JP6430168B2 - Carbon material composite, nitrogen-containing carbon material, and production method thereof - Google Patents

Description

  The present invention relates to a carbon material composite, a nitrogen-containing carbon material, and a method for producing them.

  Conventionally, carbon materials have been mainly used as adsorbents, etc., but they have basic properties such as physical properties of electronic materials such as conductivity, high thermal conductivity, low thermal expansion coefficient, lightness, and heat resistance. A wide range of applications has been studied. In particular, its chemical function has recently attracted attention and is also being studied in the field of electrodes for polymer electrolyte fuel cells.

  Such a carbon material has been conventionally produced by carbonization using coconut shell, coal coke, coal or petroleum pitch, furan resin, phenol resin, or the like as a raw material.

  In recent years, attempts have been made to further expand the range of physical properties of carbon materials by incorporating other elements into such carbon materials. Under these circumstances, a carbon material doped with nitrogen atoms (hereinafter referred to as “nitrogen-containing carbon material”) has recently been used to develop oxygen reduction activity, so that an electrode for a polymer electrolyte fuel cell, a catalyst for a chemical reaction, etc. (See, for example, Patent Document 1).

  Furthermore, an example in which a nitrogen-containing compound and a carbonized product are mixed to obtain a carbon material composite, and the obtained carbon material composite is heat-treated to provide a nitrogen-containing carbon material has been reported. For example, Patent Document 2 discloses a nitrogen-containing carbon material in which nitrogen is doped into a carbon material obtained by mixing a carbonized compound with a polymer metal complex and performing heat treatment. Patent Document 3 discloses a nitrogen-containing carbon material obtained by covalently bonding a nitrogen-containing compound to a carbonized product. Patent Document 4 discloses a nitrogen-containing carbon material obtained by wet-mixing a nitrogen-containing compound and a carbonized product to form a paste, spray-drying the obtained wet mixture, and then firing.

International Publication No. 2008/123380 JP 2008-282725 A JP 2011-195351 A Japanese Patent No. 5387791

  However, in the conventional method, the uniformity of the nitrogen-containing compound distributed on the carbonized product is insufficient, and the oxygen-reducing activity of the nitrogen-containing carbon material obtained by firing the compound is not sufficient.

  The present invention has been made in view of the above circumstances, and has a carbon material composite that provides a nitrogen-containing carbon material having a high oxygen reduction activity in an electrode reaction, a method for producing the same, and a high oxygen reduction activity in an electrode reaction. It aims at providing a nitrogen-containing carbon material and its manufacturing method.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above-mentioned basic problems can be solved if the carbon material composite manufacturing method has a predetermined process. It came to an eggplant.

That is, the present invention is as follows.
[1]
A step (1) of obtaining a carbon material composite mixture by mixing a nitrogen-containing compound, a solvent in which the nitrogen-containing compound is soluble, a carbonized product, and a transition metal compound;
And (2) obtaining a carbon material composite by removing the solvent from the carbon material composite mixed solution.
[2]
The method for producing a carbon material composite according to [1] above, wherein in the step (2), the solvent is removed by spray drying.
[3]
The method for producing a carbon material composite according to [1] or [2] above, wherein the solubility (A) of the nitrogen-containing compound in the solvent is 0.00010 or more at 20 ° C.
[4]
The method for producing a carbon material composite according to any one of [1] to [3], wherein the carbonized material contains carbon black.
[5]
The production of the carbon material composite according to any one of [1] to [4], wherein the transition metal contained in the transition metal-containing compound includes at least one selected from the group consisting of Fe, Co, and Ni. Method.
[6]
Nitrogen-containing carbon which has the process (3) which heat-processes the carbon material composite obtained by the manufacturing method of the carbon material composite in any one of the preceding clauses [1]-[5], and obtains a nitrogen-containing carbon material Material manufacturing method.
[7]
The method for producing a nitrogen-containing carbon material according to [6], wherein the heat treatment temperature in the step (3) is 400 ° C to 1500 ° C.
[8]
A carbon material composite obtained by the method for producing a carbon material composite according to any one of [1] to [5] above.
[9]
A nitrogen-containing carbon material obtained by the method for producing a nitrogen-containing carbon material according to [6] or [7].
[10]
The nitrogen-containing carbon material according to [9] above, which has a peak in a range where the diffraction angle (2θ) is 23.5 to 26.5 ° in an X-ray diffraction diagram obtained using CuKα rays as an X-ray source.

  According to the present invention, a carbon material composite that provides a nitrogen-containing carbon material having high oxygen reduction activity in an electrode reaction and a method for producing the same, and a nitrogen-containing carbon material having high oxygen reduction activity in an electrode reaction and a method for producing the same. Can be provided.

2 is an XRD chart of Example 1. FIG.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following description, and various modifications can be made within the scope of the gist thereof.

[Method for producing carbon material composite]
The method for producing a carbon material composite according to the present embodiment includes a step of mixing a nitrogen-containing compound, a solvent in which the nitrogen-containing compound is soluble, a carbonized product, and a transition metal compound to obtain a carbon material composite mixture (1 And a step (2) of obtaining the carbon material composite by removing the solvent from the carbon material composite mixture.

  By having the above steps, since the nitrogen-containing compound is soluble in the solvent, a carbon material composite in which the nitrogen-containing compound is uniformly distributed on the carbonized product can be obtained. Thereby, the nitrogen-containing carbon material which has high oxygen reduction activity in an electrode reaction can be obtained.

[Step (1)]
Step (1) is a step of obtaining a carbon material composite liquid mixture by mixing a nitrogen-containing compound, a solvent in which the nitrogen-containing compound is soluble, a carbonized product, and a transition metal compound. It does not specifically limit as a mixing method, Arbitrary methods can be used.

  The nitrogen-containing compound, the solvent in which the nitrogen-containing compound is soluble, the carbonized product, and the transition metal compound may be added simultaneously or sequentially in any order. Moreover, when mixing a nitrogen-containing compound, a carbonized material, and / or a transition-containing metal compound, you may mix as a powder and may disperse | distribute and mix in a solvent.

  Although the solvent temperature in the case of mixing is not specifically limited, It is preferable that it is more than melting | fusing point of a solvent and below boiling point or decomposition temperature of a solvent. The mixing time is preferably 1 minute to 200 hours, more preferably 10 minutes to 100 hours, and even more preferably 30 minutes to 50 hours. During mixing, it is preferable to shake, stir or apply ultrasonic waves.

(Nitrogen-containing compounds)
The nitrogen-containing compound is a nitrogen-containing organic compound containing a nitrogen element in the molecule and does not contain a transition metal element. In the step (1), the nitrogen-containing compound may form a complex with the transition metal compound. The complex thus obtained is preferably soluble in the solvent. Thereby, it exists in the tendency which can obtain the carbon material composite_body | complex in which the nitrogen-containing compound was distributed more uniformly on carbonized material.

  The ratio of the nitrogen element in the nitrogen-containing compound is preferably 1.0% by mass to 80% by mass, more preferably 10% by mass to 70% by mass, and still more preferably with respect to the molecular weight of the nitrogen-containing compound. It is 20 mass%-60 mass%, More preferably, it is 40 mass%-55 mass%. When the nitrogen element in the nitrogen-containing compound is in the above range, the oxygen reduction activity of the obtained nitrogen-containing carbon material tends to be further improved.

  The nitrogen-containing compound is not particularly limited, and examples thereof include primary to tertiary amines, amides, imines, imides, nitriles, azides, aziridines, azos, diazos, isocyanates, isocyanides. , Enamines, oximes, carbamates, nitros, nitroso, hydrazines, lactams and the like. Such nitrogen-containing compounds are not particularly limited, and examples thereof include nitrogen-containing compounds having no ring structure, nitrogen-containing compounds having no heterocyclic structure, nitrogen-containing compounds having a heterocyclic monocyclic structure, and condensed heterocyclic structures. Examples thereof include nitrogen-containing compounds and other compounds.

  The nitrogen-containing compound not having a ring structure is not particularly limited, and examples thereof include acrylonitrile, ethylenediamine, tetracyanoethylene, diaminomaleonitrile, maleonitrile, adiponitrile, cyanoacetylene, hydrazine, hydrazide, and urea.

  Although it does not specifically limit as a nitrogen-containing compound which does not have a heterocyclic structure, For example, aniline, tetracyanobenzene, a phthalonitrile, salen is mentioned.

  The nitrogen-containing compound having a heterocyclic monocyclic structure is not particularly limited, but examples thereof include 5-membered ring compounds such as pyrroles and derivatives thereof, diazoles and derivatives thereof such as pyrazole and imidazole, triazoles and derivatives thereof; and Pyridines and derivatives thereof, diazines such as pyridazine, pyrimidine and pyrazine and derivatives thereof, triazines and triazine derivatives such as melamine and cyanuric acid, six-membered ring compounds such as piperazine, morpholine and cyanuric acid; or chitin And polymers such as chitosan.

  The nitrogen-containing compound having a condensed heterocyclic structure is not particularly limited, and examples thereof include quinolines, indoles, phenanthrolines, and purines. More specifically, phenanthroline, benzimidazole, quinoxaline, azulmic acid, polyamideimide resin, polybenzimidazole, polyimide, DNA, and RNA can be mentioned.

  Other compounds are not particularly limited, for example, melamine resin, polyaniline, polypyrrole, polyvinylpyrrole, polyvinylpyridine, polyacrylonitrile, polyacrylonitrile-polymethacrylic acid copolymer, polyamide, polyamino acid, silk, hair, polyurethane, Polyamideamine, polycarbodiimide, polybismaleimide and polyaminobismaleimide are mentioned.

  In addition, a nitrogen-containing compound may be used individually by 1 type, or may use 2 or more types together. Further, the nitrogen-containing compound is preferably one in which the polymerization initiation temperature of the compound is lower than the boiling point in the standard state and does not sublime by heat treatment.

(Solubility of nitrogen-containing compounds)
The solubility (A) of the nitrogen-containing compound in the solvent is preferably at least 0.00010, more preferably at least 0.0010, and even more preferably at least 0.010 at 20 ° C. Productivity improves more because the solubility (A) with respect to the solvent of a nitrogen-containing compound is 0.00010 or more. In addition, the upper limit of the solubility (A) with respect to the solvent of a nitrogen-containing compound is so preferable that it is large, and the specific value is not restrict | limited in particular. The solubility (A) of the nitrogen-containing compound in the solvent can be measured by the method described in the examples.

(solvent)
“A solvent capable of a nitrogen-containing compound” means that the solubility of the nitrogen-containing compound in the solvent is 0.000010 or more.

  Such a solvent is not particularly limited. For example, water, alcohols (methanol, ethanol, propanol, butanol, etc.), acetone, ethers (diethyl ether, tetrahydrofuran, etc.), organic acids (formic acid, acetic acid, 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.) ) Aromatic hydrocarbons (benzene, toluene, xylene, ethylbenzene, etc.), ammonia, primary amines (methylamine, ethylamine, propylamine, isopropylamine, butylamine, amylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine , Undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, cetylamine, cyclopropylamine, cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, aniline, catecholamine, phenethylamine, amantadine, toluidine, benzyl Amine, naphthylamine, allylamine, etc.), secondary amine (dimethylamine, diethylamine, dipropylamine, di-amine) Tilamine, etc.), tertiary amine (trimethylamine, triethylamine, tripropylamine, tributylamine, dicyclohexylmethylamine, tetramethylammonium hydroxide, N-methylpyrrolidine, 1,5-diazabicyclo [4.3.0] nonene-5 (DBN), 1,8-diazabicyclo [5.4.0] undecene-7 (DBU), N, N-diisopropylethylamine, triethanolamine, etc.), quaternary amine (tetraethylammonium hydroxide, tetramethylammonium chloride) , Tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, etc.), cyclic amine (pyridine, 4-dimethylaminopyridine, pyrimidine, piperidine, morpholine, piperazine) Quinuclidine, 1,4-diazabicyclo [2.2.2] octane, etc.), polyvalent amine (trimethylenediamine, ethylenediamine, diethylethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 1,7-diaminoheptane 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, phenylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethyleneexamine, tetramethylethylenediamine, diethylenetriamine, 1,2, 3-triaminopropane, triaminobenzene, triaminophenol, melamine, spermidine, 1,8-bis (dimethylamino) naphthalene, spermine, etc.). A solvent may be used individually by 1 type, or may use 2 or more types together.

  Among these, a solvent containing at least one selected from the group consisting of methanol, ethanol, acetone, tetrahydrofuran, acetonitrile, water and the like can be preferably used. By using such a solvent, the solubility of the nitrogen-containing compound and the solvent removal efficiency in step (2) tend to be further improved.

  The boiling point of the solvent is preferably 200 ° C. or lower, more preferably 150 ° C. or lower, and further preferably 100 ° C. or lower. When the boiling point of the solvent is within the above range, the solubility of the nitrogen-containing compound and the solvent removal efficiency in step (2) tend to be further improved.

(Carbonide)
The carbonized compound is not particularly limited as long as it is a compound that does not contain a nitrogen atom and a transition metal atom. For example, various carbon blacks (acetylene black, oil furnace black, gas furnace black, channel black, lamp black, thermal black, etc.) , Coke, activated carbon, carbon fiber (PAN-based carbon fiber, pitch-based carbon fiber), carbon nanotube, fullerene, graphene and the like. Among these, carbon black and carbon nanotube are preferable, and carbon black is more preferable. By using such a carbonized product, the oxygen reduction activity tends to be further improved.

The nitrogen adsorption specific surface area of the carbonized material is preferably 100 m ² / g or more, more preferably 300 m ² / g or more, and further preferably 500 m ² / g or more. When the nitrogen adsorption specific surface area of the carbonized product is 100 m ² / g or more, the oxygen reduction activity tends to be further improved. Further, the nitrogen adsorption specific surface area of the carbonized material is preferably 3000 m ² / g or less, more preferably 2800 m ² / g or less, and further preferably 2500 m ² / g or less. When the nitrogen adsorption specific surface area of the carbonized product is 3000 m ² / g or less, the handleability of the carbonized product tends to be further improved.

(Transition metal compounds)
The transition metal compound is a compound containing a transition metal element in the molecule and may contain a nitrogen element. The transition metal-containing compound is not particularly limited, and examples thereof include transition metal complexes, inorganic acid salts, organic acid salts, and other transition metal compounds. More specifically, transition metal nitrites, nitrates, sulfates, sulfites, acetates, ammonium salts, hydrochlorides, odorates and other inorganic acid salts; oxalates, carbonates and other organic acid salts; Other transition metal compounds such as hydroxides, oxides, and alkoxides can be mentioned.

  Although it does not specifically limit as a transition metal contained in a transition metal-containing compound, Preferably Ti (titanium), V (vanadium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Ni (Nickel), Cu (copper), Y (yttrium), Zr (zirconium), Nb (niobium), Mo (molybdenum), Tc (technetium), Ru (ruthenium), Rh (rhodium), Pd (palladium), Ag (Silver), Ta (tantalum), W (tungsten), Re (rhenium), Ir (iridium), Pt (platinum), Au (gold) and at least one selected from the group consisting of lanthanoid elements, more preferably At least one selected from the group consisting of Fe, Co, Ni, Pd, Pt, Au, La and Ce, and more preferably Fe, C Is at least one selected from the group consisting of Ni and Pt, particularly preferably Fe, at least one selected from the group consisting of Co and Ni, very particularly preferably Fe. By using such a transition metal, the oxygen reduction activity tends to be improved.

  These transition metals may be used alone or in combination of two or more. When two or more transition metals are used in combination, one of the transition metals is preferably selected from the group consisting of Fe, Co, and Ni.

  When two or more transition metals are used in combination, Ti, V, Cr, Mn, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, Pt, The content of Au and lanthanoid elements is preferably 1.0 or less, more preferably 0.50 or less, and even more preferably 0.10 or less with respect to 1 part by mass of Fe, Co and Ni in total. is there.

  When the transition metal is iron, the transition metal compound is not particularly limited, and examples thereof include iron complexes, iron inorganic acid salts, iron organic acid salts, and other iron compounds. More specifically, iron (II) chloride, iron (III) chloride, ferric citrate, ferric phosphide, ferric tartrate, ferrous fumarate, ammonium hexacyanoferrate (II), shu Ammonium iron (III) trihydrate, iron (III) ammonium sulfate, iron (III) ammonium sulfate, iron ethylenediaminetetraacetate, ammonium iron citrate, ferric nitrate, iron (II) acetate, iron fumarate (II ), Iron (II) gluconate, iron oxalate, iron hydroxide (III), iron (III) acetylacetonate, iron (II) methoxide, iron (III) ethoxide, iron (III) isopropoxide, bis ( Cyclopentadienyl) iron, bis (methylcyclopentadienyl) iron, bis (ethylcyclopentadienyl) iron, bis (isopropylcyclopentadienyl) iron and Scan (tetramethylcyclopentadienyl) iron can be exemplified. Among these, from the viewpoint of obtaining a nitrogen-containing carbon material having better oxygen reduction activity in the electrode reaction, iron complexes and iron inorganic acid salts are preferable, and iron (II) chloride and iron nitrate are more preferable. Such transition metal-containing compounds are used singly or in combination of two or more.

  When the transition metal is cobalt, the transition metal compound is not particularly limited, and examples thereof include cobalt complexes, cobalt inorganic acid salts, cobalt organic acid salts, and other cobalt compounds. More specifically, cobalt (II) chloride, cobalt bromide, cobalt carbonate (II), cobalt formate (II), hexafluoroacetylacetonato cobalt (II), cobalt oxide (II), cobalt cobalt acetate (II) , Cobalt (II) lactate, cobalt nitrate, cobalt oxalate (II), cobalt (II) 2,4-pentandionate, cobalt sulfate, cobalt amidosulfate, cobalt hydroxide, hexaamminecobalt bromide (II), chloride Hexaamminecobalt (II), cobalt (II) acetate tetrahydrate, cobalt (II) acetylacetonate, cobalt ammonium sulfate, cobalt (II) trifluoroacetylacetonate, bis (cyclopentadienyl) cobalt, bis (isopropyl) Cyclopentadienyl) cobalt, bis (pen Methylcyclopentadienyl) cobalt, bis (tetramethylcyclopentadienyl) cobalt, cobalt borate, cobalt hydroxyacetate, cobalt naphthenate, bis (ethylcyclopentadienyl) cobalt, cobalt (II) ammonium sulfate, bis ( Examples include 1,5-cyclooctadiene) cobalt and bis (tetramethylcyclopentadienyl) cobalt. Among these, from the viewpoint of obtaining a nitrogen-containing carbon material having better oxygen reduction activity in the electrode reaction, a cobalt complex and an inorganic acid salt of cobalt are preferable, and cobalt (II) chloride and cobalt nitrate are more preferable. Such transition metal-containing compounds are used singly or in combination of two or more.

  When the transition metal is nickel, the transition metal compound is not particularly limited, and examples thereof include nickel complexes, nickel inorganic acid salts, nickel organic acid salts, and other nickel compounds. More specifically, nickel chloride (II), nickel bromide, nickel carbonate (II), nickel formate (II), hexafluoroacetylacetonato nickel (II), nickel oxide (II), nickel hydroxyacetate (II) , Nickel lactate (II), nickel naphthenate (II), nickel nitrate, nickel oxalate (II), 2,4-pentanedioic acid nickel (II), nickel sulfate, amido nickel sulfate, nickel hydroxide, hexabromide Ammine nickel (II), hexaammine nickel chloride (II), nickel acetate (II) tetrahydrate, nickel (II) acetylacetonate, nickel ammonium sulfate, nickel (II) trifluoroacetylacetonate, bis (cyclopentadidi) Enyl) nickel, bis (isopropylcyclopentadi) Nyl) nickel, bis (pentamethylcyclopentadienyl) nickel, bis (tetramethylcyclopentadienyl) nickel, nickel borate, nickel hydroxyacetate, nickel naphthenate, bis (ethylcyclopentadienyl) nickel, nickel sulfate (II) Ammonium, bis (1,5-cyclooctadiene) nickel and bis (tetramethylcyclopentadienyl) nickel can be exemplified. Among these, from the viewpoint of obtaining a nitrogen-containing carbon material having better oxygen reduction activity in the electrode reaction, nickel complexes and nickel inorganic acid salts are preferable, and nickel chloride (II) and nickel nitrate are more preferable. Such transition metal-containing compounds are used singly or in combination of two or more.

  When the transition metal is platinum, the transition metal compound is not particularly limited, and examples thereof include a platinum complex, a platinum compound having a halogen atom, and other platinum compounds. More specifically, platinum (II) acetylacetonate, ammonium hexabromoplatinate (IV), ammonium hexachloroplatinate (IV), ammonium tetrachloroplatinate (II), bis (acetylacetonate) platinum (II), Bis (ethylenediamine) platinum (II) chloride, chloroplatinic acid hexahydrate, chloroplatinic acid hexahydrate, dichlorodiammineplatinum (II), tetrachlorodiammineplatinum (IV), 1,1-cyclobutanedicarboxylatodiammine Platinum (II), diamminedichloroplatinum (II), diammineplatinum (II) nitrite, dichlorobis (benzonitrile) platinum (II), hexachloroplatinic acid (IV) dihydrogen, hexabromoplatinic acid (IV) dihydrogen, hexahydro Oxoplatinic acid (IV), diphenyl (1,5-cyclothio Tadiene) platinum (II), hexahydroxoplatinum (IV) acid, platinum (II) bromide, platinum (II) chloride, platinum (II) hexafluoroacetylacetonate, tetraammineplatinum chloride (II), tetraammineplatinum hydrogen carbonate (II) ), Tetraammineplatinum (II) hydroxide, tetraamineplatinum nitrate (II), tetraamineplatinum (II) tetrachloroplatinum (II) acid and hexahydroxoplatinum nitrate aqueous solution. Such transition metal-containing compounds are used singly or in combination of two or more.

(Solubility of transition metal compounds)
The solubility (B) of the transition metal compound in the solvent is preferably 0.000010 or more, more preferably 0.00010 or more, and further preferably 0.0010 or more at 20 ° C. When the solubility (B) of the transition metal compound in the solvent is 0.000010 or more, the productivity tends to be further improved. The upper limit of the solubility (B) of the transition metal compound in the solvent is preferably as large as possible, and the specific value is not particularly limited. The solubility (B) of the transition metal compound in the solvent can be measured by the method described in Examples.

(Ratio of nitrogen-containing compound and solvent)
The content of the nitrogen-containing compound is preferably 0.00010 or more and 1.0 or less, more preferably 0.0010 or more and 0.50 or less, and further preferably 0.010 or more with respect to 1 part by mass of the solvent. It is 0.20 or less. When the content of the nitrogen-containing compound is within the above range, the productivity of the nitrogen-containing carbon material tends to be further improved.

(Ratio of nitrogen-containing compounds and carbonized compounds)
The content of the carbonized product is preferably 0.00010 or more and 4.0 or less, more preferably 0.0010 or more and 2.0 or less, and still more preferably 0.010 with respect to 1 part by mass of the nitrogen-containing compound. It is 1.0 or less. When the content of the carbonized material is within the above range, the oxygen reduction activity tends to be further improved.

(Ratio of nitrogen-containing compounds and transition metal elements)
The transition metal element content of the transition metal compound is preferably 0.000010 or more and 1.0 or less, more preferably 0.000050 or more and 0.90 or less, with respect to 1 part by mass of the nitrogen compound. More preferably, it is 0.00010 or more and 0.80 or less. When the content of the transition metal element in the transition metal compound is within the above range, the oxygen reduction activity tends to be further improved.

[Step (2)]
Step (2) is a step of removing the solvent from the carbon material composite mixture to obtain a carbon material composite. Solvent removal methods include spray drying (spray spray, nozzle spray, ultrasonic spray, etc.), drying using a rotary evaporator, vacuum drying, freeze drying, and natural drying. Or a method of filtering, vacuum drying, freeze drying, natural drying, and the like.

  Among these, it is preferable to remove the solvent by spray drying from the viewpoint of efficiently removing the solvent. When using the spray drying method, the inlet temperature is preferably 80 ° C. or higher and 300 ° C. or lower, more preferably 100 ° C. or higher and 200 ° C. or lower. The outlet temperature is preferably 30 ° C. or higher, more preferably 50 ° C. or higher. With such an inlet temperature and outlet temperature, the solvent can be efficiently removed.

[Carbon material composite]
The carbon material composite of this embodiment is obtained by the method for producing a carbon material composite.

[Method for producing nitrogen-containing carbon material]
The method for producing a nitrogen-containing carbon material of this embodiment includes a step (3) of obtaining a nitrogen-containing carbon material by heat-treating the carbon material composite obtained by the carbon material composite production method.

[Step (3)]
Step (3) is a step of obtaining a nitrogen-containing carbon material by heat-treating the carbon material composite obtained by the method for producing the nitrogen-containing carbon material.

(Heat treatment method)
The heat treatment method for obtaining the nitrogen-containing carbon material by heat-treating the carbon material composite may be a process for heating the carbon material composite in the gas phase, and the ultimate temperature (maximum temperature) and temperature pattern of the heat treatment, The atmosphere around the carbon material composite during the heat treatment can be changed for each heat treatment.

  The number of heat treatments is preferably 1 to 20 times, more preferably 1 to 10 times, and further preferably 2 to 5 times, from the viewpoint of the properties of the obtained nitrogen-containing carbon material and the process.

  Although it does not specifically limit as an apparatus used for heat processing, For example, a box furnace, a rotary furnace, a tunnel furnace, a tubular furnace, a fluidized-fired furnace is mentioned. The temperature of the heat treatment is preferably increased every time the heat treatment step proceeds, from the viewpoint of proceeding carbonization while maintaining a high content ratio of the nitrogen element in the carbon material composite.

  As the gas in the ambient atmosphere of the carbon material composite during the heat treatment, an inert gas and an activation gas can be appropriately selected, and one kind or two or more kinds can be used. Although it does not specifically limit as an inert gas, For example, nitrogen gas and a noble gas (For example, argon gas, helium gas, and neon gas) are mentioned. Further, the activation gas is not particularly limited, but for example, air, hydrogen gas, water vapor, carbon monoxide gas, carbon dioxide gas, methane gas, oxygen gas, nitrogen monoxide gas, ammonia gas and the above inert gas. The diluted one is mentioned. The activation gas is preferably pure ammonia gas or ammonia-containing gas obtained by diluting pure ammonia with an inert gas from the viewpoint of high nitrogen content of the obtained nitrogen-containing carbon material.

  Further, the pressure of the gas phase during the heat treatment may be any of normal pressure, pressurization, and reduced pressure (for example, 10 kPa or less, preferably in a vacuum). The gas around the carbon material composite may be stationary or in circulation, but is preferably in circulation from the viewpoint of the yield of the nitrogen-containing carbon material. Under an inert gas atmosphere, although the specific surface area of the obtained nitrogen-containing carbon material is relatively small, the gasification reaction of the carbon material composite hardly occurs and carbonization proceeds at a high yield. On the other hand, when the carbon material composite is preferably heat-treated once in an inert gas atmosphere and carbonized to some extent, and then heat-treated in an ammonia-containing gas atmosphere, the specific surface area is maintained while maintaining a high nitrogen content. It becomes easy to obtain a large nitrogen-containing carbon material. Therefore, it is preferable to first perform the heat treatment of the carbon material composite in an inert gas atmosphere and then perform the heat treatment in an ammonia-containing gas atmosphere.

  In the inert gas, the heat treatment temperature is preferably 400 ° C to 1500 ° C, more preferably 500 ° C to 1200 ° C, and further preferably 600 ° C to 1000 ° C. Moreover, in activation gas, the heat processing temperature becomes like this. Preferably it is 400 to 1500 degreeC, More preferably, it is 600 to 1400 degreeC, More preferably, it is 700 to 1200 degreeC. The temperature of the heat treatment is preferably increased every time the heat treatment step proceeds, from the viewpoint of proceeding carbonization while maintaining a high content ratio of the nitrogen element in the carbon material composite. When the heat treatment temperature is 400 ° C. or higher, the yield of the finally obtained nitrogen-containing carbon material tends to be further improved. Moreover, when the heat treatment temperature is 1500 ° C. or lower, the nitrogen content in the raw material carbon material tends to be maintained higher.

  The heat treatment time is preferably 5.0 minutes to 50 hours, more preferably 15 minutes to 20 hours, and further preferably 30 minutes to 10 hours. When the heat treatment time is within the above range, the oxygen reduction activity is further improved, or the productivity of the nitrogen-containing carbon material is improved.

  The pressure during the heat treatment is preferably 0.010 to 5.0 MPa, more preferably 0.050 to 1.0 MPa, still more preferably 0.080 to 0.30 MPa, and particularly preferably 0. 0.090 to 0.15 MPa. When the pressure is 5.0 MPa or less, the nitrogen-containing carbon material tends to be more effectively suppressed from being constituted by sp3 orbits and having a low conductivity diamond structure. Moreover, it exists in the tendency for the maintenance of the airtightness of an installation to become easy because a pressure is 0.010 MPa or more.

[Nitrogen-containing carbon material]
The nitrogen-containing carbon material of the present embodiment is obtained by the above-described method for producing a nitrogen-containing carbon material. The nitrogen-containing carbon material of this embodiment preferably has a peak in a range where the diffraction angle (2θ) is 23.5 to 26.5 ° in an X-ray diffraction diagram obtained using CuKα rays as an X-ray source. The diffraction angle (2θ) is more preferably in the range of 24.0 to 26.5 °, and further preferably in the range of 24.5 to 26.4 °. The full width at half maximum of the peak is more preferably 0.0010 ° or more, further preferably 0.010 ° or more, and particularly preferably 0.040 ° or more. When the half width of the peak is 0.0010 ° or more, the oxygen reduction activity tends to be further improved. The half width of the peak is preferably 15 ° or less, more preferably 14 ° or less, and further preferably 12 ° or less. When the half width of the peak is 15 ° or less, the oxygen reduction activity tends to be further improved. The X-ray diffraction pattern can be measured by the method described in the examples.

  The content of the transition metal in the final nitrogen-containing carbon material obtained through the above production method is preferably 0.0010% by mass to 20% by mass with respect to 100% by mass of the nitrogen-containing carbon material. More preferably, the content is from 010 mass% to 10 mass%, more preferably from 0.050 mass% to 5.0 mass%, and from 0.10 mass% to 3.0 mass%. Is most preferred. When the content of the transition metal is within the above range, the oxygen reduction activity tends to be further improved.

[Use]
The nitrogen-containing carbon material of the present embodiment can be used as a material for various electrodes such as a fuel cell electrode represented by a solid polymer type and a metal-air battery electrode.

  The method for producing the electrode containing the nitrogen-containing carbon material of the present embodiment, that is, including the same, is not particularly limited, and can be produced by a general method similar to the conventional carbon material. For example, an electrode can be produced by mixing a nitrogen-containing carbon material and a proton conductive material in a solvent to form a paste, applying the paste directly to the proton conductive membrane, and then drying the applied layer. . Any proton-conducting material can be used as long as it can transmit protons. Nafion (trade name, manufactured by DuPont), Flemion (trade name, manufactured by Asahi Glass), Aciplex (trade name, Asahi Kasei) And fluorine-containing ion exchange resins having a sulfonic acid group. As the proton conductive membrane, a membrane made of the same material as the proton conductive substance can be used. As a method for producing an electrode, not only a method of directly applying a paste to a proton conductive membrane, but also an electrode is produced by applying a paste on a sheet such as a tetrafluoroethylene sheet, and then the electrode is applied to the proton conductive membrane. A transfer method can also be adopted.

  EXAMPLES The present invention will be described in more detail with reference to examples of the present invention below, but these are illustrative and the present invention is not limited to the following examples. Those skilled in the art can make various modifications to the embodiments described below and implement the present invention, and such modifications are included in the claims of the present application.

[Example 1]
120 g of diaminomaleonitrile, 0.273 g of iron (II) chloride and 3 kg of methanol were mixed and stirred at room temperature for 24 hours to obtain a solution. The solubility (A) of diaminomaleonitrile in methanol was 0.06. The solution and 2.4 g of Ketjen Black (ECP-600JD, manufactured by Lion Corporation) were mixed and stirred at room temperature for 24 hours to obtain a carbon material-containing mixed solution. The carbon material-containing mixed solution was spray-dried in an atmosphere of an inlet temperature of 140 ° C. and an outlet temperature of 70 ° C. with a spray dryer (CL-8i, manufactured by Okawahara Kako) to obtain a carbon material composite having an average particle diameter of about 1 μm. .

[Example 2]
120 g of diaminomaleonitrile, 0.273 g of iron (II) chloride and 3 kg of methanol were mixed and stirred at room temperature for 24 hours to obtain a solution. The solution and 4.8 g of Ketjen Black (ECP-600JD, manufactured by Lion Corporation) were mixed and stirred at room temperature for 24 hours to obtain a carbon material-containing mixed solution. The carbon material-containing mixed solution was spray-dried in an atmosphere of an inlet temperature of 140 ° C. and an outlet temperature of 70 ° C. with a spray dryer (CL-8i, manufactured by Okawahara Kako) to obtain a carbon material composite having an average particle diameter of about 1 μm. .

Example 3
120 g of diaminomaleonitrile, 0.273 g of iron (II) chloride and 3 kg of methanol were mixed and stirred at room temperature for 24 hours to obtain a solution. The solution and 9.6 g of Ketjen Black (ECP-600JD, manufactured by Lion Corporation) were mixed and stirred at room temperature for 24 hours to obtain a carbon material-containing mixed solution. The carbon material-containing mixed solution was spray-dried in an atmosphere of an inlet temperature of 140 ° C. and an outlet temperature of 70 ° C. with a spray dryer (CL-8i, manufactured by Okawahara Kako) to obtain a carbon material composite having an average particle diameter of about 1 μm. .

Example 4
120 g of diaminomaleonitrile, 0.273 g of iron (II) chloride and 3 kg of acetonitrile were mixed and stirred at room temperature for 24 hours to obtain a solution. The solubility (A) of diaminomaleonitrile in acetonitrile was 0.04. The solution and 2.4 g of Ketjen Black (ECP-600JD, manufactured by Lion Corporation) were mixed and stirred at room temperature for 24 hours to obtain a carbon material-containing mixed solution. The carbon material-containing mixed solution was spray-dried in an atmosphere of an inlet temperature of 140 ° C. and an outlet temperature of 70 ° C. with a spray dryer (CL-8i, manufactured by Okawahara Kako) to obtain a carbon material composite having an average particle diameter of about 1 μm. .

Example 5
16.0 g of diaminomaleonitrile, 0.0394 g of iron (II) chloride and 400 g of methanol were mixed and stirred at room temperature for 24 hours to obtain a solution. The solution and 0.32 g of ketjen black (ECP-600JD, manufactured by Lion Corporation) were mixed and stirred at room temperature for 24 hours to obtain a carbon material-containing mixed solution. The carbon material-containing mixed solution was dried under reduced pressure in a rotary evaporator (R-205, manufactured by BUCHI) at 40 ° C. to obtain a carbon material composite.

Example 6
120 g of urea, 0.273 g of iron (II) chloride and 3 kg of methanol were mixed and stirred at room temperature for 24 hours to obtain a solution. The solubility (A) of urea in methanol was 0.05. The solution and 2.4 g of Ketjen Black (ECP-600JD, manufactured by Lion Corporation) were mixed and stirred at room temperature for 24 hours to obtain a carbon material-containing mixed solution. The carbon material-containing mixed solution was spray-dried in an atmosphere of an inlet temperature of 140 ° C. and an outlet temperature of 70 ° C. with a spray dryer (CL-8i, manufactured by Okawahara Kako) to obtain a carbon material composite having an average particle diameter of about 1 μm. .

Example 7
120 g of melamine, 0.273 g of iron (II) chloride and 4 kg of water were mixed and stirred at room temperature for 24 hours to obtain a mixed solution. The solubility (A) of melamine in water was 0.03. The mixed solution and 2.4 g of Ketjen Black (ECP-600JD, manufactured by Lion Corporation) were mixed and stirred at room temperature for 24 hours to obtain a carbon material-containing mixed solution. The carbon material-containing mixed solution was spray-dried in an atmosphere of an inlet temperature of 140 ° C. and an outlet temperature of 70 ° C. with a spray dryer (CL-8i, manufactured by Okawahara Kako) to obtain a carbon material composite having an average particle diameter of about 1 μm. .

Example 8
A carbon material composite having an average particle diameter of about 1 μm was obtained in the same manner as in Example 1 except that 0.264 g of cobalt (II) chloride was used instead of 0.273 g of iron (II) chloride.

Example 9
A carbon material composite having an average particle diameter of about 1 μm was obtained in the same manner as in Example 1 except that 0.265 g of nickel (II) chloride was used instead of 0.273 g of iron (II) chloride.

[Comparative Example 1]
120 g of iron phthalocyanine and 3 kg of methanol were mixed and stirred at room temperature for 24 hours to obtain a mixed solution. The solubility (B) of iron phthalocyanine in methanol was less than 0.0001. The mixed solution and 2.4 g of Ketjen Black (ECP-600JD, manufactured by Lion Corporation) were mixed and stirred at room temperature for 24 hours to obtain a carbon material-containing mixed solution. The carbon material-containing mixed solution was spray-dried in an atmosphere of an inlet temperature of 140 ° C. and an outlet temperature of 70 ° C. with a spray dryer (CL-8i, manufactured by Okawahara Kako) to obtain a carbon material composite having an average particle diameter of about 1 μm. .

<Heat treatment method>
The carbon material composites obtained in Examples 1 to 9 and Comparative Example 1 were heat treated. The heat treatment method is as follows.

  7.0 g of the obtained carbon material composite was placed on a quartz boat, which was placed in a high-temperature atmosphere box furnace (KB8610N-VP, manufactured by Koyo Thermo Co., Ltd.), and the inside of the furnace was at atmospheric pressure and nitrogen at 1 NL / min. The temperature was raised from room temperature to 900 ° C. over 60 minutes under circulation and maintained at 900 ° C. for 1 hour. After cooling to room temperature, this was pulverized and classified with a planetary ball mill (Pulverisette-5, manufactured by Fritsch) to adjust the average particle size to about 1 μm. Thereafter, 1.0 g of the obtained sintered body was placed on a quartz boat, which was accommodated in a quartz tubular furnace having an inner diameter of 65 mm, and the inside of the furnace was atmospheric pressure, 0.6 NL / min nitrogen and 0.6 NL. The temperature was raised from room temperature to 950 ° C. over 60 minutes under a mixed gas flow of ammonia at / min, and kept at 950 ° C. for 1 hour. After cooling to room temperature, a nitrogen-containing carbon material was obtained.

  FIG. 1 shows a powder X-ray diffraction spectrum of the nitrogen-containing carbon material obtained by heat-treating the carbon material composite obtained in Example 1. A diffraction line peak of the carbon 002 plane was observed at 2θ = 25.7 °.

[Comparative Example 2]
In Example 1, Example 1 was repeated except that Ketjen Black (ECP-600JD, manufactured by Lion Corporation) was not added, to obtain a complex composed of diaminomaleonitrile and iron (II) chloride. The composite was heat-treated by the above heat treatment method to obtain a carbide of the composite.
[Comparative Example 3]
Ketjen black (ECP-600JD, manufactured by Lion Corporation) was heat-treated by the above heat treatment method. 0.76 g of carbide of the composite obtained in Comparative Example 2 (the solubility (B) of the composite in methanol is less than 0.000010) and ketjen black (ECP-600JD, heat-treated by the above heat treatment method) 0.24 g (manufactured by Lion Corporation) was dry mixed in an agate mortar to obtain a nitrogen-containing carbon material.

<Analysis method>
The redox activity of the nitrogen-containing carbon materials obtained in Examples 1 to 9 and Comparative Examples 1 to 3 was evaluated. The analysis method is as follows.

(Electrochemical measurement)
A linear sweep voltammetry measurement method (rotating ring disk electrode device “HR-301”, manufactured by Hokuto Denko) by the electrode manufacturing method and the rotating electrode method is shown below. First, 5 mg of a nitrogen-containing carbon material is weighed into a vial, and a glass bead is filled with a spatula, 50% by weight of a 5 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. 2.78 μL of this slurry was weighed, applied on the glassy carbon of the rotating electrode, and dried. 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 solution, and oxygen was bubbled through the electrolyte solution for 30 minutes, and then the electrochemical measurement was performed by sweeping from 1.1 V to 0 V at a sweep speed of 1 mV / s and a rotation speed of 1500 rpm.

  Table 1 shows the current when the potential is 0.8 V in Examples 1 to 9 and Comparative Examples 1 to 3.

(Method for measuring solubility of nitrogen-containing compound in solvent at 20 ° C.)
1 g of nitrogen-containing compound (prepared mass of nitrogen-containing compound) and 1 g of solvent (mass of solvent) were weighed and mixed, stirred at 20 ° C. for 10 minutes, and then manufactured by ADVANTEC, model no. Suction filtration was performed using a filter paper of 5C (retained particle diameter 1 μm (value described in the catalog)), and the nitrogen-containing compound remaining on the filter paper was recovered as a filtrate. The obtained filtrate was dried under reduced pressure at 120 ° C. for 10 hours, and the residual mass (g) of the nitrogen-containing compound was measured. Using the above values, the solubility (A) of the nitrogen-containing compound in the solvent was calculated based on the formula (I).
Solubility of nitrogen-containing compounds in solvent (A)
= (Feeding mass of nitrogen-containing compound-residual mass of nitrogen-containing compound) / Solvent mass = (1-Residual mass of nitrogen-containing compound) (I)

(Method for measuring solubility of transition metal-containing compound in solvent at 20 ° C.)
1 g of transition metal-containing compound (prepared mass of transition metal-containing compound) and 1 g of solvent (mass of solvent) were weighed and mixed, stirred for 10 minutes at 20 ° C., and then manufactured by ADVANTEC, Model: No. Suction filtration is performed using a filter paper of 5C (retained particle diameter 1 μm (value described in the catalog)), and the nitrogen-containing compound remaining on the filter paper is recovered as a filtrate. The obtained filtrate was dried under reduced pressure at 120 ° C. for 10 hours, and the residual mass (g) of the nitrogen-containing compound was measured. Using the above values, the solubility (B) of the transition metal-containing compound in the solvent was calculated based on the formula (II).
Solubility of transition metal-containing compounds in solvent (B)
= (Made mass of transition metal compound-residual mass of transition metal compound) / Solvent mass = (1-Residual mass of transition metal compound) (II)

(Carbonide content in the carbon material composite)
The content of the carbonized product in the carbon material composite was calculated based on the following formula (III).
Ratio of carbonized material in carbon material composite (mass%)
= (Mass of carbonized product / mass of nitrogen-containing compound) × 100 (III)

(Carbonide content in nitrogen-containing carbon materials)
The carbon material composite was heat-treated by the above heat treatment method, and the mass (g) of the obtained nitrogen-containing carbon material was measured. It was assumed that the mass of the carbonized product did not change even after the heat treatment by the above heat treatment method, and the mass (g) of the carbonized product in the carbon material composite used for the heat treatment was used as the mass of the carbonized product. Using the above values, the content of carbonized material in the nitrogen-containing carbon material was calculated based on the following formula (IV).
Ratio of carbonized material in nitrogen-containing carbon material (mass%)
= (Mass of carbonized material in carbon material composite used for heat treatment / mass of nitrogen-containing carbon material) × 100 (IV)

  The nitrogen-containing carbon material of the present invention is useful as various electrodes such as electrodes for fuel cells and electrodes for metal-air cells.

Claims (7)

A step (1) of obtaining a carbon material composite mixture by mixing a nitrogen-containing compound, a solvent in which the nitrogen-containing compound is soluble, a carbonized product, and a transition metal compound;
Removing the solvent from the carbon material composite mixture by spray drying to obtain a carbon material composite (2);
Heat treating the carbon material composite to obtain a nitrogen-containing carbon material (3),
The manufacturing method of the nitrogen-containing carbon material whose transition metal content rate of this nitrogen-containing carbon material is 5.0 mass% or less. The method for producing a nitrogen-containing carbon material according to claim 1, wherein the solubility (A) of the nitrogen-containing compound in the solvent is 0.00010 or more at 20 ° C. The method for producing a nitrogen-containing carbon material according to claim 1 or 2 , wherein the carbonized product contains carbon black. The method for producing a nitrogen-containing carbon material according to any one of claims 1 to 3 , wherein the transition metal contained in the transition metal-containing compound contains at least one selected from the group consisting of Fe, Co, and Ni. The manufacturing method of the nitrogen-containing carbon material of any one of Claims 1-4 whose heat processing temperature in the said process (3) is 400 to 1500 degreeC. A nitrogen-containing carbon material obtained by the method for producing a nitrogen-containing carbon material according to any one of claims 1 to 5 . The nitrogen-containing carbon material according to claim 6 , which has a peak in a range where the diffraction angle (2θ) is 23.5 to 26.5 ° in an X-ray diffraction diagram obtained using CuKα rays as an X-ray source.