Method for manufacturing a catalyst, catalyst, method for manufacturing a composition, composition, electrode, method for manufacturing an electrode, fuel cell, metal-air battery

Abstract

The present invention provides a catalyst having excellent oxygen reduction catalytic ability and excellent durability when used as an electrode for a fuel cell or metal-air battery; and a method for producing a catalyst having excellent oxygen reduction catalytic ability and excellent durability when used as an electrode for a fuel cell or metal-air battery. The catalyst production method comprises: step (a) of dissolving a metal complex in a solvent to prepare a solution; step (b) of dispersing conductive powder in the solution to prepare a dispersion; and step (c) of removing the solvent from the dispersion, allowing the metal complex to adsorb on the surface of the conductive powder to form a complex, and using the complex as a catalyst.

Description

Technical Field

[0001] The present invention relates to a method for producing a catalyst, a catalyst, a method for producing a composition, a composition, an electrode, a method for producing an electrode, a fuel cell, and a metal-air battery. Background Art

[0002] Fuel cells and metal-air batteries (hereinafter sometimes referred to as "fuel cells, etc.") that utilize redox reactions are well known. In fuel cells, platinum-supported carbon materials can be used as catalysts to promote the oxygen reduction reaction. Platinum-supported carbon materials have excellent oxygen reduction catalytic performance.

[0003] On the other hand, in metal-air batteries, a manganese dioxide-supported carbon material can be used as the catalyst.

[0004] However, since platinum is expensive and its resources are limited, attempts are being made to develop alternative materials for platinum-supported carbon materials. For example, a transition metal complex can be used as a catalyst to replace platinum. As a representative example, patent document 1 describes an air electrode catalyst using iron phthalocyanine (Fe-Pc). Example 1 of patent document 1 discloses a method for manufacturing the following air electrode catalyst: preparing an Fe-Pc dispersion obtained by ball milling iron phthalocyanine and 2-propanol, drying and solidifying the slurry obtained by mixing a conductive additive, a co-catalyst, a binder, etc. in the Fe-Pc dispersion, and manufacturing an air electrode mixture.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-85925 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] Iron phthalocyanine has low solubility in 2-propanol. Therefore, in the method described in Patent Document 1, iron phthalocyanine does not dissolve in 2-propanol but forms a dispersion in which iron phthalocyanine is dispersed in 2-propanol, and iron phthalocyanine crystals are present in the dispersion. Here, in the field of oxygen reduction catalysts such as fuel cells, it has long been believed that the presence of crystalline iron phthalocyanine helps to improve the oxygen reduction catalytic ability and durability when made into electrodes. In addition, in the existing technology using metal complex dispersions, the technical idea of improving the oxygen reduction catalytic ability and durability of the catalyst by increasing the concentration of the crystalline metal complex is common.

[0010] However, the method described in Patent Document 1 is insufficient due to the presence of iron phthalocyanine crystals in the dispersion. Specifically, iron phthalocyanine molecules are not adsorbed on the carbon surface, preventing sufficient interaction between iron phthalocyanine and carbon. Consequently, the oxygen reduction catalytic performance of existing oxygen reduction catalysts still needs improvement.

[0011] Furthermore, oxygen reduction catalysts for fuel cells and the like are required to have excellent durability when used as electrodes.

[0012] The present invention provides: a catalyst having excellent oxygen reduction catalytic ability and excellent durability when used as an electrode for a fuel cell or a metal-air battery; and a method for producing a catalyst having excellent oxygen reduction catalytic ability and excellent durability when used as an electrode for a fuel cell or a metal-air battery.

[0013] Technical means to solve problems

[0014] The inventors of the present invention conducted intensive studies and found that the oxygen reduction catalytic ability of the catalyst can be improved by using a metal complex solution having a relatively low metal complex concentration instead of a metal complex dispersion.

[0015] That is, the present invention includes the following embodiments.

[0016] [1] A method for producing a catalyst, comprising:

[0017] Step (a), dissolving the metal complex in a solvent to prepare a solution;

[0018] Step (b), dispersing conductive powder in the above solution to prepare a dispersion; and

[0019] Step (c), removing the solvent from the dispersion,

[0020] The metal complex is adsorbed on the surface of the conductive powder to form a composite, and the composite is used as a catalyst.

[0021] [2] The method for producing a catalyst according to [1], wherein the concentration of the metal complex in the solution is 0.0001 g / L to 5 g / L.

[0022] [3] The method for producing a catalyst according to [1] or [2], wherein the composite is used as a catalyst without being subjected to a heat treatment at 200°C or higher.

[0023] [4] The method for producing a catalyst according to any one of [1] to [3], wherein the steps (a) and (b) are performed at a temperature not higher than the boiling point of the solvent.

[0024] [5] The method for producing a catalyst according to any one of [1] to [4], wherein the steps (a) and (b) are performed at a temperature of 80°C or lower.

[0025] [6] The method for producing a catalyst according to any one of [1] to [5], wherein the metal complex is adsorbed on the surface of the conductive powder at a temperature not higher than the boiling point of the solvent.

[0026] [7] The method for producing a catalyst according to any one of [1] to [6], wherein the solvent is removed by filtering the dispersion.

[0027] [8] The method for producing a catalyst according to [7], wherein the absorbance of the filtrate after filtration is reduced by 10% or more compared to the solution.

[0028] [9] The method for producing a catalyst according to any one of [1] to [8], wherein the solubility of the metal complex in the solvent is 0.1 g / L or more.

[0029]

[10] The method for producing a catalyst according to any one of [1] to [9], wherein the metal complex is a metal complex represented by the following formula (1).

[0030] [Chemical Formula 1]

[0031]

[0032] In formula (1), X1 to X8 are each independently a hydrogen atom or a halogen atom, D1 to D8 are each independently a nitrogen atom or a carbon atom, a hydrogen atom or a halogen atom is bonded to the carbon atom, and M is a metal atom.

[0033]

[11] The method for producing a catalyst according to any one of [1] to

[10] , wherein the metal complex is a metal complex represented by the following formula (11).

[0034] [Chemical Formula 2]

[0035]

[0036] In formula (11), X1 to X8 are each independently a hydrogen atom or a halogen atom, D1, D3, D5, and D7 are each independently a nitrogen atom or a carbon atom, at least one of D1, D3, D5, and D7 is a carbon atom, a hydrogen atom or a halogen atom is bonded to the above-mentioned carbon atom, and M is a metal atom.

[0037]

[12] The method for producing a catalyst according to any one of [1] to

[11] , wherein the solubility parameter of the solvent is 10 (MPa) 1 / 2 ~20(MPa) 1 / 2 .

[0038]

[13] The method for producing a catalyst according to any one of [1] to

[12] , wherein the solvent is at least one selected from dimethyl sulfoxide and N,N-dimethylformamide.

[0039]

[14] The method for producing a catalyst according to any one of [1] to

[13] , wherein the conductive powder is at least one selected from a carbon material, a metal material, and a metal oxide material.

[0040]

[15] A catalyst obtained by the method for producing a catalyst according to any one of [1] to

[14] .

[0041]

[16] A method for producing a composition, comprising:

[0042] Step (a), dissolving the metal complex in a solvent to prepare a solution;

[0043] Step (b), dispersing conductive powder in the above solution to prepare a dispersion; and

[0044] Step (c), removing the solvent from the dispersion,

[0045] The metal complex is adsorbed on the surface of the conductive powder to form a composite, and the composite is used as a catalyst.

[0046] The method for producing the composition further comprises:

[0047] In step (d), the catalyst is mixed with a liquid medium.

[0048]

[17] A composition comprising a catalyst obtained by the method for producing a catalyst according to any one of [1] to

[14] and a liquid medium.

[0049]

[18] An electrode comprising a catalyst obtained by the method for producing a catalyst according to any one of [1] to

[14] .

[0050]

[19] A method for manufacturing an electrode, comprising:

[0051] Step (a), dissolving the metal complex in a solvent to prepare a solution;

[0052] Step (b), dispersing conductive powder in the above solution to prepare a dispersion; and

[0053] Step (c), removing the solvent from the dispersion;

[0054] The metal complex is adsorbed on the surface of the conductive powder to form a composite, and the composite is used as a catalyst.

[0055] The method for manufacturing the electrode further comprises:

[0056] Step (d), mixing the catalyst with a liquid medium; and

[0057] In step (e), a mixture of the catalyst and the liquid medium is applied to the surface of the substrate, and the liquid medium is removed.

[0058]

[20] A fuel cell comprising the electrode described in

[18] .

[0059]

[21] A metal-air battery comprising the electrode described in

[18] .

[0060] Effects of the Invention

[0061] The present invention can provide: a catalyst having excellent oxygen reduction catalytic ability and excellent durability when used as an electrode for a fuel cell or a metal-air battery; and a method for producing a catalyst having excellent oxygen reduction catalytic ability and excellent durability when used as an electrode for a fuel cell or a metal-air battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a schematic diagram for explaining the method for producing the catalyst of the present invention in comparison with a conventional method.

[0063] Figure 2 This is a schematic diagram for explaining a comparison between a catalyst obtained by the production method of the present invention and a catalyst obtained by a conventional method.

[0064] Figure 3 This is a photograph showing a solution of FeTPP used in Example 1 dissolved in DMSO.

[0065] Figure 4 This is a photograph showing a dispersion obtained by dispersing MWCNTs in a solution of FeTPP dissolved in DMSO in Example 1.

[0066] Figure 5 This is a photograph showing the catalyst obtained in Example 1.

[0067] Figure 6 This is a photograph showing the catalyst obtained in Example 1.

[0068] Figure 7This is an observation image of the catalyst of Example 1 obtained by TEM.

[0069] Figure 8 This is an observation image of the catalyst of Comparative Example 1 obtained by SEM.

[0070] Figure 9 This is a graph showing the comparison of the redox characteristics of each electrode of Example 1 and Comparative Examples 1 to 4 based on the LSV measurement results at 1600 rpm.

[0071] Figure 10 This is a graph showing the comparison of the redox characteristics of Example 1, Comparative Example 3, and Comparative Example 4 based on the LSV measurement results at 1600 rpm.

[0072] Figure 11 This is a graph comparing LSV curves obtained when cyclic voltammograms were performed using the electrode of Example 1 for 1 cycle, 50 cycles, and 100 cycles.

[0073] Figure 12 This is a graph comparing LSV curves obtained when the cyclic voltammogram was performed using the Pt / C electrode of Comparative Example 3 for 1 cycle, 50 cycles, and 100 cycles. DETAILED DESCRIPTION

[0074] In this specification, the metal complex represented by formula (1) is referred to as metal complex (1). Metal complexes represented by other formulae are also referred to in the same manner.

[0075] "Heteroatom" refers to atoms other than carbon and hydrogen atoms.

[0076] "To" indicating a numerical range means that the numerical values described before and after it are included as the lower limit and the upper limit.

[0077] <Method for producing catalyst>

[0078] The method for producing a catalyst of the present invention comprises the following steps (a), (b), and (c). In the method for producing a catalyst of the present invention, the metal complex is adsorbed on the surface of the conductive powder to form a composite, and the composite is used as a catalyst.

[0079] Step (a): A step of dissolving a metal complex in a solvent to prepare a solution.

[0080] Step (b): A step of dispersing conductive powder in the above solution to prepare a dispersion.

[0081] Step (c): a step of removing the solvent from the dispersion.

[0082] (Step (a))

[0083] In step (a), the metal complex is dissolved in a solvent to prepare a solution (S). The solution (S) contains the metal complex and a solvent that dissolves the metal complex. The temperature, pressure, and other conditions used in preparing the solution are not particularly limited as long as they allow the metal complex to dissolve in the solvent.

[0084] For example, the temperature during solution preparation is preferably a temperature not higher than the boiling point of the solvent. The solution is usually prepared at room temperature (eg, 25° C.) or under atmospheric pressure.

[0085] The metal complex will be described.

[0086] Specific examples of metal complexes include iron complexes, cobalt complexes, etc. However, the metal complexes may be transition metal complexes, lanthanide metal complexes, actinide metal complexes, etc., and are not limited to iron complexes, cobalt complexes, and metal complexes.

[0087] The metal complex in the present invention is preferably a metal complex (1) represented by the following formula (1). Metal complex (1) has the advantage of being useful as a platinum substitute. In particular, the four nitrogen atoms coordinated around the metal atom M constitute part of the pyridine ring structure. It is believed that the four nitrogen atoms constituting part of the pyridine ring structure contribute to excellent solubility in solvents.

[0088] [Chemical Formula 3]

[0089]

[0090] In formula (1), X1 to X8 are each independently a hydrogen atom or a halogen atom, D1 to D8 are each independently a nitrogen atom or a carbon atom, a hydrogen atom or a halogen atom is bonded to the carbon atom, and M is a metal atom.

[0091] Examples of the metal complex (1) include the following metal complex (11), metal complex (12), and metal complex (13).

[0092] [Chemical Formula 4]

[0093]

[0094] In formula (11), X1 to X8 are each independently a hydrogen atom or a halogen atom, D1, D3, D5, and D7 are each independently a nitrogen atom or a carbon atom, at least one of D1, D3, D5, and D7 is a carbon atom, a hydrogen atom or a halogen atom is bonded to the above-mentioned carbon atom, and M is a metal atom.

[0095] [Chemical Formula 5]

[0096]

[0097] In formula (12), X1 to X8 are each independently a hydrogen atom or a halogen atom, and M is a metal atom.

[0098] [Chemical Formula 6]

[0099]

[0100] In formula (13), X1 to X8 are each independently a hydrogen atom or a halogen atom, and M is a metal atom.

[0101] Specific examples of the metal complex (11) include the following metal complex (11-1). However, specific examples of the metal complex (11) are not limited to these examples.

[0102] [Chemical Formula 7]

[0103]

[0104] In formula (11-1), M is a metal atom.

[0105] Specific examples of the metal complex (12) include the following metal complex (12-1). However, specific examples of the metal complex (12) are not limited to these examples.

[0106] [Chemical Formula 8]

[0107]

[0108] In formula (12-1), M is a metal atom.

[0109] Specific examples of the metal complex (13) include the following metal complex (13-1). However, specific examples of the metal complex (13) are not limited to these examples.

[0110] [Chemical Formula 9]

[0111]

[0112] In formula (13-1), M is a metal atom.

[0113] Among metal complex (11), metal complex (12), and metal complex (13), metal complex (11) is preferred from the viewpoint of improving oxygen reduction catalytic ability. Furthermore, when metal complex (11) is used, solubility in solvents tends to improve. As a result, affinity with conductive powder is improved, and the metal complex is easily and uniformly adsorbed on the surface of the conductive powder.

[0114] Here, in the metal complex (1), isomers such as the following metal complex (11-1′) and the following metal complex (12-1′) may exist.

[0115] [Chemical Formula 10]

[0116]

[0117] In formula (11-1'), X1 to X8 are independently a hydrogen atom or a halogen atom, D1, D3, D5, and D7 are independently a nitrogen atom or a carbon atom, at least one of D1, D3, D5, and D7 is a carbon atom, a hydrogen atom or a halogen atom is bonded to the above carbon atom, and M is a metal atom.

[0118] [Chemical Formula 11]

[0119]

[0120] In formula (12-1'), X1 to X8 are each independently a hydrogen atom or a halogen atom, and M is a metal atom.

[0121] In the present invention, the metal complex is a concept that includes isomers such as those shown in the above formula (11-1') and the above formula (12-1'). Here, the isomers of the metal complex are not limited to the isomers shown in the above formula (11-1') and the above formula (12-1'). For example, in the above formula (11-1'), in at least one ring structure selected from the ring structures containing D1, D3, D5, and D7, the position of the nitrogen atom can be exchanged with any position of D1, D3, D5, and D7 within the same ring structure.

[0122] The embodiments of the metal complex (1) are described in further detail below. In any embodiment, isomers such as those represented by formula (11-1') or formula (12-1') may exist. These isomers are included in the embodiments of the metal complex of the present invention.

[0123] In the metal complex (1), M is a metal atom.

[0124] The bond between the nitrogen atom and M represents the coordination of the nitrogen atom to M. A halogen atom, a hydroxyl group, or a hydrocarbon group having 1 to 8 carbon atoms may further be bonded to M as a ligand. An anionic counter ion may also be present to achieve electrical neutrality.

[0125] The valence of M is not particularly limited. To make the metal complex electrostatically neutral, a halogen atom, a hydroxyl group, or an alkyloxy group having 1 to 8 carbon atoms (e.g., an axial ligand) may be bonded, and an anionic counterion may be present. Examples of anionic counterions include halide ions, hydroxide ions, nitrate ions, and sulfate ions.

[0126] The structure of the alkyl group in the alkyloxy group having 1 to 8 carbon atoms may be linear, branched, or cyclic.

[0127] Examples of the above-mentioned M include a scandium atom, a titanium atom, a vanadium atom, a chromium atom, a manganese atom, an iron atom, a cobalt atom, a nickel atom, a copper atom, a zinc atom, a yttrium atom, a zirconium atom, a niobium atom, a ruthenium atom, a rhodium atom, a palladium atom, a lanthanum atom, a cerium atom, a praseodymium atom, a neodymium atom, a promethium atom, a samarium atom, a europium atom, a gadolinium atom, a terbium atom, a dysprosium atom, a holmium atom, an erbium atom, a thulium atom, a ytterbium atom, a lutetium atom, an actinium atom, a thorium atom, a protactinium atom, a uranium atom, a neptunium atom, a plutonium atom, an americium atom, a curium atom, a berkelium atom, a californium atom, a einsteinium atom, a fermium atom, a mendelevium atom, a nobelium atom, and a lawrencium atom.

[0128] Among them, an iron atom, a manganese atom, a cobalt atom, a copper atom, and a zinc atom are preferred, an iron atom, a manganese atom, and a cobalt atom are more preferred, and an iron atom is particularly preferred.

[0129] When M is an iron atom, the four nitrogen atoms coordinated around the iron atom form part of the pyridine ring structure. Therefore, an FeN4 structure comprising these four nitrogen atoms and the iron atom is locally formed in the metal complex molecule. The formation of this FeN4 structure further enhances the oxygen reduction catalytic activity of the catalyst.

[0130] When M is an iron atom, specific examples of the metal complex (1) include the following metal complex (11-1-1), metal complex (12-1-1), and metal complex (13-1-1). However, specific examples of the metal complex (1) in which M is an iron atom are not limited to these examples.

[0131] [Chemical Formula 12]

[0132]

[0133] The solubility of a metal complex in a solvent is primarily determined by the combination of the metal complex and the compound serving as the solvent. For example, when the metal complex is metal complex (1), the solubility of metal complex (1) in a solvent can be adjusted by changing the number of nitrogen atoms in D1 to D8 in the structure of metal complex (1). This can increase the affinity between the conductive powder and the metal complex, further enhancing the oxygen reduction catalytic activity.

[0134] The solvent will be described.

[0135] The solvent is not particularly limited as long as it is a compound that can dissolve the metal complex, but preferably a compound that has a solubility of the metal complex of 0.1 g / L or more.

[0136] The solubility of the metal complex is preferably 0.1 g / L or more, more preferably 0.4 g / L or more, further preferably 2.0 g / L or more, and particularly preferably 10 g / L or more. The upper limit of the solubility of the metal complex (1) is not particularly limited. The upper limit of the solubility of the metal complex (1) may be, for example, 20 g / L, 50 g / L, or 100 g / L.

[0137] When the solubility of the metal complex is above the lower limit, the metal complex dissolves more readily in the solvent and is more easily and uniformly adsorbed onto the surface of the conductive powder. As a result, the oxygen reduction catalytic activity of the catalyst is further enhanced, and the durability of the fuel cell electrode is further improved.

[0138] The solubility of a metal complex in a solvent is generally the maximum amount (g) of the metal complex dissolved per 1 L of the solvent, measured using ultraviolet-visible spectroscopy at 25°C and atmospheric pressure. The conditions for measuring the solubility of a metal complex in a solvent are specific conditions that are independent of the conditions for preparing the solution.

[0139] The solubility parameter of the solvent is preferably 10 (MPa) 1 / 2 ~20(MPa) 1 / 2 , more preferably 11 (MPa) 1 / 2 ~13(MPa) 1 / 2 If the solubility parameter of the solvent is below the lower limit, the hydrophobicity is too high, which tends to reduce the solubility of the metal complex having a polar portion. If the solubility parameter of the solvent exceeds the upper limit, the polarity is too high, which tends to reduce the solubility of the metal complex having a hydrophobic portion.

[0140] The solubility parameter of a solvent can be estimated as an SP value by, for example, the Fedors method.

[0141] The concentration of the metal complex in the solution is preferably 0.0001 g / L to 5 g / L, more preferably 0.01 g / L to 1 g / L, and even more preferably 0.1 g / L to 1 g / L.

[0142] When the concentration of the metal complex is not less than the above lower limit, the adsorption efficiency of the metal complex is further improved, the adsorption rate is increased, and the productivity is improved.

[0143] When the concentration of the metal complex is below the upper limit, the metal complex in the solution is easily and uniformly adsorbed on the surface of the conductive powder, forming a uniform monomolecular layer composed of single molecules of the metal complex on the surface of the conductive powder. As a result, the oxygen reduction catalytic activity and durability of the catalyst of the present invention can be further improved.

[0144] In the prior art using metal complex dispersions, the technical concept of increasing the oxygen reduction catalytic activity of a catalyst by increasing the concentration of the crystalline metal complex is common. In contrast, the catalyst production method of the present invention uses a solution with a relatively low metal complex concentration. Thus, the inventors of the present invention have come up with the technical concept of improving the oxygen reduction catalytic activity of a catalyst by using a solution with a relatively low metal complex concentration.

[0145] The concentration of the metal complex can be measured based on, for example, the absorbance coefficient and the molar absorptivity obtained using a spectrophotometer.

[0146] The solution may also contain impurities other than the metal complex. In this case, the impurity content is preferably 20% by mass or less relative to 100% by mass of the metal complex. If the impurity content is below the above upper limit, the metal complex can be more effectively adsorbed onto the conductive powder.

[0147] The solvent can be appropriately selected depending on the metal complex. Specific examples of the solvent include alcohols such as methanol, ethanol, and hexafluoro-2-propanol; dimethyl sulfoxide; aprotic polar solvents such as N-methylpyrrolidone, dimethylformamide, and acetone; and nonpolar solvents such as chloroform, dichloromethane, and 1,4-dioxane. However, specific examples of the solvent are not limited to these examples.

[0148] The solvent may be used alone or in combination of two or more. That is, the solvent may consist of a single component or may be a mixed solvent.

[0149] For example, when the metal complex (11), metal complex (12), and metal complex (13) described above are used as the metal complex, the solvent is preferably at least one selected from dimethyl sulfoxide and N,N-dimethylformamide. Here, as an example, the solubilities of metal complex (11-1-1), metal complex (12-1-1), and metal complex (13-1-1) in dimethyl sulfoxide, N,N-dimethylformamide, and tetrahydrofuran, respectively, at 25°C and atmospheric pressure are shown in Table 1 below.

[0150] [Table 1]

[0151] DMSO DMF THF Solubility of metal complex (11-1-1) [g / L] 0.80 0.46 0.018 Solubility of metal complex (12-1-1) [g / L] 1.0 Insoluble Insoluble Solubility of metal complex (13-1-1) [g / L] 0.45 0.45 0.049

[0152] In Table 1, the "DMSO" column indicates the solubility of each metal complex in dimethyl sulfoxide at 25°C and atmospheric pressure.

[0153] In Table 1, the "DMF" column indicates the solubility of each metal complex in N,N-dimethylformamide at 25°C and atmospheric pressure.

[0154] In Table 1, the column "THF" shows the solubility of each metal complex in tetrahydrofuran at 25°C and atmospheric pressure.

[0155] Here, each solubility described in Table 1 was measured by the method described in Examples below.

[0156] (Step (b))

[0157] In the step (b), the conductive powder is dispersed in the above-mentioned solution to prepare a dispersion.

[0158] Typically, in step (b), the metal complex is adsorbed on the surface of the conductive powder to form a composite, which serves as the catalyst. The dispersion contains the catalyst in which the metal complex is adsorbed on the surface of the conductive powder.

[0159] The temperature during the preparation of the dispersion is preferably a temperature not higher than the boiling point of the solvent. The dispersion is usually prepared at room temperature (eg, 25°C).

[0160] The temperature at which the metal complex is adsorbed on the surface of the conductive powder is preferably a temperature not higher than the boiling point of the solvent. The dispersion is usually prepared at room temperature (eg, 25°C).

[0161] The conductive powder will be described.

[0162] The conductive powder is not particularly limited as long as it can be dispersed in a solvent and has conductivity. Examples of the conductive powder include at least one selected from carbon materials, metal materials, and metal oxide materials. Carbon materials are preferred as the conductive powder. One type of conductive powder may be used alone, or two or more types may be used simultaneously.

[0163] Specific examples of carbon materials include graphite, amorphous carbon, activated carbon, graphene, carbon black, carbon fibers, mesocarbon microbeads, microcapsule carbon, fullerenes, carbon nanofoams, carbon nanotubes, and carbon nanohorns. Among them, graphite, amorphous carbon, activated carbon, graphene, carbon black, carbon fibers, fullerenes, and carbon nanotubes are preferred, carbon nanotubes, carbon black, and graphene are more preferred, and carbon nanotubes and graphene are still more preferred.

[0164] Specific examples of the metal material include titanium and tin.

[0165] Specific examples of the metal oxide material include titanium oxide, tin oxide (SnO 2 , ITO, ATO), and the like.

[0166] Examples of carbon nanotubes include single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes. Of these, double-walled carbon nanotubes and multi-walled carbon nanotubes are preferred, and multi-walled carbon nanotubes are more preferred, from the perspective of improving the conductivity of the catalyst.

[0167] The carbon material may also have functional groups such as hydroxyl groups, carboxyl groups, nitrogen-containing groups, silicon-containing groups, phosphorus-containing groups such as phosphate groups, and sulfur-containing groups such as sulfonic acid groups. Among these, the carbon material preferably has carboxyl groups. Carboxyl groups facilitate adsorption of metal complexes on the surface of the carbon material, further improving the durability of the electrode when fabricated and further enhancing the oxygen reduction catalytic ability.

[0168] The carbon material may also contain heteroatoms. Examples of heteroatoms include oxygen atoms, nitrogen atoms, phosphorus atoms, sulfur atoms, and silicon atoms. When the carbon material contains heteroatoms, it may contain a single heteroatom or two or more heteroatoms. It should be noted that the carbon material may be oxidized, oxidized, nitrided, phosphided, sulfided, or silidated.

[0169] When the carbon material contains carboxyl groups, the content of the carboxyl groups is preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less relative to 100% by mass of the carbon material. If the content of the carboxyl groups is below the above upper limit, it is easy to reduce the manufacturing cost of the catalyst.

[0170] When the carbon material contains carboxyl groups, the content of the carboxyl groups is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more. If the content of the carboxyl groups is above the above lower limit, the durability and oxygen reduction catalytic ability of the electrode when prepared are further improved.

[0171] The carboxyl group content can be measured by elemental analysis, X-ray photoelectron spectroscopy, or the like.

[0172] From the viewpoint of improving the conductivity of the catalyst and the oxygen reduction catalytic ability, the carbon material is preferably a double-walled carbon nanotube having a carboxyl group or a multi-walled carbon nanotube having a carboxyl group, and more preferably a multi-walled carbon nanotube having a carboxyl group.

[0173] The specific surface area of the carbon material is preferably 0.8 m 2 / g or more, more preferably 1.0m 2 / g or more, more preferably 1.1m2 / g or more, particularly preferably 1.5m 2 / g or more, and most preferably 2.0m 2 / g or more. If the specific surface area is 0.8m 2 / g or more, it is easy to prevent the catalyst from agglomerating, and the catalyst has a better oxygen reduction catalytic ability. The upper limit of the specific surface area is not particularly limited. The upper limit of the specific surface area can be set to 2000m 2 / g.

[0174] The specific surface area can be measured using a specific surface area measuring device by a nitrogen adsorption BET method.

[0175] The average particle size of the conductive powder is not particularly limited. The average particle size of the conductive powder is preferably, for example, 5 nm to 1000 μm. Methods for adjusting the average particle size of the conductive powder to the above numerical range include the following methods (α1) to (α3).

[0176] Method (α1): A method in which particles are pulverized by a ball mill or the like, the obtained coarse particles are dispersed in a dispersant to a desired particle size, and then dried and solidified.

[0177] Method (α2): A method in which particles are crushed by a ball mill or the like, and the obtained coarse particles are sieved or the like to classify the particle size.

[0178] Method (α3): A method of optimizing the production conditions of the conductive powder and adjusting the particle size of the particles when producing the conductive powder.

[0179] The average particle size of the conductive powder can be measured using a particle size distribution analyzer, an electron microscope, or the like.

[0180] In one embodiment of the method for producing a catalyst of the present invention, a conductive powder is dispersed in a solution (S) to prepare a dispersion. The solution (S) contains a metal complex and a solvent that dissolves the metal complex.

[0181] The method for dispersing the conductive powder in the solution (S) is not particularly limited, but examples thereof include the following methods (β1) and (β2).

[0182] Method (β1): A method of mixing a solution (S) and a conductive powder, and stirring the obtained mixed liquid.

[0183] Method (β2): A method in which a solution (S) and a conductive powder are mixed and the resulting mixed solution is dispersed using a disperser such as a homogenizer.

[0184] In the method (β1), examples of the stirring treatment include use of a mixer, irradiation with ultrasonic waves, stirring with a magnetic stirrer, stirring with a stirrer, etc. However, the stirring treatment is not limited to these examples.

[0185] The method for removing the solvent from the dispersion is not particularly limited. Examples include filtration for solid-liquid separation, drying under reduced pressure, and heat drying. However, when heat drying is used, the heating temperature is preferably kept low, specifically, preferably 200°C or lower, more preferably 100°C or lower, and even more preferably 50°C or lower, in consideration of the durability of the catalyst when fabricated into an electrode.

[0186] (Step (c))

[0187] In step (c), the solvent is removed from the dispersion to obtain a composite material in which the metal complex is adsorbed on the surface of the conductive powder as a catalyst.

[0188] The method for removing the solvent from the dispersion is not particularly limited. For example, removal can be achieved by solid-liquid separation. Filtration is preferred as a solid-liquid separation method to reduce the thermal load on the catalyst. Specifically, the solvent is preferably removed by filtering the dispersion. During filtration, the absorbance of the filtrate after filtration is preferably reduced by at least 10% compared to that of the solution. This is believed to indicate that the metal complex is effectively adsorbed on the conductive powder.

[0189] In the present invention, conductive powder is dispersed in a solution (S). Therefore, the metal complex molecules can be uniformly adsorbed onto the surface of the conductive powder. As a result, catalyst molecules can be produced as a composite comprising the conductive powder and the metal complex adsorbed in a layered manner onto the surface of the conductive powder.

[0190] In the present invention, it is preferred to use the composite having a conductive powder and a metal complex adsorbed in a layered manner on the surface of the conductive powder as a catalyst without subjecting it to a heat treatment at 200°C or above, more preferably to use it as a catalyst without subjecting it to a heat treatment at 100°C or above, and even more preferably to use it as a catalyst without subjecting it to a heat treatment at 50°C or above.

[0191] Conventionally, in catalyst production methods, heat treatments such as calcination are generally performed to support metal atoms on the surface of carbon materials. Furthermore, heat treatments such as calcination are also considered important to support metal atoms, nitrogen atoms, etc. on carbon materials.

[0192] In contrast, the present invention eliminates the heat treatment considered essential in conventional catalyst production. Instead, it focuses on increasing the solubility of the metal complex in the solvent and enhancing its affinity for the carbon material. By increasing the solubility of the metal complex in the solvent and its affinity for the carbon material, a monomolecularly adsorbed metal complex layer can be formed on the surface of the carbon material. As a result, oxygen reduction catalytic activity comparable to or greater than that of platinum-supported carbon materials can be achieved.

[0193] In the method for producing the catalyst of the present invention, step (a) and step (b) may be separate steps, or they may be performed simultaneously or integrated. When steps (a) and (b) are performed simultaneously or integrated, when the solubility of the metal complex is relatively low, adsorption of the metal complex onto the conductive powder can be further promoted.

[0194] Steps (a) and (b) are preferably performed at a temperature below the boiling point of the solvent, for example, preferably at a temperature below 80° C. This reduces the temperature load on the catalyst, which is desirable from the perspective of reducing production costs.

[0195] (Effect)

[0196] In the above-described method for producing the catalyst of the present invention, a solution containing a solvent that dissolves the metal complex is used, so the metal complex is dissolved in the solvent in the solution. Therefore, it is difficult for the metal complex crystals to be present in the solution, and the metal complex molecules are uniformly adsorbed on the surface of the conductive powder. In this way, by using a complex that allows the metal complex to be molecularly adsorbed on the surface of the conductive powder as a catalyst, the efficiency of electron transfer between the metal complex and the conductive powder can be increased, thereby improving the oxygen reduction catalytic ability of the catalyst.

[0197] Furthermore, even when the metal complex is dissolved in a solvent as shown in the examples described later, a catalyst having excellent durability when used as an electrode for a fuel cell can be obtained.

[0198] Figure 1 This is a schematic diagram for explaining the method for producing the catalyst of the present invention in comparison with a conventional method. Figure 1 (a) is a schematic diagram showing a conventional method. Figure 1 (b) is a schematic diagram showing a method for producing the catalyst of the present invention.

[0199] Figure 2 This is a schematic diagram for explaining a comparison between a catalyst obtained by the production method of the present invention and a catalyst obtained by a conventional method. Figure 2(a) is a schematic diagram showing a catalyst obtained by a conventional method. Figure 2 (b) is a schematic diagram showing a catalyst obtained by the production method of the present invention.

[0200] In the past, Figure 1 As shown in (a), catalyst 103 is typically manufactured using a dispersion P containing metal complex crystals 100 dispersed in a liquid medium 101, in order to improve the durability of fuel cell electrodes. Consequently, the metal complex crystals 100, acting as catalyst molecules, are not uniformly attached to the surface of conductive powder 102; rather, the metal complex crystals 100 and conductive powder 102 are simply mixed. Consequently, in conventional catalysts, the chemical interaction between the crystalline metal complex and conductive powder 102 is not fully utilized.

[0201] In contrast, in the method for producing the catalyst of the present invention, Figure 1 As shown in (b), a solvent 51 capable of dissolving the metal complex 50 is selected, and the conductive powder is dispersed in the solution S of the metal complex 50. Therefore, the molecules of the metal complex 50 can be uniformly adsorbed on the surface of the conductive powder 52 in the form of molecules. As a result, a catalyst 53 ( Figure 2 In (b), the catalyst 53 can be said to include the conductive powder 52 and a complex layer containing the metal complex 50. The complex layer is uniformly provided on the surface of the conductive powder 52.

[0202] As described above, catalyst 53 is a complex formed by metal complex 50 adsorbed on the surface of conductive powder 52. In catalyst 53, since metal complex 50 is adsorbed on the surface of conductive powder 52, the chemical interaction between metal complex 50 and conductive powder 52 is enhanced. As a result, the oxygen reduction catalytic ability of catalyst 53 is significantly improved compared to conventional catalysts produced in the presence of crystals.

[0203] As described above, in the catalyst production method of the present invention, the metal complex, which serves as the catalyst molecule, is uniformly molecularly adsorbed on the surface of the conductive powder, resulting in a catalyst with excellent oxygen reduction catalytic ability. Furthermore, the resulting catalyst exhibits excellent durability when fabricated into an electrode.

[0204] Therefore, by selecting a solvent, it is possible to use metal complexes that have not been previously applicable to fuel cell redox catalysts in catalyst production. Therefore, by selecting a solvent that can dissolve the metal complex, various metal complexes can be used in catalyst production, expanding the range of metal complex options compared to the prior art.

[0205] (application)

[0206] According to the present invention, a catalyst having excellent oxygen reduction catalytic ability and excellent durability when used as an electrode can be obtained. Therefore, it is suitable for industrial applications utilizing oxygen reduction reactions. In particular, it is suitable for use in electrodes for fuel cells and metal-air batteries, as well as electrodes for electrochemical reactions.

[0207] The catalyst can also be used in the production of the composition described below.

[0208] <Catalyst>

[0209] The catalyst of the present invention comprises a complex layer containing a metal complex and conductive powder. Furthermore, the complex layer covers the surface of the conductive powder. The complex layer covers the surface of the conductive powder through molecular adsorption. The catalyst of the present invention can also be described as a composite formed by the complex layer containing the metal complex adsorbed on the surface of the conductive powder.

[0210] In the catalyst of the present invention, the metal complex is adsorbed on the surface of the conductive powder, thereby enhancing the chemical interaction between the metal complex and the conductive powder. As a result, the oxygen reduction catalytic activity is significantly improved compared to conventional catalysts produced in the presence of crystals.

[0211] The catalyst of the present invention can be obtained, for example, by the above-mentioned method for producing the catalyst of the present invention. That is, the catalyst of the present invention can also be said to be a catalyst obtained by the method for producing the catalyst of the present invention.

[0212] The catalyst of the present invention can be applied to, for example, the composition described below.

[0213] <Method for producing composition>

[0214] The method for producing the composition of the present invention includes: step (a), dissolving a metal complex in a solvent to prepare a solution; step (b), dispersing conductive powder in the above solution to prepare a dispersion; and step (c), removing the above solvent from the above dispersion, allowing the above metal complex to adsorb on the surface of the above conductive powder to form a complex, and using the above complex as a catalyst. The method for producing the composition also includes: step (d), mixing the above catalyst with a liquid medium.

[0215] That is, the method for producing the composition of the present invention includes the following step (d) in addition to the steps of the method for producing the catalyst of the present invention described above.

[0216] Step (d): A step of mixing the catalyst and the liquid medium.

[0217] The details and preferred embodiments of step (a), step (b), and step (c) may be the same as those described in the above-mentioned section <Method for producing a catalyst> of the present invention.

[0218] (Step (d))

[0219] In step (d), the catalyst and the liquid medium are mixed. For example, in step (d), the catalyst, the liquid medium, and, if necessary, the perfluorocarbon material may be mixed or kneaded.

[0220] During mixing or kneading, ultrasonic treatment, a mixer, a stirrer, a kneader, a homogenizer, a bead mill, a ball mill, etc. can be used. Before or after the kneading operation, the average particle size of the particles can be adjusted using a sieve or the like.

[0221] When preparing a composition containing a perfluorocarbon material, the catalyst, the perfluorocarbon material, and water and alcohol as needed may be mixed and stirred until uniform.

[0222] The liquid medium may be an inorganic medium such as water or an organic medium.

[0223] Specific examples of organic media include alcohols such as methanol, ethanol, propanol, isopropanol (2-propanol), and 1-hexanol; dimethyl sulfoxide; tetrahydrofuran; aprotic polar solvents such as N-methylpyrrolidone, dimethylformamide, and acetone; and nonpolar solvents such as chloroform, dichloromethane, 1,4-dioxane, benzene, and toluene. However, the liquid medium is not limited to these examples.

[0224] The liquid medium may be the same as or different from the solvent used in preparing the catalyst.

[0225] The liquid medium may be used alone or in combination of two or more.

[0226] During mixing or kneading, any component other than the catalyst and the liquid medium may be further mixed. Thus, a composition further comprising any component other than the catalyst and the liquid medium may be obtained. For example, a perfluorocarbon material containing a structural unit based on polytetrafluoroethylene and a perfluorinated side chain having a sulfonic acid group may be used as the optional component. If a perfluorocarbon material is used, a composition further comprising the perfluorocarbon material may be obtained.

[0227] Specific examples of perfluorocarbon materials include Nafion (product name: manufactured by DuPont). However, the perfluorocarbon material is not limited to these examples.

[0228] <Composition>

[0229] The composition of the present invention comprises a catalyst obtained by the method for producing a catalyst of the present invention and a liquid medium. Details of the liquid medium, catalyst, and optional components other than the liquid medium are the same as those described in the section <Method for producing the composition>.

[0230] For example, the composition can be used as a coating liquid for use in the manufacture of an electrode. That is, the composition can be used as a composition for electrode manufacture. The manufacture of the electrode will be described later in the <Method for manufacturing the electrode> section.

[0231] The composition may be, for example, a dispersion type in which the catalyst is dispersed in a liquid medium.

[0232] The composition may further contain a co-catalyst, a binder, etc. as needed. The composition can be used, for example, in the manufacture of electrodes.

[0233] <Method for Manufacturing Electrode>

[0234] The method for manufacturing an electrode of the present invention includes: step (a), dissolving a metal complex in a solvent to prepare a solution; step (b), dispersing a conductive powder in the above solution to prepare a dispersion; and step (c), removing the above solvent from the above dispersion, allowing the above metal complex to adsorb on the surface of the above conductive powder to form a composite, and using the above composite as a catalyst. The method for manufacturing an electrode also includes: step (d), mixing the above catalyst with a liquid medium; and step (e), applying the mixture of the above catalyst and the above liquid medium to the surface of a substrate, and removing the above liquid medium.

[0235] That is, the method for producing an electrode of the present invention includes the following steps (d) and (e) in addition to the steps of the method for producing a catalyst of the present invention described above.

[0236] Step (d): A step of mixing the catalyst with the liquid medium.

[0237] Step (e): A step of applying a mixture of a catalyst and a liquid medium to the surface of a substrate and removing the liquid medium.

[0238] The details and preferred embodiments of step (a), step (b), step (c), and step (d) may be the same as those described in the above-mentioned <Method for producing a catalyst> or <Method for producing an electrode> of the present invention.

[0239] The mixture of the catalyst and the liquid medium can be said to be the composition of the present invention. Therefore, it can be said that in one embodiment of the method for producing the catalyst of the present invention, the composition obtained by the method for producing the composition of the present invention is applied to the surface of the substrate, and the liquid medium is removed.

[0240] (Step (e))

[0241] In step (e), the composition is applied to the surface of various substrates to form a layer containing the composition on the surface of the substrate. The liquid medium is then removed from the layer containing the composition. After the liquid medium is removed, a catalyst layer containing the catalyst is formed on the surface of the substrate.

[0242] The thickness of the composition when applied to the surface of the substrate is not particularly limited. For example, the composition can be applied to the surface of the substrate so that the thickness of the catalyst layer is 0.01 μm to 100 μm. If the thickness of the catalyst layer is greater than the lower limit, the durability of the electrode is further improved. If the thickness is less than the upper limit, the performance of the electrode is less likely to deteriorate.

[0243] When removing the liquid medium, heating and drying may be performed, or pressurization may be performed after drying.

[0244] Examples of the base material (substrate) include aluminum foil, electrolytic aluminum foil, aluminum mesh (porous expanded metal), foamed aluminum, punched aluminum, duralumin and other aluminum alloys, copper foil, electrolytic copper foil, copper mesh (porous expanded metal), foamed copper, punched copper, brass and other copper alloys, brass foil, brass mesh (porous expanded metal), foamed brass, punched brass, nickel foil, nickel mesh, corrosion-resistant nickel, nickel mesh (porous expanded metal), punched nickel, foamed nickel, sponge nickel, metallic zinc, corrosion-resistant metallic zinc, zinc foil, zinc mesh (porous expanded metal), steel plate, punched steel plate, silver, and the like.

[0245] The substrate may also be a substrate-like substrate such as a silicon substrate; a metal substrate such as gold, iron, stainless steel, copper, aluminum, or lithium; an alloy substrate containing any combination of these metals; an oxide substrate such as indium tin oxide (ITO), indium zinc oxide (IZO), or antimony tin oxide (ATO); or a carbon substrate such as glassy carbon, pyrolytic graphite, or carbon felt. However, the substrate is not limited to these examples.

[0246] The electrode obtained by the production method of the present invention can be used as a fuel cell electrode by using, for example, a substrate having a porous supporting layer as a base material. When used as a fuel cell electrode, the electrode can be used as either a cathode or an anode.

[0247] The porous supporting layer is a layer that diffuses gas. The porous supporting layer is not particularly limited as long as it exhibits high electron conductivity, high gas diffusivity, and high corrosion resistance. Examples of the porous supporting layer include carbon-based porous materials such as carbon paper and carbon cloth, stainless steel foil, and aluminum foil coated with a corrosion-resistant material.

[0248] The electrode obtained by the production method of the present invention can be used as an electrode for a fuel cell. When used as an electrode for a fuel cell, an electrolyte membrane can be disposed between a pair of electrodes.

[0249] When the electrode is used as an electrode for a fuel cell, the oxygen reduction reaction represented by the following formula (2) easily proceeds under acidic conditions, and the reduction reaction represented by the following formula (3) easily proceeds under alkaline conditions.

[0250] O2+4H + +4eˉ→2H2O···(2)

[0251] O2+2H2O+4eˉ→4OHˉ···(3)

[0252] According to the method for producing an electrode of the present invention, it is possible to produce an electrode containing a catalyst that has excellent oxygen reduction catalytic ability and excellent durability when used as an electrode.

[0253] <Electrode>

[0254] The electrode of the present invention contains the catalyst of the present invention. That is, the electrode of the present invention contains the catalyst obtained by the method for producing the catalyst. The electrode of the present invention can be produced, for example, by the method for producing the electrode of the present invention described above.

[0255] The electrode can be suitably used as an electrode for power storage devices (power generation devices) such as fuel cells and metal-air batteries.

[0256] <Fuel Cell>

[0257] The fuel cell of the present invention comprises an electrode containing the catalyst of the present invention. The fuel cell comprises, for example, a first electrode, a second electrode, an electrolyte, and a separator. The first electrode is an electrode obtained by the electrode manufacturing method of the present invention described above. The second electrode is an electrode used in combination with the first electrode.

[0258] When the first electrode is a cathode, the second electrode is an anode. When the first electrode is an anode, the second electrode is a cathode.

[0259] Examples of the second electrode include simple metals such as aluminum and zinc, and metal oxides thereof, but the second electrode is not limited to these examples.

[0260] The electrolyte is preferably an aqueous electrolyte. Examples of aqueous electrolytes include alkaline aqueous solutions such as potassium hydroxide aqueous solution and sodium hydroxide aqueous solution, and acidic aqueous solutions such as sulfuric acid aqueous solution. A single electrolyte may be used, or two or more electrolytes may be used simultaneously. However, the electrolyte is not limited to these examples and may also be an inorganic solid electrolyte.

[0261] The separator is a member that separates the first electrode from the second electrode and holds an electrolyte to ensure ion conductivity between the first electrode and the second electrode.

[0262] Specific examples of the separator include: polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, cellulose, cellulose acetate, hydroxyalkyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, cellophane, polystyrene, polyacrylonitrile, polyacrylamide, polyvinyl chloride, polyamide, vinylon, polymers with micropores such as poly(meth)acrylic acid, gel compounds, ion exchange membranes, cyclized polymers, polymers containing poly(meth)acrylates, polymers containing sulfonates, polymers containing quaternary ammonium salts, polymers containing quaternary phosphonium salts, etc. However, the separator is not limited to these examples.

[0263] Fuel cells can be either primary or secondary batteries.

[0264] Examples of fuel cell forms include metal-air batteries, molten carbonate fuel cells (MCFCs), phosphoric acid fuel cells (PAFCs), solid oxide fuel cells (SOFCs), polymer electrolyte fuel cells (PEFCs), enzyme (bio) fuel cells, microbial fuel cells, hydrazine fuel cells, and direct methanol oxidation fuel cells (DMFCs). The fuel cell form is not limited to these examples, but PEFCs and DMFCs are preferred.

[0265] The fuel cell of the present invention can be manufactured by, for example, using an electrode obtained by the above-described method for manufacturing an electrode of the present invention when manufacturing a first electrode. Thus, a fuel cell having a first electrode containing a catalyst obtained by the manufacturing method of the present invention can be manufactured.

[0266] The fuel cell of the present invention has an electrode having excellent oxygen reduction catalytic ability and excellent durability.

[0267] The metal-air battery of the present invention comprises an electrode obtained by the manufacturing method of the present invention. The details of the metal-air battery can be the same as those described for the above-mentioned fuel cell. The metal-air battery of the present invention can be manufactured in a manner substantially similar to the manufacturing method of the fuel cell.

[0268] Example

[0269] Hereinafter, the present embodiment will be described in detail with reference to Examples, but the present invention is not limited to the following description.

[0270] <Abbreviated symbols>

[0271] FeTPP: iron tetrapyrido porphyrazine (synthesized by the method described below)

[0272] FePc: Iron phthalocyanine (manufactured by Tokyo Chemical Industry Co., Ltd., “P0774”)

[0273] DBU: Diazabicycloundecene

[0274] DMSO: dimethyl sulfoxide

[0275] DMF: N,N-dimethylformamide

[0276] THF: Tetrahydrofuran

[0277] MWCNT: (manufactured by Sigma Aldrich, “755125”)

[0278] TEM: Transmission Electron Microscope

[0279] SEM: Scanning Electron Microscope

[0280] XPS: X-ray photoelectron spectroscopy

[0281] RRDE: Rotating Ring Disk Electrodes

[0282] LSV: Linear Sweep Voltammetry

[0283] KL: Koutecky-Levich

[0284] Pt / C: platinum-supported carbon (manufactured by Sigma Aldrich, 738549-1G)

[0285] GC: Glassy carbon (manufactured by BAS Corporation, 01338)

[0286] <Measurement Method>

[0287] (Solubility)

[0288] The solubility of the metal complex in the solvent was measured at 25° C. and atmospheric pressure using ultraviolet-visible spectroscopy, and was taken as the maximum value of the amount (g) of the metal complex dissolved per 1 L of the solvent.

[0289] (concentration)

[0290] The concentration of the metal complex in the solution was measured using a spectrophotometer (V-760DS, manufactured by JASCO Corporation) on a solution prepared by dissolving the metal complex in DMSO. The molar absorption coefficient of FeTPP at a wavelength of 636 nm was 2189.930071 L / (mol·cm).

[0291] (Half-wave potential)

[0292] In the LSV curve, the potential at which the current value reaches half the current value when the potential is -0.5 V is defined as the half-wave potential.

[0293] (Number of reaction electrons)

[0294] The number of reaction electrons was calculated based on the KL plot. The current density of the ring electrode and disk electrode was calculated by LSV measurement, and the number of reaction electrons was calculated based on the amount of H2O2 detected in the ring electrode by RRDE (rotating ring disk electrode).

[0295] (Catalyst loading)

[0296] The measurement was performed using an X-ray photoelectron spectroscopy analyzer (ThetaProbe, manufactured by Thermo Fisher Scientific).

[0297] (TEM)

[0298] Observation images were obtained using a transmission electron microscope (H-7650, manufactured by Hitachi).

[0299] (SEM)

[0300] Observation images were obtained using a scanning transmission electron microscope (S-5200, manufactured by Hitachi).

[0301] (Cyclic voltammogram)

[0302] The cyclic voltammogram was measured using CompactStat (manufactured by Ivium, NH-COMPACT).

[0303] A solution prepared by adding hydroxymethylferrocene to a 0.1 M potassium chloride aqueous solution so as to achieve a hydroxymethylferrocene concentration of 1 mM was used as an electrolyte, a platinum plate was used as a counter electrode, and Ag / AgCl was used as a reference electrode.

[0304] (LSV curve)

[0305] LSV curves were obtained using an oxygen-saturated 0.1 M potassium hydroxide aqueous solution as the electrolyte and a rotating ring disk electrode (RRDE-3A, manufactured by BAS Corporation) at a scan rate of 5 mV / s, with the lower limit of the scan range set to -0.8 V and the upper limit set to 0.2 V. The rotating disk was rotated at 2400 rpm, a Pt wire was used as the counter electrode, and Ag / AgCl was used as the reference electrode.

[0306] (LSV determination based on RRDE)

[0307] LSV measurements were performed using a rotating ring disk electrode (RRDE-3A, manufactured by BAS Corporation) at a scan rate of 5 mV / s using an oxygen-saturated 0.1 M potassium hydroxide aqueous solution as the electrolyte. LSV measurements were performed at rotating disk speeds of 0 rpm, 400 rpm, 800 rpm, 1200 rpm, 1600 rpm, 2000 rpm, and 2400 rpm. Pt was used as the counter electrode, and Ag / AgCl was used as the reference electrode.

[0308] In the graph showing the results of LSV measurement by RRDE, the higher the applied potential shown on the horizontal axis at which current starts to be generated, the higher the oxygen reduction catalytic ability.

[0309] <Example 1>

[0310] 258 mg of pyridine-2,3-dicarbonitrile, 135 mg of iron (III) chloride hexahydrate, and 20 mg of DBU were mixed in a test tube and dissolved in a mixed solvent containing 10 ml of methanol and 10 mL of DMSO. Then, while nitrogen replacement was performed, heating was performed at 180 ° C for 3 hours to obtain a reaction product containing FeTPP. The reaction product was centrifuged 3 times with acetone and dried. The precipitate after centrifugation was dissolved in concentrated sulfuric acid and added dropwise to water to precipitate FeTPP. The precipitated FeTPP was recovered by centrifugation and washed with methanol to obtain FeTPP.

[0311] Then, 0.1 mg of the obtained FeTPP was dissolved in 1.0 mL of DMSO to prepare a solution with a concentration of 0.1 g / L of FeTPP. 5 mg of MWCNTs (diameter: 9.5 nm, length: 1.5 μm) having carboxyl groups were dispersed in the resulting solution. During dispersion, ultrasonic treatment (20 kHz) was performed for 15 minutes. DMSO, the solvent, was removed from the resulting dispersion by solid-liquid separation and methanol washing, and the solution was dried at room temperature for 24 hours to obtain the catalyst of Example 1.

[0312] Then, 0.82 mg of the catalyst of Example 1, 84 μL of Milli-Q water, 336 μL of isopropyl alcohol, and 6 μL of a 0.5 mass % Nafion aqueous solution were kneaded using an ultrasonic stirrer and applied to a GC electrode to obtain the electrode of Example 1.

[0313] <Comparative Example 1>

[0314] In Comparative Example 1, a catalyst was produced in the same manner as in Example 1, except that the obtained FeTPP was dissolved in THF. Then, an electrode containing the catalyst of Comparative Example 1 was produced in the same manner as in Example 1.

[0315] <Comparative Example 2>

[0316] In Comparative Example 2, a catalyst was produced in the same manner as in Example 1, except that FePc was used instead of FeTPP and FePc was dissolved in THF. Then, an electrode containing the catalyst of Comparative Example 2 was produced in the same manner as in Example 1.

[0317] <Comparative Example 3>

[0318] In Comparative Example 3, an electrode (Pt / C electrode) of Comparative Example 3 was produced in the same manner as in Example 1, except that Pt / C was used instead of the catalyst of Example 1.

[0319] <Comparative Example 4>

[0320] In Comparative Example 4, a MWCNT dispersion was prepared without using FeTPP. An electrode of Comparative Example 4 was produced in the same manner as in Example 1 except that the obtained MWCNT dispersion was used.

[0321] Figure 3 This is a photograph showing a solution of FeTPP used in Example 1 dissolved in DMSO. Figure 3 As shown, the solution was transparent. In addition, since the solution was blue, it was confirmed that FeTPP was dissolved in DMSO.

[0322] Figure 4 This is a photograph showing a dispersion obtained by dispersing MWCNTs in a solution of FeTPP dissolved in DMSO in Example 1. Since the entire liquid was uniformly turbid in black, it was confirmed that the dispersion was in a uniformly dispersed state.

[0323] Figure 5 and Figure 6 is a photograph showing the catalyst obtained in Example 1. Figure 5 and Figure 6As shown, it was confirmed that the catalyst can be produced on a gram scale. Based on this result, the present invention can be used industrially.

[0324] Figure 7 This is an observation image obtained by TEM showing the catalyst of Example 1. Figure 7 In the following, it was not confirmed Figure 8 The crystal structure was confirmed in . Furthermore, XPS confirmed the presence of iron atoms on the surface of the catalyst of Example 1. These results indicate that the FeTPP complex layer is molecularly adsorbed on the surface of the MWCNT.

[0325] Figure 8 This is an observation image obtained by SEM showing the catalyst of Comparative Example 1. Figure 8 In the figure, a large number of crystal structures of different sizes are confirmed as indicated by arrows. These crystal structures are derived from crystals of FeTPP that are insoluble in THF.

[0326] Figure 9 This graph compares the redox characteristics of each electrode in Example 1 and Comparative Examples 1 to 4 using LSV measurement results at 1600 rpm. In the graph showing LSV measurement results based on RRDE, a higher potential on the horizontal axis (the vertical axis) at which current generation begins indicates lower energy loss and superior oxygen reduction catalytic performance.

[0327] like Figure 9 As shown, in the LSV curve of Example 1, a current rapidly flows in the range of potential 0 to 0.05 on the horizontal axis. This result confirms that the electrode of Example 1 has a superior oxygen reduction catalytic ability compared to the electrodes of Comparative Examples 1 to 4.

[0328] Figure 10 This is a graph comparing the redox characteristics of Example 1, Comparative Example 3, and Comparative Example 4 based on the LSV measurement results at 1600 rpm. Figure 9 and Figure 10 The results of the measurement of the number of reaction electrons are shown in Table 2 together with the half-wave potential.

[0329] [Table 2]

[0330]

[0331] As shown in Table 2, the catalyst loading in the electrode of Example 1 is less than that in Comparative Examples 1 to 4. Despite this, the electrode of Example 1 exhibits excellent oxygen reduction reaction characteristics, demonstrating superior oxygen reduction catalytic activity. The measurement results of the half-wave potential and the number of reaction electrons shown in Table 2 confirm that the oxygen reduction catalytic activity of the electrode of Example 1 is superior to that of the Pt / C electrode of Comparative Example 3.

[0332] Figure 11 This is a graph comparing LSV curves obtained when the cyclic voltammogram was performed using the electrode of Example 1 for 1 cycle, 50 cycles, and 100 cycles.

[0333] like Figure 11 As shown, in Example 1, even when the number of cycles increases to 1, 50, and 100, the potential on the horizontal axis at which the current starts to be generated, as shown on the vertical axis, hardly changes.

[0334] Figure 12 This is a graph comparing LSV curves obtained when the cyclic voltammogram was performed using the Pt / C electrode of Comparative Example 3 for 1 cycle, 50 cycles, and 100 cycles.

[0335] like Figure 12 As shown, in the Pt / C electrode of Comparative Example 3, as the number of cycles increases to 1, 50, and 100, the potential on the horizontal axis at which the current starts to be generated, as shown on the vertical axis, becomes lower.

[0336] according to Figure 11 、 Figure 12 The results shown here confirm that the electrode of Example 1 is more excellent in durability than the Pt / C electrode.

[0337] From the results of the present example described above, it was confirmed that a catalyst having excellent oxygen reduction catalytic ability can be produced by using a solution in which the metal complex (1) is dissolved in a solvent.

[0338] Furthermore, it was confirmed that even when the metal complex is dissolved in a solvent, a catalyst having excellent durability when used as an electrode for a fuel cell can be produced.

[0339] Description of Reference Numerals

[0340] 50···Metal complex

[0341] 51···Solvent

[0342] 52···Conductive powder

[0343] 53···Catalyst

[0344] 100···Crystals of metal complexes

[0345] 101···Liquid medium

[0346] 102···Conductive powder

[0347] 103···Catalyst

[0348] S···Solution

[0349] P···dispersion.

Claims

1. A method for producing a catalyst, comprising: Step (a), dissolving the metal complex in a solvent to prepare a solution; Step (b) of dispersing conductive powder in the solution to prepare a dispersion; and Step (c), removing the solvent from the dispersion, The metal complex is adsorbed on the surface of the conductive powder to form a composite, and the composite is used as a catalyst, wherein the concentration of the metal complex in the solution is 0.0001 g / L to 5 g / L. The solvent is at least one selected from dimethyl sulfoxide and N,N-dimethylformamide, The conductive powder is carbon nanotubes, carbon black or graphene, The metal complex is a metal complex represented by the following formula (11): In formula (11), X1 to X8 are each independently a hydrogen atom or a halogen atom, D1, D3, D5 and D7 are each independently a nitrogen atom or a carbon atom, at least one of D1, D3, D5 and D7 is a carbon atom to which a hydrogen atom or a halogen atom is bonded, and M is a metal atom.

2. The method for producing a catalyst according to claim 1, wherein The composite is used as a catalyst without being subjected to a heat treatment at 200° C. or higher.

3. The method for producing a catalyst according to claim 1, wherein The steps (a) and (b) are performed at a temperature not higher than the boiling point of the solvent.

4. The method for producing a catalyst according to claim 1, wherein The steps (a) and (b) are performed at a temperature of 80° C. or lower.

5. The method for producing a catalyst according to claim 1, wherein The metal complex is adsorbed on the surface of the conductive powder at a temperature not higher than the boiling point of the solvent.

6. The method for producing a catalyst according to claim 1, wherein The solvent was removed by filtering the dispersion.

7. The method for producing a catalyst according to claim 6, wherein: The absorbance of the filtered filtrate is reduced by more than 10% compared with the solution.

8. The method for producing a catalyst according to claim 1, wherein The solubility of the metal complex in the solvent is 0.1 g / L or more.

9. The method for producing a catalyst according to claim 1, wherein The solubility parameter of the solvent is 10 (MPa) 1 / 2 ~20(MPa) 1 / 2 . 10 . A catalyst obtained by the method for producing a catalyst according to claim 1 .

11. A method for producing a composition, comprising: Step (a), dissolving the metal complex in a solvent to prepare a solution; Step (b) of dispersing conductive powder in the solution to prepare a dispersion; and Step (c), removing the solvent from the dispersion, The metal complex is adsorbed on the surface of the conductive powder to form a composite, and the composite is used as a catalyst. The method for producing the composition further comprises: Step (d), mixing the catalyst with a liquid medium, Wherein, the concentration of the metal complex in the solution is 0.0001 g / L to 5 g / L, The solvent is at least one selected from dimethyl sulfoxide and N,N-dimethylformamide, The conductive powder is carbon nanotubes, carbon black or graphene, The metal complex is a metal complex represented by the following formula (11): In formula (11), X1 to X8 are each independently a hydrogen atom or a halogen atom, D1, D3, D5 and D7 are each independently a nitrogen atom or a carbon atom, at least one of D1, D3, D5 and D7 is a carbon atom to which a hydrogen atom or a halogen atom is bonded, and M is a metal atom. 12 . A composition comprising a catalyst obtained by the method for producing a catalyst according to claim 1 and a liquid medium. 13 . An electrode comprising a catalyst obtained by the method for producing a catalyst according to claim 1 .

14. A method for manufacturing an electrode, comprising: Step (a), dissolving the metal complex in a solvent to prepare a solution; Step (b) of dispersing conductive powder in the solution to prepare a dispersion; and Step (c), removing the solvent from the dispersion; The metal complex is adsorbed on the surface of the conductive powder to form a composite, and the composite is used as a catalyst. The method for manufacturing the electrode further comprises: Step (d), mixing the catalyst with a liquid medium; and Step (e) of applying a mixture of the catalyst and the liquid medium to the surface of a substrate and removing the liquid medium. Wherein, the concentration of the metal complex in the solution is 0.0001 g / L to 5 g / L, The solvent is at least one selected from dimethyl sulfoxide and N,N-dimethylformamide, The conductive powder is carbon nanotubes, carbon black or graphene, The metal complex is a metal complex represented by the following formula (11): In formula (11), X1 to X8 are each independently a hydrogen atom or a halogen atom, D1, D3, D5 and D7 are each independently a nitrogen atom or a carbon atom, at least one of D1, D3, D5 and D7 is a carbon atom to which a hydrogen atom or a halogen atom is bonded, and M is a metal atom.

15. A fuel cell comprising the electrode according to claim 13. A metal-air battery comprising the electrode according to claim 13 .

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