Sintered body and fuel cell using said sintered body

Abstract

According to the present invention, a stable form, in which the electroconductivity is maintained and / or improved, is achieved with the use of an electroconductive carbon material as a starting material, and the power generation characteristics of a fuel cell are improved if this stable form is used in a catalyst layer of the fuel cell.　The present invention provides a fired body of a mixture which contains a nitrogen-containing compound component and an electroconductive carbon material.

Description

[Technical Field]

[0001] The present invention relates to a sintered body and a fuel cell using the sintered body. [Background technology]

[0002] Carbon black, a carbon material, is a submicron particle made of amorphous carbonaceous material, and is used for rubber reinforcing agents, resin colorants, printing inks, paints, electrode materials, etc. (Non-Patent Document 1). Carbon black that can impart conductivity with a small amount added is called conductive carbon black, and known types include acetylene black, oil furnace black, Vulcan, Ketjenblack, and Ketjenblack EC, depending on the manufacturing method and raw materials (Non-Patent Document 2).

[0003] Carbon black, a carbon material, is produced and activated at high temperatures, which causes some of the functional groups on the surface of the carbon black to be desorbed, resulting in graphitization, and is known to acquire high electrical conductivity (Non-Patent Document 3).

[0004] Carbon nanotubes are made of carbon isotopes sp 2 Carbon nanotubes are made up of cylindrical hexagonal mesh faces made of carbon, and are available in single-wall and multi-wall configurations. For example, vapor-grown carbon nanotubes are known as carbon nanotubes that are manufactured and sold on an industrial scale and have excellent electrical conductivity (Non-Patent Document 4).

[0005] Methods for preparing nitrogen-containing carbon materials and carbon nitrides are known (Non-Patent Document 5).

[0006] It is described that carbon nitride materials, which are nitrogen-containing carbon materials, are insoluble in organic solvents, making it difficult to form thin films and unsuitable for wet processes (Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-234308 [Non-patent literature]

[0008] [Non-Patent Document 1] Carbon Materials Society, New Introduction to Carbon Materials, "2.8 Carbon Black", Realize Science and Engineering Center Co., Ltd., 1996, pp. 129-135 [Non-patent document 2] Carbon Materials Society Serial Lecture Editorial Committee, Carbon Materials Experimental Technology (Manufacturing and Synthesis), [Chapter 3, 3-3 Conductive Carbon Black "Ketjenblack EC"], 2013, pp. 173-179 [Non-patent document 3] Carbon Materials Society Serial Lecture Editorial Committee, Carbon Materials Experimental Technology (Manufacturing and Synthesis), "Chapter 3, 3-1 Carbon Black," 2013, pp. 156-167 [Non-patent document 4] Carbon Materials Society Serial Lecture Editorial Committee, Carbon Materials Experimental Technology (Manufacturing and Synthesis), [Chapter 2, 2-3 Manufacturing Methods and Applications of Vapor-Grown Carbon Fiber], 2013, pp. 87-91 [Non-patent document 5] Carbon Materials Society, Serial Lecture Editorial Committee, Carbon Materials Experimental Technology (Manufacturing and Synthesis), [Chapter 4, 4-3 Preparation Methods of Nitrogen-Containing Carbon Materials], 2013, pp. 267-270 Summary of the Invention [Problem to be solved by the invention]

[0009] In order to obtain the conductivity of a carbon material having conductivity, for example, in the case of conductive carbon black, the surface functional groups and defective portions are reduced by high-temperature baking to improve the conductivity, so the amount of surface functional groups of carbon black is small. Also, carbon nanotubes, which are carbon materials, have sp 2 Because carbon nanotubes are made of carbon, the functional groups on their surfaces are concentrated at the edges of the tubes and at small defects, and their abundance is small.

[0010] Therefore, although it is possible to improve the functionality of carbon black and carbon nanotubes by adding other functions or enhancing their functions through the surface functional groups without deteriorating their original conductive function through chemical modification using organic synthesis techniques or methods of introducing other materials onto the carbon black surface by adsorption, it has been difficult to achieve improvements that are meaningful for practical use. For example, in the case of chemical modification, the amount of functional groups that can be introduced is limited because the amount of functional groups present on the surface of carbon materials that originally have conductivity is small, and sp 2 Introducing functional groups onto a carbon surface using covalent bonds often results in a loss of the original conductivity, depending on the amount introduced. Furthermore, adsorbing other materials onto the surface of conductive carbon materials is a physical adsorption method, which means that the adsorption easily dissolves, often resulting in a loss of the material's properties.

[0011] When a conductive carbon material is actually used, for example, in a catalyst layer of a fuel cell, a catalyst ink is prepared by dispersing the conductive carbon material and components such as a catalyst in a solvent, and the catalyst ink is then applied to a substrate to produce a catalyst layer. When a conductive carbon material such as carbon black or carbon nanotubes is added to the catalyst ink, the solid content tends to aggregate in the catalyst ink, often making application difficult. Furthermore, when preparing catalyst ink, when adding nitrogen-containing carbon materials such as graphitic carbon nitride (g-CN) or carbon nitride to the catalyst ink, it is often difficult to disperse these nitrogen-containing carbon materials in the solvent of the catalyst ink.

[0012] The present invention aims to improve power generation characteristics when a stable form made from a conductive carbon material is used in a catalyst layer of a fuel cell by obtaining a stable form that maintains and / or improves the conductivity of the carbon material, and by suppressing aggregation of solids in a catalyst ink used to prepare a catalyst layer of a fuel cell and improving coating characteristics. [Means for solving the problem]

[0013] As a result of extensive investigations, the inventors have found that a novel fired body can be obtained by firing a mixture containing a conventional electrically conductive carbon material, a nitrogen-containing compound, and an optional aromatic compound having a phenolic hydroxyl group. When this fired body is used, for example, as the electrolyte and / or catalyst support of a catalyst layer in a fuel cell or the electrolyte of a solid electrolyte membrane, it improves the proton conductivity, electronic conductivity, water transport, and gas permeability of the catalyst layer, thereby achieving excellent power generation characteristics. Furthermore, it has been found that the aggregation of solids in a catalyst ink can be avoided and coating properties can be improved when producing a catalyst layer for a fuel cell.

[0014] The present invention based on these findings includes, for example, the following [1] to

[14] . [1] A fired body of a mixture containing a nitrogen-containing compound component and a conductive carbon material. [2] The fired body of [1], wherein the mixture further contains an aromatic compound having a phenolic hydroxyl group. [3] The fired body of [1] or [2], wherein the nitrogen-containing compound-based component is at least one selected from the group consisting of a nitrogen-containing compound, a salt of a nitrogen-containing compound, a resin containing a structural unit derived from a nitrogen-containing compound, and a composite of a resin containing a structural unit derived from a nitrogen-containing compound and an inorganic compound. [4] The fired body according to any one of [1] to [3], wherein the nitrogen-containing compound component is at least one selected from the group consisting of guanidine carbonate, melamine, melamine cyanurate, a complex of crosslinked melamine resin and silica, and melamine, melam, and a salt of melem with polyphosphoric acid. [5] The fired body according to any one of [1] to [4], wherein the conductive carbon material is at least one selected from the group consisting of carbon black, carbon nanotubes, and graphene nanoplatelets. [6] The fired product of any one of [2] to [5], wherein the aromatic compound having a phenolic hydroxyl group is an aromatic compound having 3 to 6 phenolic hydroxyl groups. [7] A fired body of any one of [1] to [6], which contains a three-dimensional polymer of a nitrogen-containing compound. [8] A fired product of any one of [2] to [7], which contains a three-dimensional polymer of an aromatic compound having a phenolic hydroxyl group. [9] A fired product of any one of [1] to [8], which is at least one of an electrolyte in a catalyst layer of a polymer electrolyte fuel cell, a catalyst support in a catalyst layer, and an electrolyte in a solid electrolyte membrane.

[10] A composition containing the fired product according to any one of [1] to [9] and a metal catalyst.

[11] The composition of

[10] for use in a catalyst layer of a polymer electrolyte fuel cell.

[12] A catalyst layer for a polymer electrolyte fuel cell comprising the composition of

[11] .

[13] A membrane electrode assembly having a solid electrolyte membrane, a gas diffusion layer, and the catalyst layer for a polymer electrolyte fuel cell according to

[12] .

[14]

[13] A polymer electrolyte fuel cell having a membrane electrode assembly. [Effects of the Invention]

[0015] The fired body of the present invention is made from a conductive carbon material and has a stable form in which the conductivity is maintained and / or improved, and the coating properties are improved by suppressing the aggregation of solids in the catalyst ink used to prepare the catalyst layer of a fuel cell. Therefore, when the stable form made from the conductive carbon material is used in the catalyst layer of a fuel cell, the power generation properties are improved. [Brief explanation of the drawings]

[0016] [Figure 1] Cross-sectional view showing the structure of a polymer electrolyte fuel cell DETAILED DESCRIPTION OF THE INVENTION

[0017] As used herein, "n-" means normal, "s-" means secondary, "t-" means tertiary, "o-" means ortho, "m-" means meta, and "p-" means para. As used herein, "polymer" refers to both homopolymers and copolymers.

[0018] <<Fired body>> The present invention relates to a sintered body of a mixture containing a conductive carbon material and a nitrogen-containing compound-based component. Furthermore, from the viewpoint of power generation characteristics, the present invention relates to a sintered body of a mixture containing a conductive carbon material, an aromatic compound having a phenolic hydroxyl group, and a nitrogen-containing compound-based component. It is preferable that the mixture does not contain any components other than the conductive carbon material, the aromatic compound having a phenolic hydroxyl group, the nitrogen-containing compound-based component, and graphene oxide.

[0019] <Nitrogen-containing compound components> The mixture that will become the fired body contains a nitrogen-containing compound component. Examples of the nitrogen-containing compound-based component include nitrogen-containing compounds, salts of nitrogen-containing compounds, resins containing structural units derived from nitrogen-containing compounds, and composites of resins containing structural units derived from nitrogen-containing compounds with inorganic compounds. These may be used alone or in combination of two or more.

[0020] Examples of the nitrogen-containing compound include urea, aromatic urea compounds, guanidine compounds, triazine-based heterocyclic compounds, and nitrogen-containing condensed ring compounds.

[0021] Examples of aromatic urea compounds include phenylurea, benzylurea, N-ethyl-N'-phenylurea, p-ethoxyphenylurea, N,N'-diphenylurea, N,N-diphenylurea, tetraphenylurea, and benzoylurea.

[0022] Examples of guanidine compounds include guanidine, methylguanidine, nitroguanidine, aminoguanidine, biguanide, dicyandiamide, carbamoylguanidine, glycocyamine, creatine, N,N'-diphenylguanidine, and triphenylguanidine, with guanidine and aminoguanidine being preferred.

[0023] Examples of triazine-based heterocyclic compounds include 1,3,5-triazine, cyanuric chloride, cyanuric acid, trimethyl cyanurate, methyl isocyanurate, ethyl isocyanurate, melamine, melem, melam, ammeline, ammelide, benzoguanamine, methylguanamine, 1,3,5-trimethyltriazine, 1,3,5-triphenyltriazine, amerine, amelide, thiocyanuric acid, diaminomercaptotriazine, diaminomethyltriazine, diaminophenyltriazine, and diaminoisopropoxytriazine, and melamine is preferred.

[0024] Examples of nitrogen-containing fused ring compounds include purine, xanthine, caffeine, uric acid, adenine, guanine, 2,6-diaminopurine, 2,4,6-triaminopyridine, 3-methyluric acid, and 7-methyluric acid.

[0025] The nitrogen-containing compound may be used alone or in combination of two or more. The nitrogen-containing compound preferably has three or more functional groups, because this allows the formation of a three-dimensional polymer, as will be described later.

[0026] Examples of resins containing structural units derived from nitrogen-containing compounds include melamine resins. Melamine resins are polycondensates of nitrogen-containing compounds, such as melamine and its derivatives, with aldehyde compounds. Examples of melamine and its derivatives include methylolmelamine and benzoguanamine, and examples of aldehyde compounds include formaldehyde. These melamine and its derivatives and aldehyde compounds may be used alone or in combination of two or more.

[0027] Commercially available melamine resins can also be used, such as Cymel 202, Cymel 203, Cymel 204, Cymel 211, Cymel 212, Cymel 238, Cymel 251, Cymel 253, Cymel 254, Cymel 303, Cymel 323, Cymel 324, Cymel 325, Cymel 327, Cymel 350, Cymel 370, Cymel 380, Cymel 385, Cymel 1156, Cymel 1158, Cymel 1116, Cymel 1157, Cymel 1158, Cymel 1117, Cymel 1159, Cymel 1159, Cymel 1160, Cymel 1161, Cymel 1162, Cymel 1163, Cymel 1164, Cymel 1165, Cymel 1166, Cymel 1167, Cymel 1168, Cymel 1169, Cymel 1170, Cymel 1171, Cymel 1172, Cymel 1173, Cymel 1174, Cymel 1175, Cymel 1176, Cymel 1177, Cymel 1178, Cymel 1179, Cymel 1180, Cymel 1181, Cymel 1182, Cymel 1183, Cymel 1184, Cymel 1185, Cymel 1186, Cymel 1187, Cymel 1188, Cymel 1189, Cymel 1190, Cymel 1191, Cymel 1192, Cymel 1193, Cymel 1194, Cymel 1195, Cymel 1196, Cymel 1200, Examples of suitable surfactants include SUMIMARU 1130 (manufactured by Allnex Japan Co., Ltd.); RESIMIN 735, RESIMIN 740, RESIMIN 741, RESIMIN 745, RESIMIN 746, and RESIMIN 747 (manufactured by Monsanto Co., Ltd.); SUMIMARU 120, SUMIMARU 20HS, SUMIMARU 20SE, SUMIMARU 2021, SUMIMARU 2028, and SUMIMARU 28-60 (manufactured by Mitsui Chemicals, Inc.); and SUMIMARU M55, SUMIMARU M30W, and SUMIMARU M50W (manufactured by Sumitomo Chemical Co., Ltd.). These surfactants may be used alone or in combination of two or more.

[0028] In the salt of a nitrogen-containing compound, the acid that forms a salt with the nitrogen-containing compound is not particularly limited, but examples thereof include hydrochloric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, sulfamic acid, nitric acid, perchloric acid, carbonic acid, hydroiodic acid, hydrobromic acid, and thiocyanic acid. Examples of salts of guanidine compounds that are nitrogen-containing compounds include guanidine carbonate, guanidine phosphate, guanidine thiocyanate, and aminoguanidine hydrochloride, with guanidine carbonate being preferred. Examples of the nitrogen-containing compound salts of cyanuric acid or isocyanuric acid include melamine cyanurate and melamine isocyanurate.

[0029] Melamine cyanurate or melamine isocyanurate is an organic salt of an acidic compound, cyanuric acid or isocyanuric acid, and a basic compound, a triazine compound, and examples of such salts include those typically having a molar ratio of acidic compound:basic compound = 1: 1. These can be produced by known methods, for example, by suspending and mixing a mixture of melamine and cyanuric acid or isocyanuric acid in water to form a salt, and then filtering and drying the slurry to obtain a powder. Examples of salts of nitrogen-containing compounds include salts of basic compounds such as melamine, melam, and melem with polyphosphoric acid, and examples of commercially available products in which the basic compound composition is 43 to 57% melamine, 31 to 46% melam, and 8 to 17% melem include "PHOSMEL-200 (average particle size of 5 μm or less)" and "PHOSMEL-200FINE (average particle size of 3 μm or less)" (manufactured by Nissan Chemical Industries, Ltd.) The salts of nitrogen-containing compounds may be used singly or in combination of two or more.

[0030] An example of a composite of a resin containing structural units derived from a nitrogen-containing compound and an inorganic compound is crosslinked melamine resin microparticles, which are spherical particles of a composite consisting of a crosslinked melamine resin as the resin containing structural units derived from a nitrogen-containing compound and silica as the inorganic compound. Commercially available crosslinked melamine resin microparticles include, for example, Optobeads (registered trademark) 500SL (average particle diameter 0.5 μm), Optobeads (registered trademark) 500S (average particle diameter 0.5 μm), Optobeads (registered trademark) 2000M (average particle diameter 2 μm), and Optobeads (registered trademark) 3500M (manufactured by Nissan Chemical Industries, Ltd.) (average particle diameter 3.5 μm). Preferred examples include Optobeads 500SL and Optobeads (registered trademark) 2000M. The composite of an inorganic compound and a resin containing a structural unit derived from a nitrogen-containing compound may be used alone or in combination of two or more.

[0031] The nitrogen-containing compound component is preferably at least one selected from the group consisting of guanidine carbonate, melamine, melamine cyanurate, composite spherical particles composed of crosslinked melamine resin and silica, and melamine, melam, and salts of melem and polyphosphoric acid, and more preferably at least one selected from the group consisting of guanidine carbonate and melamine.

[0032] <Conductive carbon materials> The mixture that will become the fired body contains a conductive carbon material. An electrically conductive carbon material refers to a carbon material having a conductivity of 1 S / cm or more at 2 kN. Examples of conductive carbon materials (hereinafter also referred to as "carbon materials") include carbon black, carbon nanotubes, graphene nanoplatelets, etc. These may be used alone or in combination of two or more. Examples of carbon black include ketjen black, ketjen black EC, channel black, oil furnace black, vulcan, furnace black, thermal black, acetylene black, lamp black, graphitized black, and oxide black. Acetylene black, ketjen black, and ketjen black EC are preferred because of their good conductivity, and ketjen black and ketjen black EC are more preferred. Carbon black may be used alone or in combination of two or more. Carbon black may be surface-treated.

[0033] Specific examples of carbon black include Denka Black (manufactured by Denka Company Limited); LACK PEARLS® 2000, VULCAN® XC-72, VULCAN® P, and TERLING® C (manufactured by Cabot Corporation); Asahi HS-500, Asahi #8, Asahi #15, Asahi #15HS, Asahi #22K, Asahi Thermal, Asahi #35, Asahi #50, Asahi #50U, Asahi #50HG, Asahi #51, Asahi #52, Asahi #55, Asahi #60U, Asahi #60HN, Asahi #65, Asahi F-200GS, Asahi #70, Asahi #80, Asahi #95, Asahi AX-015, and Asahi #15HS (manufactured by Asahi Carbon); and Ketjen Black. Examples include EC300J, Carbon ECP, Ketjenblack EC600JD, and Carbon ECP600JD (manufactured by Lion Specialty Chemicals); Ketjenblack EC and Ketjenblack EC-600JD (manufactured by Ketjenblack International); Carbon black CP (manufactured by Aldrich), TOKABLACK #5500, TOKABLACK #4500, TOKABLACK #4400, and Aqua-black 001 (manufactured by Tokai Carbon).

[0034] Examples of carbon nanotubes include single-walled nanotubes and multi-walled carbon nanotubes obtained by vapor phase growth, catalytic vapor phase growth, catalytic chemical vapor growth, chemical vapor growth, super propagation, catalytic carbon deposition, arc discharge, laser evaporation, etc., and these can take any shape, such as needle-like, coiled, or tubular. Carbon nanotubes have a cylindrical shape formed by wrapping a single surface of hexagonal carbon graphite, and examples include multi-walled carbon nanotubes wrapped in three or more layers (multi-walled carbon nanotubes), single-walled carbon nanotubes (single-walled carbon nanotubes: SWNTs) wrapped around a single surface of graphite, double-walled carbon nanotubes (double-walled carbon nanotubes: DWNTs) wrapped around two layers, and vapor-grown carbon fiber (VGCF, a registered trademark of Showa Denko K.K.). Specifically, the TC series such as TC-2010, TC-2020, TC-3210L, and TC-1210LN (manufactured by Toda Kogyo Co., Ltd.), supergrowth CNT (manufactured by the New Energy and Industrial Technology Development Organization), eDIPS-CNT (manufactured by the New Energy and Industrial Technology Development Organization), SWNT series (manufactured by Meijo Nanocarbon Co., Ltd.: trade name), VGCF (registered trademark) series such as VGCF, VGCF-H, and VGCF-X (manufactured by Showa Denko K.K.: registered trademark), FloTube series (manufactured by CNano Technology: trade name), AMC (manufactured by Ube Industries, Ltd.: trade name), NANOCYL NC7000 series (manufactured by Nanocyl SA: trade name), Baytubes (manufactured by Bayer: trade name), GRAPHISTRENGTH (manufactured by Arkema: trade name), MWNT7 (manufactured by Hodogaya Chemical Co., Ltd.: trade name), and Hyperion CNT (Hypeprion Preferred are the TC series such as TC-2010, TC-2020, TC-3210L, and TC-1210LN, and the VGCF (registered trademark) series such as VGCF, VGCF-H, and VGCF-X.

[0035] The carbon nanotubes may be used singly or in combination of two or more. The carbon nanotubes may be surface-treated. Furthermore, carbon black and carbon nanotubes may be used in combination.

[0036] Examples of graphene nanoplatelets include xGnP (registered trademark: manufactured by XG Sciences) such as xGnP C-grade (750), xGnP Dispersion, xGnP R-grade, xGnP graphene nanoplatelets-grade C-500, xGnP graphene nanoplatelets-grade C-300, and xGnP M-5, as well as graphene nanoplatelets manufactured by Cheap Tubes and graphene nanoplatelets manufactured by Strem. xGnP graphene nanoplatelets-grade C-500, xGnP graphene nanoplatelets-grade C-300, xGnP M-5, and graphene nanoplatelets manufactured by Strem are preferred.

[0037] The conductive carbon material is preferably at least one selected from the group consisting of carbon black and carbon nanotubes, and more preferably at least one selected from the group consisting of Ketjenblack, Ketjenblack EC, and carbon nanotubes.

[0038] The conductive carbon material preferably has at least one substituent selected from the group consisting of a hydroxyl group, a carboxyl group, a carbonyl group, a formyl group, a sulfonic acid group, an oxysulfonic acid group, a carboxylic anhydride structure, a chromene structure, a lactone structure, an ester structure, and an ether structure, more preferably has at least one substituent selected from the group consisting of a hydroxyl group, a carboxyl group, a formyl group, a carboxylic anhydride structure, a lactone structure, an ester structure, and an ether structure, and even more preferably has at least one substituent selected from the group consisting of a hydroxyl group, a lactone structure, and an ester structure.

[0039] This paper describes the manufacturing methods for conductive carbon materials: carbon black, carbon nanotubes, and graphene nanoplatelets. Carbon black is produced by pyrolysis or incomplete combustion of hydrocarbons such as oil and natural gas. The main methods for producing carbon nanotubes are arc discharge, laser evaporation, and chemical vapor deposition. In the arc discharge method, carbon nanotubes are obtained by generating a direct current arc between two carbon rods in an inert gas or hydrogen gas environment. In the laser evaporation method, carbon nanotubes are obtained by irradiating a carbon source such as graphite with a laser. In the chemical vapor deposition method, carbon nanotubes are obtained by flowing a carbon source gas through an electric furnace and growing the carbon on a catalyst. Graphene nanoplatelets are generally obtained by chemical exfoliation or dry exfoliation using plasma to exfoliate 5-15 atomic layers of graphite.

[0040] <Aromatic compounds having a phenolic hydroxyl group> The mixture that will become the fired body preferably contains an aromatic compound having a phenolic hydroxyl group. Examples of aromatic compounds having a phenolic hydroxyl group include monocyclic or condensed polycyclic aromatic compounds having one or more phenolic hydroxyl groups.

[0041] Among these, monocyclic aromatic compounds having 1 to 6 phenolic hydroxyl groups are exemplified. Examples of phenols which are monocyclic aromatic compounds and have one phenolic hydroxyl group include phenol, ethylphenol, pt-butylphenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, thymol, mesitol, buisocumenol, 2,6-di-t-butyl-p-cresol, pentamethylphenol, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, capicol, o-allylphenol, anol, diethylstilbestrol, p-(methylthio)phenol, phenol, o-aminophenol, m-aminophenol, p-aminophenol, o-(methylamino)phenol, m-(methylamino)phenol, p-(methylamino)phenol, m-(dimethylamino)phenol, o-anilinophenol, m-anilinophenol, p-anilinophenol, 2-amino-p-cresol, 3-amino-o-cresol, 3-amino-p-cresol, 4-amino-o-cresol, 4-amino-p-cresol, 5-amino-o-cresol, 6-amino-m-cresol, 2,4-diaminophenol, and 2,4,6-triaminophenol.

[0042] Phenols are monocyclic aromatic compounds having two phenolic hydroxyl groups, and examples thereof include catechol, resorcinol, hydroquinone, 3,4-toluenediol, 2,5-toluenediol, 3,5-toluenediol, 2,4-toluenediol, urushiol, p-xylene-2,6-diol, m-xylene-4,6-diol, p-xylene-2,5-diol, and 2-isopropyl-5-methylhydroquinone.

[0043] Examples of phenols that are monocyclic aromatic compounds and have three phenolic hydroxyl groups include pyrogallol, 1,2,4-benzenetriol, phloroglucinol, 2-methylphloroglucinol, m-xylene-2,4,6-triol, and 2,4,6-trimethylphloroglucinol. Phenols are monocyclic aromatic compounds having four phenolic hydroxyl groups, and examples thereof include 1,2,3,5-benzenetetraol and 1,2,4,5-benzenetetraol. Phenols are monocyclic aromatic compounds having six phenolic hydroxyl groups, and examples thereof include hexahydroxybenzene.

[0044] As the monocyclic aromatic compound having a phenolic hydroxyl group, a 3-6 phenol having 3 to 6 phenolic hydroxyl groups is more preferred, and as the monocyclic aromatic compound, a phenol having 3 phenolic hydroxyl groups is even more preferred, and phloroglucinol represented by the following formula (I) is particularly preferred.

[0045] [ka]

[0046] Examples of the fused polycyclic aromatic compound include naphthalene, azulene, heptalene, biphenylene, acenaphthylene, fluorene, phenalene, phenanthrene, anthracene, aceanthrylene, triphenylene, pyrene, chrysene, tetracene, perylene, pentacene, picene, and coronene, and naphthalene, anthracene, and triphenylene are preferred.

[0047] Examples of condensed polycyclic aromatic compounds having a phenolic hydroxyl group include 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,4-dihydroxynaphthalene, 2,5-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 1,3,8-trihydroxynaphthalene, 9,10-anthracene, and the like. Examples of the hydroxybenzoates include ellagic acid and 2,3,6,7,10,11-hexahydroxytriphenylene, and preferably 2,6-dihydroxynaphthalene, 1,3,8-trihydroxynaphthalene, 9,10-anthracene, ellagic acid, and 2,3,6,7,10,11-hexahydroxytriphenylene, and more preferably ellagic acid represented by the following formula (II) and 2,3,6,7,10,11-hexahydroxytriphenylene represented by the following formula (III).

[0048] [ka]

[0049] The aromatic compounds having a phenolic hydroxyl group may be used alone or in combination of two or more. The aromatic compound having a phenolic hydroxyl group, whether monocyclic or fused polycyclic, preferably has three or more phenolic hydroxyl groups, and more preferably has 3 to 6 phenolic hydroxyl groups, because this allows the formation of a three-dimensional polymer, as will be described later.

[0050] The amount of each component in the mixture of the nitrogen-containing compound and conductive carbon material, which are the raw materials for the fired body, optionally added with an aromatic compound having a phenolic hydroxyl group, is not particularly limited, but based on 100% by mass of the mixture, the nitrogen-containing compound is preferably 25 to 65% by mass, more preferably 30 to 60% by mass, the conductive carbon material is preferably 25 to 65% by mass, more preferably 30 to 60% by mass, the aromatic compound having a phenolic hydroxyl group is preferably 0 to 40% by mass, more preferably 0 to 30% by mass, and the amounts of each component within the above ranges are preferred from the viewpoint of improving proton conductivity, electronic conductivity, water transport, and gas permeability, and obtaining excellent power generation characteristics.

[0051] <Graphene oxide> The mixture to be fired may optionally contain graphene oxide. Graphene oxide is a carbon material containing oxygen atoms. Graphene oxide is preferably used as an aqueous dispersion. The concentration of graphene oxide in the aqueous dispersion is not particularly limited, but is preferably 0.1 to 10 mass %. The amount of graphene oxide in each component in the mixture is not particularly limited, but is preferably 0 to 30 mass %, more preferably 0 to 20 mass %. The graphene oxide is preferably insulating graphene oxide.

[0052] <Method for manufacturing fired body> The fired body is obtained by firing a mixture of a nitrogen-containing compound component and a conductive carbon material, to which, as the case may be, at least one selected from the group consisting of an aromatic compound having a phenolic hydroxyl group and any graphene oxide is added.

[0053] The calcination temperature may be any temperature at which the nitrogen-containing compound component and any aromatic compound having a phenolic hydroxyl group can be polymerized or carbonized, and is preferably 150 to 1000°C, more preferably 200 to 800°C, and even more preferably 250 to 600°C. Calcination is carried out at the calcination temperature for preferably 1 to 10 hours, more preferably 1 to 5 hours. Calcination can be carried out in air or in an inert gas, and examples of the inert gas include nitrogen and argon.

[0054] It is also possible to mix graphene oxide with at least one selected from a nitrogen-containing compound, an aromatic compound having a phenolic hydroxyl group, and a conductive carbon material in advance and then calcinate the mixture. For example, dispersing the nitrogen-containing compound or the aromatic compound having a phenolic hydroxyl group in an aqueous graphene oxide dispersion and then stirring the dispersion or disintegrating it using a homogenizer or the like is believed to produce a mixture in which the nitrogen-containing compound or the aromatic compound having a phenolic hydroxyl group is intercalated between the graphene oxide layers. This is believed to prevent the nitrogen-containing compound or the aromatic compound having a phenolic hydroxyl group intercalated between the layers from being directly vaporized, which is preferable because it allows for efficient calcination.

[0055] Before being placed in a firing furnace and fired, the conductive carbon material, the nitrogen-containing compound-based component, any aromatic compound having a phenolic hydroxyl group, and graphene oxide may be mixed together.

[0056] <Structure of fired body> The nitrogen-containing compound component of the raw material and the aromatic compound having a phenolic hydroxyl group of the preferred raw material may be contained in the fired body in the form of the core structure of the raw material. Alternatively, at least a portion of the raw material nitrogen-containing compound component and the preferred raw material aromatic compound having a phenolic hydroxyl group may be contained in the fired body as their respective three-dimensional polymers. The raw material nitrogen-containing compound component and the preferred raw material aromatic compound having a phenolic hydroxyl group may undergo a thermal condensation reaction and a thermal polymerization reaction upon firing to form a three-dimensional polymer of the aromatic compound having a phenolic hydroxyl group, and a three-dimensional polymer of the nitrogen-containing compound constituting the raw material nitrogen-containing compound component, respectively. When the thermal condensation reaction and thermal polymerization reaction occur in three dimensions, the raw material aromatic compound having a phenolic hydroxyl group has three or more phenolic hydroxyl groups, and the nitrogen-containing compound constituting the raw material nitrogen-containing compound component has three or more functional groups.

[0057] When phloroglucinol represented by the following formula (I) is used as a raw material, the three-dimensional polymer of an aromatic compound having a phenolic hydroxyl group is, for example, represented by the following formula (a). [ka]

[0058] A three-dimensional polymer of a nitrogen-containing compound is produced, for example, by calcining melamine (i) as a raw material, while eliminating ammonia, via ammonia-eliminating condensation products such as melam represented by the following formula (ii), melem represented by the following formula (iii), a compound represented by the following formula (iv) or formula (v), and melon represented by the following formula (vi), formula (vii) or formula (viii). [ka] Three-dimensional polymers of nitrogen-containing compounds include structures in which many of the structures (i) to (viii) are linked together, such as those represented by the following formula (ix): By proceeding with the polymerization reaction, a layered structure of g-CN, which is graphite-like carbon nitride represented by the following formula (x), is formed. [ka]

[0059] The structure of graphite carbon nitride can be found in the following non-patent literature: (Non-patent Document A) Industrial Chemistry Journal, 1963, Vol. 66, No. 6, pp. 804-809 (Non-Patent Document B) Chem.Eur.J. 2007, Vol. 13, pp. 4969-4980

[0060] Whether the raw material nitrogen-containing compound components and the preferred raw material aromatic compound having a phenolic hydroxyl group are contained in the fired body in the original core structure or as a three-dimensional polymer is thought to depend on firing conditions such as the firing temperature and time, and the structures of the raw material nitrogen-containing compound components and the preferred raw material aromatic compound having a phenolic hydroxyl group.

[0061] Regarding the structure of the fired body, for example, when phloroglucinol, melanin, and Ketjen black are used as raw materials, it is considered that the three-dimensional polymer of formula (a) and the three-dimensional polymer of formula (ix) described above are mutually entangled on the surface and in the gaps of the Ketjen black.

[0062] <Uses of fired body> The sintered body can be used for the electrolyte, catalyst support, and solid electrolyte membrane in the catalyst layer of a polymer electrolyte fuel cell, thereby improving the power generation characteristics of the fuel cell. Furthermore, the sintered body can be used in the catalyst layer as a material for an electrode catalyst for water electrolysis, etc., thereby improving the power generation characteristics of the fuel cell and the voltage balance performance of water electrolysis. Examples of its use in fuel cells are described below.

[0063] <<Polymer electrolyte fuel cell>> FIG. 1 is a cross-sectional view showing a schematic configuration of a polymer electrolyte fuel cell (hereinafter also referred to as a "fuel cell"). A polymer electrolyte fuel cell 100 has an anode catalyst layer 103, a cathode catalyst layer 105, and a solid electrolyte membrane 107 sandwiched between the two catalyst layers, and each catalyst layer has a gas diffusion layer (hereinafter abbreviated as "GDL") 101 on the outside. This configuration is called a membrane electrode assembly (hereinafter abbreviated as "MEA"). In a fuel cell, the MEA is usually sandwiched between separators 109.

[0064] At least one of the anode catalyst layer 103 and the cathode catalyst layer 105 contains the fired body. Furthermore, the solid electrolyte membrane 107 may also contain the fired body. From the viewpoint of suppressing an increase in overvoltage during high current driving, it is preferable to use the fired body in at least the cathode catalyst layer 105.

[0065] The fired body has proton conductivity, electron conductivity, water transportability, and gas permeability, and also has the function of supporting a catalyst due to its structure, and can therefore be used as a catalyst support, an electrolyte, or both in a catalyst layer of a fuel cell, or as an electrolyte in a solid electrolyte membrane. The main functions of the sintered body are thought to be, in addition to the electronic conductivity and specific surface area already possessed by the carbon material that is the base of the sintered body, the proton transfer effect of the phenolic hydroxyl groups imparted by the aromatic compound having phenolic hydroxyl groups after sintering, the suppression of aggregation of the carbon material after sintering and the resulting improvement in the dispersion stability of the catalyst ink, the improvement in the solid catalyst supporting capacity, the water transport function through water adsorption and desorption, the proton transfer effect of the triazine skeleton or melon skeleton possessed by the three-dimensional polymer of the nitrogen-containing compound, the effect of adsorbing reactive gases to the surface of the base carbon material, and the improvement in the solid catalyst supporting capacity; and further, the pores in the carbon material itself are thought to have a gas diffusion function.

[0066] The anode catalyst layer 103 and the cathode catalyst layer 105 are obtained by preparing a catalyst ink from a composition containing at least one selected from the group consisting of the fired bodies and a metal catalyst, and then applying the catalyst ink to a target substrate and drying it. That is, the anode catalyst layer 103 and the cathode catalyst layer 105 have a composition containing a metal catalyst and at least one selected from the group consisting of the fired bodies.

[0067] The sintered body is preferably a type of electrolyte and a type of catalyst support. By using the sintered body as both an electrolyte and a catalyst support, the catalyst support, which has not previously had proton conductivity, is given proton conductivity, which is expected to improve the electrical properties of fuel cells.

[0068] A catalyst supported on a catalyst carrier is called an electrode catalyst. In this specification, the anode catalyst layer 103 and the cathode catalyst layer 105 may be abbreviated to catalyst layers.

[0069] The metal catalyst contained in the catalyst ink can be any known metal catalyst without any particular limitations. The main function of the metal catalyst used in such anode catalyst layer 103 and cathode catalyst layer 105 is to cause an electrochemical reaction. Examples of metal catalysts include platinum, alloys of platinum with other metals, platinum-containing catalysts such as core-shell catalysts with platinum as the shell, and other metal catalysts. These may be used alone or in combination of two or more. Among these, platinum-containing catalysts are preferred in terms of catalytic activity.

[0070] In alloys of platinum with other metals, the metals constituting the alloy with platinum are not particularly limited as long as they are other than platinum, and examples thereof include boron, magnesium, aluminum, silicon, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, indium, tin, antimony, barium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, gold, lead, bismuth, lanthanum, cerium, etc. These may be used alone or in combination of two or more.

[0071] In the core-shell type having a platinum shell, the core is made of a metal other than platinum, and the shell is platinum. The metal used for the core is not particularly limited as long as it is other than platinum, and examples thereof include nickel, copper, palladium, silver, gold, iridium, titanium, iron, cobalt, ruthenium, osmium, chromium, molybdenum, and tungsten. These may be used alone or in combination of two or more.

[0072] As the catalyst, a platinum-containing catalyst is preferably used, but is not limited thereto, and other metal catalysts can also be used, such as noble metals such as gold, silver, ruthenium, rhodium, palladium, osmium, and iridium, base metals such as iron, nickel, manganese, cobalt, chromium, copper, zinc, molybdenum, tungsten, germanium, and tin, alloys of these noble and base metals, or compounds such as metal oxides and metal complexes. These may be used alone or in combination of two or more.

[0073] The composition used as the catalyst ink may contain, in addition to the metal catalyst and the calcined body, a catalyst carrier other than the calcined body, an electrolyte other than the calcined body, a binder, and a solvent. These components other than the solvent, like the metal catalyst and the calcined body, are contained in at least one of the anode catalyst layer 103 and the cathode catalyst layer 105.

[0074] Examples of catalyst supports other than the calcined body that may be contained in the composition used as a catalyst ink include carbon black such as channel black, furnace black, and thermal black; activated carbon obtained by carbonizing and activating various carbon-containing materials; coke; natural graphite; artificial graphite; and graphitized carbon. Of these, carbon black is preferred as a catalyst support other than the calcined body because of its high specific surface area and excellent electronic conductivity. The primary function of a catalyst support is to conduct electrons. Another primary function of a catalyst support is the transport of gas and water through the pores in the catalyst support.

[0075] In order to suppress a decrease in the electronic conductivity of the electrode catalyst, a binder that binds the catalyst supports together can be used in the catalyst layer. Examples of binders include fluorine-based sulfonic acid polymers such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), Nafion (registered trademark, manufactured by DuPont), Aquivion (registered trademark, manufactured by Solvay), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), and Aciplex (registered trademark, manufactured by Asahi Kasei Corporation).

[0076] Examples of electrolytes other than the calcined body that may be contained in the composition used as a catalyst ink include fluorine-based sulfonic acid polymers, hydrocarbon-based sulfonic acid polymers, and partially fluorinated hydrocarbon-based sulfonic acid polymers, such as Nafion (registered trademark, manufactured by DuPont), Aquivion (registered trademark, manufactured by Solvay), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), and Aciplex (registered trademark, manufactured by Asahi Kasei Corporation). Preferred electrolytes other than the calcined body are perfluoroacid polymers such as Nafion (registered trademark, manufactured by DuPont), Aquivion (registered trademark, manufactured by Solvay), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), and Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), with Nafion (registered trademark, manufactured by DuPont) being more preferred. The calcined body may be used alone as the electrolyte, or the calcined body may be used in combination with one of the above-mentioned electrolytes. The main function of the electrolyte in the catalyst layer is to conduct protons, but from the viewpoint that fuel gas permeability and water transport are also required at the same time, the electrolyte in the composition used as the catalyst ink preferably contains, in addition to the sintered body, a perfluoroacid polymer such as Nafion, from the viewpoint of voltage characteristics in the high current region. The catalyst layer containing the sintered body can be made of any of the materials used for the solid electrolyte membrane, namely, a fluorine-based sulfonic acid polymer, a hydrocarbon-based sulfonic acid polymer, and a partially fluorinated hydrocarbon-based sulfonic acid polymer, and it is preferable to use a fluorine-based sulfonic acid polymer or a partially fluorinated hydrocarbon-based sulfonic acid polymer.

[0077] Examples of solvents used in compositions used as catalyst inks include water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, pentanol, dimethyl sulfoxide, and N,N-dimethylformamide. Preferred examples of the solvent include water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and isobutyl alcohol. Two or more of the above-mentioned solvents can also be mixed and used. From the viewpoints of preventing re-aggregation of the ink, facilitating application, and further preventing residual solvent in the catalyst layer, water, ethanol, 1-propanol, and 2-propanol are more preferred as solvents used in catalyst inks.

[0078] The content of each component in the catalyst ink is adjusted appropriately depending on the purpose, but in the catalyst ink, based on 100% by mass of the solids excluding the mass of the solvent, the metal catalyst is preferably 14 to 44% by mass, more preferably 20 to 34% by mass, the sintered body is preferably 1 to 25% by mass, more preferably 5 to 20% by mass, other electrolytes are preferably 20 to 45% by mass, more preferably 25 to 40% by mass, other catalyst supports are preferably 20 to 55% by mass, more preferably 25 to 45% by mass, and binders are preferably 0 to 5% by mass, more preferably 0 to 3% by mass. The solvent used in the catalyst ink is preferably 70 to 99 mass %, more preferably 80 to 96 mass %, per 100 mass % of the catalyst ink.

[0079] By adjusting the composition of the catalyst ink, it is possible to improve functions and performance such as suppressing the decline in electronic conductivity, improving proton conductivity, improving gas diffusivity, making water transport more efficient, and improving the mechanical strength of the catalyst layer.

[0080] The method for producing catalyst layer 103 and catalyst layer 105 will be described below. After preparing the catalyst ink, the catalyst ink is applied to a target substrate and dried to produce a catalyst layer. Examples of the target substrate include a solid electrolyte membrane, GDL, and a sheet made of fluororesin, and the catalyst layer can be produced by a known production method. When the catalyst ink is applied to a sheet made of fluororesin, the applied catalyst layer is transferred to the solid electrolyte. A typical fluororesin sheet is a sheet made of polytetrafluoroethylene (PTFE).

[0081] Examples of catalyst ink compositions include a catalyst ink composition in which the metal catalyst is platinum, the catalyst support is carbon black, and the electrolyte is the calcined body and Nafion (registered trademark, manufactured by DuPont Co.), and a catalyst ink composition in which the metal catalyst is platinum, the catalyst support is carbon black, and the electrolyte is the calcined body. Further examples include a catalyst ink composition in which the catalyst is platinum, the catalyst support is carbon black and the calcined body, or the calcined body alone, and the electrolyte is the calcined body. In this way, catalyst ink in which at least a portion of the catalyst support is the calcined body is produced by subjecting catalyst ink containing the calcined body and a metal catalyst to a crushing treatment, thereby obtaining a catalyst ink containing a calcined body supporting a metal catalyst. Addition of the calcined body suppresses aggregation of solid components such as the catalyst, catalyst support, and calcined body in the catalyst ink, improving the coatability of the catalyst ink.

[0082] Examples of the crushing treatment include dry crushing treatment and wet crushing treatment. Examples of dry crushing treatment include a ball mill, a planetary mill, a pin mill, and a jet mill. Examples of wet crushing treatment include an ultrasonic homogenizer, an ultrasonic disperser, a bead mill, a sand grinder, a homogenizer, and a wet jet mill. Among these, preferred crushing treatments are a ball mill, a bead mill, an ultrasonic homogenizer, an ultrasonic disperser, and a homogenizer, with a bead mill, an ultrasonic homogenizer, and an ultrasonic disperser being particularly preferred. There are no particular limitations on the solvent used in the wet crushing treatment, and the solvent used in the catalyst ink can be used.

[0083] The fired body is used in preparing the catalyst ink to produce a membrane electrode assembly (MEA), which is then incorporated into a single cell, thereby obtaining power generation characteristics.

[0084] The proportion of the amount of the calcined body used in the catalyst layer is calculated using the following formula. In the calculation, the mass of the electrode catalyst, calcined body, electrolyte, and binder is the solid mass minus the water and solvent. In the calculation, the electrolyte and electrode catalyst do not include the calcined body of the present invention.

[0085] Sintered body ratio (mass%) = [calcined body (mass) / [total mass in catalyst layer (mass of solids)]] × 100 (mass%) = [calcined body (mass) / [electrode catalyst (mass) + electrolyte other than calcined body (mass) + binder (mass) + calcined body (mass)]] x 100 (mass%) The proportion of the fired body is preferably 1 to 25 mass %, more preferably 5 to 20 mass %.

[0086] The mass ratio of the calcined body to the electrolyte other than the calcined body in the catalyst layer (calcined body:electrolyte other than the calcined body) is preferably 1:1 to 1:10, more preferably 10:12 to 1:5.

[0087] Examples of materials for the solid electrolyte membrane 107 include the sintered body, fluorine-based sulfonic acid polymers such as Nafion (registered trademark, manufactured by DuPont), Aquivion (registered trademark, manufactured by Solvay), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), and Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), hydrocarbon-based sulfonic acid polymers, and partially fluorinated hydrocarbon-based sulfonic acid polymers.

[0088] The thickness of the solid electrolyte membrane 107 is preferably 10 to 100 μm, more preferably 20 to 60 μm, from the viewpoints of conductivity, durability, and gas cross-leakage.

[0089] The gas diffusion layer 101 is not particularly limited, but a conductive porous material is preferably used. Examples of such materials include carbonaceous paper and nonwoven fabric, felt, and nonwoven fabric. Furthermore, some GDLs are coated with a layer called a microporous layer (hereinafter abbreviated as "MPL"), which is a coating layer primarily composed of a water-repellent resin and a carbon material. It has been reported that this effectively transports water during power generation in fuel cells. A gas diffusion layer having this MPL can also be used as the catalyst layer containing the fired body. In the power generation tests of the present invention, water-repellent carbon paper, which is a GDL having this MPL, was used. [Example]

[0090] Synthesis examples and test examples of the present invention will be described in more detail below, but the present invention is not limited to these. The conductivity of the conductive carbon material in this specification was determined by analyzing the resistance value of the compacted powder under a load of 2 kN using a powder resistivity measurement system (MCP-PD51, manufactured by Mitsubishi Chemical Analytech Co., Ltd.) to determine the conductivity (S / cm).

[0091] [Synthesis Example 1: Production of fired body (1)] Carbon black (0.33 g of carbon black manufactured by Asahi Carbon Co., Ltd. (electric conductivity 15 S / cm at 2 kN)), melamine (0.33 g of melamine manufactured by Nissan Chemical Industries, Ltd.), and phloroglucinol (0.33 g of phloroglucinol manufactured by Tokyo Chemical Industry Co., Ltd.) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (manufactured by Yamada Electric Co., Ltd.), and fired at a firing temperature of 400°C for 2 hours, raising the temperature at a rate of 10°C per minute. After firing, a black fired product (0.80 g, 61% recovery when the charged mass is taken as 100%) was obtained.

[0092] [Synthesis Example 2: Production of fired body (2)] Carbon black (0.50 g of carbon black manufactured by Asahi Carbon Co., Ltd. (the same as in Synthesis Example 1)) and melamine (0.50 g of melamine manufactured by Nissan Chemical Industries, Ltd.) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR, and the temperature was increased at a rate of 10°C per minute, followed by firing at a firing temperature of 400°C for 2 hours. After firing, a black fired product (0.73 g, 73% recovery when the charged mass was taken as 100%) was obtained.

[0093] [Synthesis Example 3: Production of fired body (3)] Carbon black (0.68 g of carbon black manufactured by Asahi Carbon Co., Ltd. (conductivity 50 S / cm at 2 kN)), melamine (0.34 g of melamine manufactured by Nissan Chemical Industries, Ltd.), and phloroglucinol (0.34 g of phloroglucinol manufactured by Tokyo Chemical Industry Co., Ltd.) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (manufactured by Yamada Electric Co., Ltd.), and fired at a firing temperature of 400°C for 2 hours, increasing the temperature at a rate of 10°C per minute. After firing, a black fired product (0.96 g, 70% recovery when the charged mass is taken as 100%) was obtained.

[0094] [Synthesis Example 4: Production of fired body (4)] Ketjen Black EC (Lion Corporation, EC300J, 1.00 g), melamine (Nissan Chemical Industries, 0.50 g), and phloroglucinol (Tokyo Chemical Industry Co., Ltd., 0.50 g) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (Yamada Electric Co., Ltd.), heated at a rate of 10°C per minute, and fired at 400°C for 2 hours. After firing, a black fired product (1.32 g, 66% recovery when the charged mass is taken as 100%) was obtained.

[0095] [Synthesis Example 5: Production of fired body (5)] Ketjen Black EC (Lion Corporation, EC300J, 0.50 g) and Optobeads 500SL (Nissan Chemical Industries, Ltd., 0.50 g) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (Yamada Electric Co., Ltd.), heated at a rate of 10°C per minute, and fired at 480°C for 2 hours. After firing, a black fired product (0.62 g, 62% recovery when the charged mass is taken as 100%) was obtained.

[0096] [Synthesis Example 6: Production of fired body (6)] Carbon black (0.33 g of carbon black manufactured by Asahi Carbon Co., Ltd. (the same as in Synthesis Example 1)), melamine (0.30 g of melamine manufactured by Nissan Chemical Industries, Ltd.), and guanidine carbonate (0.50 g of guanidine carbonate manufactured by Tokyo Chemical Industry Co., Ltd.) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (manufactured by Yamada Electric Co., Ltd.), and fired at a firing temperature of 480°C for 2 hours, raising the temperature at a rate of 10°C per minute. After firing, a black fired product (0.28 g, 25% recovery when the charged mass was taken as 100%) was obtained.

[0097] [Synthesis Example 7: Production of fired body (7)] Carbon black (0.45 g of carbon black manufactured by Asahi Carbon Co., Ltd. (the same as in Synthesis Example 1)), melamine (0.60 g of melamine manufactured by Nissan Chemical Industries, Ltd.), and ellagic acid (0.30 g of ellagic acid manufactured by Tokyo Chemical Industry Co., Ltd.) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (manufactured by Yamada Electric Co., Ltd.), and fired at a firing temperature of 480°C for 2 hours, with the temperature rising at a rate of 10°C per minute. After firing, a black fired product (0.57 g, 42% recovery when the charged mass was taken as 100%) was obtained.

[0098] [Synthesis Example 8: Production of fired body (8)] Carbon black (Asahi Carbon Co., Ltd. carbon black (same as in Synthesis Example 2), 0.58 g) and Optobeads 500SL (Nissan Chemical Co., Ltd., 0.58 g) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (Yamada Electric Co., Ltd.), and the temperature was increased at a rate of 10°C per minute, followed by firing at a firing temperature of 400°C for 2 hours. After firing, a black fired product (0.88 g, 76% recovery when the charged mass was taken as 100%) was obtained.

[0099] [Synthesis Example 9: Production of fired body (9)] Carbon black (Asahi Carbon Co., Ltd. carbon black (same as in Synthesis Example 2), 0.83 g) and Optobeads 2000M (Nissan Chemical Co., Ltd., 0.83 g) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (Yamada Electric Co., Ltd.), and the temperature was increased at a rate of 10°C per minute, followed by firing at a firing temperature of 400°C for 2 hours. After firing, a black fired product (1.26 g, 76% recovery when the charged mass was taken as 100%) was obtained.

[0100] [Synthesis Example 10: Production of fired body (10)] Carbon nanotubes (1.22 g of VGCF-X manufactured by Showa Denko), melamine (0.61 g of Nissan Chemical Industries, Ltd.), and phloroglucinol (0.61 g of Tokyo Chemical Industry Co., Ltd.) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (manufactured by Yamada Electric Co., Ltd.), and fired at 400°C for 2 hours, heating at a rate of 10°C per minute. After firing, a black fired product (1.60 g, 65% recovery when the charged mass is taken as 100%) was obtained.

[0101] [Synthesis Example 11: Production of fired body (11)] Graphene nanoplatelets (Ström, 0.75 g), melamine (Nissan Chemical Industries, 0.38 g), and phloroglucinol (Tokyo Chemical Industry, 0.38 g) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop rapid heating electric furnace MSFT-1520-P-TR (Yamada Electric Co., Ltd.), heated at a rate of 10°C per minute, and fired at 400°C for 2 hours. After firing, a black fired product (0.89 g, 59% recovery when the charged mass is taken as 100%) was obtained.

[0102] [Synthesis Example 12: Production of fired body (12)] Carbon black (1.15 g of carbon black manufactured by Asahi Carbon Co., Ltd. (the same as in Synthesis Example 2)) and melamine cyanurate (1.15 g of melamine cyanurate manufactured by Nissan Chemical Industries, Ltd.) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (manufactured by Yamada Electric Co., Ltd.), and the temperature was increased at a rate of 10°C per minute, followed by firing at a firing temperature of 400°C for 2 hours. After firing, a black fired product (1.23 g, 53% recovery when the charged mass was taken as 100%) was obtained.

[0103] [Synthesis Example 13: Production of fired body (13)] Water (60.0 g) and melamine (Nissan Chemical, 1.40 g) were added to a 1.0% by mass graphene oxide aqueous dispersion (EMD Millipore, 60.0 g), and the mixture was uniformly dispersed by ultrasonic irradiation for 5 minutes to prepare a dispersion. 2-Propanol (Junsei Chemical, 480 mL) was added to a stirring vessel, and the resulting dispersion was poured into the stirring vessel while stirring. The resulting brown precipitate was collected by filtration, washed three times with 2-propanol, and then dried under reduced pressure to obtain a dark brown powder (0.93 g, 46% recovery when the charged mass is taken as 100%) as graphene oxide-melanin composition (13a). Carbon black (Asahi Carbon Co., Ltd., carbon black (same as in Synthesis Example 3), 400 mg), graphene oxide-melanin composition (13a) (200 mg), and phloroglucinol (Tokyo Chemical Industry Co., Ltd., 200 mg) were mixed in a mortar and placed in an alumina crucible. The crucible was placed in a tabletop high-speed heating electric furnace MSFT-1520-P-TR (Yamada Electric Co., Ltd.), and fired at a firing temperature of 400°C for 2 hours, with the temperature rising at a rate of 10°C per minute. After firing, a black fired product (540 mg, 68% recovery when the charged mass was taken as 100%) was obtained.

[0104] In the following test examples, power generation tests were carried out in the following manner. <Fuel cell power generation test A> The fabricated MEA was placed in a 1cm 2 After incorporating it into a single cell (JARI standard cell, manufactured by FC Development Co., Ltd.) with an electrode area of ​​1000mV, a power generation test of the fuel cell was carried out. Evaluation was carried out using a fuel cell evaluation system (AutoPEM, manufactured by Toyo Corporation) at a temperature of 80°C, a relative humidity of 95%, and a hydrogen gas flow of 1 L / min and an air gas flow of 2 L / min, and the current density and voltage were measured.

[0105] [Test Example 1 (Power Generation Test Using Sintered Body (1)] The catalyst ink was prepared using a platinum-supported carbon electrode catalyst (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., platinum content: 46.5 mass%, product name "TEC10E50E"), the fired body (1), a Nafion dispersion solution (manufactured by Wako Pure Chemical Industries, Ltd., product name "5% Nafion Dispersion Solution DE520 CS type"), and 2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.). The electrode catalyst, fired body, Nafion dispersion solution, and 2-propanol were added to a glass vial in this order, and the dispersion solution was subjected to ultrasonic irradiation for 30 minutes using an AS ONE Corporation ultrasonic cleaner ASU-6 with the oscillation power set to high, to prepare the catalyst ink. The conditions for preparing the catalyst ink are described below.

[0106] Catalyst ink preparation conditions: Nafion ratio (mass%) = [Nafion solid content (mass) / [electrode catalyst (mass) + Nafion solid content (mass) + calcined body (mass)]] x 100 (mass%) was set to 29 mass %.

[0107] Sintered body ratio (mass%) = [calcined body (mass) / electrode catalyst (mass) + Nafion solid content (mass) + calcined body (mass)] × 100 (mass%) The concentration was adjusted to 16% by mass. Specifically, when the mass of the electrode catalyst was 27.5 mg, the catalyst ink was prepared using a Nafion dispersion solution (294.8 mg), the calcined body (1) (8.0 mg), and 2-propanol (1 mL). The Nafion dispersion solution (294.8 mg) corresponds to a Nafion solid content (14.7 mg).

[0108] Catalyst ink application conditions (decal creation): The catalyst ink was applied using a Teflon (registered trademark) sheet target with an area of ​​8 cm x 8 cm and a thickness of 130 μm and an applicator, and the entire amount of the prepared catalyst ink was used to apply the ink to a surface of 1 cm. 2 A decal was created with a catalyst layer of 0.2 mg of platinum per Teflon sheet. The decal sheet was cut into decals measuring 1 cm x 1 cm. The platinum weights of the anode and cathode were confirmed to be 0.2 mg based on the mass difference between the decal and the decal after transfer. Ink application was excellent.

[0109] Steps for preparing an MEA: The membrane electrode assembly (MEA) was fabricated using a solid electrolyte membrane, a gas diffusion layer (GDL), and a decal using catalyst ink. The GDL was made of carbon paper with MPL (product name "28BC" manufactured by SGL Carbon Japan Co., Ltd.). A 5cm x 5cm square Nafion 211 membrane (registered trademark, manufactured by DuPont, film thickness: 25µm) was placed in the center as a solid electrolyte membrane, and decals (area 1cm x 1cm) with catalyst layers on Teflon sheets were placed on both sides of the solid electrolyte membrane. The resulting mixture was then thermocompressed at a platen temperature of 132°C, a load of 0.6kN, and a compression time of 120 seconds. The Teflon sheets were then peeled off to produce a catalyst-coated membrane (CCM). The platinum weights of the anode and cathode were determined by the mass difference between the decal and the decal after transfer. The GDL was made of carbon paper (manufactured by SGL Carbon Japan Co., Ltd., product name "28BC", area 1cm x 1cm) and was stacked on both the anode and cathode sides with the MPL layer side facing the electrolyte membrane.The JARI standard cell was then tightened with a torque wrench in 1Nm increments up to 4Nm to press the GDL and CCM together. Using the fabricated MEA, fuel cell power generation test A was carried out. The results of open circuit voltage, voltage, and current density are shown in Table 1. Open circuit voltage (hereinafter also referred to as OCV) is the voltage when no voltage or current is applied to a single cell.

[0110] [Test Example 2] An MEA was prepared in the same manner as in Test Example 1, except that in Test Example 2, sintered body (2) (8.0 mg) was used to prepare the catalyst ink instead of sintered body (1). The ink application properties were good. A fuel cell power generation test A was performed using the prepared MEA. The results of the OCV, voltage, and current density are shown in Table 1.

[0111] [Comparative Example 1] In Comparative Example 1, an MEA was prepared in the same manner as in Test Example 1, except that instead of the fired body (1), carbon black (8.0 mg of carbon black manufactured by Asahi Carbon Co., Ltd. (the same as in Synthesis Example 1)) was used to prepare the catalyst ink. Although the ink could be applied, the transferability of the decal tended to be poor. Using the prepared MEA, a fuel cell power generation test A was carried out. The results of the OCV, voltage, and current density are shown in Table 1.

[0112] [Table 1]

[0113] From the comparison of the above Test Examples 1 and 2 with Comparative Example 1, it was found that the sintered body of the present invention has good power generation characteristics. In Comparative Example 1, the current density was 1.0 (A / cm 2 ), a voltage drop was observed. However, in the power generation test of the present invention, 2 ), the voltage could be maintained at 0.2 V or higher. This is thought to be because the use of the fired body of the present invention in the catalyst layer improves drainage of the generated water and improves the diffusion of oxygen (air) in the fuel, and it can be said that the water transport and gas permeability of the catalyst layer are improved.

[0114] [Test Examples 3, 4 and 5] MEAs were prepared in the same manner as in Test Example 1, except that instead of the sintered body (1), 8.0 mg of the sintered body (10) in Test Example 3, 8.0 mg of the sintered body (11) in Test Example 4, and 8.0 mg of the sintered body (13) in Test Example 5 were used to prepare the catalyst ink. The ink application properties were good. A fuel cell power generation test A was performed using the prepared MEAs. The results of the OCV, voltage, and current density are shown in Table 2.

[0115] [Table 2]

[0116] The results of Test Examples 3 to 5 above all showed good power generation characteristics. In the power generation tests of Test Examples 3 to 5, the current density was 2.5 (A / cm 2 ), the voltage was able to be maintained at 0.2 V or higher. It was found that improved power generation characteristics were also observed in sintered bodies using carbon nanotubes and graphene nanoplatelets as conductive carbon materials. It was also found that improved power generation characteristics were observed in sintered bodies obtained by blending the optional components phloroglucinol and graphene oxide. [Industrial Applicability]

[0117] The sintered body of the present invention is useful, for example, as an electrolyte material for fuel cells (e.g., an electrolyte used in a catalyst layer, a catalyst support, and an electrolyte for a solid electrolyte membrane), and is expected to improve the power generation characteristics and durability of fuel cells. [Explanation of symbols]

[0118] 100 fuel cell 101 Gas diffusion layer 103 Anode catalyst layer 105 Cathode catalyst layer 107 Solid electrolyte membrane 109 Separator

Claims

1. A fired body of a mixture containing a nitrogen-containing compound component, a conductive carbon material, and an aromatic compound having a phenolic hydroxyl group, The fired body, wherein the nitrogen-containing compound component is at least one selected from the group consisting of guanidine carbonate, melamine, melamine cyanurate, a complex of crosslinked melamine resin and silica, and melamine, melam, and a salt of melem with polyphosphoric acid.

2. 2. The fired body according to claim 1, wherein the conductive carbon material is at least one selected from the group consisting of carbon black, carbon nanotubes, and graphene nanoplatelets.

3. 3. The fired body according to claim 1, wherein the aromatic compound having a phenolic hydroxyl group is an aromatic compound having 3 to 6 phenolic hydroxyl groups.

4. A sintered body described in any one of claims 1 to 3, which contains a three-dimensional polymer of the nitrogen-containing compound.

5. A sintered body described in any one of claims 1 to 4, which contains a three-dimensional polymer of an aromatic compound having a phenolic hydroxyl group.

6. 6. The fired body according to claim 1, which is at least one of an electrolyte in a catalyst layer of a polymer electrolyte fuel cell, a catalyst support in a catalyst layer, and an electrolyte in a solid electrolyte membrane.

7. A composition comprising the fired body according to any one of claims 1 to 6 and a metal catalyst.

8. The composition according to claim 7, which is used for a catalyst layer of a polymer electrolyte fuel cell.

9. A catalyst layer for a polymer electrolyte fuel cell, comprising the composition according to claim 8.

10. A membrane / electrode assembly comprising a solid electrolyte membrane, a gas diffusion layer, and the catalyst layer for a polymer electrolyte fuel cell according to claim 9.

11. A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 10.

Images