7 g of phenol resin (PSK2320 manufactured by Gunei Chemical Co., Ltd.) were added.

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.32 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.92 V, the current when the potential was 0.5 V was −3.94 mA / cm ² , and the current when the potential was 0.6 V was −3.56 mA / cm ² .

[Example 10]
<Preparation of tetra-2-pyridinylpyrazine-iron-nickel complex>
In a 0.5 L eggplant-shaped flask, 2.00 g of tetra-2-pyridinylpyrazine (manufactured by Sigma-Aldrich), 0.25 g of nickel (II) chloride hexahydrate (manufactured by Sigma-Aldrich), and 200 g of methanol The mixture was further stirred at room temperature for 1 hour. Further, 1.18 g of iron (II) chloride (manufactured by Sigma-Aldrich) was added and stirred at room temperature for 1 hour. Thereafter, the solvent was removed using a rotary evaporator in a 50 ° C. water bath, dried at 80 ° C. for 2 hours in a vacuum dryer, and 3.30 g of tetra-2-pyridinylpyrazine-iron-nickel complex. Got.

<Preparation of precursor>
4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 0.194 g of tetra-2-pyridinylpyrazine-iron-nickel complex, and diaminomaleonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) 4 A precursor was prepared in the same manner as in Example 1 except that 0.0 g was added.

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.04 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.93 V, the current when the potential was 0.5 V was −4.32 mA / cm ² , and the current when the potential was 0.6 V was −3.86 mA / cm ² .

[Example 11]
<Preparation of tetra-2-pyridinylpyrazine-iron-copper complex>
In a 0.5 L eggplant-shaped flask, 2.00 g of tetra-2-pyridinylpyrazine (manufactured by Sigma-Aldrich), 0.18 g of copper (II) chloride dihydrate (manufactured by Sigma-Aldrich), and 200 g of methanol The mixture was further stirred at room temperature for 1 hour. Further, 1.18 g of iron (II) chloride (manufactured by Sigma-Aldrich) was added and stirred at room temperature for 1 hour. Thereafter, the solvent was removed using a rotary evaporator in a 50 ° C. water bath, dried at 80 ° C. for 2 hours in a vacuum dryer, and 3.20 g of tetra-2-pyridinylpyrazine-iron-copper complex. Got.

<Preparation of precursor>
4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 0.194 g of tetra-2-pyridinylpyrazine-iron-copper complex, and diaminomaleonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) 1 A precursor was prepared in the same manner as in Example 1 except that .3 g and 2.7 g of polyacrylonitrile (manufactured by Sigma-Aldrich) were added.

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.40 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.93 V, the current when the potential was 0.5 V was −4.32 mA / cm ² , and the current when the potential was 0.6 V was −4.04 mA / cm ² .

[Example 12]
<Preparation of 2,2′-bipyrimidine-iron complex>
To a 0.5 L eggplant-shaped flask, 2.00 g of 2,2′-bipyrimidine (manufactured by Sigma-Aldrich), 3.21 g of iron (II) chloride (manufactured by Sigma-Aldrich), and 200 g of methanol were added, and the mixture was stirred for 5 hours at room temperature Stir. Then, the solvent was removed using a rotary evaporator in a 50 ° C. water bath, and dried at 80 ° C. for 2 hours using a vacuum dryer to obtain 5.10 g of a 2,2′-bipyrimidine-iron complex.

<Preparation of precursor>
A precursor was prepared in the same manner as in Example 1, except that 4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 5.00 g of 2,2′-bipyrimidine-iron complex. .

<Synthesis of nitrogen-containing carbon materials>
Using 2.0 g of the prepared precursor, a nitrogen-containing carbon material was synthesized in the same manner as in Example 1. Finally, 0.06 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.93 V, the current when the potential was 0.5 V was −4.24 mA / cm ² , and the current when the potential was 0.6 V was −3.48 mA / cm ² .

[Example 13]
<Preparation of precursor>
4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex is changed to 5.00 g of 2,2′-bipyrimidine-iron complex, and 2.5 g of diaminomaleonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) is added. A precursor was prepared in the same manner as in Example 1 except that.

<Synthesis of nitrogen-containing carbon materials>
Using 2.0 g of the prepared precursor, a nitrogen-containing carbon material was synthesized in the same manner as in Example 1. Finally, 0.14 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.93 V, the current when the potential was 0.5 V was −3.67 mA / cm ² , and the current when the potential was 0.6 V was −3.02 mA / cm ² .

[Comparative Example 1]
<Synthesis of azulmic acid>
12 g of 25% aqueous ammonia (manufactured by Wako Pure Chemical Industries, Ltd.) was added to a mixed solution of 80 g of hydrocyanic acid, 8.6 g of acetic acid and 130 g of pure water. Thereafter, the mixture was gradually heated and finally stirred at 80 ° C. for 7 hours. The black solid content generated in the mixed solution was filtered through a membrane filter and vacuum-dried to obtain 40 g of azulmic acid. Details are described in Patent Documents 3 and 4.

<Preparation of precursor>
Except not adding 4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex, but adding 4.0 g of azulmic acid and 0.027 g of iron (II) chloride (manufactured by Wako Pure Chemical Industries), A precursor was prepared in the same manner as in Example 1.

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.07 g of nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.83 V, the current when the potential was 0.5 V was −1.94 mA / cm ² , and the current when the potential was 0.6 V was −1.04 mA / cm ² .

[Comparative Example 2]
<Preparation of precursor>
Without adding 4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex, 4.0 g of diaminomaleonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.027 g of iron (II) chloride (manufactured by Wako Pure Chemical Industries, Ltd.) ) Was added in the same manner as in Example 1 except that the precursor was added.

<Synthesis of nitrogen-containing carbon materials>
A nitrogen-containing carbon material was prepared in the same manner as in Example 1 except that 2.0 g of the prepared precursor was not used to dissolve and remove the metal species on the carbide surface with 36 mass% concentrated hydrochloric acid after each heat treatment. Was synthesized. Finally, 0.05 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction start potential E ₀ was 0.89 V, the current when the potential was 0.5 V was −3.26 mA / cm ² , and the current when the potential was 0.6 V was −2.57 mA / cm ² .

[Comparative Example 3]
<Preparation of 1,10-phenanthroline-iron complex>
Add 2.00 g of 1,10-phenanthroline (manufactured by Sigma-Aldrich), 1.41 g of iron (II) chloride (manufactured by Sigma-Aldrich), and 200 g of methanol to a 0.5 L eggplant-shaped flask, and stir at room temperature for 5 hours. did. Thereafter, the solvent was removed using a rotary evaporator in a 50 ° C. water bath, and dried at 80 ° C. for 2 hours using a vacuum dryer, to obtain 3.20 g of 1,10-phenanthroline-iron complex.

<Preparation of precursor>
A precursor was prepared in the same manner as in Example 1, except that 4.00 g of 2,3-bis (2-pyridyl) pyrazine-iron complex was changed to 3.0 g of 1,10-phenanthroline-iron complex.

<Synthesis of nitrogen-containing carbon materials>
Using 2.0 g of the prepared precursor, a nitrogen-containing carbon material was synthesized in the same manner as in Example 1. Finally, 0.42 g of a nitrogen-containing carbon material was obtained.

<Electrochemical measurement>
The electrochemical measurement was performed on the obtained nitrogen-containing carbon material. The oxygen reduction starting potential E ₀ was 0.88 V, the current when the potential was 0.5 V was −3.15 mA / cm ² , and the current when the potential was 0.6 V was −2.34 mA / cm ² .

  Table 1 shows the precursors of the nitrogen-containing carbon material and the electrochemical evaluation results in Examples 1 to 13 and Comparative Examples 1 to 3.

ＢＰＰ：２，３−ビス（２−ピリジル）ピラジン、ＴＰＰ：テトラ−２−ピリジニルピラジン、ＢＰＭ：２，２’−ビピリミジン、ＦｅＣｌ_２：塩化鉄（ＩＩ）、ＭｎＣｌ_２：塩化マンガン（ＩＩ）、ＣｏＣｌ_２：塩化コバルト（ＩＩ）、ＮｉＣｌ_２−６Ｈ_２Ｏ：塩化鉄ニッケル（ＩＩ）六水和物、ＣｕＣｌ_２−２Ｈ_２Ｏ：塩化銅（ＩＩ）二水和物、ＤＡＭＮ：ジアミノマレオニトリル、ＰＡＮ：ポリアクリロニトリル、ＰｈＲｓ：フェノール樹脂、ＡＺＡ：アズルミン酸、ＰＨＥＮ：１，１０−フェナントロリン

BPP: 2,3-bis (2-pyridyl) pyrazine, TPP: tetra-2-pyridinylpyrazine, BPM: 2,2′-bipyrimidine, FeCl ₂ : iron (II) chloride, MnCl ₂ : manganese chloride (II ), CoCl ₂ : Cobalt (II) chloride, NiCl ₂ -6H ₂ O: Nickel (II) chloride hexahydrate, CuCl ₂ -2H ₂ O: Copper (II) chloride dihydrate, DAMN: Diaminomaleo Nitrile, PAN: Polyacrylonitrile, PhRs: Phenolic resin, AZA: Azulmic acid, PHEN: 1,10-phenanthroline

  The nitrogen-containing carbon material obtained by the production method of the present invention has industrial applicability as an electrode material application for fuel cells and the like.

Claims (4)

The aromatic ring structure has 4 or more nitrogen atoms, and —N ¹ —C ¹ —C ² —N ² — (where N ¹ and C ¹ are the first aromatic ring). , C ² and N ² represent an atom forming a second aromatic ring), or —N ¹ —C ¹ —C ² —N ² —C ³ —C ⁴ —N ³ — (where N ¹ And C ¹ are the first aromatic rings, C ² , N ² and C ³ are the second aromatic rings, and C ⁴ and N ³ are the atoms forming the third aromatic ring). Nitrogen-containing aromatic ring compounds having two or more pairs of position sites (however, one or both of the ring skeleton constituent atoms at the 3-position and 4-position with respect to the linking group bonded to the aromatic ring structure is a nitrogen atom) and excluding), a first step of obtaining a nitrogen-containing carbon material precursor composition by mixing a transition metal salt, and
Heat-treating the obtained precursor composition for nitrogen-containing carbon material to obtain a nitrogen-containing carbon material, and
A method for producing a nitrogen-containing carbon material. The aromatic ring structure has 4 or more nitrogen atoms, and —N ¹ —C ¹ —C ² —N ² — (where N ¹ and C ¹ are the first aromatic ring). , C ² and N ² represent an atom forming a second aromatic ring), or —N ¹ —C ¹ —C ² —N ² —C ³ —C ⁴ —N ³ — (where N ¹ And C ¹ are the first aromatic rings, C ² , N ² and C ³ are the second aromatic rings, and C ⁴ and N ³ are the atoms forming the third aromatic ring). Nitrogen-containing aromatic ring compounds having two or more pairs of position sites (however, one or both of the ring skeleton constituent atoms at the 3-position and 4-position with respect to the linking group bonded to the aromatic ring structure is a nitrogen atom) and excluding), made by carbonizing a nitrogen-containing carbon material precursor composition comprising a transition metal salt, a nitrogen-containing carbon material.   A fuel cell electrode comprising the nitrogen-containing carbon material according to claim 2. The aromatic ring structure has 4 or more nitrogen atoms, and —N ¹ —C ¹ —C ² —N ² — (where N ¹ and C ¹ are the first aromatic ring). , C ² and N ² represent an atom forming a second aromatic ring), or —N ¹ —C ¹ —C ² —N ² —C ³ —C ⁴ —N ³ — (where N ¹ And C ¹ are the first aromatic rings, C ² , N ² and C ³ are the second aromatic rings, and C ⁴ and N ³ are the atoms forming the third aromatic ring). Nitrogen-containing aromatic ring compounds having two or more pairs of position sites (however, one or both of the ring skeleton constituent atoms at the 3-position and 4-position with respect to the linking group bonded to the aromatic ring structure is a nitrogen atom) and excluding) comprises a transition metal salt, a nitrogen-containing carbon material precursor composition.