Catalyst for fuel cell, method for producing the same, electrode catalyst layer, membrane electrode assembly, and solid polymer fuel cell

Abstract

The fuel cell catalyst of the present application is a rutile-type oxide containing oxygen atoms, nitrogen atoms, and transition metal atoms and having a fiber shape. The transition metal atoms are at least one selected from the group consisting of titanium atoms, tantalum atoms, niobium atoms, and zirconium atoms. When M represents the transition metal atoms, the fuel cell catalyst is represented by the chemical formula MO x N y . The x in the chemical formula satisfies x = 2 - (y + j) (j ≥ 0).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a catalyst for fuel cells, an electrode catalyst layer, a membrane electrode assembly, a solid polymer fuel cell, a method for producing titanium oxide for a catalyst support, and a method for producing a catalyst for fuel cells. BACKGROUND

[0002] Fuel cells are classified into an alkaline type, a phosphoric acid type, a solid polymer type, a molten carbonate type, a solid oxide type, and the like, depending on the kind of electrolyte. The solid polymer fuel cell (PEFC) can operate at low temperature and has a high output power density. In addition, the solid polymer fuel cell is expected to be applied as a portable power source, a household power source, and a vehicle-mounted power source because it can be downsized and lightened.

[0003] The solid polymer fuel cell has a polymer electrolyte membrane, a fuel electrode (anode), and an air electrode (cathode). The fuel electrode and the air electrode sandwich the polymer electrolyte membrane in the thickness direction of the polymer electrolyte membrane. The solid polymer fuel cell generates electricity by the following electrochemical reactions by supplying a hydrogen-containing fuel gas to the fuel electrode and a oxygen-containing oxidant gas to the air electrode. In the following chemical formulas, formula (1) represents a reaction that occurs at the anode. Formula (2) represents a reaction that occurs at the cathode.

[0004] H2 → 2H + + 2e - Formula (1)

[0005] 1 / 2O2 + 2H + + 2e - → H2O Formula (2)

[0006] The anode and the cathode each have a structure in which an electrode catalyst layer and a gas diffusion layer are stacked. The electrode catalyst layer of the anode generates protons and electrons (formula (1)) from the fuel gas supplied to the electrode catalyst layer. The protons move to the cathode through the polymer electrolyte included in the electrode catalyst layer of the anode and the polymer electrolyte membrane. The electrons move to the cathode through an external circuit. In the electrode catalyst layer of the cathode, a reaction occurs by the protons, the electrons, and the oxidant gas supplied from the outside, and water is generated (formula (2)).

[0007] The catalyst included in the electrode catalyst layer of the anode and the catalyst included in the electrode catalyst layer of the cathode promote the redox reactions represented by formula (1) and formula (2). A membrane electrode assembly having an electrode catalyst layer including a catalyst having high catalytic activity for the redox reaction exhibits high power generation characteristics. For example, as a catalyst having high catalytic activity, a platinum-containing catalyst is used (for example, see Patent Literature 1).

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2016-219179 SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] However, platinum is a rare metal and is also an expensive metal. Therefore, there is a demand for a catalyst for fuel cells that has catalytic activity even if the content of platinum is suppressed.

[0013] An object of the present disclosure is to provide a catalyst for fuel cells that has catalytic activity even if the content of platinum is suppressed, an electrode catalyst layer, a membrane electrode assembly, a solid polymer fuel cell, a method for producing titanium oxide for a catalyst carrier, and a method for producing a catalyst for fuel cells.

[0014] MEANS FOR SOLVING THE PROBLEMS

[0015] In one aspect, a catalyst for fuel cells is provided. The catalyst for fuel cells is a rutile-type oxide containing oxygen atoms, nitrogen atoms, and transition metal atoms and having a fiber shape. The transition metal atoms are at least one selected from the group consisting of titanium atoms, tantalum atoms, niobium atoms, and zirconium atoms. When M represents the transition metal atoms, the catalyst for fuel cells is represented by the chemical formula MOxNy (where x and y satisfy the following conditions). x N y In the above chemical formula, x satisfies the following conditions.

[0016] x = 2 - (y + j) (j ≥ 0)

[0017] In another aspect, a catalyst for fuel cells is provided. The catalyst for fuel cells is a rutile-type oxide containing oxygen atoms, nitrogen atoms, phosphorus atoms of valence 5, and transition metal atoms and having a fiber shape. The transition metal atoms are at least one selected from the group consisting of titanium atoms, tantalum atoms, niobium atoms, and zirconium atoms. When M represents the transition metal atoms, the catalyst for fuel cells is represented by the chemical formula MwOxNyPz (where w, x, and z satisfy the following conditions). w O x N y P z In the above chemical formula, w and x satisfy the following conditions.

[0018] w = 1 - (z + i) (i ≥ 0)

[0019] x = 2 - (y + j) (j ≥ 0)

[0020] In another aspect, an electrode catalyst layer is provided. The electrode catalyst layer is an electrode catalyst layer to be bonded to a solid polymer electrolyte layer in a solid polymer fuel cell. The electrode catalyst layer includes the above-described catalyst for fuel cells and a polymer electrolyte.

[0021] In another aspect, a membrane electrode assembly is provided. The membrane electrode assembly includes a solid polymer electrolyte membrane and the above-described electrode catalyst layer. The above-described electrode catalyst layer is bonded to the above-described solid polymer electrolyte membrane.

[0022] In another aspect, a solid polymer fuel cell is provided. The solid polymer fuel cell includes the above-described membrane electrode assembly.

[0023] In another aspect, a method for producing titanium oxide for catalyst carriers is provided. The method for producing titanium oxide for catalyst carriers includes the steps of mixing titanium oxide with two or more kinds of salts, and obtaining a rutile-type titanium oxide having a fiber shape by heating the mixture of the titanium oxide and the salts at a temperature higher than a eutectic point of the salts.

[0024] In another aspect, a method for producing a catalyst for fuel cells is provided. The method for producing a catalyst for fuel cells includes the steps of obtaining a rutile-type titanium oxide having a fiber shape by the above-described method for producing titanium oxide for catalyst carriers, mixing the rutile-type titanium oxide, titanyl sulfate, and urea to produce a dispersion liquid, heating the dispersion liquid, drying the heated dispersion liquid to produce a powder, and obtaining TiO x N y in the chemical formula TiO x N y satisfies the following condition.

[0025] x = 2 - (y + j) (j ≥ 0)

[0026] In another aspect, a method for producing a catalyst for fuel cells is provided. The method for producing a catalyst for fuel cells includes the steps of obtaining a rutile-type titanium oxide having a fiber shape by the above-described method for producing titanium oxide for catalyst carriers, mixing the rutile-type titanium oxide, titanyl sulfate, urea, and phosphoric acid to produce a dispersion liquid, heating the dispersion liquid, drying the heated dispersion liquid to produce a powder, and obtaining TiO w O x N y P z in the chemical formula TiO w O x Ny P z w and x in the above formula satisfy the following conditions.

[0027] w = 1 - (z + i) (i ≥ 0)

[0028] x = 2 - (y + j) (j ≥ 0) BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a cross-sectional view showing a structure of a membrane electrode assembly of one embodiment.

[0030] Figure 2 is a view schematically showing Figure 1 the electrode catalyst layer of the membrane electrode assembly.

[0031] Figure 3 is a view showing Figure 1 a structure of a solid-state polymer fuel cell including the membrane electrode assembly.

[0032] Figure 4 is a view showing an X-ray diffraction pattern of the titanium oxide for a catalyst support of Example 1 and Comparative Example 1.

[0033] Figure 5 is an SEM image of the titanium oxide for a catalyst support of Example 1.

[0034] Figure 6 is an SEM image of the titanium oxide for a catalyst support of Example 2.

[0035] Figure 7 is an SEM image of the titanium oxide for a catalyst support of Example 3.

[0036] Figure 8 is an SEM image of the titanium oxide for a catalyst support of Example 4.

[0037] Figure 9 is a view showing a fluid voltammogram of an example. DETAILED DESCRIPTION

[0038] One embodiment of a fuel cell catalyst, an electrode catalyst layer, a membrane electrode assembly, a solid-state polymer fuel cell, a method for manufacturing a catalyst support titanium oxide, and a method for manufacturing a fuel cell catalyst will be described with reference to Figures 1-9 [Membrane electrode assembly]

[0039] A structure of a membrane electrode assembly will be described with reference to

[0040] Figure 1 Figure 1 ​​A structure of a cross section of a membrane electrode assembly along a thickness direction.

[0041] As Figure 1 shown, the membrane electrode assembly 10 is provided with a polymer electrolyte membrane 11, a cathode-side electrode catalyst layer 12C, and an anode-side electrode catalyst layer 12A. The polymer electrolyte membrane 11 is a solid polymer electrolyte membrane. Of the pair of facing surfaces of the polymer electrolyte membrane 11, the cathode-side electrode catalyst layer 12C is joined to a first surface, and the anode-side electrode catalyst layer 12A is joined to a second surface. The cathode-side electrode catalyst layer 12C is an electrode catalyst layer that constitutes an air electrode (cathode), and the anode-side electrode catalyst layer 12A is an electrode catalyst layer that constitutes a fuel electrode (anode). The outer peripheral portions of the cathode-side electrode catalyst layer 12C and the anode-side electrode catalyst layer 12A can also be sealed with a gasket or the like.

[0042] [Electrode catalyst layer]

[0043] Referring Figure 2 to, the electrode catalyst layer will be described in more detail. The electrode catalyst layer described below is applicable to both the cathode-side electrode catalyst layer 12C and the anode-side electrode catalyst layer 12A. Furthermore, the electrode catalyst layer described below can also be applicable to only either of the cathode-side electrode catalyst layer 12C and the anode-side electrode catalyst layer 12A.

[0044] As Figure 2 shown, the electrode catalyst layer 12 includes a fibrous catalyst 21 and a polymer electrolyte 22. The fibrous catalyst 21 is an example of a catalyst for a fuel cell.

[0045] The thickness of the electrode catalyst layer 12 is preferably 5 μm or more and 30 μm or less, and more preferably 10 μm or more and 20 μm or less. By making the thickness of the electrode catalyst layer 12 5 μm or more, flooding becomes difficult to occur, and thus a decrease in output power can be suppressed. In addition, by making the thickness of the electrode catalyst layer 12 30 μm or less, an increase in the resistance of the electrode catalyst layer 12 can be suppressed, and as a result, a decrease in output power can be suppressed.

[0046] The density of the electrode catalyst layer 12 is preferably 1000 mg / cm 3 or more and 5000 mg / cm 3 or less, and more preferably 1500 mg / cm 3 or more and 4000 mg / cm 3 or less. Furthermore, the density of the electrode catalyst layer 12 is the ratio (M / V) of the mass (M) of the non-volatile components to the volume of the electrode catalyst layer 12. The volume (V) of the electrode catalyst layer 12 can be found from the product of the thickness of the electrode catalyst layer and the electrode area.

[0047] The density of the electrode catalyst layer 12 is preferably 1000 mg / cm 3 If the density of the electrode catalyst layer 12 is less than 1000 mg / cm 3 If the density of the electrode catalyst layer 12 is more than 5000 mg / cm 3 In this case, the structure of the electrode catalyst layer 12 is difficult to be damaged, and thus the durability of the electrode catalyst layer 12 can be improved. In addition, the density of the electrode catalyst layer 12 is 5000 mg / cm 3 In this case, the decrease in the water drainage and the gas diffusion of the electrode catalyst layer 12 can be suppressed, and in addition, the decrease in the flexibility of the electrode catalyst layer 12 can be suppressed.

[0048] The fibrous catalyst 21 is a rutile-type metal oxide containing oxygen atoms, nitrogen atoms, and transition metal atoms, and has a fibrous shape. The transition metal atoms are at least one selected from the group consisting of titanium atoms, tantalum atoms, niobium atoms, and zirconium atoms. When M represents the transition metal atoms, the fibrous catalyst 21 is represented by the chemical formula MO x N y The x in the chemical formula satisfies the following condition.

[0049] x = 2 - (y + j) (j > 0)

[0050] In addition, in the fibrous catalyst 21, a part of the oxygen atoms in the rutile-type metal oxide is replaced with nitrogen atoms. In the metal oxide, a part of the oxygen atoms is deficient in order to eliminate the imbalance of the electric charge due to the replacement of the oxygen atoms with the nitrogen atoms. Thus, the number of the oxygen atoms in the fibrous catalyst 21 is represented by the above formula.

[0051] According to the fibrous catalyst 21, since the catalyst has a fibrous shape, the mechanical strength of the electrode catalyst layer 12 having the fibrous catalyst 21 can be improved, and thus the durability of the electrode catalyst layer 12 can be improved. For example, the generation of cracks in the electrode catalyst layer 12 can be suppressed. Thus, the durability of the solid polymer fuel cell having the electrode catalyst layer 12 can be improved. In addition, in the passage of electrons generated in the electrode catalyst layer 12, the interface that becomes a resistance to the conduction of the electrons is difficult to be generated, as compared with the case where the fuel cell catalyst has a particulate shape. Thus, in the solid polymer fuel cell having the electrode catalyst layer 12, the resistance can be reduced. As a result, the performance of the solid polymer fuel cell can be improved.

[0052] Further, the electrode catalyst layer 12 can include a fibrous substance formed of a substance having no catalytic ability. At this time, the mechanical strength of the electrode catalyst layer 12 can be improved by the fibrous substance. However, by the electrode catalyst layer 12 including the fibrous substance, the distance between catalysts in the electrode catalyst layer 12 can be enlarged compared to the case where the fibrous substance is not included. Thus, the performance of the solid polymer fuel cell provided with the electrode catalyst layer 12 can be deteriorated due to the large distance between catalysts. In this regard, according to the fibrous catalyst 21, the deterioration of the performance of the solid polymer fuel cell due to the enlarged distance between catalysts can be suppressed, and the durability of the electrode catalyst layer 12 can be improved.

[0053] The fibrous catalyst 21 is preferably a rutile-type oxide further including a pentavalent phosphorus atom and having a fiber shape. When M represents a transition metal atom, the fibrous catalyst 21 is represented by the chemical formula M w O x N y P z in the chemical formula. The w and x in the chemical formula satisfy the following conditions.

[0054] w = 1 - (z + i) (i ≥ 0)

[0055] x = 2 - (y + j) (j ≥ 0)

[0056] Further, in the fibrous catalyst 21, in the rutile-type metal oxide (MO2), a part of the transition metal atoms is substituted with phosphorus atoms. In addition, in the metal oxide, a part of the transition metal atoms is deficient in order to eliminate the imbalance of electric charges due to the substitution of the transition metal atoms with the phosphorus atoms.

[0057] The fibrous catalyst 21, by including the pentavalent phosphorus atom, at least one of the pentavalent phosphorus atom itself doped in the rutile-type metal oxide and the metal deficiency formed by the doping of the pentavalent phosphorus atom for flattening the imbalance of electric charges, sometimes forms a new active site for the oxygen reduction reaction, and thus the catalytic activity of the fibrous catalyst 21 is improved.

[0058] The transition metal atom is preferably a titanium atom.

[0059] In the fibrous catalyst 21, the ratio (N P / N Ti ) of the number of phosphorus atoms (N P ) to the number of titanium atoms (N Ti ) is preferably 0.1 or more and 2.0 or less. That is, in Ti w O x N y P z , the following formula is preferably satisfied.

[0060] 0.1 ≤ z ≤ 2.0

[0061] Thus, the catalytic activity for the oxygen reduction reaction can be improved.

[0062] Further, in the fibrous catalyst 21, the ratio (N N ) of the number of nitrogen atoms (N Ti ) to the number of Ti atoms (N N / N Ti ) is preferably 1.0 or greater and 1.5 or less. That is, in the Ti w O x N y P z , the following formula is preferably satisfied.

[0063] 1.0 ≤ y ≤ 1.5

[0064] Thus, the catalytic activity for the oxygen reduction reaction can be improved.

[0065] The fibrous catalyst 21 is formed of a core portion and a surface layer portion covering the core portion. The core portion contains a titanium nitride (TiN) lattice. The surface layer portion contains a titanium dioxide (TiO2) lattice. Further, both the core portion and the surface layer portion contain a phosphorus atom of valence 5. Thus, high catalytic activity for the oxygen reduction reaction can be obtained.

[0066] The length of the fibrous catalyst 21 is preferably 500 nm or greater and 10 μm or less. By the length of the fibrous catalyst 21 being included in this range, cracks are less likely to occur in the electrode catalyst layer 12. As a result, the durability of the electrode catalyst layer 12 can be improved. By the length of the fibrous catalyst 21 being 500 nm or greater, the fibrous catalyst 21 becomes easy to entangle with each other, and cracks in the electrode catalyst layer 12 can be suppressed. Further, by the length of the fibrous catalyst 21 being 10 μm or less, a catalyst layer ink can be manufactured, and thus the electrode catalyst layer 12 can be formed.

[0067] The aspect ratio of the fibrous catalyst 21 is preferably 10 or greater and 1000 or less. Further, the aspect ratio is the ratio (L / D) of the length (L) of the fibrous catalyst 21 to the diameter (D) of the fibrous catalyst 21. By the aspect ratio of the fibrous catalyst 21 being included in this range, the membrane-electrode assembly 10 can have good power generation characteristics.

[0068] By the aspect ratio being 10 or greater, the electrode catalyst layer 12 can have a density that can have good power generation performance in a region where the density of the current flowing through the electrode catalyst layer 12 is high. Further, by the aspect ratio being 1000 or less, a catalyst layer ink can be manufactured, and thus the electrode catalyst layer 12 can be formed.

[0069] The volume resistivity of the fibrous catalyst 21 is preferably 10 Ωcm or less. By making the volume resistivity of the fibrous catalyst 21 10 Ωcm or less, the conduction of electrons within the electrode catalyst layer 12 can be improved, and the ohmic resistance can be reduced. As a result, the power generation characteristics of the membrane electrode assembly 10 can be improved.

[0070] [SOFC]

[0071] Reference Figure 3 The structure of a solid polymer fuel cell provided with a membrane electrode assembly is described. The structure described below is one example of the structure of a solid polymer fuel cell. In addition, Figure 3 The structure of a single cell provided in a solid polymer fuel cell is shown. A solid polymer fuel cell can be provided with a plurality of single cells and have a structure in which the plurality of single cells are stacked on each other.

[0072] As shown in Figure 3 , the solid polymer fuel cell 30 is provided with a membrane electrode assembly 10, a pair of gas diffusion layers, and a pair of separators. The pair of gas diffusion layers is a cathode-side gas diffusion layer 31C and an anode-side gas diffusion layer 31A. The pair of separators is a cathode-side separator 32C and an anode-side separator 32A.

[0073] The cathode-side gas diffusion layer 31C is in contact with the cathode-side electrode catalyst layer 12C. The cathode-side electrode catalyst layer 12C and the cathode-side gas diffusion layer 31C form an air electrode (cathode) 30C. The anode-side gas diffusion layer 31A is in contact with the anode-side electrode catalyst layer 12A. The anode-side electrode catalyst layer 12A and the anode-side gas diffusion layer 31A form a fuel electrode (anode) 30A.

[0074] In the polymer electrolyte membrane 11, the face to which the cathode-side electrode catalyst layer 12C is joined is a cathode face, and the face to which the anode-side electrode catalyst layer 12A is joined is an anode face. In the cathode face, the portion not covered by the cathode-side electrode catalyst layer 12C is a peripheral portion. The cathode-side gasket 13C is present on the peripheral portion. In the anode face, the portion not covered by the anode-side electrode catalyst layer 12A is a peripheral portion. The anode-side gasket 13A is present on the peripheral portion. By the cathode-side gasket 13C and the anode-side gasket 13A, gas leakage from the peripheral portions of the respective faces can be suppressed.

[0075] The cathode-side separator 32C and the anode-side separator 32A sandwich, in the thickness direction of the solid polymer fuel cell 30, a multilayer body composed of the membrane electrode assembly 10 and the two gas diffusion layers 31C, 31A. The cathode-side separator 32C faces the cathode-side gas diffusion layer 31C. The anode-side separator 32A faces the anode-side gas diffusion layer 31A.

[0076] The pair of facing surfaces of the cathode-side separator 32C each have a plurality of grooves. The grooves of the facing surface of the pair of surfaces that faces the cathode-side gas diffusion layer 31C are gas flow paths 32Cg. The grooves of the surface of the pair of surfaces that is on the opposite side from the facing surface are cooling water flow paths 32Cw. The pair of facing surfaces of the anode-side separator 32A each have a plurality of grooves. The grooves of the facing surface of the pair of surfaces that faces the anode-side gas diffusion layer 31A are gas flow paths 32Ag. The grooves of the surface of the pair of surfaces that is on the opposite side from the facing surface are cooling water flow paths 32Aw. Each of the separators 32C, 32A is formed of a material that has electrical conductivity and a low permeability to gas.

[0077] In the solid polymer fuel cell 30, the oxidant gas is supplied to the air electrode 30C via the gas flow paths 32Cg of the cathode-side separator 32C. The fuel gas is supplied to the fuel electrode 30A via the gas flow paths 32Ag of the anode-side separator 32. Thus, the solid polymer fuel cell 30 generates electricity. In addition, air, oxygen, or the like can be used as the oxidant gas. Hydrogen can be used as the fuel gas.

[0078] [Method for producing titanium oxide for catalyst support]

[0079] The method for producing titanium oxide for catalyst support includes the steps of mixing titanium oxide with two or more kinds of salts, and obtaining rutile-type titanium oxide having a fiber shape by heating the mixture of titanium oxide and the salts at a temperature higher than the eutectic point of the salts.

[0080] In the production of the rutile-type titanium oxide, it is preferable to use a salt containing a sodium atom and a salt containing a phosphorus atom. That is, when two kinds of salts are used in the production of the titanium oxide for catalyst support, it is preferable to use a salt containing a sodium atom and a salt containing a phosphorus atom. For example, it is preferable to use sodium chloride (NaCl) and sodium hexametaphosphate ((NaPO3)6). In addition, the eutectic point when sodium chloride and sodium hexametaphosphate are used in a mass ratio of 8:1 is about 785°C. That is, when the mass ratio of sodium hexametaphosphate to sodium chloride is 1 / 8, the eutectic point is about 785°C.

[0081] [Method for producing catalyst for fuel cell]

[0082] The method for producing the fibrous catalyst 21 includes the steps of obtaining rutile-type titanium oxide having a fiber shape, mixing the rutile-type titanium oxide, titanyl sulfate, and urea to produce a dispersion liquid, heating the dispersion liquid, drying the heated dispersion liquid to produce a powder, and obtaining TiO x N y the catalyst. The chemical formula TiO x Ny x in the formula satisfies the following condition.

[0083] x = 2 - (y + j) (j > 0)

[0084] In addition, in the method of manufacturing the fibrous catalyst 21, the step of generating the dispersion liquid can also be a step of mixing the rutile-type titanium oxide, the titanyl sulfate, the urea, and the phosphoric acid to generate the dispersion liquid. Thereby, the powder generated can be subjected to thermal decomposition to obtain the Ti w O x N y P z catalyst. The formula Ti w O x N y P z w and x in the formula satisfy the following conditions.

[0085] w = 1 - (z + i) (i > 0)

[0086] x = 2 - (y + j) (j > 0)

[0087] In the manufacturing of the fibrous catalyst 21, the ratio of the number of phosphorus atoms to the number of titanium atoms used in the manufacturing of the fibrous catalyst 21 is a phosphorus / titanium ratio (R p ). That is, the ratio of the number of phosphorus atoms from the phosphoric acid to the number of titanium atoms from the titanyl sulfate is a phosphorus / titanium ratio (R p ). The phosphorus / titanium ratio (R p ) is preferably 0.2 or more and 0.5 or less. Thereby, the Ti w O x N y P z catalyst having improved catalytic activity for the oxygen reduction reaction can be obtained.

[0088] In the dispersion liquid generating process of generating the dispersion liquid, the powder of the titanyl sulfate (IV) can be mixed with the phosphoric acid for a time of several hours. In the heating process of heating the dispersion liquid, the dispersion liquid can be heated while stirring the dispersion liquid. In the thermal decomposition process of subjecting the powder generated in the powder generating process to thermal decomposition, the powder can be subjected to thermal decomposition in an environment supplied with nitrogen gas. In the thermal decomposition process, the temperature of the thermally decomposed powder is preferably set to a temperature higher than 973 K (700°C), and for example, can be set to 1123 K (850°C). In the thermal decomposition process, the period of the thermally decomposed powder can be set to, for example, several hours.

[0089] After the thermal decomposition process, a post-annealing process can also be performed. In the post-annealing process, the Ti w O x N y Pz The catalyst is heated. In the post-annealing process, the heated Ti w O x N y P z The temperature of the catalyst is set to, for example, 923 K (650°C).

[0090] [Forming material of membrane electrode assembly]

[0091] The polymer electrolyte membrane 11 is formed of, for example, a polymer having proton conductivity. The polymer having proton conductivity can be, for example, a fluorine-based resin, a hydrocarbon-based resin, or the like. The fluorine-based resin can be, for example, Nafion (manufactured by Dupont, registered trademark), Flemion (manufactured by Asahi Glass, registered trademark), Gore-Select (manufactured by Gore, registered trademark), or the like. The hydrocarbon-based resin can be, for example, an engineering plastic, a copolymer of an engineering plastic into which a sulfonic acid group is introduced, or the like.

[0092] The polymer electrolyte 22 can be, for example, a polymer substance having proton conductivity. The polymer electrolyte 22 can use a material that can be used in the formation of the above-described polymer electrolyte membrane 11.

[0093] In the polymer electrolyte 22, the dry mass value (equivalent weight: EW) per 1 mole of the proton-donating group is preferably included in a range of 400 or more and 1200 or less, and more preferably included in a range of 600 or more and 1000 or less. By the equivalent weight EW being 400 or more, a decrease in power generation performance due to flooding can be suppressed, and by the equivalent weight EW being 1200 or less, a decrease in proton conductivity can be suppressed, whereby a decrease in power generation performance can be suppressed.

[0094] In the cathode-side electrode catalyst layer 12C, the ratio (MH / MC) of the mass (MH) of the polymer electrolyte 22 to the mass (MC) of the fibrous catalyst 21 is preferably included in a range of 0.3 or more and 4.0 or less, and more preferably included in a range of 0.4 or more and 2.5 or less. By the ratio being 0.3 or more, a decrease in diffusion speed of protons can be suppressed, whereby a decrease in power generation performance can be suppressed. In addition, by the ratio being 0.3 or more, a decrease in mechanical properties of the electrode catalyst layer 12 can be suppressed. On the other hand, by the ratio being 4.0 or less, a decrease in power generation performance due to flooding can be suppressed.

[0095] [Manufacturing method of catalyst layer]

[0096] In manufacturing the electrode catalyst layer 12, first, a catalyst layer ink is prepared. Next, the prepared catalyst layer ink is applied to a substrate or a polymer electrolyte membrane 11 or the like, and a film formed by the application is dried, thereby manufacturing the electrode catalyst layer 12.

[0097] The ink for the catalyst layer contains the fibrous catalyst 21, the polymer electrolyte 22, and a solvent. The solvent can be a liquid that disperses or dissolves the polymer electrolyte 22. The solvent can be, for example, water, an alcohol, a ketone, an ether, an amine, an ester, acetic acid, propionic acid, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, a glycol, and a glycol ether, or the like.

[0098] The alcohol can be methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, and tert-butyl alcohol, or the like. The ketone can be acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, pentanone, heptanone, cyclohexanone, methyl cyclohexanone, propionyl acetone, diethyl ketone, dipropyl ketone, and diisobutyl ketone, or the like. The ether can be tetrahydrofuran, tetrahydropyran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, diethyl ether, dipropyl ether, and dibutyl ether, or the like. The amine can be isopropylamine, butylamine, isobutylamine, cyclohexylamine, diethylamine, and aniline, or the like. The ester can be propyl formate, isobutyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and butyl propionate, or the like. The glycol and the glycol ether can be, for example, ethylene glycol, diethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diacetone alcohol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, or the like.

[0099] The solid content concentration of the ink for the catalyst layer is preferably included in a range of 5 mass% or more and 30 mass% or less, and more preferably included in a range of 8 mass% or more and 20 mass% or less. By the solid content concentration being 5 mass% or more, the ink for the catalyst layer can have a viscosity that can suppress unevenness in the coating amount. By the solid content concentration being 30 mass% or less, the ink for the catalyst layer can have a viscosity that can suppress deterioration in the appearance of the electrode catalyst layer formed by the coating of the ink for the catalyst layer.

[0100] The coating method of the ink for the catalyst layer can be, for example, a doctor blade method, a die coating method, an immersion method, a screen printing method, a laminating roll coating method, a spray method, or the like.

[0101] The drying method of the catalyst layer ink can be, for example, warm air drying, IR (Infrared ray) drying, or the like. The drying temperature is preferably included in a range of 40°C or higher and 200°C or lower, and more preferably included in a range of 40°C or higher and 120°C or lower. By setting the drying temperature to 40°C or higher, the remaining of the solvent can be suppressed. By setting the drying temperature to 200°C or lower, the ignition of the catalyst layer ink can be suppressed. The drying time of the catalyst layer ink is preferably included in a range of 0.5 minutes or longer and 1 hour or shorter, and more preferably included in a range of 1 minute or longer and 30 minutes or shorter. By setting the drying time to 0.5 minutes or longer, the remaining of the solvent can be suppressed. By setting the drying time to 1 hour or shorter, the deformation of the polymer electrolyte membrane 11 caused by drying of the polymer electrolyte membrane 11 can be suppressed.

[0102] Alternatively, the catalyst ink for forming the electrode catalyst layer 12 can also be prepared by the following method. That is, in preparing the catalyst ink, first, a first catalyst ink is prepared, and then a second catalyst ink is prepared. The first catalyst ink includes a catalyst, a first polymer electrolyte, and a first solvent. The second catalyst ink includes a catalyst-embedded body formed from the first catalyst ink, a second polymer electrolyte, and a second solvent.

[0103] After the first catalyst ink is prepared, the catalyst-embedded body in which the catalyst is embedded with the first polymer electrolyte is generated by drying the first catalyst ink. Then, using the generated catalyst-embedded body, the second catalyst ink is prepared.

[0104] In preparing the second catalyst ink, the catalyst-embedded body can be heated before being mixed with the second solvent. In heating the catalyst-embedded body, the catalyst-embedded body is preferably heated at a temperature included in a range of 50°C or higher and 180°C or lower. Thereby, the second catalyst ink can be prepared without the first polymer electrolyte in the catalyst-embedded body being dissolved in the solvent and without hindering the proton conductivity.

[0105] A polymer electrolyte having proton conductivity can be used in the first polymer electrolyte and the second polymer electrolyte. From the aspect of improving the adhesion of the electrode catalyst layers 12A, 12C to the polymer electrolyte membrane 11, it is preferable that the first polymer electrolyte and the second polymer electrolyte are the same electrolyte as the polymer electrolyte membrane 11 or similar electrolytes. The first polymer electrolyte and the second polymer electrolyte can use, for example, fluorine-based resins and hydrocarbon-based resins. The fluorine resin can use, for example, Nafion (registered trademark) (manufactured by Dupont) or the like. The hydrocarbon-based resin can use, for example, sulfonated polyether ketone, sulfonated polyether sulfone, sulfonated polysulfide, and sulfonated polyphenyl or the like.

[0106] The first solvent and the second solvent are, for example, preferably a liquid capable of dispersing the high-molecular electrolyte or a liquid capable of dissolving the high-molecular electrolyte. The solvent can be water, an alcohol, a ketone, an ether, a sulfoxide, an amide, or the like. The alcohol can be methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 3-butanol, pentanol, ethylene glycol, diacetone alcohol, 1-methoxy-2-propanol, or the like. The ketone can be acetone, methyl ethyl ketone, pentanone, methyl isobutyl ketone, diisobutyl ketone, or the like. The ether can be dioxane, tetrahydrofuran, or the like. The sulfoxide can be dimethyl sulfoxide or the like. The amide can be dimethylformamide, dimethylacetamide, or the like. The first solvent and the second solvent can be used alone from among the above-described solvents or a plurality of solvents can be used in combination. The first solvent and the second solvent are preferably solvents that are easily removed by heating.

[0107] The solvent containing the catalyst or the like can also be subjected to a dispersion treatment when the first catalyst ink is prepared and when the second catalyst ink is prepared. The dispersion treatment can be performed, for example, using a ball mill, a bead mill, a roll mill, a shear mill, a wet mill, an ultrasonic disperser, a homogenizer, or the like.

[0108] The second catalyst ink can be applied, for example, using a roll coater, an air knife coater, a blade coater, a rod coater, a reverse coater, a bar coater, a comma coater, a die coater, a gravure coater, a screen coater, spraying, a spinner, or the like.

[0109] The method of drying the first catalyst ink and the method of drying the second catalyst ink can be warm air drying, IR drying, or the like. Either one of the warm air drying and the IR drying or both can be used when the first catalyst ink and the second catalyst ink are dried. When the first catalyst ink is dried to form the catalyst-embedded body, the first catalyst ink is preferably dried at a temperature included in a range of 30°C or higher and 140°C or lower. Thus, in the process of preparing the second catalyst ink, the first high-molecular electrolyte contained in the catalyst-embedded body is not dissolved in the solvent, and a decrease in the proton conductivity on the surface of the catalyst can be suppressed.

[0110] The ratio (C:P) of the mass (C) of the catalyst to the mass (P) of the first high-molecular electrolyte in the catalyst-embedded body is preferably included in a range of 1:0.01 to 1:30. That is, the ratio (P / C) of the mass (P) of the first high-molecular electrolyte to the mass (C) of the catalyst is preferably included in a range of 1 / 30 or more and 100 or less. Thus, the diffusivity of oxygen or the like in the catalyst-embedded body is not hindered, and the proton conductivity on the surface of the catalyst is improved, and thus the number of active sites can be increased.

[0111] [Method for manufacturing membrane-electrode assembly]

[0112] The membrane-electrode assembly 10 is manufactured, for example, by hot-pressing the electrode catalyst layers 12A, 12C to the polymer electrolyte membrane 11 after forming the electrode catalyst layers 12A, 12C on a transfer substrate or gas diffusion layers 31A, 31C. Alternatively, the membrane-electrode assembly 10 is manufactured by directly forming the electrode catalyst layers 12A, 12C on the polymer electrolyte membrane 11.

[0113] When using the transfer substrate, a substrate with an electrode catalyst layer is manufactured by applying the catalyst ink on the transfer substrate, and then drying the catalyst ink. Thereafter, the electrode catalyst layers 12A, 12C are joined to the polymer electrolyte membrane 11, for example, by heating and pressing in a state where the surface of the electrode catalyst layers 12A, 12C in the substrate with an electrode catalyst layer is in contact with the polymer electrolyte membrane 11. By joining the electrode catalyst layers 12A, 12C to both surfaces of the polymer electrolyte membrane 11, the membrane-electrode assembly 10 can be manufactured.

[0114] The transfer substrate is a substrate that satisfies at least the following conditions: the catalyst ink can be applied on one surface; the catalyst ink can be dried by heating; and the electrode catalyst layers 12A, 12C can be transferred to the polymer electrolyte membrane 11. The transfer substrate can include, for example, a polymer film and a fluororesin film having heat resistance. The polymer forming the polymer film can be, for example, polyethylene terephthalate, polyamide, polyimide, polystyrene, polysulfone, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyether imide, polybenzimidazole, polyamide-imide, polyacrylate, polyethylene naphthalate, and poly-m-xylylene amide, or the like. The resin forming the fluororesin film can be, for example, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoro-perfluoroalkyl vinyl ether copolymer, or the like.

[0115] The transfer substrate can also be a substrate in which a release treatment is applied to the surface of the above-described polymer film or fluororesin film, or a substrate in which the above-described film and a release layer are formed in one body by co-extrusion or the like.

[0116] The transfer substrate can have a single-layer structure, or can have a multi-layer structure. When the transfer substrate has a multi-layer structure, the layer on the outermost surface can have an opening portion. The opening portion is a position where a portion of the layer is removed by cutting or punching, or the like. In addition, the electrode catalyst layers 12A, 12C in which the catalyst ink is dried can have a shape corresponding to the opening portion.

[0117] When the electrode catalyst layers 12A, 12C are formed directly on the polymer electrolyte membrane 11, for example, the electrode catalyst layers 12A, 12C are formed by applying a catalyst ink on the surface of the polymer electrolyte membrane 11 and then removing the solvent from the catalyst ink. The method of forming the electrode catalyst layers 12A, 12C directly on the polymer electrolyte membrane 11 is preferable in that the adhesion between the polymer electrolyte membrane 11 and the electrode catalyst layers 12A, 12C is high, and there is no risk of the electrode catalyst layers 12A, 12C being broken by heat press bonding.

[0118] When the solid polymer fuel cell 30 is provided with the gaskets 13A, 13C, the gaskets 13A, 13C are arranged on the portions of the polymer electrolyte membrane 11 that are not covered by the electrode catalyst layers 12A, 12C. The gaskets 13A, 13C only need to satisfy the conditions of being able to be applied or attached with an adhesive material on at least one side, and being able to be attached to the polymer electrolyte membrane 11. The forming material of the gaskets 13A, 13C can use the forming material of the above-mentioned transfer substrate. The average value of the thickness of one gasket 13A, 13C is preferably 1 μm or more and 500 μm or less, more preferably 3 μm or more and 200 μm or less, and further preferably 5 μm or more and 100 μm or less.

[0119] The average value of the thickness of one polymer electrolyte membrane 11 is preferably 1 μm or more and 500 μm or less, more preferably 3 μm or more and 200 μm or less, and further preferably 5 μm or more and 100 μm or less.

[0120] According to the above-mentioned manufacturing method, since the catalyst for fuel cells is embedded with the first polymer electrolyte, the proton conductivity on the surface of the catalyst can be improved.

[0121] [Example]

[0122] Reference Figures 4-9 An example will be described.

[0123] [Titanium oxide for catalyst carrier]

[0124] [Example 1]

[0125] Titanium oxide (TiO2) (IV) (P25, manufactured by Japan Aerosil Co., Ltd.) 2 g, sodium chloride (NaCl) 8 g, and sodium hexametaphosphate ((NaPO3)6) 1 g were mixed using a marver. The mixture was put in a zirconia crucible, and the zirconia crucible was covered with an alumina lid. Further, the zirconia crucible was heated using a small muffle furnace under an atmospheric environment gas at 900°C for 8 hours. Further, the eutectic point of sodium chloride and sodium hexametaphosphate when mixed at a mass ratio of 8:1 was about 785°C.

[0126] After the zirconia crucible was cooled to room temperature, the contents of the zirconia crucible were repeatedly washed with warm water and centrifuged. Thus, the catalyst support titania of Example 1 was obtained.

[0127] [Example 2]

[0128] The heating temperature under the atmospheric environment gas in Example 1 was changed to 867°C, and otherwise, the catalyst support titania of Example 2 was obtained using the method described in Example 1.

[0129] [Example 3]

[0130] The heating temperature under the atmospheric environment gas in Example 1 was changed to 825°C, and otherwise, the catalyst support titania of Example 3 was obtained using the method described in Example 1.

[0131] [Example 4]

[0132] Sodium hexametaphosphate ((NaPO3)6) 1 g in Example 1 was changed to disodium hydrogen phosphate (Na2HPO4) 2 g, and otherwise, the catalyst support titania of Example 4 was obtained using the method described in Example 1. Furthermore, the eutectic point when sodium chloride and disodium hydrogen phosphate are mixed at a mass ratio of 4: 1 is about 735°C.

[0133] [Comparative Example 1]

[0134] Titanium oxysulfate (IV) (TiOSO4) 12 g was added to a mixture of glycerol (CH2(OH)CH(OH)CH2(OH)) 45 mL, ethanol (CH3CH2OH) 90 mL, and diethyl ether ((CH3CH2)2O) 45 mL. After that, the mixture was simultaneously subjected to ultrasonic irradiation and stirring, and the obtained suspension was moved to a Teflon (registered trademark) autoclave. The suspension was subjected to a solvothermal treatment while stirring for 6 hours at 140°C, and after that, the treatment target was naturally cooled, and thus a powder was obtained. The obtained powder was repeatedly washed with ethanol and centrifuged. After that, the washed treatment target was heated and dried using an open quartz tube furnace for 12 hours. Thus, the catalyst support titania of Comparative Example 1 was obtained.

[0135] [Method of Evaluation]

[0136] [X-ray Diffraction Measurement]

[0137] X-ray diffraction patterns of the titanium oxide for catalyst support of Examples 1 to 4 and the titanium oxide for catalyst support of Comparative Example 1 were obtained using an X-ray diffractometer (MiniFlex600, manufactured by Rigaku Corporation). At this time, the X-ray diffraction patterns were measured in a range of 20° to 80°.

[0138] [Scanning Electron Microscope Images]

[0139] Scanning electron microscope (SEM) images of the titanium oxide for catalyst support of Examples 1 to 4 and the titanium oxide for catalyst support of Comparative Example 1 were taken using a field emission type electron microscope (JSM-7000F, manufactured by JEOL Ltd.). At this time, the magnification was set to 5000 times.

[0140] [Results of Evaluation]

[0141] The X-ray diffraction patterns of Example 1 and Comparative Example 1 are shown in Figure 4 .

[0142] As shown in Figure 4 , the titanium oxide for catalyst support of Example 1 was a rutile-type titanium oxide, and the titanium oxide for catalyst support of Comparative Example 1 was an anatase-type titanium oxide. As such, it was found that, by using a molten salt as in the production method of Example 1, a rutile-type titanium oxide having a fiber shape could be obtained. Further, the same X-ray diffraction patterns as in Example 1 were obtained for the titanium oxide for catalyst support of Examples 2 to 4.

[0143] SEM images of the titanium oxide for catalyst support of Examples 1 to 4 are shown in Figures 5-8 . Further, Figure 5 is an SEM image of the titanium oxide for catalyst support of Example 1, Figure 6 is an SEM image of the titanium oxide for catalyst support of Example 2, Figure 7 is an SEM image of the titanium oxide for catalyst support of Example 3, Figure 8 is an SEM image of the titanium oxide for catalyst support of Example 4.

[0144] As shown in Figures 5-8 , the titanium oxide for catalyst support of Examples 1 to 4 had a fiber shape. In addition, as shown in Figures 5-7 , by lowering the heating temperature of the mixture, the aspect ratio of the titanium oxide for catalyst support could be increased. In addition, from Figure 5 and Figure 8It is seen from the comparison that the aspect ratio of the titanium oxide for a catalyst support becomes larger by using NaCl and (NaPO3)6than by using NaCl and Na2HPO4. It is thus seen that the aspect ratio of the fibrous titanium oxide can be controlled by selecting the heating temperature at the time of manufacturing the titanium oxide for a catalyst support and the kind of the salt mixed with the titanium oxide.

[0145] It is also seen that the titanium oxide for a catalyst support of Comparative Example 1 has a fibrous shape when observed by the field emission type electron microscope.

[0146] [Catalyst for fuel cell]

[0147] [Example 5]

[0148] The titanium oxide for a catalyst support of Example 3, titanyl sulfate (IV), urea ((NH2)2CO), and hydrochloric acid (HCl) were mixed and stirred in distilled water, whereby a dispersion liquid was produced. At this time, the mass ratio (R) of the titanium oxide for a catalyst support to the titanium oxide (TiO2) from titanyl sulfate (IV) was set to 1. The ratio of the mass of urea to the mass of the titanium oxide from titanyl sulfate was set to 100. In addition, the concentration of hydrochloric acid was set to 1.0 mol / dm3. 3 After the dispersion liquid was heated at 250°C while being stirred, the dispersion liquid was dried, whereby a powder was obtained. The powder obtained by the drying was heated at 1123 K (850°C) for 2 hours in an environment supplied with nitrogen. Thus, the TiO2of Example 5 was obtained. x N y Catalyst.

[0149] [Example 6]

[0150] The mass ratio R in Example 5 was set to 5, and otherwise, the TiO2of Example 6 was obtained using the method described in Example 5. x N y Catalyst.

[0151] [Example 7]

[0152] The mass ratio R in Example 5 was set to 20, and otherwise, the TiO2of Example 7 was obtained using the method described in Example 5. x N y Catalyst.

[0153] [Method of evaluation]

[0154] [Measurement by fluid voltammetry]

[0155] The activity of the manufactured catalyst for fuel cells was evaluated using the rotating disk method, one of the fluid voltammetry methods. In obtaining the fluid voltammogram, the mass fraction of Nafion (Nafion is a registered trademark) in the electrode catalyst layer was set to 0.05, and the catalyst packing amount m was constant at 0.86 mg / cm 2 . A 3-electrode cell was used in the electrochemical measurement at room temperature in 0.1 mol / dm 3 of sulfuric acid. After bubbling oxygen and nitrogen continuously for 1800 seconds, the fluid voltammogram was recorded. At this time, the disk potential (E) with respect to the reversible hydrogen electrode (RHE) was set to 0.05 V to 1.2 V, the scan rate was set to 5 mV / s, and the rotation speed of the rotating disk electrode was set to 1500 rpm. The value obtained by subtracting the current density (j N ) measured in the nitrogen-saturated solution from the current density (j O ) measured in the oxygen-saturated solution was used for the evaluation.

[0156] [Results of Evaluation]

[0157] The fluid voltammograms obtained for the catalyst for fuel cells of Examples 5, 6, and 7 are shown in Figure 9 .

[0158] As shown in Figure 9 , the catalyst for fuel cells had the highest catalytic activity when the mass ratio R was 1. It is considered that the catalyst for fuel cells had the highest catalytic activity when the mass ratio R was 1 because the electrical conductivity of the catalyst for fuel cells could be improved by the mass ratio R being small.

[0159] As described above, according to one embodiment of the catalyst for fuel cells, the electrode catalyst layer, the membrane-electrode assembly, the solid polymer fuel cell, the manufacturing method of the titanium oxide for catalyst carrier, and the manufacturing method of the catalyst for fuel cells, the effects described below can be obtained.

[0160] According to the fibrous catalyst 21, the catalyst had the catalytic activity for the redox reaction even if the composition in which the content of platinum was suppressed.

[0161] [Manufacturing Example]

[0162] Hereinafter, a manufacturing example of the electrode catalyst layer using the above-described catalyst for fuel cells (TiO x N y catalyst) is described.

[0163] [Manufacturing Example 1]

[0164] The fuel cell catalyst of Example 5 and 20 mass% of a polymer electrolyte solution (trade name: Nafion (registered trademark), manufactured by Dupont) were mixed in a solvent, and the solvent containing the fuel cell catalyst and the polymer electrolyte was subjected to dispersion treatment using a planetary ball mill. Thus, a first catalyst ink was obtained. In the first catalyst ink, the ratio of the mass of the fuel cell catalyst to the mass of the polymer electrolyte was set to 1 : 0.25. The solvent was a mixture of ultrapure water and 1-propanol. In the solvent, the ratio of the volume of the ultrapure water to the volume of the 1-propanol was set to 1 : 1. In the first catalyst ink, the solid content was set to 15 mass%.

[0165] As a substrate for drying the first catalyst ink, a polytetrafluoroethylene (PTFE) sheet was used. The first catalyst ink was applied to the PTFE sheet using a doctor blade, and then the first catalyst ink was dried at 80°C under an atmospheric environment gas for 5 minutes. Thereafter, a catalyst-embedded body, which was a fuel cell catalyst embedded with a polymer electrolyte, was recovered from the substrate. Subsequently, the catalyst-embedded body was subjected to heat treatment at 70°C.

[0166] The heat-treated catalyst-embedded body and 20 mass% of a polymer electrolyte solution (trade name: Nafion (registered trademark), manufactured by Dupont) were mixed in a solvent, and the solvent containing the catalyst-embedded body was subjected to dispersion treatment using a planetary ball mill. Thus, a second catalyst ink was obtained. In the second catalyst ink, the ratio of the mass of the fuel cell catalyst to the mass of the polymer electrolyte was set to 1 : 0.8. The solvent was a mixture of ultrapure water and 1-propanol. In the solvent, the ratio of the volume of the ultrapure water to the volume of the 1-propanol was set to 1 : 1. In addition, in the second catalyst ink, the solid content was set to 15 mass%.

[0167] A PTFE sheet was used as a substrate for transfer. The second catalyst ink was applied to the PTFE sheet using a doctor blade, and then the second catalyst ink was dried at 80°C under an atmospheric environment gas for 5 minutes. At this time, the thickness of the electrode catalyst layer was adjusted so that the catalyst carrying amount reached 5.0 mg / cm 2 Thus, a cathode-side electrode catalyst layer of Production Example 1 was obtained.

[0168] [Production Example 2]

[0169] The same catalyst for fuel cells as that of Production Example 1 and a 20 mass% polymer electrolyte solution were mixed in a solvent, and a planetary ball mill was used to perform dispersion treatment on the solvent containing the catalyst for fuel cells and the polymer electrolyte. Thus, a catalyst ink was obtained. In the catalyst ink, the ratio of the mass of the catalyst for fuel cells to the mass of the polymer electrolyte was set to 1 : 0.8. The solvent used was a mixture of ultrapure water and 1-propanol. In the solvent, the ratio of the volume of the ultrapure water to the volume of the 1-propanol was set to 1 : 1. In addition, the solid content in the catalyst ink was set to 15 mass%.

[0170] A PTFE sheet was prepared as a transfer substrate in the same manner as in Production Example 1. The catalyst ink was applied to the PTFE sheet by the same method as in Production Example 1, and the catalyst ink was dried. At this time, the thickness of the electrode catalyst layer was adjusted so that the supported amount of the catalyst would be 5.0 mg / cm 2 of the cathode-side electrode catalyst layer of Production Example 2 was obtained.

[0171] [Anode-side electrode catalyst layer]

[0172] A platinum-supported carbon catalyst having a platinum supported amount of 50 mass% and a 20 mass% polymer electrolyte solution were mixed in a solvent, and a planetary ball mill was used to perform dispersion treatment on the solvent containing the platinum-supported carbon catalyst and the polymer electrolyte. At this time, the dispersion time was set to 60 minutes. Thus, a catalyst ink for the anode-side electrode catalyst layer was obtained. In addition, in the catalyst ink, the ratio of the mass of the carbon in the platinum-supported carbon to the mass of the polymer electrolyte was set to 1 : 1. The solvent used was a mixture of ultrapure water and 1-propanol. In the solvent, the ratio of the volume of the ultrapure water to the volume of the 1-propanol was set to 1 : 1. In addition, the solid content in the catalyst ink was set to 10 mass%. The catalyst ink was applied to a transfer substrate by the same method as in Production Example 1, and the catalyst ink was dried. At this time, the thickness of the electrode catalyst layer was adjusted so that the supported amount of the catalyst would be 0.1 mg / cm 2 of the anode-side electrode catalyst layer was obtained.

Claims

1. A method for producing a catalyst for fuel cells, comprising the steps of: a step of obtaining a rutile-type titanium oxide having a fiber shape by a method for producing a catalyst support titanium oxide; a step of mixing the rutile-type titanium oxide, titanyl sulfate, and urea to produce a dispersion liquid; a step of heating the dispersion liquid; a step of drying the heated dispersion liquid to produce a powder; and The powder thus obtained is subjected to thermal decomposition to obtain TiO x N y the step of the catalyst, the method for producing a catalyst support titanium oxide comprises the steps of: a step of mixing a titanium oxide with two or more kinds of salts to produce a mixture; and a step of obtaining the rutile-type titanium oxide having a fiber shape by heating the mixture at a temperature higher than a eutectic point of the two or more kinds of salts, The TiO x N y In the catalyst, a part of oxygen atoms in the metal oxide of the rutile type is replaced by nitrogen atoms, Chemical formula TiO x N y x in the chemical formula satisfies the following conditions: x = 2 - (y + j), where j > 0.

2. A method for producing a catalyst for fuel cells, comprising the steps of: a step of obtaining a rutile-type titanium oxide having a fiber shape by a method for producing a catalyst support titanium oxide; a step of mixing the rutile-type titanium oxide, titanyl sulfate, urea, and phosphoric acid to produce a dispersion liquid; a step of heating the dispersion liquid; a step of drying the heated dispersion liquid to produce a powder; and subjecting the generated powder to thermal decomposition to obtain Ti w O x N y P z catalyst, the method for producing a catalyst support titanium oxide comprises the steps of: a step of mixing a titanium oxide with two or more kinds of salts to produce a mixture; and a step of obtaining the rutile-type titanium oxide having a fiber shape by heating the mixture at a temperature higher than a eutectic point of the two or more kinds of salts, The Ti w O x N y P z In the catalyst, a part of oxygen atoms in the metal oxide of the rutile type is replaced by nitrogen atoms, and a part of Ti atoms is replaced by phosphorus atoms, Chemical formula Ti w O x N y P z w and x in the above formula satisfy the following conditions: w = 1 - (z + i), where i > 0; x = 2 - (y + j), where j > 0.

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