WO2019142695A1 - Oxygen reduction catalyst - Google Patents

Oxygen reduction catalyst Download PDF

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Publication number
WO2019142695A1
WO2019142695A1 PCT/JP2019/000193 JP2019000193W WO2019142695A1 WO 2019142695 A1 WO2019142695 A1 WO 2019142695A1 JP 2019000193 W JP2019000193 W JP 2019000193W WO 2019142695 A1 WO2019142695 A1 WO 2019142695A1
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oxygen reduction
reduction catalyst
content
titanium
catalyst
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PCT/JP2019/000193
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French (fr)
Japanese (ja)
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建燦 李
海林 汪
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昭和電工株式会社
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Priority to JP2019531180A priority Critical patent/JP6659916B2/en
Publication of WO2019142695A1 publication Critical patent/WO2019142695A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
    • B01J27/04—Sulfides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to an oxygen reduction catalyst comprising titanium oxide.
  • Titanium oxide has high catalytic properties and is used as a photocatalyst or an organic matter decomposition catalyst. However, there has been no report on a titanium oxide catalyst which is stable under strong acidity and has a high oxygen reducing ability.
  • Patent Document 1 discloses a sulfur-containing titanium oxide powder used for a dispersion in which a photocatalyst is dispersed. Although the visible light absorption characteristics of the sulfur-containing titanium oxide powder are described, the oxygen reduction characteristics have not been studied, and there is no suggestion to use them as an oxygen reduction catalyst.
  • Patent Document 2 discloses an oxygen reduction catalyst having titanium, carbon, nitrogen and oxygen as constituent elements and satisfying a specific elemental composition and a specific relational expression for a peak intensity ratio determined in an XRD spectrum. It is described that it may contain anatase type crystal structure and may contain elemental sulfur. It is described that the oxygen reduction catalyst contains a large amount of cubic crystal structure, so that the durability confirmed from the time-dependent change of the cell voltage in the constant current load measurement test is high.
  • Non-Patent Document 1 discloses partially oxidized titanium carbonitride having improved oxygen reduction activity by nitrogen doping, but the oxygen reduction onset potential does not reach 0.8 V, and further nitrogen element is added.
  • the contained titanium oxide catalyst is unstable to the strongly acidic condition at the time of fuel cell operation and is easily eluted and the durability is inferior.
  • anatase-type titanium dioxide treated with the same nitrogen element is also described, their oxygen reduction onset potential is as low as about 0.4 V.
  • Non-Patent Document 2 describes that an electrolyte membrane doped with sulfurized titanium oxide is used as an electrolyte membrane of a polymer electrolyte fuel cell. It is described that the fuel cell characteristics are high even at low relative humidity due to the increase in proton conductivity of the electrolyte membrane, but there is no description or suggestion that a sulfurized titanium oxide is used as a catalyst instead of a platinum catalyst.
  • the above prior art does not disclose an oxygen reduction catalyst having an anatase type titanium dioxide crystal structure and an improved oxygen reduction property by containing a specific amount of sulfur atoms.
  • the present invention has the following configuration.
  • a fuel cell electrode catalyst comprising the oxygen reduction catalyst according to item 1 above.
  • An electrode for a fuel cell having a catalyst layer containing the electrode catalyst for a fuel cell according to the preceding item 2.
  • a membrane electrode assembly comprising a cathode, an anode, and a polymer electrolyte membrane disposed between the cathode and the anode, wherein the cathode is the electrode for a fuel cell according to the above 3 Membrane electrode assembly.
  • a fuel cell comprising the membrane electrode assembly according to the above 4.
  • the oxygen reduction catalyst of the present invention has a high oxygen reduction ability.
  • a fuel cell catalyst of a cathode electrode when it is used as a fuel cell catalyst of a cathode electrode, a fuel cell having high power generation characteristics can be obtained.
  • FIG. 1 It is a X-ray-diffraction spectrum of the oxidation-reduction catalyst (1) produced in Example 1.
  • FIG. Among the diffraction peaks the peak of the strongest diffraction intensity among peaks corresponding to the anatase type titanium dioxide crystal is indicated by A.
  • 7 is an X-ray diffraction spectrum of the redox catalyst (3) produced in Example 3.
  • the peak of the strongest diffraction intensity of the peaks corresponding to the anatase titanium dioxide crystal is indicated by A
  • the peak of the strongest diffraction intensity of the peaks corresponding to the rutile titanium dioxide crystal is indicated by R.
  • . 7 is an X-ray diffraction spectrum of the redox catalyst (4) produced in Example 4.
  • FIG. Among the diffraction peaks the peak of the strongest diffraction intensity among peaks corresponding to the anatase type titanium dioxide crystal is indicated by A. 7 is an X-ray diffraction spectrum of the redox catalyst (5) produced in Example 5.
  • the peak of the strongest diffraction intensity of the peaks corresponding to the anatase titanium dioxide crystal is indicated by A
  • the peak of the strongest diffraction intensity of the peaks corresponding to the rutile titanium dioxide crystal is indicated by R.
  • FIG. Among the diffraction peaks the peak of the strongest diffraction intensity among the peaks corresponding to rutile titanium dioxide crystals is indicated by R. It is a X-ray-diffraction spectrum of the oxidation-reduction catalyst (c2) produced by the comparative example 2.
  • FIG. 7 is an X-ray diffraction spectrum of the redox catalyst (c3) produced in Comparative Example 3.
  • FIG. Among the diffraction peaks the peak of the strongest diffraction intensity of the peaks corresponding to the anatase titanium dioxide crystal is indicated by A, and the peak of the strongest diffraction intensity of the peaks corresponding to the rutile titanium dioxide crystal is indicated by R. .
  • FIG. 7 is an X-ray diffraction spectrum of the redox catalyst (c3) produced in Comparative Example 3.
  • FIG. 7 is an X-ray diffraction spectrum of the redox catalyst (c4) produced in Comparative Example 4.
  • FIG. Among the diffraction peaks the peak of the strongest diffraction intensity of the peaks corresponding to the anatase titanium dioxide crystal is indicated by A, and the peak of the strongest diffraction intensity of the peaks corresponding to the rutile titanium dioxide crystal is indicated by R. .
  • the peak of the strongest diffraction intensity among peaks corresponding to the anatase type titanium dioxide crystal is indicated by A.
  • the oxygen reduction catalyst of the present invention In the oxygen reduction catalyst of the present invention, the content of anatase type titanium dioxide in the titanium dioxide crystal confirmed in X-ray diffraction measurement is more than 50.0%, and the sulfur atom content is 0.1 to 3.0% by mass It is a titanium compound which is In other words, the oxygen reduction catalyst of the present invention can be said to be an oxygen reduction catalyst consisting of a specific titanium compound. However, this does not strictly exclude the presence of impurities in the oxygen reduction catalyst of the present invention, and unavoidable impurities resulting from the raw material and / or the production process and the like, and other impurities within a range not deteriorating the characteristics of the catalyst. Is included in the oxygen reduction catalyst of the present invention.
  • the oxygen reduction catalyst of the present invention is mainly composed of titanium oxide, but may contain other transition metal element oxygen-containing compounds.
  • the transition metal element include Group 4 elements, Group 5 elements, Group 6 elements, and iron group elements in the periodic table.
  • the iron group elements include elemental species of iron, cobalt and nickel.
  • group 4 elements other than titanium include zirconium and hafnium.
  • the crystal structure of titanium oxide among the titanium compounds may be the crystal structure of anatase (Anatase) titanium dioxide, the crystal structure of rutile (Rutile) titanium dioxide, brookite (Brookite)
  • the crystal structure of type titanium dioxide can be mentioned.
  • these crystal structures can be distinguished by the presence and appearance patterns of peaks characteristic of the respective crystal structures.
  • a peak of the strongest diffraction intensity tends to appear at a position of 2 ⁇ of 25 ° to 26 °.
  • the peak of the strongest diffraction intensity appears at the position of 27 ° to 28 °, but the pattern does not appear at the position of 30 ° to 31 ° of 2 ⁇ .
  • a peak of the strongest diffraction intensity appears at a position of 25 ° to 26 °, and a peak also tends to appear at a position of 30 ° to 31 ° of 2 ⁇ . Therefore, the distinction between the crystal structure of brookite type titanium dioxide and the crystal structure of anatase type titanium dioxide can be determined by the presence or absence of a peak at a position of 30 ° to 31 ° in 2 ⁇ .
  • titanium compound the case where the crystal structure of the cubic crystal represented by titanium nitride is contained in an oxygen reduction catalyst is also considered. In this case, peaks tend to appear at positions of 37 ° to 38 ° and 43 ° to 44 °, respectively.
  • titanium disulfide (TiS 2 ) is used as one of the raw materials, it is also conceivable that titanium sulfide is contained in the obtained oxygen reduction catalyst. In this case, the peak of the strongest diffraction intensity tends to appear at the position of 2 ⁇ of 34 ° to 35 °.
  • the oxygen reduction catalyst of the present invention has an anatase type titanium dioxide content (hereinafter sometimes referred to as “anatase content”) in titanium dioxide crystals confirmed in X-ray diffraction (XRD) measurement from 50.0%. Many are included.
  • the anatase content is a value determined from XRD measurement, as described later.
  • the anatase content is preferably 60% or more, more preferably 95% or more. When the anatase content is in the above range, the stability under strong acidity is high.
  • the content of rutile type titanium dioxide in the titanium dioxide crystal confirmed in the X-ray diffraction measurement of the oxygen reduction catalyst is preferably less than 50.0%, and more preferably 40.0% or less. When the content of rutile titanium dioxide is within the above range, the stability under strong acidity is high.
  • the content of the titanium compound having a cubic crystal structure contained in the oxygen reduction catalyst of the present invention determined in the same manner as the determination of the content of the anatase type titanium dioxide described above (hereinafter referred to as "cubic content" Some of them are preferably less than 30%, and more preferably 20% or less, in the titanium compound crystals confirmed in the X-ray diffraction measurement of the oxygen reduction catalyst of the present invention.
  • the content of the cubic titanium compound is in the above range, the stability under strong acidity is high.
  • the obtained oxygen reduction catalyst contains the sulfur-containing titanium compound of the raw material.
  • the content of the sulfur-containing titanium compound (hereinafter sometimes referred to as "sulfur-containing titanium compound content") of the raw material contained in the obtained oxygen reduction catalyst is the same as the method for determining the anatase-type titanium dioxide content described above Desired.
  • the titanium compound crystals confirmed in the X-ray diffraction measurement of the oxygen reduction catalyst of the present invention it is preferably less than 10%, preferably 5% or less, and more preferably 1% or less.
  • the sulfur atom content of the oxygen reduction catalyst of the present invention is in the range of 0.1 to 3.0% by mass.
  • the lower limit of the sulfur atom content is preferably 0.4% by mass, more preferably 0.5% by mass.
  • the upper limit of the sulfur atom content is preferably 2.0% by mass, more preferably 1.5% by mass.
  • the state in which the sulfur atom content is larger than the above upper limit value includes the state in which the sulfur atom is not doped in titanium oxide, and such a sulfur atom does not contribute to the oxygen reduction property.
  • the above-described oxygen reduction catalyst of the present invention is not particularly limited in use, but can be suitably used as an electrode catalyst for a fuel cell, an electrode catalyst for an air cell, and the like.
  • One of the preferred embodiments of the present invention is a fuel cell electrode having a catalyst layer containing the above-described oxygen reduction catalyst of the present invention.
  • the fuel cell electrode includes a fuel cell electrode catalyst comprising the oxygen reduction catalyst of the present invention.
  • the catalyst layer constituting the fuel cell electrode includes an anode catalyst layer and a cathode catalyst layer, but the oxygen reduction catalyst of the present invention can be used for any of them. Since the oxygen reduction catalyst of the present invention has high oxygen reduction ability, it is preferably used in the cathode catalyst layer.
  • the catalyst layer preferably further comprises a polyelectrolyte.
  • the polymer electrolyte is not particularly limited as long as it is generally used in a fuel cell catalyst layer.
  • a perfluorocarbon polymer having a sulfo group for example, Nafion (NAFION (registered trademark)
  • NAFION registered trademark
  • hydrocarbon-based polymer compound having a sulfo group a polymer compound doped with an inorganic acid such as phosphoric acid
  • the organic / inorganic hybrid polymer partially substituted with a proton conductive functional group, a proton conductor obtained by impregnating a polymer matrix with a phosphoric acid solution or a sulfuric acid solution, etc.
  • the catalyst layer may further include electron conductive particles made of carbon, conductive polymer, conductive ceramics, metal or conductive inorganic oxide such as tungsten oxide or iridium oxide, as necessary. Good.
  • the fuel cell electrode may further have a porous support layer in addition to the catalyst layer.
  • the porous support layer is a layer that diffuses a gas (hereinafter also referred to as a "gas diffusion layer").
  • gas diffusion layer Any gas diffusion layer may be used as long as it has electron conductivity, high gas diffusivity, and high corrosion resistance, but generally it is a carbon-based porous material such as carbon paper or carbon cloth. Materials are used.
  • the membrane electrode assembly of the present invention is a membrane electrode assembly having a cathode, an anode, and a polymer electrolyte membrane disposed between the cathode and the anode, and at least one of the cathode and the anode.
  • One of the electrodes is the fuel cell electrode of the present invention described above.
  • a conventionally known fuel cell electrode for example, a fuel cell electrode containing a platinum-based catalyst such as platinum-supported carbon.
  • a platinum-based catalyst such as platinum-supported carbon.
  • the membrane electrode assembly of the present invention when the fuel cell electrode of the present invention has a gas diffusion layer, in the membrane electrode assembly of the present invention, this gas diffusion layer is disposed on the opposite side of the catalyst layer as viewed from the polymer electrolyte membrane.
  • the polymer electrolyte membrane for example, an electrolyte membrane or a hydrocarbon-based electrolyte membrane using a perfluorosulfonic acid type is generally used, but a membrane or a porous membrane in which a polymer microporous membrane is impregnated with a liquid electrolyte A membrane filled with a polymer electrolyte may be used.
  • the membrane / electrode assembly of the present invention can be appropriately formed using a conventionally known method.
  • the fuel cell of the present invention comprises the above-mentioned membrane electrode assembly.
  • the fuel cell of the present invention further includes two current collectors in a state in which the membrane electrode assembly is sandwiched.
  • the current collector can be a conventionally known one generally employed for fuel cells.
  • the method for producing the oxygen reduction catalyst of the present invention is not particularly limited as long as the oxygen reduction catalyst within the range of the above constitution can be obtained.
  • a method of mixing a titanium oxide powder obtained by using a sol-gel method and a sulfur-containing substance and baking it in an atmosphere containing oxygen gas (Production method 1) or a sulfur-containing titanium compound in an atmosphere containing oxygen gas is mentioned. These two methods are described in detail below.
  • Production method 1 comprises a precursor preparation step of preparing a titanium oxide powder as a titanium oxide precursor using a sol-gel method, a mixing step of mixing the titanium oxide precursor and the sulfur-containing material, and the mixing And a firing step of firing the mixture obtained in the step under an atmosphere containing oxygen gas.
  • a sol-gel method is used to produce a titanium oxide powder as a titanium oxide precursor.
  • Known methods can be used as the sol-gel method. That is, it can be obtained by hydrolyzing titanium-containing compounds such as alkoxides of titanium, organic acid salts, nitrates and chlorides.
  • the specific titanium-containing compound is not particularly limited, but titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, titanium tetrabutoxide, titanium tetraisobutoxide, titanium tetrapentoxide, Titanium tetraacetylacetonate, titanium oxydiacetylacetonate, tris (acetylacetonato) nitrinium chloride ([Ti (acac) 3 ] 2 [TiC 1 6 ]), titanium tetrachloride, titanium trichloride, titanium oxychloride, four Examples thereof include titanium compounds such as titanium bromide, titanium tribromide, titanium oxybromide, titanium tetraiodide, titanium triiodide, titanium oxyiodide and the like.
  • the method of hydrolysis is not particularly limited, but, for example, the titanium-containing compound is dissolved in an organic solvent such as ethanol to form a titanium-containing compound solution, water is added to the titanium-containing compound solution to hydrolyze, It is possible to precipitate a substance sol. The solvent is removed from the solution in which the titanium oxide sol has been deposited, followed by washing with water and drying to obtain a titanium oxide powder as a titanium oxide precursor.
  • an organic solvent such as ethanol
  • the titanium oxide precursor prepared in the precursor preparation step and the sulfur-containing material are mixed.
  • the sulfur-containing substance is not particularly limited, but from the viewpoint of easiness of mixing with the titanium oxide precursor, reactivity and catalytic activity, elemental sulfur or a solid or liquid compound is preferable.
  • the sulfur containing material which does not contain metal elements other than titanium is preferable.
  • sulfur-containing substance examples include sulfur, carbon sulfide, sulfur chloride, sulfides, thioureas, thioamides, thioalcohols, thioaldehydes, thiazils, mercaptals, thiols, thiocyans and the like.
  • thiourea sulfoacetic acid, thiophenol, thiophene, benzothiophene, dibenzothiophene, thiobenzophenone, bithiophene, phenothiazine, sulfolane, thiazine, thiazole, thiadiazole, thiazoline, thiazolidine, thianthrene, thiane, thioacetanilide, thioacetamide , Thiobenzamide, thioanisole, thionine, dimethyl sulfide, methylphenyl sulfide, diallyl sulfide, thiocyanate, sulfuric acid, sulfonic acid, sulfonamide, sulfinic acid, sulfoxide, sulfin, sulfane, and titanium salts thereof as appropriate.
  • the sulfur-containing substance is solid, for example, the titanium oxide precursor and the sulfur-containing substance can be mixed by a dry mixing method or a wet mixing method.
  • the dry mixing method is more preferable from the viewpoint of cost reduction of the mixing process and simplification of the process.
  • mixing can be performed using a ball mill, roll rolling mill, bead mill, medium stirring mill, air flow grinder, mortar or automatic kneading mortar, and from the viewpoint of mixing uniformity and cost, ball mill, bead mill, automatic kneading A mortar is preferred, and a ball mill or an automatic kneading mortar is more preferred.
  • the mixing time in these cases is, for example, 1 to 10 hours.
  • sulfur or thiourea is preferable, and thiourea is more preferable.
  • the sulfur content is a liquid, the titanium oxide precursor can be dispersed and mixed in the sulfur content.
  • the sulfur content can be dissolved in a solvent to form a solution, a sulfur content solution may be used.
  • a solvent for dissolving the sulfur-containing substance although depending on the kind of the sulfur-containing substance, water, ethanol, ethylene glycol and the like can be mentioned.
  • the above sulfur-containing substances may be used alone or in combination of two or more.
  • the solvent is removed by heating appropriately to obtain a mixture in which the titanium oxide precursor and the sulfur-containing solution are mixed.
  • the proportions of the titanium oxide precursor and the sulfur-containing substance to be mixed are preferably mixed in such a proportion that the molar ratio of titanium atoms to sulfur atoms contained in the mixture is in the range of 1: 3 to 1: 9.
  • the firing atmosphere of the mixture is preferably an oxygen gas-containing atmosphere, and more preferably a mixed gas atmosphere of nitrogen gas and / or argon gas and oxygen gas.
  • the oxygen gas content of the oxygen gas-containing atmosphere is preferably 10% by volume or more and 30% by volume or less.
  • the firing can be performed in an air atmosphere.
  • the firing temperature and time are preferably 400 to 800 ° C., more preferably 500 to 700 ° C., preferably 1 to 5 hours, and more preferably 2 to 4 hours. The temperature and time of calcination are adjusted to one another.
  • the sulfur atom of the oxygen reduction catalyst obtained is contained in a necessary and sufficient amount, and the anatase content is preferably more than 50.0%.
  • Production method 2 comprises the step of firing the sulfur-containing titanium compound in an oxygen gas-containing atmosphere.
  • sulfur-containing titanium compounds used as raw materials include titanium disulfide, titanium monosulfide, titanium sulfate, titanium sulfite and the like. It is preferable to use titanium disulfide from the ease of handling.
  • the oxygen gas-containing atmosphere is more preferably a nitrogen gas and / or a mixed gas atmosphere of argon gas and oxygen gas.
  • the oxygen gas content of the oxygen gas-containing atmosphere is preferably 0.1 to 10.0% by volume, more preferably 0.1 to 1.0% by volume, and still more preferably 0.1 to 0.5% by volume.
  • the firing temperature is preferably in the range of higher than 500 ° C.
  • the baking time is preferably 1 to 5 hours, and more preferably 2 to 4 hours.
  • the firing time and temperature are adjusted to one another.
  • titanium disulfide when heated under the conditions of the above-mentioned range, for example, when titanium disulfide is used, titanium disulfide is completely decomposed, and a necessary and sufficient amount of sulfur atoms of the obtained oxygen reduction catalyst is contained, and the anatase content is 50 More than 0% is preferable.
  • Example 1 (1) Preparation of oxygen reduction catalyst Preparation of the oxygen reduction catalyst was performed by the above-mentioned manufacturing method 1. Details are described below. (Precursor preparation process) After adding 26 mL of titanium (IV) isopropoxide (manufactured by Junsei Chemical Co., Ltd.) to 250 mL of dehydrated ethanol (manufactured by Wako Pure Chemical Industries) and slowly adding 25 mL of ultrapure water while stirring, the titanium oxide sol is stirred for 2 hours It was precipitated.
  • titanium (IV) isopropoxide manufactured by Junsei Chemical Co., Ltd.
  • dehydrated ethanol manufactured by Wako Pure Chemical Industries
  • titanium oxide precursor (1) a titanium oxide precursor
  • Mating process 7.0 g of the titanium oxide precursor (1) obtained in the precursor preparation step and 27.4 g of thiourea (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed using a mortar to obtain a mixture.
  • the mixing ratio is 4 mol of sulfur atom to 1 mol of titanium atom.
  • the mixture obtained in the mixing step is placed in a quartz tube furnace, heated to 500 ° C. at a heating rate of 10 ° C./min under an air atmosphere (gas flow rate of 300 mL / min), and calcined at 500 ° C. for 3 hours Thus, 10 g of an oxygen reduction catalyst (1) was obtained.
  • a fuel cell electrode (hereinafter referred to as "catalyst electrode") provided with a catalyst layer containing an oxygen reduction catalyst was produced as follows.
  • the electrochemical evaluation of the oxygen reduction activity catalytic ability of the oxygen reduction catalyst (1) was performed as follows.
  • the catalyst electrode prepared in the above "catalyst electrode preparation” is polarized at a potential scanning speed of 5 mV / sec in an aqueous solution of sulfuric acid at 30 ° C. and 0.5 mol / dm 3 in each of an oxygen gas atmosphere and a nitrogen gas atmosphere. -The potential curve was measured.
  • a natural potential (open circuit potential) in a non-polarized state in an oxygen gas atmosphere was obtained.
  • a reversible hydrogen electrode in a sulfuric acid aqueous solution of the same concentration was used as a reference electrode.
  • an electrode potential at 10 ⁇ A (hereinafter also referred to as electrode potential) was obtained from the difference between the reduction current curve in the oxygen gas atmosphere and the reduction current curve in the nitrogen gas atmosphere.
  • the oxygen reduction catalytic ability of the oxygen reduction catalyst (1) was evaluated using the electrode potential and the natural potential.
  • the natural potential obtained as an index of the oxygen reduction activity is shown in Table 1.
  • the height (Hs) of the peak of the strongest diffraction intensity among the peaks corresponding to the sulfur-containing titanium compound is determined, and the anatase in the oxygen reduction catalyst produced by the following formula
  • the content of type titanium dioxide (anatase content) and the like were respectively determined.
  • Example 2 (Preparation of oxygen reduction catalyst) An oxygen reduction catalyst (2) was obtained in the same manner as in Example 1 except that the firing temperature was changed to 600 ° C. (Electrochemical measurement, XRD measurement, sulfur atom content) The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG. In the XRD spectrum of the oxygen reduction catalyst (2), only anatase type titanium dioxide was observed, and it was confirmed that the anatase content is 100%. The rutile content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
  • Example 3 (Preparation of oxygen reduction catalyst) An oxygen reduction catalyst (3) was obtained in the same manner as in Example 1 except that the firing temperature was changed to 700 ° C. (Electrochemical measurement, XRD measurement, sulfur atom content) The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG. In the XRD spectrum of the oxygen reduction catalyst (3), only anatase type titanium dioxide and rutile type titanium dioxide were observed, and it was confirmed that the anatase content is 66.5%. The rutile content was determined to be 33.5%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
  • Example 4 (Preparation of oxygen reduction catalyst) The amount of thiourea was set to 61.7 g with respect to 7.0 g of the titanium oxide precursor (1) to be mixed in the mixing step of the preparation of the oxygen reduction catalyst, and the mixing ratio was changed to 9 mol of sulfur atoms to 1 mol of titanium atoms.
  • An oxygen reduction catalyst (4) was obtained in the same manner as in Example 1 except for the above.
  • (Electrochemical measurement, XRD measurement, sulfur atom content) The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively.
  • the obtained X-ray diffraction (XRD) spectrum is shown in FIG.
  • Comparative Example 1 (Preparation of oxygen reduction catalyst) An oxygen reduction catalyst (c1) was obtained in the same manner as in Example 1 except that the firing temperature was changed to 900 ° C. (Electrochemical measurement, XRD measurement, sulfur atom content) The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG. In the XRD spectrum of the oxygen reduction catalyst (c1), only rutile titanium dioxide was observed, and it was confirmed that the rutile content is 100%. The anatase content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
  • Example 5 (Preparation of oxygen reduction catalyst) Preparation of the oxygen reduction catalyst was performed by the above-mentioned production method 2. Details are described below. Weigh 0.3 g of titanium disulfide powder (product of Alfa Aesar, purity 99.8% by mass based on titanium, 200 mesh item), put in a quartz inner case, and use a rotary calciner (made by Motoyama) In a mixed gas flow of nitrogen gas (gas flow rate 100 mL / min) and oxygen gas (gas flow rate 0.5 mL / min), the temperature is raised to 700 ° C. at a heating rate of 10 ° C./min and calcined at 700 ° C. for 3 hours , 0.2 g of an oxygen reduction catalyst (5) was obtained.
  • Comparative example 2 (Preparation of oxygen reduction catalyst) Example except that the calcination temperature for preparation of the oxygen reduction catalyst in Example 5 was 500 ° C., and the mixed gas stream was changed to nitrogen gas (gas flow rate 100 mL / min) and oxygen gas (gas flow rate 1.0 mL / min) In the same manner as in 5, an oxygen reduction catalyst (c2) was obtained.
  • (Electrochemical measurement, XRD measurement, sulfur atom content) The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG.
  • Comparative example 3 (Preparation of oxygen reduction catalyst) An oxygen reduction catalyst (c3) was obtained in the same manner as in Example 5, except that the calcination temperature for producing the oxygen reduction catalyst in Example 5 was changed to 600 ° C. (Electrochemical measurement, XRD measurement, sulfur atom content) The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG. In the XRD spectrum of the oxygen reduction catalyst (c3), only anatase titanium dioxide and rutile titanium dioxide were observed, and it was confirmed that the anatase content is 55.1%. The rutile content was determined to be 44.9%. The sulfur-containing titanium compound content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
  • Comparative example 4 (Preparation of oxygen reduction catalyst) An oxygen reduction catalyst (c4) was obtained in the same manner as in Example 5, except that the calcination temperature for preparation of the oxygen reduction catalyst in Example 5 was changed to 800 ° C. (Electrochemical measurement, XRD measurement, sulfur atom content) The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG. In the XRD spectrum of the oxygen reduction catalyst (c4), only anatase titanium dioxide and rutile titanium dioxide were observed, and it was confirmed that the anatase content is 7.9%. The rutile content was determined to be 92.1%. The sulfur-containing titanium compound content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
  • Comparative example 5 (Preparation of oxygen reduction catalyst) Anatase type titanium dioxide powder (model number: F-6, manufactured by Showa Denko) was used as it was as an oxygen reduction catalyst (c5) without heat treatment. (Electrochemical measurement, XRD measurement, sulfur atom content) The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG. In the XRD spectrum of the oxygen reduction catalyst (c5), only anatase type titanium dioxide was observed, and it was confirmed that the anatase content is 100%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
  • the oxygen reduction catalyst having an anatase content of more than 50.0% and a sulfur atom content of 0.1 to 3.0% by mass has a high natural potential.
  • the oxygen reduction catalyst of the present invention is high in acid resistance because of the large content of anatase type titanium dioxide, and is high in natural potential in a non-polarized state in an oxygen gas atmosphere. It can be suitably used for battery electrodes.

Abstract

Provided is an oxygen reduction catalyst having high oxygen reduction ability. This oxygen reduction catalyst is a titanium compound characterized in that the contained amount of sulfur atoms is 0.1-3.0 mass% and the contained amount of anatase-type titanium dioxide is more than 50.0% in titanium dioxide crystals as determined in an X-ray diffraction measurement.

Description

酸素還元触媒Oxygen reduction catalyst
　本発明は、チタン酸化物を含む酸素還元触媒に関する。 The present invention relates to an oxygen reduction catalyst comprising titanium oxide.
　チタン酸化物は、高い触媒特性を有し、光触媒や有機物分解触媒として用いられている。しかしながら、強酸性下において安定であるとともに酸素還元能の高いチタン酸化物触媒の報告はない。 Titanium oxide has high catalytic properties and is used as a photocatalyst or an organic matter decomposition catalyst. However, there has been no report on a titanium oxide catalyst which is stable under strong acidity and has a high oxygen reducing ability.
　特許文献１においては、光触媒が分散された分散体に用いられる硫黄含有酸化チタン粉末が開示されている。硫黄含有酸化チタン粉末の可視光吸収特性について記載されているが、酸素還元特性の検討はなされておらず酸素還元触媒として用いる示唆はない。 Patent Document 1 discloses a sulfur-containing titanium oxide powder used for a dispersion in which a photocatalyst is dispersed. Although the visible light absorption characteristics of the sulfur-containing titanium oxide powder are described, the oxygen reduction characteristics have not been studied, and there is no suggestion to use them as an oxygen reduction catalyst.
　また、特許文献２においては、チタン、炭素、窒素および酸素を構成元素として有し、特定の元素組成と、ＸＲＤスペクトルにおいて求められるピーク強度比について特定の関係式とを満たす酸素還元触媒が開示されており、アナターゼ型の結晶構造を含む場合があることと、硫黄元素を含む場合があることが記載されている。この酸素還元触媒は割合として立方晶構造を多く含むことにより、定電流負荷測定試験におけるセル電圧の経時変化から確認される耐久性が高いことが記載されている。
　非特許文献１においては、窒素ドープすることにより酸素還元活性を改善した部分酸化されたチタン炭窒化物が開示されているが、その酸素還元開始電位は０．８Ｖに及ばず、さらに窒素元素を含有したチタン酸化物触媒は燃料電池運転時の強酸性条件に対して不安定であり溶出が起きやすく耐久性が劣ると考えられる。同じ窒素元素含有処理を施したアナターゼ型二酸化チタンも記載されているが、これらの酸素還元開始電位は０．４Ｖ程度とさらに低い。 Further, Patent Document 2 discloses an oxygen reduction catalyst having titanium, carbon, nitrogen and oxygen as constituent elements and satisfying a specific elemental composition and a specific relational expression for a peak intensity ratio determined in an XRD spectrum. It is described that it may contain anatase type crystal structure and may contain elemental sulfur. It is described that the oxygen reduction catalyst contains a large amount of cubic crystal structure, so that the durability confirmed from the time-dependent change of the cell voltage in the constant current load measurement test is high.
Non-Patent Document 1 discloses partially oxidized titanium carbonitride having improved oxygen reduction activity by nitrogen doping, but the oxygen reduction onset potential does not reach 0.8 V, and further nitrogen element is added. It is considered that the contained titanium oxide catalyst is unstable to the strongly acidic condition at the time of fuel cell operation and is easily eluted and the durability is inferior. Although anatase-type titanium dioxide treated with the same nitrogen element is also described, their oxygen reduction onset potential is as low as about 0.4 V.
　非特許文献２においては、高分子電解質型燃料電池の電解質膜として、硫化した酸化チタンをドープした電解質膜を用いることが記載されている。電解質膜のプロトン伝導性が高くなることにより低い相対湿度においても燃料電池特性が高いことが記載されているが、白金触媒に替えて硫化した酸化チタンを触媒として用いる記載や示唆はない。 Non-Patent Document 2 describes that an electrolyte membrane doped with sulfurized titanium oxide is used as an electrolyte membrane of a polymer electrolyte fuel cell. It is described that the fuel cell characteristics are high even at low relative humidity due to the increase in proton conductivity of the electrolyte membrane, but there is no description or suggestion that a sulfurized titanium oxide is used as a catalyst instead of a platinum catalyst.
特開２００６－００１７７４号公報JP, 2006-001774, A 特開２０１３－２４０７８５号公報JP, 2013-240785, A
　上記の従来の技術においては、アナターゼ型二酸化チタンの結晶構造を有するとともに、硫黄原子を特定量含有することにより酸素還元特性を向上させた酸素還元触媒は開示されていない。 The above prior art does not disclose an oxygen reduction catalyst having an anatase type titanium dioxide crystal structure and an improved oxygen reduction property by containing a specific amount of sulfur atoms.
　本発明は以下に示す構成を備える。 The present invention has the following configuration.
［１］Ｘ線回折測定において確認される二酸化チタン結晶中のアナターゼ型二酸化チタンの含有量が５０．０％より多く、硫黄原子含有量が０．１～３．０質量％であることを特徴とするチタン化合物である酸素還元触媒。
［２］前項１に記載の酸素還元触媒からなる燃料電池用電極触媒。
［３］前項２に記載の燃料電池用電極触媒を含む触媒層を有する燃料電池用電極。
［４］カソードと、アノードと、当該カソードと当該アノードとの間に配置された高分子電解質膜とを有する膜電極接合体であって、前記カソードが前項３に記載の燃料電池用電極である膜電極接合体。
［５］前項４に記載の膜電極接合体を備える燃料電池。 [1] It is characterized in that the content of anatase type titanium dioxide in the titanium dioxide crystal confirmed in X-ray diffraction measurement is more than 50.0%, and the sulfur atom content is 0.1 to 3.0% by mass An oxygen reduction catalyst that is a titanium compound to be used.
[2] A fuel cell electrode catalyst comprising the oxygen reduction catalyst according to item 1 above.
[3] An electrode for a fuel cell having a catalyst layer containing the electrode catalyst for a fuel cell according to the preceding item 2.
[4] A membrane electrode assembly comprising a cathode, an anode, and a polymer electrolyte membrane disposed between the cathode and the anode, wherein the cathode is the electrode for a fuel cell according to the above 3 Membrane electrode assembly.
[5] A fuel cell comprising the membrane electrode assembly according to the above 4.
　本発明の酸素還元触媒は酸素還元能が高く、例えば、カソード電極の燃料電池触媒として用いたとき、発電特性の高い燃料電池を得ることができる。 The oxygen reduction catalyst of the present invention has a high oxygen reduction ability. For example, when it is used as a fuel cell catalyst of a cathode electrode, a fuel cell having high power generation characteristics can be obtained.
実施例１で作製した酸化還元触媒（１）のＸ線回折スペクトルである。回折ピークのうち、アナターゼ型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＡで示す。It is a X-ray-diffraction spectrum of the oxidation-reduction catalyst (1) produced in Example 1. FIG. Among the diffraction peaks, the peak of the strongest diffraction intensity among peaks corresponding to the anatase type titanium dioxide crystal is indicated by A. 実施例２で作製した酸化還元触媒（２）のＸ線回折スペクトルである。回折ピークのうち、アナターゼ型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＡで示す。It is a X-ray-diffraction spectrum of the oxidation-reduction catalyst (2) produced in Example 2. FIG. Among the diffraction peaks, the peak of the strongest diffraction intensity among peaks corresponding to the anatase type titanium dioxide crystal is indicated by A. 実施例３で作製した酸化還元触媒（３）のＸ線回折スペクトルである。回折ピークのうち、アナターゼ型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＡで示し、ルチル型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＲで示す。7 is an X-ray diffraction spectrum of the redox catalyst (3) produced in Example 3. FIG. Among the diffraction peaks, the peak of the strongest diffraction intensity of the peaks corresponding to the anatase titanium dioxide crystal is indicated by A, and the peak of the strongest diffraction intensity of the peaks corresponding to the rutile titanium dioxide crystal is indicated by R. . 実施例４で作製した酸化還元触媒（４）のＸ線回折スペクトルである。回折ピークのうち、アナターゼ型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＡで示す。7 is an X-ray diffraction spectrum of the redox catalyst (4) produced in Example 4. FIG. Among the diffraction peaks, the peak of the strongest diffraction intensity among peaks corresponding to the anatase type titanium dioxide crystal is indicated by A. 実施例５で作製した酸化還元触媒（５）のＸ線回折スペクトルである。回折ピークのうち、アナターゼ型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＡで示し、ルチル型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＲで示す。7 is an X-ray diffraction spectrum of the redox catalyst (5) produced in Example 5. Among the diffraction peaks, the peak of the strongest diffraction intensity of the peaks corresponding to the anatase titanium dioxide crystal is indicated by A, and the peak of the strongest diffraction intensity of the peaks corresponding to the rutile titanium dioxide crystal is indicated by R. . 比較例１で作製した酸化還元触媒（ｃ１）のＸ線回折スペクトルである。回折ピークのうち、ルチル型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＲで示す。It is a X-ray-diffraction spectrum of the oxidation-reduction catalyst (c1) produced by the comparative example 1. FIG. Among the diffraction peaks, the peak of the strongest diffraction intensity among the peaks corresponding to rutile titanium dioxide crystals is indicated by R. 比較例２で作製した酸化還元触媒（ｃ２）のＸ線回折スペクトルである。回折ピークのうち、アナターゼ型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＡで示し、ルチル型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＲで示す。It is a X-ray-diffraction spectrum of the oxidation-reduction catalyst (c2) produced by the comparative example 2. FIG. Among the diffraction peaks, the peak of the strongest diffraction intensity of the peaks corresponding to the anatase titanium dioxide crystal is indicated by A, and the peak of the strongest diffraction intensity of the peaks corresponding to the rutile titanium dioxide crystal is indicated by R. . 比較例３で作製した酸化還元触媒（ｃ３）のＸ線回折スペクトルである。回折ピークのうち、アナターゼ型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＡで示し、ルチル型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＲで示す。FIG. 7 is an X-ray diffraction spectrum of the redox catalyst (c3) produced in Comparative Example 3. FIG. Among the diffraction peaks, the peak of the strongest diffraction intensity of the peaks corresponding to the anatase titanium dioxide crystal is indicated by A, and the peak of the strongest diffraction intensity of the peaks corresponding to the rutile titanium dioxide crystal is indicated by R. . 比較例４で作製した酸化還元触媒（ｃ４）のＸ線回折スペクトルである。回折ピークのうち、アナターゼ型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＡで示し、ルチル型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＲで示す。FIG. 7 is an X-ray diffraction spectrum of the redox catalyst (c4) produced in Comparative Example 4. FIG. Among the diffraction peaks, the peak of the strongest diffraction intensity of the peaks corresponding to the anatase titanium dioxide crystal is indicated by A, and the peak of the strongest diffraction intensity of the peaks corresponding to the rutile titanium dioxide crystal is indicated by R. . 比較例５で用意した酸素還元触媒（ｃ５）のＸ線回折スペクトルである。回折ピークのうち、アナターゼ型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークをＡで示す。It is an X-ray diffraction spectrum of the oxygen reduction catalyst (c5) prepared in Comparative Example 5. Among the diffraction peaks, the peak of the strongest diffraction intensity among peaks corresponding to the anatase type titanium dioxide crystal is indicated by A.
　以下、本発明の酸素還元触媒について詳細に説明する。 Hereinafter, the oxygen reduction catalyst of the present invention will be described in detail.
（酸素還元触媒）
　本発明の酸素還元触媒は、Ｘ線回折測定において確認される二酸化チタン結晶中のアナターゼ型二酸化チタンの含有量が５０．０％より多く、硫黄原子含有量が０．１～３．０質量％であるチタン化合物である。いいかえると、本発明の酸素還元触媒は、特定のチタン化合物からなる酸素還元触媒ともいえる。ただ、このことは、本発明の酸素還元触媒における不純物の存在を厳密に排除するものでなく、原料及び／または製造過程などに起因する不可避不純物、その他、触媒の特性を劣化させない範囲内の不純物が本発明の酸素還元触媒に含まれることは差し支えない。 (Oxygen reduction catalyst)
In the oxygen reduction catalyst of the present invention, the content of anatase type titanium dioxide in the titanium dioxide crystal confirmed in X-ray diffraction measurement is more than 50.0%, and the sulfur atom content is 0.1 to 3.0% by mass It is a titanium compound which is In other words, the oxygen reduction catalyst of the present invention can be said to be an oxygen reduction catalyst consisting of a specific titanium compound. However, this does not strictly exclude the presence of impurities in the oxygen reduction catalyst of the present invention, and unavoidable impurities resulting from the raw material and / or the production process and the like, and other impurities within a range not deteriorating the characteristics of the catalyst. Is included in the oxygen reduction catalyst of the present invention.
　本発明の酸素還元触媒は、チタン酸化物を主成分とするが、他の遷移金属元素の酸素含有化合物を含んでもよい。遷移金属元素としては、周期表における４族元素、５族元素、６族元素、鉄族元素が挙げられる。鉄族元素は、鉄、コバルトおよびニッケルの元素種を含む。チタン以外の４族元素としては、ジルコニウム、ハフニウムが挙げられる。 The oxygen reduction catalyst of the present invention is mainly composed of titanium oxide, but may contain other transition metal element oxygen-containing compounds. Examples of the transition metal element include Group 4 elements, Group 5 elements, Group 6 elements, and iron group elements in the periodic table. The iron group elements include elemental species of iron, cobalt and nickel. Examples of group 4 elements other than titanium include zirconium and hafnium.
（結晶構造）
　本発明の酸素還元触媒を構成するチタン化合物のうちのチタン酸化物が取り得る結晶構造として、アナターゼ（Ａｎａｔａｓｅ）型二酸化チタンの結晶構造、ルチル（Ｒｕｔｉｌｅ）型二酸化チタンの結晶構造、ブルッカイト（Ｂｒｏｏｋｉｔｅ）型二酸化チタンの結晶構造が挙げられる。Ｘ線回折測定から得られるＸ線回折スペクトルにおいて、これらの結晶構造は、それぞれの結晶構造に特徴的なピークの存在および出現パターンによって判別することができる。
　アナターゼ型二酸化チタンの結晶構造では２θが２５°～２６°の位置に、最も強い回折強度のピークが現れる傾向がある。
　一方、ルチル型二酸化チタンの結晶構造では、２θが２７°～２８°の位置に最も強い回折強度のピークが現れるが、２θが３０°～３１°の位置にはピークが出現しないパターンとなる傾向がある。
　また、ブルッカイト型二酸化チタンの結晶構造では２θが２５°～２６°の位置に最も強い回折強度のピークが現れるとともに、２θが３０°～３１°の位置にもピークが現れる傾向がある。したがって、ブルッカイト型二酸化チタンの結晶構造と、アナターゼ型二酸化チタンの結晶構造との区別は、２θが３０°～３１°の位置におけるピークの有無によって判別することができる。
　また、チタン化合物としては、窒化チタンに代表される立方晶の結晶構造が酸素還元触媒に含まれる場合も考えられる。この場合、２θが３７°～３８°の位置および４３°～４４°の位置にそれぞれピークが現れる傾向にある。
　原料のひとつとして二硫化チタン（ＴｉＳ2）を用いる場合、得られる酸素還元触媒に硫化チタンが含まれる場合も考えられる。この場合、２θが３４°～３５°の位置に最も強い回折強度のピークが現れる傾向にある。 (Crystal structure)
Among the titanium compounds constituting the oxygen reduction catalyst of the present invention, the crystal structure of titanium oxide among the titanium compounds may be the crystal structure of anatase (Anatase) titanium dioxide, the crystal structure of rutile (Rutile) titanium dioxide, brookite (Brookite) The crystal structure of type titanium dioxide can be mentioned. In the X-ray diffraction spectrum obtained from X-ray diffraction measurement, these crystal structures can be distinguished by the presence and appearance patterns of peaks characteristic of the respective crystal structures.
In the crystal structure of anatase type titanium dioxide, a peak of the strongest diffraction intensity tends to appear at a position of 2θ of 25 ° to 26 °.
On the other hand, in the crystal structure of rutile type titanium dioxide, the peak of the strongest diffraction intensity appears at the position of 27 ° to 28 °, but the pattern does not appear at the position of 30 ° to 31 ° of 2θ. There is.
Further, in the crystal structure of brookite type titanium dioxide, a peak of the strongest diffraction intensity appears at a position of 25 ° to 26 °, and a peak also tends to appear at a position of 30 ° to 31 ° of 2θ. Therefore, the distinction between the crystal structure of brookite type titanium dioxide and the crystal structure of anatase type titanium dioxide can be determined by the presence or absence of a peak at a position of 30 ° to 31 ° in 2θ.
Moreover, as a titanium compound, the case where the crystal structure of the cubic crystal represented by titanium nitride is contained in an oxygen reduction catalyst is also considered. In this case, peaks tend to appear at positions of 37 ° to 38 ° and 43 ° to 44 °, respectively.
When titanium disulfide (TiS 2 ) is used as one of the raw materials, it is also conceivable that titanium sulfide is contained in the obtained oxygen reduction catalyst. In this case, the peak of the strongest diffraction intensity tends to appear at the position of 2θ of 34 ° to 35 °.
（アナターゼ型二酸化チタンの含有率）
　本発明の酸素還元触媒は、Ｘ線回折（ＸＲＤ）測定において確認される二酸化チタン結晶中のアナターゼ型二酸化チタンの含有量（以下、「アナターゼ含有率」ということがある）が５０．０％より多く含まれる。このアナターゼ含有率は、後述するとおり、ＸＲＤ測定から求めた値である。アナターゼ含有率は、好ましくは６０％以上であり、より好ましくは９５％以上である。アナターゼ含有率が上記範囲であると、強酸性下における安定性が高い。 (Content of anatase type titanium dioxide)
The oxygen reduction catalyst of the present invention has an anatase type titanium dioxide content (hereinafter sometimes referred to as “anatase content”) in titanium dioxide crystals confirmed in X-ray diffraction (XRD) measurement from 50.0%. Many are included. The anatase content is a value determined from XRD measurement, as described later. The anatase content is preferably 60% or more, more preferably 95% or more. When the anatase content is in the above range, the stability under strong acidity is high.
（ルチル型二酸化チタンの含有率）
　前述のアナターゼ型二酸化チタンの含有率の求め方と同様にして求められる本発明の酸素還元触媒が含むルチル型二酸化チタンの含有量（以下、「ルチル含有率」ということがある）は、本発明の酸素還元触媒のＸ線回折測定において確認される二酸化チタン結晶中のルチル型二酸化チタンの含有量は５０．０％より少ないことが好ましく、４０．０％以下であることがより好ましい。ルチル型二酸化チタンの含有量が上記の範囲内であると、強酸性下における安定性が高い。 (Content of rutile titanium dioxide)
The rutile titanium dioxide content (hereinafter sometimes referred to as "rutile content") contained in the oxygen reduction catalyst of the present invention determined in the same manner as the determination of the anatase type titanium dioxide content described above is the present invention The content of rutile type titanium dioxide in the titanium dioxide crystal confirmed in the X-ray diffraction measurement of the oxygen reduction catalyst is preferably less than 50.0%, and more preferably 40.0% or less. When the content of rutile titanium dioxide is within the above range, the stability under strong acidity is high.
（立方晶の結晶構造を有するチタン化合物の含有量）
　前述のアナターゼ型二酸化チタンの含有率の求め方と同様にして求められる本発明の酸素還元触媒が含む立方晶の結晶構造を有するチタン化合物の含有量（以下、「立方晶含有率」ということがある）は、本発明の酸素還元触媒のＸ線回折測定において確認されるチタン化合物結晶中に、３０％未満であることが好ましく、２０％以下であることがより好ましい。立方晶のチタン化合物の含有量が上記の範囲内であると、強酸性下における安定性が高い。 (Content of titanium compound having cubic crystal structure)
The content of the titanium compound having a cubic crystal structure contained in the oxygen reduction catalyst of the present invention determined in the same manner as the determination of the content of the anatase type titanium dioxide described above (hereinafter referred to as "cubic content" Some of them are preferably less than 30%, and more preferably 20% or less, in the titanium compound crystals confirmed in the X-ray diffraction measurement of the oxygen reduction catalyst of the present invention. When the content of the cubic titanium compound is in the above range, the stability under strong acidity is high.
（硫黄含有チタン化合物の含有量）
　原料のひとつとして二硫化チタン等の硫黄含有チタン化合物を用いる場合、得られる酸素還元触媒に原料の硫黄含有チタン化合物が含まれる場合も考えられる。得られる酸素還元触媒が含む原料の硫黄含有チタン化合物の含有量（以下、「硫黄含有チタン化合物含有率」ということがある）は、前述のアナターゼ型二酸化チタンの含有率の求め方と同様にして求められる。本発明の酸素還元触媒のＸ線回折測定において確認されるチタン化合物結晶中に、１０％未満であることが好ましく、５％以下であることが好ましく、１％以下であることがより好ましい。硫黄含有チタン化合物の含有量が上記の範囲内であると、強酸性下における安定性が高い。 (Content of sulfur-containing titanium compound)
In the case of using a sulfur-containing titanium compound such as titanium disulfide as one of the raw materials, it is also conceivable that the obtained oxygen reduction catalyst contains the sulfur-containing titanium compound of the raw material. The content of the sulfur-containing titanium compound (hereinafter sometimes referred to as "sulfur-containing titanium compound content") of the raw material contained in the obtained oxygen reduction catalyst is the same as the method for determining the anatase-type titanium dioxide content described above Desired. In the titanium compound crystals confirmed in the X-ray diffraction measurement of the oxygen reduction catalyst of the present invention, it is preferably less than 10%, preferably 5% or less, and more preferably 1% or less. When the content of the sulfur-containing titanium compound is in the above range, the stability under strong acidity is high.
（硫黄原子含有量）
　本発明の酸素還元触媒の硫黄原子含有量は、０．１～３．０質量％の範囲である。硫黄原子含有量の下限は、好ましくは０．４質量％であり、より好ましくは０．５質量％である。硫黄原子含有量の上限は、好ましくは２．０質量％であり、より好ましくは１．５質量％である。硫黄原子含有量が上記下限値より少ない状態は、酸化チタンの硫黄ドープが不十分な状態であり、触媒としての活性点の量が十分でない傾向にある。硫黄原子含有量が上記上限値より大きい状態は、硫黄原子が酸化チタンにドープされていない状態のものも含んでおり、そのような硫黄原子は酸素還元特性に寄与しない。 (Sulfur atom content)
The sulfur atom content of the oxygen reduction catalyst of the present invention is in the range of 0.1 to 3.0% by mass. The lower limit of the sulfur atom content is preferably 0.4% by mass, more preferably 0.5% by mass. The upper limit of the sulfur atom content is preferably 2.0% by mass, more preferably 1.5% by mass. When the sulfur atom content is less than the above lower limit, the sulfur doping of titanium oxide is insufficient, and the amount of active sites as a catalyst tends to be insufficient. The state in which the sulfur atom content is larger than the above upper limit value includes the state in which the sulfur atom is not doped in titanium oxide, and such a sulfur atom does not contribute to the oxygen reduction property.
（電極・膜電極接合体・燃料電池）
　上述した本発明の酸素還元触媒は、特に用途に限りがあるわけではないが、燃料電池用電極触媒、空気電池用電極触媒などに好適に用いることができる。 (Electrode, membrane electrode assembly, fuel cell)
The above-described oxygen reduction catalyst of the present invention is not particularly limited in use, but can be suitably used as an electrode catalyst for a fuel cell, an electrode catalyst for an air cell, and the like.
　（燃料電池用電極）
　本発明の好適な態様の１つとして、上述した本発明の酸素還元触媒を含む触媒層を有する燃料電池用電極が挙げられる。この態様では、燃料電池用電極は、本発明の酸素還元触媒からなる燃料電池用電極触媒を含むことになる。
　燃料電池用電極を構成する触媒層には、アノード触媒層、カソード触媒層があるが、本発明の酸素還元触媒はいずれにも用いることができる。本発明の酸素還元触媒は、高い酸素還元能を有するので、カソード触媒層に用いることが好ましい。
　ここで、前記触媒層は、好ましくは高分子電解質をさらに含む。前記高分子電解質としては、燃料電池用触媒層において一般的に用いられているものであれば特に限定されない。具体的には、スルホ基を有するパーフルオロカーボン重合体（例えば、ナフィオン（ＮＡＦＩＯＮ（登録商標））、スルホ基を有する炭化水素系高分子化合物、リン酸などの無機酸をドープさせた高分子化合物、一部がプロトン伝導性の官能基で置換された有機／無機ハイブリッドポリマー、高分子マトリックスにリン酸溶液や硫酸溶液を含浸させたプロトン伝導体などが挙げられる。これらの中でも、ナフィオン（ＮＡＦＩＯＮ（登録商標）が好ましい。前記触媒層を形成する際のナフィオン（ＮＡＦＩＯＮ（登録商標））の供給源としては、５％ナフィオン（ＮＡＦＩＯＮ（登録商標））溶液（ＤＥ５２１、デュポン社）などが挙げられる。
　また、前記触媒層は、必要に応じて、炭素、導電性高分子、導電性セラミックス、金属または酸化タングステンもしくは酸化イリジウム等の導電性無機酸化物などからなる電子伝導性粒子をさらに含んでいてもよい。
　触媒層の形成方法としては、特に制限はなく、公知の方法を適宜採用しうる。
　前記燃料電池用電極は、上記触媒層に加えて、さらに、多孔質支持層を有していてもよい。
　多孔質支持層とは、ガスを拡散する層（以下「ガス拡散層」とも記す。）である。ガス拡散層としては、電子伝導性を有し、ガスの拡散性が高く、耐食性の高いものであれば何であっても構わないが、一般的にはカーボンペーパー、カーボンクロスなどの炭素系多孔質材料が用いられる。 (Electrode for fuel cell)
One of the preferred embodiments of the present invention is a fuel cell electrode having a catalyst layer containing the above-described oxygen reduction catalyst of the present invention. In this aspect, the fuel cell electrode includes a fuel cell electrode catalyst comprising the oxygen reduction catalyst of the present invention.
The catalyst layer constituting the fuel cell electrode includes an anode catalyst layer and a cathode catalyst layer, but the oxygen reduction catalyst of the present invention can be used for any of them. Since the oxygen reduction catalyst of the present invention has high oxygen reduction ability, it is preferably used in the cathode catalyst layer.
Here, the catalyst layer preferably further comprises a polyelectrolyte. The polymer electrolyte is not particularly limited as long as it is generally used in a fuel cell catalyst layer. Specifically, a perfluorocarbon polymer having a sulfo group (for example, Nafion (NAFION (registered trademark)), a hydrocarbon-based polymer compound having a sulfo group, a polymer compound doped with an inorganic acid such as phosphoric acid, The organic / inorganic hybrid polymer partially substituted with a proton conductive functional group, a proton conductor obtained by impregnating a polymer matrix with a phosphoric acid solution or a sulfuric acid solution, etc. Among these, Nafion (NAFION (registered trademark) As a source of Nafion (NAFION (registered trademark)) in forming the catalyst layer, a 5% Nafion (NAFION (registered trademark) solution (DE 521, DuPont) and the like can be mentioned.
In addition, the catalyst layer may further include electron conductive particles made of carbon, conductive polymer, conductive ceramics, metal or conductive inorganic oxide such as tungsten oxide or iridium oxide, as necessary. Good.
There is no restriction | limiting in particular as a formation method of a catalyst layer, A well-known method can be employ | adopted suitably.
The fuel cell electrode may further have a porous support layer in addition to the catalyst layer.
The porous support layer is a layer that diffuses a gas (hereinafter also referred to as a "gas diffusion layer"). Any gas diffusion layer may be used as long as it has electron conductivity, high gas diffusivity, and high corrosion resistance, but generally it is a carbon-based porous material such as carbon paper or carbon cloth. Materials are used.
（膜電極接合体）
　本発明の膜電極接合体は、カソードと、アノードと、当該カソードと当該アノードとの間に配置された高分子電解質膜とを有する膜電極接合体であって、カソードおよびアノードのうちの少なくともいずれか一方が上述した本発明の燃料電池用電極である。このとき、本発明の燃料電池用電極を採用しなかった方の電極として、従来公知の燃料電池用電極、例えば、白金担持カーボンなど白金系触媒を含む燃料電池用電極を用いることができる。本発明の膜電極接合体の好適な態様の一例として、少なくとも前記カソードが本発明の燃料電池用電極であるものが挙げられる。
　ここで、本発明の燃料電池用電極がガス拡散層を有する場合、本発明の膜電極接合体においてこのガス拡散層は、高分子電解質膜から見て、触媒層の反対側に配置される。
　高分子電解質膜としては、例えば、パーフルオロスルホン酸系を用いた電解質膜または炭化水素系電解質膜などが一般的に用いられるが、高分子微多孔膜に液体電解質を含浸させた膜または多孔質体に高分子電解質を充填させた膜などを用いてもよい。
　本発明の膜電極接合体は、従来公知の方法を用いて適宜形成することができる。 (Membrane electrode assembly)
The membrane electrode assembly of the present invention is a membrane electrode assembly having a cathode, an anode, and a polymer electrolyte membrane disposed between the cathode and the anode, and at least one of the cathode and the anode. One of the electrodes is the fuel cell electrode of the present invention described above. At this time, as the electrode not using the fuel cell electrode of the present invention, it is possible to use a conventionally known fuel cell electrode, for example, a fuel cell electrode containing a platinum-based catalyst such as platinum-supported carbon. As an example of the suitable aspect of the membrane electrode assembly of this invention, that by which the said cathode is an electrode for fuel cells of this invention is mentioned.
Here, when the fuel cell electrode of the present invention has a gas diffusion layer, in the membrane electrode assembly of the present invention, this gas diffusion layer is disposed on the opposite side of the catalyst layer as viewed from the polymer electrolyte membrane.
As the polymer electrolyte membrane, for example, an electrolyte membrane or a hydrocarbon-based electrolyte membrane using a perfluorosulfonic acid type is generally used, but a membrane or a porous membrane in which a polymer microporous membrane is impregnated with a liquid electrolyte A membrane filled with a polymer electrolyte may be used.
The membrane / electrode assembly of the present invention can be appropriately formed using a conventionally known method.
（燃料電池）
　本発明の燃料電池は、上述した膜電極接合体を備える。ここで、本発明の典型的な態様において、本発明の燃料電池は、膜電極接合体を挟む態様でさらに２つの集電体を備える。集電体は、燃料電池用に一般的に採用される従来公知のものとすることができる。 (Fuel cell)
The fuel cell of the present invention comprises the above-mentioned membrane electrode assembly. Here, in a typical aspect of the present invention, the fuel cell of the present invention further includes two current collectors in a state in which the membrane electrode assembly is sandwiched. The current collector can be a conventionally known one generally employed for fuel cells.
（酸素還元触媒の製造方法）
　本発明の酸素還元触媒の製造方法は、上記の構成の範囲内の酸素還元触媒が得られる限り特に限定されない。例えば、ゾルゲル法を利用して得られるチタン酸化物粉末と硫黄含有物とを混合して酸素ガス含有雰囲気下で焼成する方法（製造方法１）や、硫黄含有チタン化合物を酸素ガス含有雰囲気下で焼成する方法（製造方法２）が挙げられる。以下、これらの２つの方法について詳細に説明する。 (Method for producing oxygen reduction catalyst)
The method for producing the oxygen reduction catalyst of the present invention is not particularly limited as long as the oxygen reduction catalyst within the range of the above constitution can be obtained. For example, a method of mixing a titanium oxide powder obtained by using a sol-gel method and a sulfur-containing substance and baking it in an atmosphere containing oxygen gas (Production method 1) or a sulfur-containing titanium compound in an atmosphere containing oxygen gas The method (the manufacturing method 2) to bake is mentioned. These two methods are described in detail below.
（製造方法１）
　製造方法１は、ゾルゲル法を利用してチタン酸化物粉末をチタン酸化物前駆体として準備する前駆体準備工程と、前記チタン酸化物前駆体と硫黄含有物とを混合する混合工程と、前記混合工程で得られた混合物を酸素ガス含有雰囲気下で焼成する焼成工程とを有する。 (Manufacturing method 1)
Production method 1 comprises a precursor preparation step of preparing a titanium oxide powder as a titanium oxide precursor using a sol-gel method, a mixing step of mixing the titanium oxide precursor and the sulfur-containing material, and the mixing And a firing step of firing the mixture obtained in the step under an atmosphere containing oxygen gas.
（前駆体準備工程）
　前駆体準備工程においては、ゾルゲル法を利用してチタン酸化物前駆体とするチタン酸化物粉末を製造する。ゾルゲル法としては、公知の方法を用いることができる。すなわち、チタンのアルコキシド、有機酸塩、硝酸塩、塩化物などのチタン含有化合物を加水分解して得ることができる。具体的なチタン含有化合物としては、特に限定はされないが、チタンテトラメトキシド、チタンテトラエトキシド、チタンテトラプロポキシド、チタンテトライソプロポキシド、チタンテトラブトキシド、チタンテトライソブトキシド、チタンテトラペントキシド、チタンテトラアセチルアセトナート、チタンオキシジアセチルアセトナート、トリス(アセチルアセトナト)第ニチタン塩化物（[Ti(acac)3]2[TiC16]）、四塩化チタン、三塩化チタン、オキシ塩化チタン、四臭化チタン、三臭化チタン、オキシ臭化チタン、四ヨウ化チタン、三ヨウ化チタン、オキシヨウ化チタン等のチタン化合物を挙げることができる。これらは１種単独で用いてもよく２種以上を併用してもよい。
　加水分解の方法としては、特に限定はされないが、例えば、前記チタン含有化合物をエタノール等の有機溶媒に溶解させてチタン含有化合物溶液とし、チタン含有化合物溶液に水を加えて加水分解させ、チタン酸化物ゾルを析出させることができる。
　チタン酸化物ゾルの析出した溶液から溶媒を除去し、水洗して乾燥させることにより、チタン酸化物前駆体としてチタン酸化物粉末を得ることができる。 (Precursor preparation process)
In the precursor preparation step, a sol-gel method is used to produce a titanium oxide powder as a titanium oxide precursor. Known methods can be used as the sol-gel method. That is, it can be obtained by hydrolyzing titanium-containing compounds such as alkoxides of titanium, organic acid salts, nitrates and chlorides. The specific titanium-containing compound is not particularly limited, but titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, titanium tetrabutoxide, titanium tetraisobutoxide, titanium tetrapentoxide, Titanium tetraacetylacetonate, titanium oxydiacetylacetonate, tris (acetylacetonato) nitrinium chloride ([Ti (acac) 3 ] 2 [TiC 1 6 ]), titanium tetrachloride, titanium trichloride, titanium oxychloride, four Examples thereof include titanium compounds such as titanium bromide, titanium tribromide, titanium oxybromide, titanium tetraiodide, titanium triiodide, titanium oxyiodide and the like. These may be used alone or in combination of two or more.
The method of hydrolysis is not particularly limited, but, for example, the titanium-containing compound is dissolved in an organic solvent such as ethanol to form a titanium-containing compound solution, water is added to the titanium-containing compound solution to hydrolyze, It is possible to precipitate a substance sol.
The solvent is removed from the solution in which the titanium oxide sol has been deposited, followed by washing with water and drying to obtain a titanium oxide powder as a titanium oxide precursor.
（混合工程）
　混合工程においては、前駆体準備工程において準備したチタン酸化物前駆体と硫黄含有物とを混合する。硫黄含有物としては、特に限定はされないが、チタン酸化物前駆体との混合の容易さや反応性および触媒活性を高める観点からは、単体の硫黄もしくは、固体または液体の化合物が好ましい。また、後述する焼成工程後に得られる酸素還元触媒へのチタン以外の金属不純物の混入を防ぐためには、硫黄含有物としてはチタン以外の金属元素を含まない硫黄含有物が好ましい。
　硫黄含有物としては、硫黄、硫化炭素、塩化硫黄、スルフィド類、チオ尿素類、チオアミド類、チオアルコール類、チオアルデヒド類、チアジル類、メルカプタール類、チオール類、チオシアン類などが挙げられる。また詳細には、チオ尿素、スルホ酢酸、チオフェノール、チオフェン、ベンゾチオフェン、ジベンゾチオフェン、チオベンゾフェノン、ビチオフェン、フェノチアジン、スルホラン、チアジン、チアゾール、チアジアゾール、チアゾリン、チアゾリジン、チアントレン、チアン、チオアセトアニリド、チオアセトアミド、チオベンズアミド、チオアニソール、チオニン、ジメチルスルフィド、メチルフェニルスルフィド、ジアリルスルフィド、チオシアン、硫酸、スルホン酸、スルホンアミド、スルフィン酸、スルホキシド、スルフィン、スルファンおよび該当するものについてはそのチタン塩などが挙げられる。これらは１種単独で用いてもよく２種以上を併用してもよい。
　混合の方法としては、硫黄含有物が固体であれば、例えば、チタン酸化物前駆体と硫黄含有物とを乾式混合法または湿式混合法により混合することができる。混合工程のコスト削減や工程の簡素化の観点からは、乾式混合法がより好ましい。例えば、ボールミル、ロール転動ミル、ビーズミル、媒体攪拌ミル、気流粉砕機、乳鉢あるいは自動混練乳鉢を用いて混合することができ、混合の均一性とコスト的な観点からはボールミル、ビーズミル、自動混練乳鉢が好ましく、ボールミルまたは自動混練乳鉢がより好ましい。これらの場合の混合時間は、例えば１～１０時間である。固体の硫黄含有物としては、硫黄またはチオ尿素が好ましく、チオ尿素がより好ましい。硫黄含有物が液体であれば、硫黄含有物にチタン酸化物前駆体を分散させて混合することができる。硫黄含有物が溶媒に溶解させて溶液とすることができる場合には、硫黄含有物溶液を用いてもよい。硫黄含有物を溶解する溶媒としては、硫黄含有物の種類にもよるが、水、エタノール、エチレングリコールなどを挙げることができる。上記の硫黄含有物は１種単独で用いてもよく２種以上を併用してもよい。混合物が溶媒を含む場合には適宜加温して溶媒を除去して、チタン酸化物前駆体と硫黄含有物溶液とが混合された混合物を得る。混合するチタン酸化物前駆体と硫黄含有物の割合は、混合物が含むチタン原子と硫黄原子のモル比が１：３～１：９の範囲となる割合で混合することが好ましい。 (Mixing process)
In the mixing step, the titanium oxide precursor prepared in the precursor preparation step and the sulfur-containing material are mixed. The sulfur-containing substance is not particularly limited, but from the viewpoint of easiness of mixing with the titanium oxide precursor, reactivity and catalytic activity, elemental sulfur or a solid or liquid compound is preferable. Moreover, in order to prevent mixing of metal impurities other than titanium to the oxygen reduction catalyst obtained after the baking process mentioned later, as a sulfur containing material, the sulfur containing material which does not contain metal elements other than titanium is preferable.
Examples of the sulfur-containing substance include sulfur, carbon sulfide, sulfur chloride, sulfides, thioureas, thioamides, thioalcohols, thioaldehydes, thiazils, mercaptals, thiols, thiocyans and the like. Also, in detail, thiourea, sulfoacetic acid, thiophenol, thiophene, benzothiophene, dibenzothiophene, thiobenzophenone, bithiophene, phenothiazine, sulfolane, thiazine, thiazole, thiadiazole, thiazoline, thiazolidine, thianthrene, thiane, thioacetanilide, thioacetamide , Thiobenzamide, thioanisole, thionine, dimethyl sulfide, methylphenyl sulfide, diallyl sulfide, thiocyanate, sulfuric acid, sulfonic acid, sulfonamide, sulfinic acid, sulfoxide, sulfin, sulfane, and titanium salts thereof as appropriate. . These may be used alone or in combination of two or more.
As a method of mixing, if the sulfur-containing substance is solid, for example, the titanium oxide precursor and the sulfur-containing substance can be mixed by a dry mixing method or a wet mixing method. The dry mixing method is more preferable from the viewpoint of cost reduction of the mixing process and simplification of the process. For example, mixing can be performed using a ball mill, roll rolling mill, bead mill, medium stirring mill, air flow grinder, mortar or automatic kneading mortar, and from the viewpoint of mixing uniformity and cost, ball mill, bead mill, automatic kneading A mortar is preferred, and a ball mill or an automatic kneading mortar is more preferred. The mixing time in these cases is, for example, 1 to 10 hours. As a solid sulfur-containing substance, sulfur or thiourea is preferable, and thiourea is more preferable. If the sulfur content is a liquid, the titanium oxide precursor can be dispersed and mixed in the sulfur content. If the sulfur content can be dissolved in a solvent to form a solution, a sulfur content solution may be used. As a solvent for dissolving the sulfur-containing substance, although depending on the kind of the sulfur-containing substance, water, ethanol, ethylene glycol and the like can be mentioned. The above sulfur-containing substances may be used alone or in combination of two or more. When the mixture contains a solvent, the solvent is removed by heating appropriately to obtain a mixture in which the titanium oxide precursor and the sulfur-containing solution are mixed. The proportions of the titanium oxide precursor and the sulfur-containing substance to be mixed are preferably mixed in such a proportion that the molar ratio of titanium atoms to sulfur atoms contained in the mixture is in the range of 1: 3 to 1: 9.
（焼成工程）
　焼成工程においては、混合工程において得られた混合物を焼成する。混合物の焼成雰囲気は、酸素ガス含有雰囲気が好ましく、窒素ガスおよび／またはアルゴンガスと酸素ガスとの混合ガス雰囲気であることがより好ましい。酸素ガス含有雰囲気の酸素ガス含有率は１０体積％以上３０体積％以下が好ましい。焼成は空気雰囲気で行うことができる。焼成の温度と時間はそれぞれ、４００～８００℃が好ましく、５００～７００℃がより好ましく、１～５時間が好ましく、２～４時間がより好ましい。焼成の温度と時間は互いに合わせて調整される。前述の範囲の条件で焼成すると、得られる酸素還元触媒の硫黄原子が必要十分な量含有されるとともに、アナターゼ含有率が５０．０％より多くなり好ましい。 (Firing process)
In the firing step, the mixture obtained in the mixing step is fired. The firing atmosphere of the mixture is preferably an oxygen gas-containing atmosphere, and more preferably a mixed gas atmosphere of nitrogen gas and / or argon gas and oxygen gas. The oxygen gas content of the oxygen gas-containing atmosphere is preferably 10% by volume or more and 30% by volume or less. The firing can be performed in an air atmosphere. The firing temperature and time are preferably 400 to 800 ° C., more preferably 500 to 700 ° C., preferably 1 to 5 hours, and more preferably 2 to 4 hours. The temperature and time of calcination are adjusted to one another. When calcinating under the conditions of the above-mentioned range, the sulfur atom of the oxygen reduction catalyst obtained is contained in a necessary and sufficient amount, and the anatase content is preferably more than 50.0%.
（製造方法２）
　製造方法２は、硫黄含有チタン化合物を酸素ガス含有雰囲気下で焼成する工程からなる。
　原料とする硫黄含有チタン化合物としては、二硫化チタン、一硫化チタン、硫酸チタン、亜硫酸チタンなどを挙げることができる。取扱いの簡便さから二硫化チタンを用いることが好ましい。酸素ガス含有雰囲気は、窒素ガスおよび／またはアルゴンガスと酸素ガスの混合ガス雰囲気であることがより好ましい。酸素ガス含有雰囲気の酸素ガス含有率は０．１～１０．０体積％が好ましく、０．１～１．０体積％がより好ましく、０．１～０．５体積％がさらに好ましい。焼成温度としては、５００℃より高く８００℃より低い範囲が好ましく、６５０～７５０℃がより好ましい。焼成時間は、１～５時間が好ましく、２～４時間が好ましい。焼成の時間と温度は互いに合わせて調整される。前述の範囲の条件で加熱すると、例えば二硫化チタンを用いた場合、二硫化チタンは完全に分解し、得られる酸素還元触媒の硫黄原子が必要十分な量含有されるとともに、アナターゼ含有率が５０．０％より多くなり好ましい。 (Manufacturing method 2)
Production method 2 comprises the step of firing the sulfur-containing titanium compound in an oxygen gas-containing atmosphere.
Examples of sulfur-containing titanium compounds used as raw materials include titanium disulfide, titanium monosulfide, titanium sulfate, titanium sulfite and the like. It is preferable to use titanium disulfide from the ease of handling. The oxygen gas-containing atmosphere is more preferably a nitrogen gas and / or a mixed gas atmosphere of argon gas and oxygen gas. The oxygen gas content of the oxygen gas-containing atmosphere is preferably 0.1 to 10.0% by volume, more preferably 0.1 to 1.0% by volume, and still more preferably 0.1 to 0.5% by volume. The firing temperature is preferably in the range of higher than 500 ° C. and lower than 800 ° C., and more preferably 650 to 750 ° C. The baking time is preferably 1 to 5 hours, and more preferably 2 to 4 hours. The firing time and temperature are adjusted to one another. When heated under the conditions of the above-mentioned range, for example, when titanium disulfide is used, titanium disulfide is completely decomposed, and a necessary and sufficient amount of sulfur atoms of the obtained oxygen reduction catalyst is contained, and the anatase content is 50 More than 0% is preferable.
　以下、本発明を実施例に基づいて具体的に説明する。なお、本発明はこれらの実施例にのみ限定されるものではない。 Hereinafter, the present invention will be specifically described based on examples. The present invention is not limited to only these examples.
実施例１：
　（１）酸素還元触媒の作製
　酸素還元触媒の作製は前述の製造方法１で行った。詳細を以下に記す。
（前駆体準備工程）
　チタニウム（ＩＶ）イソプロポキシド（純正化学製）２６ｍＬを脱水エタノール（和光純薬工業製）２５０ｍＬに添加し攪拌しながら超純水２５ｍＬをゆっくり添加した後、２時間攪拌してチタン酸化物ゾルを析出させた。チタン酸化物ゾルの析出した溶液からろ過して溶媒を除去し、次いで水洗し、乾燥させてチタン酸化物粉末をチタン酸化物前駆体（以下、「チタン酸化物前駆体（１）」）として７．０ｇ得た。
（混合工程）
　前駆体準備工程で得られたチタン酸化物前駆体（１）７．０ｇとチオ尿素（和光純薬工業製）２７．４ｇとを乳鉢を用いて混合して混合物を得た。なお、この混合比は、チタン原子１ｍｏｌに対して硫黄原子４ｍｏｌである。
（焼成工程）
　混合工程で得られた混合物を石英製管状炉に入れ、空気雰囲気（ガス流量３００ｍＬ／分）下、昇温速度１０℃／分で５００℃まで昇温し、５００℃で３時間焼成を行うことにより酸素還元触媒（１）１０ｇを得た。 Example 1:
(1) Preparation of oxygen reduction catalyst Preparation of the oxygen reduction catalyst was performed by the above-mentioned manufacturing method 1. Details are described below.
(Precursor preparation process)
After adding 26 mL of titanium (IV) isopropoxide (manufactured by Junsei Chemical Co., Ltd.) to 250 mL of dehydrated ethanol (manufactured by Wako Pure Chemical Industries) and slowly adding 25 mL of ultrapure water while stirring, the titanium oxide sol is stirred for 2 hours It was precipitated. The solution from which the titanium oxide sol precipitates is filtered to remove the solvent, and then washed with water and dried to obtain a titanium oxide powder as a titanium oxide precursor (hereinafter, "titanium oxide precursor (1)") 7 Obtained .0 g.
(Mixing process)
7.0 g of the titanium oxide precursor (1) obtained in the precursor preparation step and 27.4 g of thiourea (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed using a mortar to obtain a mixture. The mixing ratio is 4 mol of sulfur atom to 1 mol of titanium atom.
(Firing process)
The mixture obtained in the mixing step is placed in a quartz tube furnace, heated to 500 ° C. at a heating rate of 10 ° C./min under an air atmosphere (gas flow rate of 300 mL / min), and calcined at 500 ° C. for 3 hours Thus, 10 g of an oxygen reduction catalyst (1) was obtained.
　（２）電気化学測定
　（触媒電極作製）
　酸素還元触媒を含む触媒層を備える燃料電池用電極（以下「触媒電極」）の作製は次のように行った。得られた酸素還元触媒（１）１５ｍｇ、２－プロパノール１．０ｍＬ、イオン交換水１．０ｍＬおよびナフィオン（ＮＡＦＩＯＮ（登録商標）、５％ナフィオン水溶液、和光純薬工業製）６２μＬを含む溶液に超音波を照射して攪拌し、懸濁して懸濁液を得た。この懸濁液２０μＬをグラッシーカーボン電極（東海カーボン社製、直径：５．２ｍｍ）に塗布し、７０℃で１時間乾燥し、酸素還元触媒活性測定用の触媒電極を得た。
　（酸素還元触媒活性測定）
　酸素還元触媒（１）の酸素還元活性触媒能の電気化学評価を次のように行った。上記「触媒電極作製」にて作製した触媒電極を、酸素ガス雰囲気および窒素ガス雰囲気のそれぞれにおいて、３０℃０．５ｍｏｌ／ｄｍ3の硫酸水溶液中、５ｍＶ／秒の電位走査速度で分極し、電流―電位曲線を測定した。また、酸素ガス雰囲気で分極していない状態の自然電位（開回路電位）を得た。その際、同濃度の硫酸水溶液中での可逆水素電極を参照電極とした。
　前記電気化学評価で得た電流―電位曲線のうち酸素ガス雰囲気での還元電流曲線と窒素ガス雰囲気での還元電流曲線との差分から１０μＡにおける電極電位（以下、電極電位とも記す。）を得た。また、前記電極電位と前記自然電位を用いて酸素還元触媒（１）の酸素還元触媒能を評価した。酸素還元活性の指標として得られた自然電位を表１に示す。 (2) Electrochemical measurement (preparation of catalyst electrode)
A fuel cell electrode (hereinafter referred to as "catalyst electrode") provided with a catalyst layer containing an oxygen reduction catalyst was produced as follows. A solution containing 15 mg of the obtained oxygen reduction catalyst (1), 1.0 mL of 2-propanol, 1.0 mL of ion-exchanged water and 62 μL of Nafion (NAFION®, 5% Nafion aqueous solution, Wako Pure Chemical Industries, Ltd.) The mixture was sonicated, stirred and suspended to obtain a suspension. 20 μL of this suspension was applied to a glassy carbon electrode (manufactured by Tokai Carbon Co., Ltd., diameter: 5.2 mm) and dried at 70 ° C. for 1 hour to obtain a catalyst electrode for measuring the oxygen reduction catalyst activity.
(Oxygen reduction catalyst activity measurement)
The electrochemical evaluation of the oxygen reduction activity catalytic ability of the oxygen reduction catalyst (1) was performed as follows. The catalyst electrode prepared in the above "catalyst electrode preparation" is polarized at a potential scanning speed of 5 mV / sec in an aqueous solution of sulfuric acid at 30 ° C. and 0.5 mol / dm 3 in each of an oxygen gas atmosphere and a nitrogen gas atmosphere. -The potential curve was measured. In addition, a natural potential (open circuit potential) in a non-polarized state in an oxygen gas atmosphere was obtained. At that time, a reversible hydrogen electrode in a sulfuric acid aqueous solution of the same concentration was used as a reference electrode.
Of the current-potential curves obtained in the electrochemical evaluation, an electrode potential at 10 μA (hereinafter also referred to as electrode potential) was obtained from the difference between the reduction current curve in the oxygen gas atmosphere and the reduction current curve in the nitrogen gas atmosphere. . Further, the oxygen reduction catalytic ability of the oxygen reduction catalyst (1) was evaluated using the electrode potential and the natural potential. The natural potential obtained as an index of the oxygen reduction activity is shown in Table 1.
　（３）粉末Ｘ線回折（ＸＲＤ）測定
　粉末Ｘ線回折測定装置パナリティカルＭＰＤ（スペクトリス株式会社製）を用いて、試料の粉末Ｘ線回折測定を行った。Ｘ線回折測定条件としては、Ｃｕ－Ｋα線（出力４５ｋＶ、４０ｍＡ）を用いて回折角２θ＝１０～７０°の範囲で測定を行い、酸素還元触媒（１）のＸ線回折スペクトルを得た。得られたＸ線回折（ＸＲＤ）スペクトルを図１に示す。
　アナターゼ型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピーク高さ（Ｈａ）、ルチル型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピークの高さ（Ｈｒ）、ブルッカイト型二酸化チタン結晶に対応するピークのうちの最も強い回折強度のピーク高さ（Ｈｂ）、立方晶の窒化チタンに対応するピークのうちの最も強い回折強度のピークの高さ（Ｈｃ）および原料として硫黄含有チタン化合物がある場合には、硫黄含有チタン化合物に対応するピークのうちの最も強い回折強度のピークの高さ（Ｈｓ）を求め、下記の計算式により、作製した酸素還元触媒中におけるアナターゼ型二酸化チタンの含有量（アナターゼ含有率）等をそれぞれ求めた。なお、最も強い回折強度のピークの高さは、装置付属のソフトウェアＨｉｇｈＳｃｏｒｅ　Ｐｌｕｓを用いてバックグラウンド指定処理（処理条件、バックグラウンド指定：自動、粒状度：２０、ベンディングファクタ：１３）したうえで、ピークの高さとした。
　アナターゼ含有率（％）＝｛Ｈａ／（Ｈａ＋Ｈｒ＋Ｈｂ））｝×１００
　ルチル含有率（％）＝｛Ｈｒ／（Ｈａ＋Ｈｒ＋Ｈｂ））｝×１００
　立方晶含有率（％）＝｛Ｈｃ／（Ｈａ＋Ｈｒ＋Ｈｂ＋Ｈｃ＋Ｈｓ））｝×１００
　硫黄含有チタン化合物含有率（％）＝｛Ｈｓ／（Ｈａ＋Ｈｒ＋Ｈｂ＋Ｈｃ＋Ｈｓ））｝×１００
　酸素還元触媒（１）のＸＲＤスペクトルでは、アナターゼ型二酸化チタンのみが観測され、アナターゼ含有率が１００％であることが確認された。ルチル含有率は０％と求められた。ＸＲＤ測定において確認された結晶構造と、アナターゼ含有率および自然電位と併せて表１に示す。 (3) Powder X-ray Diffraction (XRD) Measurement A powder X-ray diffraction measurement of a sample was performed using a powder X-ray diffraction measurement apparatus PANalytical MPD (manufactured by Spectris Co., Ltd.). As the X-ray diffraction measurement conditions, measurement was performed in the range of a diffraction angle 2θ = 10 to 70 ° using a Cu-Kα ray (output 45 kV, 40 mA) to obtain an X-ray diffraction spectrum of the oxygen reduction catalyst (1) . The obtained X-ray diffraction (XRD) spectrum is shown in FIG.
Peak height (Ha) of the strongest diffraction intensity of peaks corresponding to anatase type titanium dioxide crystals, peak height (Hr) of the strongest diffraction intensity peaks of peaks corresponding to rutile type titanium dioxide crystals, brookite Height (Hc) of the strongest diffraction intensity of the peaks corresponding to crystalline titanium dioxide crystals, the height (Hc) of peaks of the strongest diffraction intensity among the peaks corresponding to cubic titanium nitride and as a raw material When there is a sulfur-containing titanium compound, the height (Hs) of the peak of the strongest diffraction intensity among the peaks corresponding to the sulfur-containing titanium compound is determined, and the anatase in the oxygen reduction catalyst produced by the following formula The content of type titanium dioxide (anatase content) and the like were respectively determined. The height of the peak of the strongest diffraction intensity is subject to background designation processing (processing conditions, background designation: automatic, granularity: 20, bending factor: 13) using the software HighScore Plus supplied with the device. It was the height of the peak.
Anatase content (%) = {Ha / (Ha + Hr + Hb))} × 100
Rutile content (%) = {Hr / (Ha + Hr + Hb))} × 100
Cubic crystal content (%) = {Hc / (Ha + Hr + Hb + Hc + Hs))} × 100
Sulfur-containing titanium compound content (%) = {Hs / (Ha + Hr + Hb + Hc + Hs))} × 100
In the XRD spectrum of the oxygen reduction catalyst (1), only anatase type titanium dioxide was observed, and it was confirmed that the anatase content was 100%. The rutile content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content and the spontaneous potential are shown in Table 1.
　（４）硫黄原子含有量
　酸素還元触媒（１）１０ｍｇをセラミックるつぼに秤量し、助燃剤としてタングステン粉およびスズ粉を適当量加えて、炭素硫黄分析装置（型番：ＥＭＩＡ－９２０Ｖ、堀場製作所製）を用いて酸素ガス気流下で昇温して赤外線吸収法で測定した。ここで得られた硫黄原子含有量（質量％）を表１に併せて示す。 (4) Sulfur atom content Weigh 10 mg of oxygen reduction catalyst (1) into a ceramic crucible, add appropriate amounts of tungsten powder and tin powder as a flame retardant, and use a carbon / sulfur analyzer (model: EMIA-920V, manufactured by Horiba, Ltd.) The temperature was raised under an oxygen gas flow using an infrared absorption method. The sulfur atom content (% by mass) obtained here is shown together in Table 1.
　実施例２：
（酸素還元触媒の作製）
　焼成する温度を６００℃に変更した以外は、実施例１と同様にして酸素還元触媒（２）を得た。
（電気化学測定、ＸＲＤ測定、硫黄原子含有量）
　電気化学測定、ＸＲＤ測定および硫黄原子含有量は、それぞれ実施例１と同様に測定および分析を行った。得られたＸＲＤスペクトルを図２に示す。
　酸素還元触媒（２）のＸＲＤスペクトルでは、アナターゼ型二酸化チタンのみが観測され、アナターゼ含有率が１００％であることが確認された。ルチル含有率は０％と求められた。ＸＲＤ測定において確認された結晶構造と、アナターゼ含有率、硫黄原子含有量および自然電位とを併せて表１に示す。 Example 2:
(Preparation of oxygen reduction catalyst)
An oxygen reduction catalyst (2) was obtained in the same manner as in Example 1 except that the firing temperature was changed to 600 ° C.
(Electrochemical measurement, XRD measurement, sulfur atom content)
The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG.
In the XRD spectrum of the oxygen reduction catalyst (2), only anatase type titanium dioxide was observed, and it was confirmed that the anatase content is 100%. The rutile content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
　実施例３：
（酸素還元触媒の作製）
　焼成する温度を７００℃に変更した以外は、実施例１と同様にして酸素還元触媒（３）を得た。
（電気化学測定、ＸＲＤ測定、硫黄原子含有量）
　電気化学測定、ＸＲＤ測定および硫黄原子含有量は、それぞれ実施例１と同様に測定および分析を行った。得られたＸＲＤスペクトルを図３に示す。
　酸素還元触媒（３）のＸＲＤスペクトルでは、アナターゼ型二酸化チタンおよびルチル型二酸化チタンのみが観測され、アナターゼ含有率が６６．５％であることが確認された。ルチル含有率は３３．５％と求められた。ＸＲＤ測定において確認された結晶構造と、アナターゼ含有率、硫黄原子含有量および自然電位とを併せて表１に示す。 Example 3:
(Preparation of oxygen reduction catalyst)
An oxygen reduction catalyst (3) was obtained in the same manner as in Example 1 except that the firing temperature was changed to 700 ° C.
(Electrochemical measurement, XRD measurement, sulfur atom content)
The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG.
In the XRD spectrum of the oxygen reduction catalyst (3), only anatase type titanium dioxide and rutile type titanium dioxide were observed, and it was confirmed that the anatase content is 66.5%. The rutile content was determined to be 33.5%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
　実施例４：
（酸素還元触媒の作製）
　酸素還元触媒の作製の混合工程において混合するチタン酸化物前駆体（１）７．０ｇに対するチオ尿素の量を６１．７ｇとし、混合比をチタン原子１ｍｏｌに対して硫黄原子９ｍｏｌとなるように変更した以外は、実施例１と同様にして酸素還元触媒（４）を得た。
（電気化学測定、ＸＲＤ測定、硫黄原子含有量）
　電気化学測定、ＸＲＤ測定および硫黄原子含有量は、それぞれ実施例１と同様に測定および分析を行った。得られたＸ線回折（ＸＲＤ）スペクトルを図４に示す。
　酸素還元触媒（４）のＸＲＤスペクトルでは、アナターゼ型二酸化チタンのみが観測され、アナターゼ含有率が１００％であることが確認された。ルチル含有率は０％と求められた。ＸＲＤ測定において確認された結晶構造と、アナターゼ含有率、硫黄原子含有量および自然電位とを併せて表１に示す。 Example 4:
(Preparation of oxygen reduction catalyst)
The amount of thiourea was set to 61.7 g with respect to 7.0 g of the titanium oxide precursor (1) to be mixed in the mixing step of the preparation of the oxygen reduction catalyst, and the mixing ratio was changed to 9 mol of sulfur atoms to 1 mol of titanium atoms. An oxygen reduction catalyst (4) was obtained in the same manner as in Example 1 except for the above.
(Electrochemical measurement, XRD measurement, sulfur atom content)
The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained X-ray diffraction (XRD) spectrum is shown in FIG.
In the XRD spectrum of the oxygen reduction catalyst (4), only anatase titanium dioxide was observed, and it was confirmed that the anatase content was 100%. The rutile content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
　比較例１：
（酸素還元触媒の作製）
　焼成する温度を９００℃に変更した以外は、実施例１と同様にして酸素還元触媒（ｃ１）を得た。
（電気化学測定、ＸＲＤ測定、硫黄原子含有量）
　電気化学測定、ＸＲＤ測定および硫黄原子含有量は、それぞれ実施例１と同様に測定および分析を行った。得られたＸＲＤスペクトルを図６に示す。
　酸素還元触媒（ｃ１）のＸＲＤスペクトルでは、ルチル型二酸化チタンのみが観測され、ルチル含有率は１００％であることが確認された。アナターゼ含有率が０％と求められた。ＸＲＤ測定において確認された結晶構造と、アナターゼ含有率、硫黄原子含有量および自然電位とを併せて表１に示す。 Comparative Example 1:
(Preparation of oxygen reduction catalyst)
An oxygen reduction catalyst (c1) was obtained in the same manner as in Example 1 except that the firing temperature was changed to 900 ° C.
(Electrochemical measurement, XRD measurement, sulfur atom content)
The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG.
In the XRD spectrum of the oxygen reduction catalyst (c1), only rutile titanium dioxide was observed, and it was confirmed that the rutile content is 100%. The anatase content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
実施例５：
（酸素還元触媒の作製）
　酸素還元触媒の作製は前述の製造方法２で行った。詳細を以下に記す。
　二硫化チタン粉末（Ａｌｆａ　Ａｅｓａｒ社製、チタン基準で純度９９．８質量％、２００メッシュ品）０．３ｇを秤量して石英製インナーケースに入れ、回転型焼成炉（モトヤマ社製）を用いて窒素ガス（ガス流量１００ｍＬ／分）と酸素ガス（ガス流量０．５ｍＬ／分）の混合ガス気流下、昇温速度１０℃／分で７００℃まで昇温し、７００℃で３時間焼成して、酸素還元触媒（５）０．２ｇを得た。
（電気化学測定、ＸＲＤ測定、硫黄原子含有量）
　電気化学測定、ＸＲＤ測定および硫黄原子含有量は、それぞれ実施例１と同様に測定および分析を行った。得られたＸＲＤスペクトルを図５に示す。
　酸素還元触媒（５）のＸＲＤスペクトルでは、アナターゼ型二酸化チタンおよびルチル型二酸化チタンのみが観測され、アナターゼ含有率が５２．５％であることが確認された。ルチル含有率は４７．５％と求められた。硫黄含有チタン化合物含有率は０％と求められた。ＸＲＤ測定において確認された結晶構造と、アナターゼ含有率、硫黄原子含有量および自然電位とを併せて表１に示す。 Example 5:
(Preparation of oxygen reduction catalyst)
Preparation of the oxygen reduction catalyst was performed by the above-mentioned production method 2. Details are described below.
Weigh 0.3 g of titanium disulfide powder (product of Alfa Aesar, purity 99.8% by mass based on titanium, 200 mesh item), put in a quartz inner case, and use a rotary calciner (made by Motoyama) In a mixed gas flow of nitrogen gas (gas flow rate 100 mL / min) and oxygen gas (gas flow rate 0.5 mL / min), the temperature is raised to 700 ° C. at a heating rate of 10 ° C./min and calcined at 700 ° C. for 3 hours , 0.2 g of an oxygen reduction catalyst (5) was obtained.
(Electrochemical measurement, XRD measurement, sulfur atom content)
The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG.
In the XRD spectrum of the oxygen reduction catalyst (5), only anatase type titanium dioxide and rutile type titanium dioxide were observed, and it was confirmed that the anatase content is 52.5%. The rutile content was determined to be 47.5%. The sulfur-containing titanium compound content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
　比較例２：
（酸素還元触媒の作製）
　実施例５における酸素還元触媒の作製の焼成温度を５００℃とし、混合ガス気流を窒素ガス（ガス流量１００ｍＬ／分）と酸素ガス（ガス流量１．０ｍＬ／分）に変更した以外は、実施例５と同様にして酸素還元触媒（ｃ２）を得た。
（電気化学測定、ＸＲＤ測定、硫黄原子含有量）
　電気化学測定、ＸＲＤ測定および硫黄原子含有量は、それぞれ実施例１と同様に測定および分析を行った。得られたＸＲＤスペクトルを図７に示す。
　酸素還元触媒（ｃ２）のＸＲＤスペクトルでは、アナターゼ型二酸化チタンおよびルチル型二酸化チタンのみが観測され、アナターゼ含有率が６６．１％であることが確認された。ルチル含有率は３３．９％と求められた。硫黄含有チタン化合物含有率は０％と求められた。ＸＲＤ測定において確認された結晶構造と、アナターゼ含有率、硫黄原子含有量および自然電位とを併せて表１に示す。 Comparative example 2:
(Preparation of oxygen reduction catalyst)
Example except that the calcination temperature for preparation of the oxygen reduction catalyst in Example 5 was 500 ° C., and the mixed gas stream was changed to nitrogen gas (gas flow rate 100 mL / min) and oxygen gas (gas flow rate 1.0 mL / min) In the same manner as in 5, an oxygen reduction catalyst (c2) was obtained.
(Electrochemical measurement, XRD measurement, sulfur atom content)
The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG.
In the XRD spectrum of the oxygen reduction catalyst (c2), only anatase titanium dioxide and rutile titanium dioxide were observed, and it was confirmed that the anatase content is 66.1%. The rutile content was determined to be 33.9%. The sulfur-containing titanium compound content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
　比較例３：
（酸素還元触媒の作製）
　実施例５における酸素還元触媒の作製の焼成温度を６００℃に変更した以外は、実施例５と同様にして酸素還元触媒（ｃ３）を得た。
（電気化学測定、ＸＲＤ測定、硫黄原子含有量）
　電気化学測定、ＸＲＤ測定および硫黄原子含有量は、それぞれ実施例１と同様に測定および分析を行った。得られたＸＲＤスペクトルを図８に示す。
　酸素還元触媒（ｃ３）のＸＲＤスペクトルでは、アナターゼ型二酸化チタンおよびルチル型二酸化チタンのみが観測され、アナターゼ含有率が５５．１％であることが確認された。ルチル含有率は４４．９％と求められた。硫黄含有チタン化合物含有率は０％と求められた。ＸＲＤ測定において確認された結晶構造と、アナターゼ含有率、硫黄原子含有量および自然電位とを併せて表１に示す。 Comparative example 3:
(Preparation of oxygen reduction catalyst)
An oxygen reduction catalyst (c3) was obtained in the same manner as in Example 5, except that the calcination temperature for producing the oxygen reduction catalyst in Example 5 was changed to 600 ° C.
(Electrochemical measurement, XRD measurement, sulfur atom content)
The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG.
In the XRD spectrum of the oxygen reduction catalyst (c3), only anatase titanium dioxide and rutile titanium dioxide were observed, and it was confirmed that the anatase content is 55.1%. The rutile content was determined to be 44.9%. The sulfur-containing titanium compound content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
　比較例４：
（酸素還元触媒の作製）
　実施例５における酸素還元触媒の作製の焼成温度を８００℃に変更した以外は、実施例５と同様にして酸素還元触媒（ｃ４）を得た。
（電気化学測定、ＸＲＤ測定、硫黄原子含有量）
　電気化学測定、ＸＲＤ測定および硫黄原子含有量は、それぞれ実施例１と同様に測定および分析を行った。得られたＸＲＤスペクトルを図９に示す。
　酸素還元触媒（ｃ４）のＸＲＤスペクトルでは、アナターゼ型二酸化チタンおよびルチル型二酸化チタンのみが観測され、アナターゼ含有率が７．９％であることが確認された。ルチル含有率は９２．１％と求められた。硫黄含有チタン化合物含有率は０％と求められた。ＸＲＤ測定において確認された結晶構造と、アナターゼ含有率、硫黄原子含有量および自然電位とを併せて表１に示す。 Comparative example 4:
(Preparation of oxygen reduction catalyst)
An oxygen reduction catalyst (c4) was obtained in the same manner as in Example 5, except that the calcination temperature for preparation of the oxygen reduction catalyst in Example 5 was changed to 800 ° C.
(Electrochemical measurement, XRD measurement, sulfur atom content)
The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG.
In the XRD spectrum of the oxygen reduction catalyst (c4), only anatase titanium dioxide and rutile titanium dioxide were observed, and it was confirmed that the anatase content is 7.9%. The rutile content was determined to be 92.1%. The sulfur-containing titanium compound content was determined to be 0%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
　比較例５：
（酸素還元触媒の作製）
　アナターゼ型二酸化チタン粉末（型番：Ｆ－６、昭和電工製）につき、熱処理を実施することなくそのまま酸素還元触媒（ｃ５）として用いた。
（電気化学測定、ＸＲＤ測定、硫黄原子含有量）
　電気化学測定、ＸＲＤ測定および硫黄原子含有量は、それぞれ実施例１と同様に測定および分析を行った。得られたＸＲＤスペクトルを図１０に示す。酸素還元触媒（ｃ５）のＸＲＤスペクトルでは、アナターゼ型二酸化チタンのみが観測され、アナターゼ含有率が１００％であることが確認された。ＸＲＤ測定において確認された結晶構造と、アナターゼ含有率、硫黄原子含有量および自然電位とを併せて表１に示す。 Comparative example 5:
(Preparation of oxygen reduction catalyst)
Anatase type titanium dioxide powder (model number: F-6, manufactured by Showa Denko) was used as it was as an oxygen reduction catalyst (c5) without heat treatment.
(Electrochemical measurement, XRD measurement, sulfur atom content)
The electrochemical measurement, the XRD measurement and the sulfur atom content were measured and analyzed in the same manner as in Example 1, respectively. The obtained XRD spectrum is shown in FIG. In the XRD spectrum of the oxygen reduction catalyst (c5), only anatase type titanium dioxide was observed, and it was confirmed that the anatase content is 100%. The crystal structure confirmed in the XRD measurement and the anatase content, the sulfur atom content and the natural potential are shown together in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　実施例の結果より、アナターゼ含有率が５０．０％より多く、硫黄原子含有量が０．１～３．０質量％の範囲の酸素還元触媒は、自然電位が高い。 From the results of the examples, the oxygen reduction catalyst having an anatase content of more than 50.0% and a sulfur atom content of 0.1 to 3.0% by mass has a high natural potential.
　本発明の酸素還元触媒は、アナターゼ型二酸化チタンの含有量が多いので耐酸性が高く、酸素ガス雰囲気で分極していない状態での自然電位が高いので、酸素還元触媒を含む触媒層を有する燃料電池用電極に好適に用いることができる。 The oxygen reduction catalyst of the present invention is high in acid resistance because of the large content of anatase type titanium dioxide, and is high in natural potential in a non-polarized state in an oxygen gas atmosphere. It can be suitably used for battery electrodes.

Claims (5)

  1. 　Ｘ線回折測定において確認される二酸化チタン結晶中のアナターゼ型二酸化チタンの含有量が５０．０％より多く、硫黄原子含有量が０．１～３．０質量％であることを特徴とするチタン化合物である酸素還元触媒。 Content of anatase type titanium dioxide in titanium dioxide crystal confirmed in X-ray diffraction measurement is more than 50.0%, and sulfur atom content is 0.1 to 3.0% by mass. Compound oxygen reduction catalyst.
  2. 　請求項１に記載の酸素還元触媒からなる燃料電池用電極触媒。 A fuel cell electrode catalyst comprising the oxygen reduction catalyst according to claim 1.
  3. 　請求項２に記載の燃料電池用電極触媒を含む触媒層を有する燃料電池用電極。 A fuel cell electrode comprising a catalyst layer comprising the fuel cell electrode catalyst according to claim 2.
  4. 　カソードと、アノードと、当該カソードと当該アノードとの間に配置された高分子電解質膜とを有する膜電極接合体であって、前記カソードが請求項３に記載の燃料電池用電極である膜電極接合体。 A membrane electrode assembly comprising a cathode, an anode, and a polymer electrolyte membrane disposed between the cathode and the anode, wherein the cathode is a fuel cell electrode according to claim 3. Zygote.
  5. 　請求項４に記載の膜電極接合体を備える燃料電池。 A fuel cell comprising the membrane electrode assembly according to claim 4.
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