JP7397309B2 - Method for producing alloy catalyst and alloy catalyst - Google Patents

Description

The present invention relates to a method for producing an alloy catalyst and an alloy catalyst.

An alloy catalyst is one in which catalyst particles obtained by alloying multiple metals are supported on a porous body (porous material), and has a higher catalytic activity than a catalyst using a single metal as the active metal. It is also possible to vary the mechanism of the pod's activity itself. Hereinafter, the term "catalyst," such as "alloy catalyst," refers to a porous material that supports catalyst particles that have catalytic ability, and when referring to the catalyst particles that have catalytic ability themselves, the term "catalyst particles." Describe it. Therefore, depending on the application or in order to obtain higher catalytic activity, it is used in various fields, such as catalysts for polymer electrolyte fuel cells, catalysts for chemical processes such as petrochemistry and petroleum refining, and catalysts for exhaust gas treatment. The development of alloy catalysts is progressing.

In general, such an alloy catalyst is required to be sufficiently alloyed with a plurality of metals in order to fully exhibit its catalytic performance. Furthermore, alloy catalysts are required to have a high surface area in order to increase the number of active sites, and for this reason, it is preferred that small diameter catalyst particles be dispersed within the porous body. Furthermore, if the catalyst particles aggregate to form coarse particles when the catalytic reaction is repeated, the number of active sites that can contribute to the catalytic reaction of the alloy catalyst will decrease. Therefore, the catalyst particles are required to be highly dispersed so that even when the catalytic reaction is repeated, agglomeration of the catalyst particles is prevented and durability is increased.

Regarding the above points, a catalyst for a polymer electrolyte fuel cell will be explained in detail as an example of an alloy catalyst. Conventionally, platinum supported on a porous carbon material has been used as a catalyst for polymer electrolyte fuel cells. In recent years, more active platinum-based alloy catalysts have been used to further improve power generation performance. Among alloy catalysts for polymer electrolyte fuel cells, those made of platinum and base metals are considered to have particularly high activity.

Here, if the particle size of the catalyst particles of the alloy catalyst is large, the power generation performance decreases. If agglomeration is observed in the catalyst particles, durability will be reduced. When the alloying rate of catalyst particles is low, power generation performance decreases. Therefore, alloy catalysts with "small particle size, high dispersion, and high alloying ratio" are generally suitable as catalysts for solid fuel cells.

The following methods are generally used to synthesize alloy catalysts. One method is to separately support multiple metals on a carrier. In this method, first, one of the metal species is supported on a carrier, and then the other metal species is further supported, and the metal species are alloyed by heat treatment. The other method is to simultaneously support multiple metals on a carrier. A reducing agent is added to a solution containing a carrier and metal species to reduce multiple types of metal species simultaneously (for example, Patent Document 1). In addition, as an intermediate method between the above two methods, there is a method in which a carrier is impregnated with a solution containing a metal species, dried and then heat-treated in an atmosphere containing a reducing gas such as hydrogen to form an alloy. There is (for example, Patent Document 2).

Furthermore, as a general method for suppressing agglomeration of catalyst particles, a method is known in which a protective agent made of a polymer, an organic acid, or the like is adsorbed onto the surface of the catalyst particles.

JP2012-41622A International Publication No. 2014/025049

Incidentally, an alloy catalyst for a polymer electrolyte fuel cell is one in which catalyst particles, which are an alloy of a noble metal such as platinum and a base metal, are supported on a porous material. When reducing a noble metal precursor and a base metal precursor, the noble metal is preferentially reduced, and then the base metal is reduced, and the noble metal and the base metal tend to precipitate separately. As a result, it is difficult to increase the alloying ratio of alloy catalysts that simultaneously contain noble metals and base metals, such as alloy catalysts for polymer electrolyte fuel cells.

On the other hand, it is possible to promote alloying by heat treatment, but in this case, agglomeration and grain growth of catalyst particles tend to occur. It becomes difficult to obtain particles.

Furthermore, as described above, as a method for suppressing agglomeration of catalyst particles, a method of adsorbing a protective agent made of a polymer, an organic acid, or the like onto the surface of catalyst particles has conventionally been generally used. However, in this case, if the protective agent is not removed, the surface area of the catalyst that can contribute to the power generation reaction will be reduced, and heat treatment, which is a common method for removing the protective agent, tends to cause aggregation and grain growth of the catalyst particles. In addition, when a protective agent is used, the particle size increases accordingly, resulting in problems such as the inability to support catalyst particles inside the pores of the carrier. Furthermore, when the present inventor studied the characteristics that contribute to the power generation performance of the alloy catalyst, it became clear that the smaller the variation in the composition of each catalyst particle, the better the power generation performance, especially the initial power generation performance.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to support catalyst particles having a small particle size, high dispersion, small variation in composition, and high alloying rate. An object of the present invention is to provide a method for producing an alloy catalyst and an alloy catalyst.

As a result of intensive studies to solve the above problems, the present inventors impregnated a porous material with a solution containing a noble metal compound and a base metal compound that will become a precursor of catalyst particles, and then removed the solvent in the solution. Furthermore, by bringing the porous material into contact with a solution containing a reducing agent with relatively strong reducing power, catalyst particles with a small particle size, high dispersion, small variation in composition, and high alloying rate were supported. It was discovered that an alloy catalyst could be manufactured, and as a result of further study, the present invention was achieved.

The gist of the present invention, which was completed based on the above findings, is as follows.
[1] A first step of obtaining a mixture by mixing a noble metal compound containing a noble metal element, a base metal compound containing a base metal element, a first solvent, and a porous material;
The following formula (1):

(Volume of first solvent in mixture) ≦ (pore volume of porous material) x 5 (1)

a second step of fixing the noble metal compound and the base metal compound to the porous material by removing the first solvent from the mixture until
a third step of contacting the porous material with a reducing solution containing a reducing agent having an oxidation-reduction potential of -1.20 V or less and a second solvent,
The amount of the reducing agent in the reducing solution is 5 times or more the total amount of the noble metal element,
A method for producing an alloy catalyst , wherein the pH of the reducing solution at 25° C. is 8.0 or more and 12.0 or less .
[2] In the second step, the following formula (2):

(Volume of first solvent in mixture) ≦ (pore volume of porous material) x 2 (2)

The method for producing an alloy catalyst according to [1], wherein the first solvent is removed from the mixture until the following is satisfied.
[3] The first solvent and the second solvent contain the same solvent, or
The alloy catalyst according to [1] or [2], wherein the absolute value of the difference between the octanol/water partition coefficient of the first solvent and the octanol/water partition coefficient of the second solvent is 1.2 or less. manufacturing method.
[4] The first solvent contains water, and the second solvent has an octanol/water partition coefficient of 0.8 or less.
the second solvent contains water, and the first solvent has an octanol/water partition coefficient of 0.8 or less, or
The method for producing an alloy catalyst according to [1] or [2], wherein the first solvent and the second solvent both contain water.
[5] The reducing agent is one selected from the group consisting of an alkali metal salt of borohydride, a transition metal salt of borohydride, an alkali metal salt of aluminum hydride, an alkali metal salt of cyanoborohydride, and diisobutylaluminum hydride. or the method for producing an alloy catalyst according to any one of [1] to [4], which contains two or more types.
[6] The reducing agent is lithium borohydride, sodium borohydride, potassium borohydride, lithium triethylborohydride, nickel borohydride, zinc borohydride, lithium aluminum hydride, sodium aluminum hydride, hydrogen One or two selected from the group consisting of potassium aluminum oxide, sodium bis(2-methoxyethoxy)aluminum hydride, lithium cyanoborohydride, sodium cyanoborohydride, potassium cyanoborohydride, and diisobutylaluminum hydride. The method for producing an alloy catalyst according to any one of [1] to [5], which includes the above.
[7] The reducing agent according to any one of [1] to [6], wherein the reducing agent contains one or more selected from the group consisting of sodium borohydride, potassium borohydride, and lithium borohydride. Method for producing alloy catalyst.
[8] The method for producing an alloy catalyst according to any one of [1] to [7], wherein the amount of the reducing agent in the reducing solution is 10 times or more the total amount of the noble metal elements. .
[ 9 ] The pH of the reducing solution is adjusted using a base selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonia water, according to any one of [1] to [ 8 ]. A method for producing an alloy catalyst.
[ 10 ] The alloy catalyst according to any one of [1] to [ 9 ], wherein the noble metal element in the noble metal compound contains one or more selected from the group consisting of platinum, gold, and palladium. Production method.
[ 11 ] The above-mentioned noble metal compounds include dinitrodiammine platinum, bis(acetylacetonato)platinum, hexachloroplatinic (IV) acid, potassium hexachloroplatinate (IV), sodium hexachloroplatinate (IV) hexahydrate, and hexaammineplatinum. (IV) Chloride, hexaammineplatinum(IV) hydroxide solution, tetraammineplatinum(II) dichloride, platinum(II) bromide, platinum(IV) bromide, platinum(II) cyanide, platinum iodide, dimethyl( acetylacetonate) gold (III), gold chloride, chloroauric acid, gold bromide, gold iodide, gold cyanide, potassium gold cyanide, palladium chloride, palladium iodide, palladium bromide, palladium nitrate, palladium sulfate, [1] to [ 10 ] containing one or more selected from the group consisting of bis(acetylacetonato)palladium (II), sodium tetrachloropalladate, ammonium tetrachloropalladate, and potassium tetrachloropalladate. A method for producing an alloy catalyst according to any one of the items.
[ 12 ] The alloy catalyst according to any one of [1] to [ 11 ], wherein the base metal element in the base metal compound contains one or more selected from the group consisting of Co, Fe, Ni and Ti. Production method.
[ 13 ] The base metal compounds include cobalt chloride, cobalt bromide, cobalt iodide, cobalt cyanide, cobalt thiocyanate, cobalt sulfate, cobalt nitrate, cobalt acetylacetonate, iron chloride, iron bromide, iron iodide, and sulfuric acid. Iron, iron nitrate, iron (III) acetylacetonate, nickel chloride, nickel bromide, nickel iodide, nickel sulfate, nickel nitrate, nickel (II) potassium cyanide, nickel (II) acetylacetonate, titanium chloride, odor The method for producing an alloy catalyst according to any one of [1] to [ 12 ], which contains one or more selected from the group consisting of titanium oxide, titanium iodide, titanium tetraisopropoxide, and titanium sulfate.

As explained above, according to the present invention, it is possible to provide a method for producing an alloy catalyst and an alloy catalyst in which catalyst particles having a small particle size, high dispersion, little variation in composition, and high alloying ratio are supported. becomes.

These are a secondary electron image (left) and a transmission image (right) of the alloy catalyst according to Example 2-15, observed with a scanning transmission electron microscope at an accelerating voltage of 30 kV. These are a secondary electron image (left) and a transmission image (right) of an alloy catalyst according to Comparative Example 2-9, observed with a scanning transmission electron microscope at an acceleration voltage of 30 kV.

Hereinafter, the present invention will be described in detail based on preferred embodiments. In addition, in the following explanation, the method for producing an alloy catalyst for polymer electrolyte fuel cells and the alloy catalyst produced by the production method will be mainly described, but the method for producing an alloy catalyst according to the present invention will be described. It goes without saying that the present invention is applicable to the production of alloy catalysts for any purpose based on the principle.

<1. Idea leading to the present invention>
First, prior to a detailed description of the present invention, studies conducted by the present inventors to arrive at the present invention will be explained. As described above, the present inventors conducted studies to obtain an alloy catalyst having catalyst particles having a small particle size, high dispersion, small variation in composition, and high alloying ratio.

As mentioned above, one possible way to increase the alloying rate is to promote alloying by heat treatment, but in this case, agglomeration and grain growth of the catalyst particles tend to occur, so alloying by heat treatment alone is not possible. If this is done, it becomes difficult to obtain small-sized, highly dispersed catalyst particles.

Therefore, the present inventors focused on the difference in the reduction rate between noble metal compounds and base metal compounds, and reduced the noble metal compound and base metal compound simultaneously using a strong reducing agent, thereby reducing the reduction rate between the noble metal compound and the base metal compound. An attempt was made to reduce the influence of the difference. Here, since a strong reducing agent usually acts in a liquid phase, the above reduction reaction is carried out in a liquid phase. However, even in such a reduction reaction in the liquid phase, it is not possible to sufficiently eliminate the influence of the difference in reduction rate between noble metal compounds and base metal compounds, and it is difficult to obtain catalyst particles with a high alloying rate. there were. Note that there were cases where the alloying ratio became high, but in this case, other problems such as low dispersibility occurred. As a result, the present inventors were able to adjust the synthesis conditions, such as the type of reducing agent, the temperature during the reduction reaction, the respective concentrations of the metal species and reducing agent, and the type of compound used as the metal species, in the same liquid phase as in the conventional method. Through various studies, we came to the understanding that simple reactions in the liquid phase cannot eliminate the effects of differences in reduction rates.

Faced with this problem, the present inventors thought of limiting the reaction field in the reduction reaction to near the surface of the porous material in order to further reduce the effect of the difference in reduction rate between the noble metal compound and the base metal compound. It's arrived. That is, by impregnating a porous material with a solution containing a noble metal compound and a base metal compound, and then removing at least a portion of the solvent, the noble metal compound and the base metal compound are applied to the surface including the inside of the pores of the porous material. Unevenly distributed nearby. By bringing a solution containing a strong reducing agent into contact with such a porous material, the reaction field for the reduction reaction can be restricted to the vicinity of the surface of the porous material, and as a result, the noble metal compound and the base metal compound are simultaneously produced. The present inventors came up with the idea that it becomes easier to reduce.

Based on this idea, the present inventors investigated various conditions and found that it was possible to generate catalyst particles with a high alloying rate on the surface of a porous material. The obtained catalyst particles are formed on the surface of the porous material in a short time using a strong reducing agent, so they have a small particle size and are uniformly dispersed over the surface of the porous material. Furthermore, it was found that the variation in composition among catalyst particles was also small. Such catalyst particles were uniformly distributed not only on the surface outside the pores of the porous material but also inside the pores. As a result of the above, it has been found that an alloy catalyst can be obtained in which catalyst particles having a small particle size, high dispersion, small variation in composition, and high alloying ratio are supported on a porous material. In this way, the present inventor extracted a new problem (issue) that had not been recognized in the past, conceived a policy for solving it, and based on such an idea, developed a new and novel problem according to the present embodiment. An improved method for producing an alloy catalyst has been completed. An alloy catalyst manufactured by such an alloy catalyst manufacturing method can dramatically improve the power generation characteristics, durability, etc. of, for example, a polymer electrolyte fuel cell.

<2. Manufacturing method of alloy catalyst>
Next, a method for manufacturing an alloy catalyst according to this embodiment will be explained. The method for producing an alloy catalyst according to the present embodiment includes a first step of mixing a noble metal compound containing a noble metal element, a base metal compound containing a base metal element, a first solvent, and a porous material to obtain a mixture;
The following formula (1):

(Volume of first solvent in mixture) ≦ (pore volume of porous material) x 5 (1)

a second step of fixing the noble metal compound and the base metal compound to the porous material by removing the first solvent from the mixture until the following is satisfied;
a third step of contacting the porous material with a reducing solution containing a reducing agent having an oxidation-reduction potential of -1.20 V or less and a second solvent;
The amount of the reducing agent in the reducing solution is 5 times or more the total amount of the noble metal elements.
Each step will be explained in detail below.

[2.1. First step]
First, in the first step, a mixture is obtained by mixing a noble metal compound containing a noble metal element, a base metal compound containing a base metal element, a first solvent, and a porous material.

(Noble metal compounds and base metal compounds)
The noble metal element in the noble metal compound and the base metal element in the base metal compound become constituent elements of the obtained catalyst particles. Therefore, noble metal compounds and base metal compounds are precursors of catalyst particles.

The noble metal element is not particularly limited as long as it can be used as a constituent element of the catalyst particles, and examples thereof include gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), and rhodium ( Rh), iridium (Ir), ruthenium (Ru), and osmium (Os), among which one type can be used alone or two or more types can be used in combination.

The noble metal element can be selected as appropriate depending on the application, but in particular when producing an alloy catalyst for polymer electrolyte fuel cells, it is preferable to include one or more selected from the group consisting of platinum, gold and palladium. Preferably, platinum is more preferably included.

As the noble metal compound containing the above-mentioned noble metal element, for example, inorganic and/or organic salts, oxides, sulfides, halides, etc. of the noble metal element can be used alone or in combination of two or more. Specifically, the noble metal compounds include gold hydroxide, gold (III) oxide, gold fluoride, gold chloride, chloroauric acid, gold bromide, gold iodide, gold cyanide, potassium gold cyanide, and gold sulfite. Sodium, dichloro(1,10-phenanthroline)gold(III) chloride, tetrametal octachloride, chloro(trimethylphosphine)gold(I), chloro(triethylphosphine)gold(I), chloro(triphenylphosphine)gold(I) ), bromo(triphenylphosphine)gold(I), chloro[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]gold(I), hydroxide[1,3-bis(2, 6-diisopropylphenyl)imidazol-2-ylidene] gold(I), chlorodiphenyl(3-sulfonatophenyl)phosphine gold(I) sodium salt, gold sodium thiosulfate, gold(III) acetate, dimethyl (acetylacetonate) Gold (III), dimethyl (trifluoroacetylacetonate) gold (III), trichloropyridine gold (III), methyltriphenylphosphine gold (I), triphenylphosphine gold (I) bis(trifluoromethanesulfonyl) imidate, etc. Gold compounds, silver hydroxide, silver fluoride, silver chloride, silver chlorate, silver perchlorate, silver bromide, silver iodide, silver iodate, silver nitrate, silver nitrite, silver cyanide, potassium silver cyanide, acetic acid Silver, silver carbonate, silver thiocyanate, silver thiocyanate, silver (I) tetrafluoroborate, silver trifluoromethanesulfonate, silver trifluoroacetate, silver (I) hexafluorophosphate, silver sulfide, silver sulfate, silver sulfite , silver phosphate, silver oxide, silver citrate, silver methanesulfonate, silver lactate hemihydrate, silver toluenesulfonate, silver 2-ethylhexane, 2,2,6,6-tetramethyl-3, Silver compounds such as silver (I) 5-heptanedionate, copper azide, copper azide, copper (II) benzoate, copper hydroxide, copper fluoride, copper chloride, copper bromide, copper iodide, copper iodate, Copper nitrate, copper cyanide, dichlorocopper(I) acid, copper carbonate, copper thiocyanate, copper(I) thiophene-2-carboxylate, copper sulfide, copper sulfate, copper ammonium sulfate, copper acetate, copper oxide, copper peroxide , copper (II) ethoxide, copper isopropoxide, copper (II) bis(acetylacetonate), copper ethyl acetoacetate, diammonium chloride copper (II) dihydrate, copper (II) formate tetrahydrate, Copper phthalate, copper oleate, copper oxalate, copper citrate, copper phosphate, copper gluconate, copper methacrylate, copper isobutyrate, copper(II) tartrate hydrate, copper(II) terephthalate acid hydrate copper(II) trifluoromethanesulfonate, copper(II) trifluoroacetylacetonate, dipotassium tricyanocopper(I), copper(I) phenylacetylide, copper(II) 2-ethylhexanoate, cyclopentadienyl (triethylphosphine) ) Copper(I), tetraammine copper(II) sulfate hydrate, tetrakis(acetonitrile)copper(I) hexafluorophosphate, dihydroxobis(tetramethylethylenediamine)copper(II) chloride, phthalocyanine copper, phthalocyanine copper tetra Copper compounds such as tetrasodium sulfonic acid salt, trisodium copper chlorophyllin salt, copper benzenesulfinate, copper bis(triphenylphosphine) borohydride, copper(II) ethylenediaminetetraacetate disodium salt tetrahydrate, hexachloroplatinum ( IV) Acid, potassium hexachloroplatinate (IV), sodium hexachloroplatate (IV) hexahydrate, ammonium chloroplatinate (IV), hexahydroxoplatinate (IV) acid, potassium hexahydroxoplatate (IV), hexachloroplatinate (IV) Sodium hydroxoplatinate(IV), platinum sulfite, platinum(II) nitrate, platinum(II) chloride, platinum(IV) chloride, potassium hexacyanoplatinate(IV), potassium tetrabromoplatinate(II), hexabromo Ammonium (IV) platinate, sodium hexabromoplatinate (IV), hexabromoplatinic acid (IV) nonahydrate, potassium hexaiodoplatinate (IV), dinitrodiammineplatinum (II), hexaammineplatinum (IV) chloride, hexabromoplatinum (IV) chloride Ammineplatinum(IV) hydroxide solution, Tetraammineplatinum(II) dichloride, Tetraammineplatinum(II) dichloride, Tetraammineplatinum(II) hydroxide, Tetraammineplatinum(II) tetrachloroplatinic(II) acid, Tetraammineplatinum nitrate ( II), tetrakis(triphenylphosphine)platinum(O), bis(acetylacetonato)platinum(II), potassium tetrachloroplatinate(II), ammonium tetrachloroplatinate(II), tetrachloroplatinic(II) acid Sodium, platinum (IV) oxide, platinum (II) bromide, platinum (IV) bromide, platinum (IV) sulfide, platinum iodide, platinum (II) cyanide, platinum iodotrimethylplatinum (IV), platinum phthalocyanine, carbonic acid Tetraammineplatinum(II) hydrogen, dichloro(ethylenediamine)platinum(II), dichlorobis(benzonitrile)platinum(II), dinitrosulfatoplatinum(II), bis(pyridine)platinum(II) chloride, tetraammineplatinum phosphate( II), platinum compounds such as dichlorobis(diethylsulfide)platinum(II), dichlorobis(chlorocyclohexene)platinum(II), dichlorobis(triphenylphosphine)platinum(II), palladium chloride, palladium iodide, palladium bromide, nitric acid Palladium, palladium sulfate, palladium acetate, tetraamminepalladium (II) chloride, tetraamminepalladium (II) bromide, tetraamminepalladium (II) hydroxide, palladium hydroxide, diaminepalladium (II) nitrite, diamminedinitropalladium (II), Diamminedichloropalladium(II), palladium(II) acetate, bis(acetylacetonato)palladium(II), bis(acetonitrile)dichloropalladium(II), dichlorobis(pyridine)palladium(II), trans-dichlorobis(triphenylphosphine) ) Palladium(II), dichloro(tetramethylethylenediamine)palladium(II), trans-dibromobis(triphenylphosphine)palladium(II), palladium(II) oxide, tetrakis(triphenylphosphine)palladium, sodium tetrachloropalladate, Ammonium tetrachloropalladate, potassium tetrachloropalladate, sodium tetrabromopalladate (II), potassium hexachloropalladate (IV), sodium hexachloropalladate (IV), dichloro(ethylenediamine) palladium (II), tetranitropalladium ( II) acid potassium, palladium sulfide, dichloro[bis(1,2-diphenylphosphino)ethane]palladium(II), dichloro[bis(1,4-diphenylphosphino)butane]palladium(II), 2,2' -bis(diphenylphosphino)-1,1'-binaphthyldichloropalladium(II), 2,2'-bis(diphenylphosphino)-1,1'-binaphthyldibromopalladium(II), bis(tri-t- butylphosphine)palladium, bis(di-t-butylphenylphosphine)dichloropalladium(II), bis(tri-o-tolylphosphine)dibromopalladium(II), dichlorobis(benzonitrile)palladium(II), [4,5 -bis(diphenylphosphino)-9,9-dimethylxanthene]dichloropalladium(II), dichloro(cyclooctadiene)palladium, dichlorobis[di-t-butyl(p-dimethylaminophenyl)phosphino]palladium(II), Palladium compounds such as (ethylenediamine)dinitratopalladium (II), rhodium oxide, rhodium chloride, rhodium iodide, rhodium bromide, rhodium sulfate, rhodium nitrate, rhodium (II) acetate, potassium hexachlororhodate (III), hexachlororhodium Sodium (III) acid, potassium hexachlororhodate (III), ammonium hexachlororhodate (III), potassium hexanitrithrodate (III), tris(acetylacetonato)rhodium(III), chlorotris(triphenylphosphine)rhodium (I), rhodium compounds such as acetylacetonatodicarbonylrhodium (I), acetylacetonatocarbonyltriphenylphosphine rhodium (I), iridium oxide, iridium bromide, iridium iodide, iridium (III) chloride, iridium chloride ( IV) Acids, Tris(acetylacetonato)iridium(II), Acetylacetoneiridium(III), (acetylacetonato)dicarbonyliridium(I), Iridium Nitrate, Iridium Acetate, Hexamine Iridium Hydroxide, Iridium Chloride (IV) ) acid ammonium, potassium iridium chloride (IV), iridium carbonyl, dodecacarbonyl tetrairidium, sodium hexanitroidylium (III), potassium hexachloroiridate (IV), ammonium hexachloroiridate (IV), hexachloroiridium Iridium compounds such as sodium (IV) acid, ruthenium chloride, ruthenium oxide, ruthenium nitrate, hexaammineruthenium (III) chloride, dodecacarbonyltriruthenium (O), tris(acetylacetonate)ruthenium (III), sodium ruthenate , potassium ruthenate, ruthenium carbonyl, ruthenium iodide, ruthenium bromide, potassium perruthenate, tetrabutylammonium perruthenate, tetrapropylammonium perruthenate, ruthenium nitrosyl chloride, ruthenium nitrosyl nitrate, potassium hexacyanoruthenate(II) , potassium pentachlororuthenate(III), ammonium hexachlororuthenate(IV), carbonyldihydridotris(triphenylphosphine)ruthenium, carbonylchlorohydridotris(triphenylphosphine)ruthenium, ruthenium porphyrin complex, tris(2,2' -Ruthenium compounds such as bipyridyl)ruthenium(II) dichloride, osmium oxide, osmium carbonyl, osmium chloride, bis(cyclopentadienyl)osmium, sodium hexachloroosmate(IV), potassium hexachloroosmate(IV), hexachloroosmate (IV) ammonium, ammonium hexabromoosmate (IV), potassium hexabromoosmate (IV), potassium osmate (VI), and other osmium compounds.

Among the above-mentioned, the noble metal compound is preferably a platinum compound (dinitrodiammine platinum, bis(acetylacetonato)platinum, hexachloroplatinic (IV) acid, potassium hexachloroplatinate (IV), sodium hexachloroplatinate (IV) hexahydrate). hexaammineplatinum(IV) chloride, hexaammineplatinum(IV) hydroxide solution, tetraammineplatinum(II) dichloride, platinum(II) bromide, platinum(IV) bromide, platinum(II) cyanide and iodine platinum chloride), gold compounds (dimethyl(acetylacetonato)gold(III), gold chloride, chloroauric acid, gold bromide, gold iodide, gold cyanide, potassium gold cyanide) and palladium compounds (palladium chloride, gold iodine) 1 selected from the group consisting of palladium chloride, palladium bromide, palladium nitrate, palladium sulfate, bis(acetylacetonato)palladium (II), sodium tetrachloropalladate, ammonium tetrachloropalladate, potassium tetrachloropalladate) Contains more than one species. Such a compound has a relatively low reduction rate and can contribute to reducing the influence of the difference in reduction rate between the noble metal compound and the base metal compound. This prevents only the noble metal compound from being reduced and turned into particles, and increases the alloying rate when formed into catalyst particles.

In particular, when the noble metal compound comprises a platinum compound, the noble metal compound is preferably dinitrodiammine platinum, bis(acetylacetonato)platinum, hexachloroplatinic (IV) acid, potassium hexachloroplatinate (IV), hexachloroplatinic (IV) acid. It contains one or more selected from the group consisting of sodium hexahydrate and platinum iodide. Such a platinum compound has a relatively low reduction rate and can contribute to reducing the difference in reduction rate between the noble metal compound and the base metal compound.

The content of the noble metal compound in the mixture is not particularly limited, and is appropriately set depending on the solubility of the noble metal compound in the first solvent and the ratio with the base metal compound.

Base metal elements are added to improve the catalytic performance of the alloy catalyst, for example by combining with noble metal elements. For example, in the case of alloy catalysts for polymer electrolyte fuel cells, alloying a noble metal element with a base metal element shortens the interatomic distance between noble metal atoms, thereby optimizing the ease with which they bond with and desorb oxygen. It is thought that the catalytic activity of the catalyst particles is improved due to this.

The base metal element is not particularly limited as long as it can be used as a constituent element of catalyst particles, and any metal element other than noble metals may be used singly or in combination of two or more depending on the use and purpose of the alloy catalyst. be able to.

Examples of such base metal elements include various elements of Groups 1 to 16 of the periodic table that have the properties of metals and semimetals and are not noble metals. Specifically, the base metal elements include alkali metal elements (Li, Na, K, Rb, Cs, Fr), alkaline earth metal elements (Ca, Sr, Ba, Ra), and transition metal elements (Sc, Y, Ti). , Zr, Hf, V, Nb, Ta, Cr, Mo, Mn, Fe, Co, Ni), rare earth elements (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er , Tm, Yb, Lu), actinides (Ac, Th, Pa, U, Np, Pu), and other typical elements exhibiting metallic properties (Be, Mg, Zn, Cd, Hg, Al, Ga, In, Tl , Sn, Pb, Bi, Po), metalloid elements (B, Si, Ge, As, Sb, Te, At, Se).

Base metal elements can be selected as appropriate depending on the application, but in particular when producing an alloy catalyst for polymer electrolyte fuel cells, preferably Ti, Zr, V, Nb, Mn, Fe, Co, Ni, Al. , Sn, and Si, more preferably one or more selected from the group consisting of Co, Fe, Ni, and Ti.

As the base metal compound containing the above-mentioned base metal element, for example, inorganic and/or organic salts, oxides, sulfides, halides, etc. of the base metal element can be used alone or in combination of two or more. Such base metal compounds include Co, Fe, Ni and Ti, specifically cobalt oxide, cobalt hydroxide, cobalt fluoride, cobalt chloride, cobalt bromide, cobalt iodide, cobalt iodate, and nitric acid. Cobalt, cobalt sulfate, cobalt cyanide, cobalt acetylacetonate, cobalt formate, cobalt oxalate, cobalt oleate, cobalt carbonyl, cobaltocene, cobalt cyclohexane butyrate, cobalt stearate, cobalt thiocyanate, cobalt tetramethoxyphenylporphyrin, naphthene Cobalt compounds such as cobalt acid, cobalt phthalocyanine, potassium hexacyanocobalt(III), sodium hexanitrocobaltate(III), cobalt carbonate, cobalt acetate, iron oxide, iron hydroxide, iron fluoride, iron chloride, iron bromide , iron iodide, iron nitrate, iron sulfate, iron(II) cyanide, iron sulfide, hydroxylammonium chloride, sodium ferrocyanide, potassium ferrocyanide, potassium ferricyanide, iron perchlorate, iron carbonate, iron acetate, iron oxalate. , ferric potassium oxalate, ferric ammonium oxalate, iron hydroxide oxide, iron(II) lactate, ammonium iron(II) sulfate, iron phosphate, iron citrate, ammonium iron citrate, iron ethylenediaminetetraacetate Sodium, iron pentacarbonyl, triiron dodecacarbonyl, iron phthalocyanine, iron compounds such as iron (III) acetylacetonate, nickel (II) oxide, nickel (II) hydroxide, nickel (II) fluoride, nickel (II) chloride ), nickel (II) bromide, nickel (II) iodide, nickel (II) nitrate, nickel (II) sulfate, nickel carbonate, nickel citrate, nickel oxalate, nickel stearate, nickel benzoate, nickel acetate, Nickel compounds such as nickel perchlorate, potassium nickel(II) cyanide, nickel bis(triphenylphosphine) chloride, nickel dicarbonylbis(triphenylphosphine), nickel(II) acetylacetonate, nickel phthalocyanine, titanium fluoride , titanium compounds such as titanium chloride, titanium bromide, titanium iodide, titanium sulfate, titanium carbide, titanium nitride, potassium titanium oxalate, titanium tetraisopropoxide, and titanium tetra-n-butoxide.

Among the above-mentioned, the base metal compounds are preferably cobalt chloride, cobalt bromide, cobalt iodide, cobalt cyanide, cobalt thiocyanate, cobalt sulfate, cobalt nitrate, cobalt acetylacetonate, iron chloride, iron bromide, and cobalt iodide. Iron, iron sulfate, iron nitrate, iron (III) acetylacetonate, nickel chloride, nickel bromide, nickel iodide, nickel sulfate, nickel nitrate, nickel (II) potassium cyanide, nickel (II) acetylacetonate, chloride One or more selected from the group consisting of titanium, titanium bromide, titanium iodide, titanium tetraisopropoxide, and titanium sulfate, more preferably cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt acetylacetonate, iron sulfate, One or more selected from the group consisting of iron nitrate, iron (III) acetylacetonate, nickel (II) chloride, nickel sulfate, nickel nitrate, nickel (II) acetylacetonate, titanium tetraisopropoxide, and titanium sulfate. include. These base metal compounds have a relatively high reduction rate, and therefore contribute to reducing the influence of the difference in reduction rate between the base metal compound and the noble metal compound. This prevents only the noble metal compound from being reduced and turned into particles, and increases the alloying rate when formed into catalyst particles.

Further, the noble metal compound and the base metal compound are preferably selected so that the difference in reduction rate is as small as possible. Specifically, it is preferable to combine a noble metal compound that is difficult to reduce and has a low reduction rate with a base metal compound that is easy to reduce and has a high reduction rate. Such a combination includes, for example, when the noble metal compound is dinitrodiammine platinum, bis(acetylacetonato)platinum, hexachloroplatinic (IV) acid, potassium hexachloroplatinate (IV), sodium hexachloroplatinate (IV) hexahydrate, Consists of platinum iodide, dimethyl(acetylacetonato)gold(III), gold chloride, chloroauric acid, palladium chloride, palladium nitrate, palladium sulfate, diaminedinitropalladium(II) and bis(acetylacetonato)palladium(II) The base metal compound includes one or more selected from the group, and the base metal compound is cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt acetylacetonate, iron sulfate, iron nitrate, iron (III) acetylacetonate, nickel (II) chloride, Examples include cases in which one or more selected from the group consisting of nickel sulfate, nickel nitrate, nickel (II) acetylacetonate, titanium tetraisopropoxide, and titanium sulfate are included. These compounds are easily and inexpensively available on the market. Note that such a combination can be selected by determining the stability of each compound in a reduction reaction based on, for example, the HSAB rule (Hard and Soft Acids and Bases).

The content of the base metal compound in the mixture is not particularly limited, and is appropriately set depending on the solubility of the base metal compound in the first solvent and the ratio to the noble metal compound. Specifically, when manufacturing an alloy catalyst for polymer electrolyte fuel cells, for example, the base metal element in the base metal compound is, for example, 0.1 mol or more and 5 mol or less, preferably 0.1 mol or more and 5 mol or less, preferably 0. The content of the base metal compound is set to be .3 mol or more and 3 mol or less.

(First solvent)
The first solvent used in the mixture is not particularly limited as long as it can dissolve the above-mentioned noble metal compound and base metal compound, and water and various organic solvents can be used, and one type or two types of these can be used. The above can be used in combination. Examples of organic solvents include alcohol solvents, ketone solvents, ether solvents, ester solvents, glycol solvents, hydrocarbon solvents, aromatic solvents, halogenated hydrocarbons, amide solvents, and carboxylic acid solvents. etc. Among these, water, alcohol-based solvents, ether-based solvents, ketone-based solvents, and carboxylic acid-based solvents are relatively easy to dissolve noble metal compounds and base metal compounds. Further, these solvents can be relatively easily removed from the porous material in the second step described below. Furthermore, these solvents have high affinity with polar solvents such as water when used as the second solvent.

In particular, in consideration of the solubility of the noble metal compound and the base metal compound and the mixing with the reducing solution described below, it is preferable that the first solvent contains water.

Examples of the alcohol solvent include branched, cyclic, or linear alcohol compounds having 1 to 10 carbon atoms, and these can be used alone or in combination of two or more. Further, the alcohol compound contained in the alcohol solvent may be any of primary, secondary, and tertiary alcohols, and may be polyhydric alcohols. More specifically, examples of alcoholic solvents include methanol, ethanol, 1-propanol, isopropyl alcohol, 1-butyl alcohol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, and 2-pen. Tanol, cyclopentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, methylcyclohexanol, cyclohexanol, benzyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene Examples include glycol, pentaethylene glycol, and the like.

Examples of ether solvents include dimethyl ether, methyl ethyl ether, diethyl ether, methyl-n-propyl ether, ethyl-n-propyl ether, di-n-propyl ether, methyl isopropyl ether, diisopropyl ether, and methyl-n-butyl ether. , branched or linear alkyl ethers having 1 to 4 carbon atoms such as ethyl-n-butyl ether, methyl isobutyl ether, and ethyl isobutyl ether; cyclic ethers such as tetrahydrofuran, tetrahydropyran, oxacycloheptane, and 1,4-dioxane; can be mentioned.

Examples of the ketone solvent include acetone, methyl isobutyl ketone, methyl-n-butyl ketone, methyl ethyl ketone, cyclohexanone, methyl cyclohexanone, pentanal, diethyl ketone, methyl propyl ketone, diisobutyl ketone, diacetone alcohol, and the like.

Examples of ester solvents include esters of branched, cyclic, or linear alcohol compounds having 1 to 5 carbon atoms and organic acids or carbonic acid having 1 to 5 carbon atoms, which may be used alone or in combination of two or more. It can be used as Specifically, the ester solvents include ethyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, n-butyl acetate, sec-butyl acetate, tert-butyl acetate, isobutyl acetate, and benzyl acetate. Amyl, isoamyl acetate, diethyl carbonate, propylene carbonate, methyl butyrate, ethyl butyrate, propyl butyrate, isopropyl butyrate, n-butyl butyrate, sec-butyl butyrate, tert-butyl butyrate, isobutyl butyrate, isoamyl butyrate, methyl valerate , ethyl valerate, n-butyl valerate, sec-butyl valerate, tert-butyl valerate, butyl isovalerate, methyl lactate, ethyl lactate, n-butyl lactate, sec-butyl lactate, lactic acid -tert-butyl, isobutyl lactate and the like.

Examples of the carboxylic acid solvent include organic acids having 1 to 5 carbon atoms, and these can be used alone or in combination of two or more. Specifically, examples of carboxylic acid solvents include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, and lactic acid.

(Porous material)
The porous material is a carrier that supports catalyst particles in the resulting alloy catalyst. Porous materials usually have constituent particles with a large number of pores and a large surface area. The porous material is capable of supporting catalyst particles inside its pores and on its exposed external surface.

Porous materials are not particularly limited as long as they can be used as catalyst carriers, and include porous carbon materials (for example, activated carbon, etc.), silica, silica alumina, silica calcia, molecular sieve, alumina, zeolite, titania, clay, diatomaceous earth. , silicon carbide, and the like.

Among the above-mentioned porous materials, silica, molecular sieve, alumina, zeolite, titania, and porous carbon materials are preferred because they have a relatively large pore volume and are easy to obtain and handle.

Further, when the types of materials are different, the surface areas of the porous materials can be compared by comparing the porosity. Porosity indicates the ratio of the volume of space to the volume occupied by the material. For example, in the case of a porous material, calculate the pore volume per 1 g, and calculate the pore volume from the density (true density) of the porous material. It can be calculated by dividing by the calculated volume per 1 g. It is also possible to measure by a mercury porosity method using mercury porosimetry. The porosity is preferably 3% or more and 75% or less, more preferably 5% or more and 50% or less.

Note that in the case of porous materials of the same type, the surface areas of the porous materials can be compared by comparing the specific surface areas (for example, BET specific surface areas). For example, when the porous material is a porous carbon material, the BET specific surface area thereof is preferably 300 cm ² /g or more, more preferably 450 cm ² /g or more and 2500 cm ² /g or less.

(Other ingredients)
Further, in the mixture, an acid or a base may be added as appropriate to assist in dissolving the noble metal compound or base metal compound. Here, the above-mentioned "acid" refers to an acid based on the so-called Brønsted-Lori definition, and refers to a substance that provides protons. Similarly, the above-mentioned "base" refers to a base based on the so-called Brønsted-Lori definition, and refers to a substance that accepts protons. Examples of such acids include inorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, boric acid, phosphoric acid, and acetic acid, citric acid, formic acid, lactic acid, oxalic acid, and methane. Examples include organic acids such as sulfonic acid and benzenesulfonic acid, and one type of these can be used alone or two or more types can be used in combination. Further, examples of the base include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides, ammonia, and the like.

The pH of the mixture at 25° C. is not particularly limited, but may be, for example, 1.0 or more and 11.0 or less, preferably 2.0 or more and 9.0 or less. When it is within the above range, the noble metal compound and the base metal compound can be suitably dissolved in the mixture while preventing deterioration of the porous material.

The materials explained above are mixed to obtain a mixture (mixed liquid). The mixing method and the order of addition of the materials are not particularly limited, and the mixing method can be appropriately selected so that the porous material is sufficiently dispersed in the mixture and the noble metal compound and the base metal compound are dissolved.

An example of the mixing method is shown below. First, a porous material is added to a first solvent, and the porous material is dispersed in the first solvent using an ultrasonic homogenizer or the like. Then, the noble metal compound and the base metal compound are added to the first solvent and stirred for a predetermined period of time. In this case, the order of addition of the noble metal compound and the base metal compound is not particularly limited, and one may be added first, or both may be added at the same time. During the above mixing, heating or the like may be performed as necessary to promote dissolution of the noble metal compound and the base metal compound in the first solvent.

Alternatively, the mixture may be obtained by dividing the first solvent, dispersing the porous material in one, dissolving the noble metal compound and the base metal compound in the other, and finally mixing these. Furthermore, the noble metal compound and the base metal compound may be dissolved in the first solvent in advance, and then the porous material may be dispersed.

[2.2. Second process]
In the second step, the noble metal compound and the base metal compound are fixed in the porous material by removing the first solvent from the mixture until the following formula (1) is satisfied.
(Volume of first solvent in mixture) ≦ (pore volume of porous material) x 5 (1)

In this way, by making the first solvent in the mixture sufficiently small relative to the pore volume of the porous material, the noble metal compound and the base metal compound can be uniformly dispersed and attached to the pore surface of the porous material. , fixed. Thereby, the reaction field for the reduction reaction of the noble metal compound and the base metal compound is fixed on the pore surface of the porous material in the third step described later.

On the other hand, if the volume of the first solvent in the mixture exceeds five times the pore volume of the porous material, the amount of the first solvent relative to the porous material becomes too large, resulting in The noble metal compound and the base metal compound are not sufficiently retained inside the pores, and a large amount of the noble metal compound and the base metal compound end up remaining dissolved in the first solvent outside the porous material. As a result, in the third step described below, the reaction field for the reduction reaction of the noble metal compound and the base metal compound is not sufficiently fixed on the pore surface of the porous material, and the influence of the difference in the reduction rate of the noble metal compound and the base metal compound cannot be made smaller. For this reason, it is not possible to increase the alloying ratio of the obtained catalyst particles.

Preferably, the noble metal compound and the base metal compound are fixed to the porous material by removing the first solvent from the mixture until the following formula (2) is satisfied.
(Volume of first solvent in mixture) ≦ (pore volume of porous material) x 2 (2)

The first solvent can be removed, for example, by heating, reduced pressure, air drying, or the like. In order to efficiently remove the first solvent, it is preferable to evaporate the first solvent under reduced pressure using, for example, an evaporator such as a rotary evaporator.

When reducing the pressure, the first removal efficiency is improved by combining it with heating. The heating temperature can be, for example, 50°C or more and 110°C or less, preferably 65°C or more and 95°C or less.

Further, when removing the first solvent, stirring may be performed as necessary in order to uniformly remove the first solvent. The volume of the first solvent in the mixture is determined by measuring the weight of the entire sample during removal of the first solvent and subtracting the weight of the porous material, noble metal compound, and base metal compound from this weight. By determining the weight of the first solvent, the volume of the first solvent in the mixture can be calculated. Alternatively, it can be calculated by collecting the removed solvent while removing the first solvent, measuring the weight of the collected solvent, and subtracting the weight from the original solvent weight. The pore volume of the porous material can be measured using, for example, nitrogen adsorption measurement (eg, Microtrac BEL-MAX, manufactured by BEL). Specifically, a nitrogen adsorption/desorption isotherm is measured, and a BET plot is created by applying the BET method to this nitrogen adsorption/desorption isotherm. The total pore volume can then be calculated from the BET plot. In the Examples described below, the pore volume of the porous material was calculated by the above method using BEL-MAX manufactured by Microtrac Bell.

[2.3. Third step]
In the third step, the porous material is brought into contact with a reducing solution containing a reducing agent having an oxidation-reduction potential of −1.20 V or less and a second solvent. Here, the amount of the reducing agent in the reducing solution is five times or more the total amount of noble metal elements. As a result, the noble metal compound and the base metal compound are simultaneously reduced, and alloy particles with a high alloying rate are uniformly deposited as catalyst particles inside the pores of the porous material.

To explain in detail, in the second step, the noble metal compound and the base metal compound are uniformly supported and fixed inside the pores of the porous material. In this way, the noble metal compound and the base metal compound are uniformly supported and fixed inside the pores of the porous material, and a large amount of a reducing agent with a relatively high reducing power with an oxidation-reduction potential of -1.20V or less is applied. By contacting, the noble metal compound and base metal compound uniformly supported and fixed inside the pores of the porous material are rapidly reduced in a limited reaction field. As a result, the influence of the difference in reduction rate between the noble metal compound and the base metal compound is reduced, and catalyst particles with a high alloying rate are formed. In addition, since noble metal compounds and base metal compounds are quickly reduced while being uniformly supported and fixed inside the pores of the porous material, fine catalyst particles are uniformly distributed inside the pores of the porous material. It will precipitate. Furthermore, variations in composition among catalyst particles are also reduced. As a result of the above, the catalyst particles of the alloy catalyst have a small particle size and high dispersion, have small variations in composition, and have a high alloying ratio.

As described above, the reducing solution includes a reducing agent having a redox potential of −1.20 V or less and a second solvent.
The redox potential of the reducing agent is -1.20V or less. Thereby, the noble metal compound and the base metal compound can be reduced simultaneously and quickly. On the other hand, when the redox potential of the reducing agent exceeds -1.20V, the reducing power becomes weaker, and the reduction rate of the noble metal compound becomes slower, and the difference in the reduction rate between the noble metal compound and the base metal compound increases, and the reduction rate of the noble metal compound becomes large. It is not possible to increase the alloying ratio of the catalyst particles. The redox potential of the reducing agent is preferably -1.20V or less, more preferably -1.28V or more and -1.23V or less. In this specification, the oxidation-reduction potential is measured using an oxidation-reduction potential measurement electrode (for example, ORP electrode 9300-10D manufactured by Horiba, Ltd. or manufactured by Toa DKK Co., Ltd.) that has a built-in saturated silver chloride electrode as a comparison electrode. Values measured in an aqueous solution of a reducing agent using an ORP composite electrode PST-5821C) and an ORP meter (for example, portable pH meter D-72 manufactured by Horiba, Ltd. or pH meter HM-42X manufactured by Toa DKK Co., Ltd.) is the potential determined by correcting the value to that of a standard hydrogen electrode. If the reducing solution uses a solvent other than water, it is difficult to measure the redox potential of the reducing agent, so it is possible to judge the strength of the reducing power of the reducing agent by the carbonyl compound that can be converted to alcohol. It is. For example, a reducing agent that can reduce carboxylic acids and esters in addition to ketones and aldehydes is a more powerful reducing agent than a reducing agent that can reduce only ketones and aldehydes to alcohol. It can be determined that

Such a reducing agent is not particularly limited as long as it has the above-mentioned redox potential, but for example, lithium borohydride (LiBH ₄ ), sodium borohydride (NaBH ₄ ), potassium borohydride (KBH ₄ ), borohydride alkali metal salts such as lithium triethylborohydride, borohydride transition metal salts such as nickel borohydride (Ni(BH ₄ ) ₂ ), zinc borohydride (Zn(BH ₄ ) ₂ ), Alkali metal salts of aluminum hydride such as lithium aluminum hydride (LiAlH ₄ ), sodium aluminum hydride (NaAlH ₄ ), potassium aluminum hydride (KAlH ₄ ), sodium bis(2-methoxyethoxy)aluminum hydride, cyanohydride Examples include cyanoborohydride alkali metal salts such as lithium boron (LiBH ₃ CN), sodium cyanoborohydride (NaBH ₃ CN), potassium cyanoborohydride (KBH ₃ CN), diisobutylaluminum hydride (DIBAL), etc. , one kind among these can be used alone or two or more kinds can be used in combination.

Therefore, the reducing agent is one or two selected from the group consisting of an alkali metal salt of borohydride, a transition metal salt of borohydride, an alkali metal salt of aluminum hydride, an alkali metal salt of cyanoborohydride, and diisobutylaluminum hydride. More specifically, lithium borohydride (LiBH ₄ ), sodium borohydride (NaBH ₄ ), potassium borohydride (KBH ₄ ), lithium triethylborohydride, borohydride Nickel (Ni(BH ₄ ) ₂ ), zinc borohydride (Zn(BH ₄ ) ₂ ), lithium aluminum hydride (LiAlH ₄ ), sodium aluminum hydride (NaAlH ₄ ), potassium aluminum hydride (KAlH ₄ ), Sodium bis(2-methoxyethoxy)aluminum hydride, lithium cyanoborohydride (LiBH ₃ CN), sodium cyanoborohydride (NaBH ₃ CN), potassium cyanoborohydride (KBH ₃ CN), diisobutylaluminum hydride ( DIBAL) or two or more selected from the group consisting of:

Among the above, it has a high reducing power capable of reducing both noble metal compounds and base metal compounds, is soluble in multiple solvents, is easily available as a reagent, and has a low risk of ignition etc. From the viewpoint of the Contains one or more selected from the group consisting of lithium boron. These reducing agents have sufficient reducing power to simultaneously reduce noble metal compounds and base metal compounds, and are relatively easily available.

Further, the amount of the reducing agent in the reducing solution is 5 times or more as compared to the total amount of noble metal elements in the noble metal compound supported on the porous material. As a result, the reducing agent exists in a sufficient excess amount relative to the noble metal compound and the base metal compound and can contact the noble metal compound and the base metal compound, so that the noble metal compound and the base metal compound can be reduced simultaneously and quickly. can. If the amount of reducing agent in the reducing solution is less than 5 times the total amount of precious metal elements, even if a very strong reducing agent with a redox potential of less than -1.28V is used, the amount of reducing agent Because the amount is insufficient for the noble metal compound and base metal compound, the reduction rate of the noble metal compound and base metal compound becomes slow, or the noble metal compound and base metal compound cannot be reduced sufficiently, and the noble metal compound and base metal compound The influence of the difference in the reduction rate becomes large, and the alloying ratio of the obtained catalyst particles cannot be increased. Furthermore, as a result of not being able to sufficiently reduce the noble metal compound and the base metal compound, catalyst particles may not be supported on the porous material, and the supporting ratio may not reach the initial value.

The amount of the reducing agent in the reducing solution is preferably 10 times or more, more preferably 100 times or more, relative to the total amount of noble metal elements, from the viewpoint of reducing the difference in reduction rate between the noble metal compound and the base metal compound. Note that the upper limit of the amount of the reducing agent in the reducing solution is not particularly limited, but from the viewpoint of reducing costs, it can be, for example, 200 times or less with respect to the total amount of noble metal elements.

The concentration of the reducing agent in the reducing solution is not particularly limited, but may be, for example, 0.1 mol/L or more and 5.5 mol/L or less, preferably 1.0 mol/L or more and 5.0 mol/L or less. Thereby, it is possible to prevent the reducing agent from being excessively diluted and the reduction rate becoming slow, and since the concentration of the reducing agent is appropriate, the reduction reaction can be sufficiently controlled.

Furthermore, the second solvent contained in the reducing solution is not particularly limited as long as it can dissolve the above-mentioned reducing agent, and may be one or more solvents that can be used in the above-mentioned first solvent. Can be used in combination.

Among these, water, alcohol-based solvents, and ether-based solvents can be preferably used because they dissolve the reducing agent relatively easily.

Here, a preferred relationship between the first solvent contained in the mixture and the second solvent contained in the reducing solution will be explained. As described above, in this embodiment, the noble metal compound and the base metal compound are rapidly reduced by bringing the reducing solution into contact with the porous material. For this reason, it is preferable that the first solvent and the second solvent have high miscibility.

Therefore, the first solvent and the second solvent either contain the same solvent, or the absolute value of the difference between the octanol/water partition coefficient of the first solvent and the octanol/water partition coefficient of the second solvent is , is preferably 1.2 or less.

On the other hand, the first solvent is required to dissolve the noble metal compound and the base metal compound, and the second solvent is required to dissolve the reducing agent. From the viewpoint of dissolving such noble metal compounds, base metal compounds, and reducing agents, water and a solvent with high affinity for water are advantageous. Therefore, it is particularly preferable that the first solvent and the second solvent satisfy any one of the following combinations or relationships (i) to (iii).

(i) The first solvent contains water, and the octanol/water partition coefficient of the second solvent is 0.8 or less.
(ii) The second solvent contains water, and the first solvent has an octanol/water partition coefficient of 0.8 or less.
(iii) Both the first solvent and the second solvent contain water.

Here, "octanol/water partition coefficient" refers to "JIS Z 7260-107:2000 Measurement of partition coefficient (1-octanol/water) shaking flask method" or "JIS Z 7260-117:2006 partition coefficient ( 1-octanol/water) can be determined based on high performance liquid chromatography. For example, the octanol/water partition coefficients of the following solvents are: ethanol: -0.32, isopropanol: 0.05, acetone: -0.24, methanol: -0.82, 1-propanol: 0.25, diethyl Ether: -0.36, acetic acid: -0.17, toluene: 2.73, benzene: 2.13, and tetrahydrofuran: 0.46.

Further, the pH of the reducing solution at 25° C. is not particularly limited, but is preferably 8.0 or more and 12.0 or less, more preferably 8.5 or more and 11.5 or less. This stabilizes the reducing agent appropriately and suppresses undesired decomposition and deactivation of the reducing agent. Further, by having a pH of 12.0 or less, the stability of the reducing agent is prevented from becoming excessively high, and a decrease in the reduction rate is suppressed.

The pH of the reducing solution can be adjusted, for example, by acids, bases, especially bases, as mentioned above. In particular, the liquid containing the alloy catalyst obtained in the third step is washed in the post-process described below, but at this time, if many types of ions are contained in the liquid, it is necessary to remove the ions. Since the number of washings required increases, it is preferable that the pH of the reducing solution is adjusted using a base selected from the group consisting of sodium hydroxide, potassium hydroxide, and aqueous ammonia.

Further, the temperature during the reduction reaction is not particularly limited, and can be appropriately determined in consideration of the type of the second solvent and the speed of the reduction reaction. The temperature during the reduction reaction can be, for example, 0°C or more and 270°C or less, preferably 3°C or more and 150°C or less.

Further, the time for the reduction reaction is not particularly limited and can be appropriately selected depending on the reduction state of the noble metal compound and the base metal compound, and may be, for example, 10 minutes or more and 24 hours or less, preferably 15 minutes or more and 15 hours or less.

Further, during the reduction reaction, the mixed solution of the porous material and the reducing solution may be stirred as necessary.
In addition, when the first and second solvents contain a solvent other than water during the reduction reaction, in order to reduce the risk of ignition due to the reaction, the reduction should be carried out in an inert gas (rare gas, nitrogen, etc.) atmosphere. Preferably, the reaction is carried out. When the first solvent and the second solvent do not contain any solvent other than water, the reduction reaction can be carried out in any atmosphere such as the air or an inert gas.
In the manner described above, it is possible to obtain an alloy catalyst in which catalyst particles having a small particle size, high dispersion, and high alloying rate are supported inside the pores of a porous material.

[2.4. Post-process〕
The obtained alloy catalyst can be used after being subjected to post-treatments such as washing and drying according to known methods, if necessary.

Further, the obtained alloy catalyst may be subjected to heat treatment. The heat treatment improves the alloying rate of the catalyst particles. It is known that when a conventional alloy catalyst is heat-treated, the alloying rate improves, but the catalyst particles fuse together, the particle size of the catalyst particles increases, and aggregation progresses. However, in the method for producing an alloy catalyst according to the present embodiment described above, since the catalyst particles are highly dispersed and uniformly distributed inside the pores of the porous material, even when heat treatment is performed, the catalyst particles do not interact with each other. It is difficult for the particles to come into contact with each other, and as a result, an increase in particle size and a decrease in dispersibility are unlikely to occur.

The temperature of the heat treatment is not particularly limited, but can be, for example, 450°C or more and 1200°C or less, preferably 600°C or more and 900°C or less. Further, the heat treatment time is not particularly limited, and can be, for example, 10 minutes or more and 3 hours or less, preferably 20 minutes or more and 1 hour or less.
Note that the heat treatment is preferably performed in an inert gas (rare gas, nitrogen, etc.) atmosphere, a reducing gas (hydrogen, etc.) atmosphere, a mixed atmosphere of an inert gas and a reducing gas, or a vacuum atmosphere.

The preferred embodiments of the present invention have been described above. According to the method for manufacturing an alloy catalyst according to the present embodiment, in the second step, the first solvent is removed until a predetermined amount is reached, so that the noble metal compound and Base metal compounds can be fixed. In the third step, a sufficient amount of a strong reducing agent is brought into contact with the porous material on which the noble metal compound and the base metal compound are fixed, thereby creating a reaction field for the reduction reaction of the noble metal compound and the base metal compound. It is restricted to the vicinity of the surface inside the pores of the porous material, and the influence of the difference in reduction rate between the noble metal compound and the base metal compound is reduced. As a result, small-sized particles with a high alloying ratio are generated uniformly and in large quantities over the inner surface of the pores of the porous material. Therefore, it is possible to obtain an alloy catalyst in which catalyst particles having a small particle size, high dispersion, small variation in composition, and high alloying rate are supported inside the pores of the porous material.

It should be noted that while it has been known in the past to remove a solvent from a porous material as a pretreatment for alloying treatment by heat treatment or reduction reaction in a gas phase, as in this embodiment, the reduction reaction using a reducing solution is It was not previously known to previously remove the solvent from the porous material as a pretreatment.

In addition, since a protective agent to maintain the dispersibility of the catalyst particles is not required, there is no need to remove the protective agent, thereby preventing deterioration of the alloy catalyst (e.g., coarsening of catalyst particles, agglomeration, etc.) due to removal. can do. Furthermore, by eliminating the need for a protective agent, the amount of catalyst particles supported inside the pores of the porous material can be increased.

<3. Alloy catalyst＞
Next, the alloy catalyst according to this embodiment will be explained. The alloy catalyst according to this embodiment is manufactured by the method for manufacturing an alloy catalyst described above. Therefore, in the alloy catalyst according to the present embodiment, catalyst particles having a small particle size, high dispersion, small variation in composition, and high alloying rate are supported on the porous material. Hereinafter, the structure of the alloy catalyst will be explained in detail.

[3.1. Catalyst particles, noble metal elements, base metal elements, and porous materials]
The catalyst particles contain a noble metal element and a base metal element. Within the catalyst particles, the noble metal element and the base metal element are alloyed. The noble metal elements and base metal elements are derived from the above-mentioned noble metal compounds and base metal compounds, and the specific types are as described above. Preferably, the noble metal element includes one or more selected from the group consisting of platinum, gold, and palladium, and the base metal element includes one or more selected from the group consisting of Co, Fe, Ni, and Ti. is preferred. The specific structure of the porous material is as described above.

[3.2. Particle size of catalyst particles]
As described above, in the alloy catalyst according to this embodiment, the catalyst particles supported on the porous material have a small particle size. To explain more specifically, the particle size of the catalyst particles in this embodiment is calculated using the following Scherrer equation from the results of XRD (X-ray diffraction analysis) measurement using an X-ray diffraction device. Therefore, the particle size here is the so-called average particle size. Note that although the alloy catalyst may be heat-treated, the particle size of the catalyst particles in this embodiment is the average particle size measured by this method regardless of whether or not the alloy catalyst is heat-treated.
Scherrer equation: D=Kλ/βcosθ
D: crystallite diameter, K: Scherrer constant (0.94), λ: X-ray wavelength of CuKα, β: half width, θ: Bragg angle

In the alloy catalyst according to this embodiment, when the alloy catalyst is heat-treated at 900°C for 20 minutes while flowing a mixed gas consisting of 50 vol% hydrogen and 50 vol% argon at 150 mL/min, the catalyst particles after the heat treatment are The particle size is 3 nm or more and 7.5 nm or less. In this way, in the alloy catalyst according to the present embodiment, the catalyst particles are supported on the porous material in a small particle size and highly dispersed manner, so that even after heat treatment, the catalyst particles hardly aggregate with each other, and the particles are small. Particle size can be maintained.

[3.3. Dispersibility]
As described above, in the alloy catalyst according to this embodiment, the catalyst particles are supported on the porous material in a highly dispersed manner. The dispersibility of catalyst particles is expressed by the following formula (5):
(Degree of dispersion) = {(Particle size of the catalyst particles after the above heat treatment) - (Particle size of the catalyst particles before the above heat treatment)}/(Particle size of the catalyst particles before the above heat treatment) (5)
It is evaluated by the degree of dispersion defined by . In the alloy catalyst according to this embodiment, the degree of dispersion is 1.5 or less. It can be said that the smaller the degree of dispersion, the higher the dispersibility of the catalyst particles.

[3.4. Alloying rate]
As described above, in the alloy catalyst according to this embodiment, the alloying rate of the catalyst particles is extremely high. Here, the alloying rate is expressed by the following formula (3):
Alloying rate [%] = {(Lattice constant of bulk noble metal) - (Lattice constant of catalyst particles)} / {(Lattice constant of bulk noble metal) - (Lattice constant of maximum peak of bulk alloy)} x 100 (3)
Defined by In the alloy catalyst according to this embodiment, the alloying ratio is 80% or more. It can be said that the higher the alloying ratio is, the more advanced the alloying between the noble metal element and the base metal element is.

The alloying ratio is conceptually a value indicating the degree of solid solution of the base metal element within the catalyst particles, and the higher the alloying ratio, the more uniformly the base metal element and the noble metal element are solid dissolved within the catalyst particle. By alloying the noble metal element and the base metal element, the interatomic distance changes compared to catalyst particles made only of the noble metal element, and the power generation performance of the polymer electrolyte fuel cell, especially the initial power generation performance, improves. However, the alloying rate determined here is just the average alloying rate of the entire catalyst particle, and just because the alloying rate is high does not necessarily mean that each individual catalyst particle is sufficiently alloyed. . Therefore, in this embodiment, in addition to the alloying ratio, the standard deviation of the base metal element concentration, which will be described later, was evaluated, and a requirement for the alloy catalyst was that this standard deviation be low. When the alloying rate determined by equation (3) is high and the standard deviation is low, it is considered that the compositional variation among catalyst particles is small and that the individual catalyst particles are also sufficiently alloyed.

In formula (3), the lattice constant of the catalyst particles is a value determined by X-ray diffraction analysis. The lattice constant of a bulk noble metal is a lattice constant obtained by X-ray diffraction analysis of a standard sample of a noble metal element, and is stored in a database (for example, the International Center for Diffraction Date; a database distributed by ICDD). Registered.In addition, if the catalyst particles contain multiple types of noble metal elements, the lattice constant of the noble metal element with the largest amount of substance in the catalyst particles can be used as the lattice constant of the bulk noble metal.Bulk alloy The lattice constant of the maximum peak is the lattice constant obtained by X-ray diffraction analysis of a standard sample with the same composition as the catalyst particles, and is a lattice constant obtained from a database (e.g., International Center for Diffraction Date; distributed by ICDD). The composition of the catalyst particles here is the average composition of the entire catalyst particles, that is, the mass % of noble metal elements and base metal elements supported on the porous material.Porous The mass % of noble metal elements and base metal elements supported on the material is evaluated as the support rate of catalyst particles in the examples described below.In the examples described later, based on the database distributed by the International Diffraction Data Center, The alloying rate was calculated.

[3.5. Composition variation]
As described above, in the alloy catalyst according to this embodiment, the variation in composition among catalyst particles is small. In other words, the composition of more catalyst particles is derived from the charged composition (i.e., the composition of catalyst particles derived from the chemical formula and usage amount of the noble metal compound and base metal compound used to prepare the alloy catalyst. For example, the composition of catalyst particles is derived from the porous (expressed as mass % of total noble metal elements and mass % of total base metal elements supported on the material). Therefore, more catalyst particles can efficiently perform the catalytic reaction (oxygen reduction reaction), and as a result, the power generation performance of the polymer electrolyte fuel cell, especially the initial power generation performance, can be improved. If there is a large variation in composition, the composition will vary greatly between catalyst particles, resulting in a coexistence of catalyst particles that perform catalytic reactions with high efficiency and catalyst particles that do not, resulting in a decrease in initial power generation performance.

In the alloy catalyst according to this embodiment, the compositional variation of each catalyst particle is evaluated by the standard deviation of the base metal element concentration of the catalyst particles. The standard deviation is 6.5 or less. In this case, it can be evaluated that the compositional variations are sufficiently small. That is, when the standard deviation is 6.5 or less, more catalyst particles can efficiently perform the catalytic reaction. It can be said that the lower the standard deviation, the smaller the variation in composition. The standard deviation is preferably 6.0 or less. The lower limit value of the standard deviation is not particularly limited and is ideally 0. However, in reality, the standard deviation will be a value exceeding 0.

The compositional variation of each catalyst particle, that is, the standard deviation of the base metal element concentration of the catalyst particles, is measured by STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive X-ray Spectroscopy). Specifically, a total of 100 or more catalyst particles are randomly extracted from each test sample, and the atomic concentration of noble metals and base metals is measured for each catalyst particle by EDS point analysis. At this time, the magnification during observation is 500,000 times, and in order to know the average variation of the entire sample, it is preferable to observe three or more visual fields per test sample. That is, a total of 100 or more catalyst particles are extracted from these fields of view. Note that when extracting catalyst particles, the observed image may be binarized separately, and this binarized image may be referred to. In the binarized image, the image of the catalyst particles may be clearer. Next, the standard deviation is calculated based on the base metal element concentration (atomic concentration) for each catalyst particle. In addition, when the catalyst particles contain multiple types of base metal elements, it is sufficient that the standard deviation of at least one type of base metal element is 6.5 or less, and preferably the standard deviation of all base metal elements is 6.5 or less. .

As described above, in the alloy catalyst according to the present embodiment, catalyst particles having a small particle size, high dispersion, small variation in composition, and high alloying rate are supported on the porous material. Therefore, by using the alloy catalyst according to this embodiment in a polymer electrolyte fuel cell, the durability and power generation performance of the polymer electrolyte fuel cell can be improved.

[3.6. Internal carrying rate]
In the alloy catalyst according to this embodiment, it is preferable that catalyst particles are further supported inside the pores of the porous material. More specifically, when observing the alloy catalyst with a scanning transmission electron microscope, the following formula (4):
Internal loading rate [%] = (b-2×a)/b (4)
It is preferable that the internal loading rate defined by is 26% or more. Here, b is the total number of catalyst particles within the observation field, and a is the number of catalyst particles present at and near the outermost surface of the porous material. a and b are measured by observing the same visual field at different accelerating voltages. For example, in the examples described below, a is measured as the number of catalyst particles in a 3 kV reflection image, and b is measured as the number of catalyst particles in a 30 kV transmission image. Therefore, the fact that the catalyst particles are supported inside the pores of the porous material is evaluated by the internal loading rate. When the internal loading rate is 26% or more, it can be evaluated that the number of catalyst particles supported inside the pores of the porous material is sufficiently large. Although the details will be described later, since the alloy catalyst according to this embodiment is manufactured by the above-mentioned manufacturing method, many catalyst particles are supported inside the pores of the porous material, and the internal loading rate is low. It exceeds 26%. Therefore, the power generation performance and durability of the polymer electrolyte fuel cell are further improved. It can be said that the larger the internal loading rate, the larger the number of catalyst particles supported inside the pores, which is preferable.

Note that the alloy catalyst manufactured by the method for manufacturing an alloy catalyst according to the present embodiment described above is not particularly limited, and can be applied to any purpose depending on the catalyst components constituting the alloy catalyst. In particular, the alloy catalyst supports catalyst particles having a small particle size, high dispersion, small variation in composition, and high alloying rate. Therefore, the alloy catalyst is suitable for use in fields where catalyst particles are required to have small particle size and high dispersion, small variations in composition, and high alloying ratio, such as catalysts for polymer electrolyte fuel cells. can do.

When the alloy catalyst manufactured by the method for manufacturing an alloy catalyst according to the present embodiment is applied to a catalyst for a polymer electrolyte fuel cell, the power generation performance and durability will be significantly excellent for the following reasons.

First, the catalyst particles have a small particle size, and the particle size after the above heat treatment is 3 nm or more and 7.5 nm or less, so the effective specific surface area of the catalyst particles that can contribute to the power generation reaction of the alloy catalyst is large.
Furthermore, since the catalyst particles do not aggregate with each other and have good dispersibility, it is possible to maintain a small particle size even after heat treatment, and grain growth due to heat treatment is small (for example, the particle size after heat treatment is 3 nm or more and 7.5 nm). Therefore, even after heat treatment, the catalyst particles still have a large effective specific surface area that can contribute to the power generation reaction. At the same time, since the dispersibility of the catalyst particles is good, there is little deterioration of the alloy catalyst due to the coarsening of the catalyst particles (for example, the formation of coarse particles with a particle size of 15 nm or more) when repeated power generation reactions are performed, and the durability of the alloy catalyst is reduced. is high.

Furthermore, in this embodiment, the alloying rate of the catalyst particles is high. Alloying a noble metal element with a base metal element shortens the interatomic distance between noble metal atoms, thereby optimizing the ease with which they bond with and desorb oxygen. If the adsorption of oxygen on the catalyst particles is too high, it will be difficult to desorb after the reduction reaction, and if the desorption of the catalyst particles is too high, no oxygen will be adsorbed and the reduction reaction will not occur. In the power generation reaction of polymer electrolyte fuel cells, the oxygen reduction reaction on the cathode side is rate-determining, so if the ease of bonding and desorption between catalyst particles and oxygen is optimized through alloying, power generation The reaction is accelerated and power generation performance is improved.

Furthermore, in the method according to this embodiment, it is possible to support a sufficient amount of catalyst particles inside the pores of the porous material. As a result, the surface area of the porous material as a carrier can be effectively utilized. As a result, compared to catalyst particles supported outside the pores (on the outer surface of the porous material), the catalyst particles supported inside the pores undergo deterioration such as coarsening of the particles due to repeated power generation reactions. Hard and durable. Furthermore, compared to catalyst particles supported outside the pores (on the outer surface of the porous material), the catalyst particles supported inside the pores are less likely to be coated with the ionomer as a polymer electrolyte contained in the catalyst layer. Therefore, the effective specific surface area that can contribute to the power generation reaction due to the ionomer coating is less reduced, and the power generation performance is less reduced. As described above, in this embodiment, by supporting a sufficient amount of catalyst particles inside the pores of the porous material, it contributes to improving the power generation performance and durability of the polymer electrolyte fuel cell.

Embodiments of the present invention will be specifically described below with reference to Examples. Note that the examples shown below are merely examples of the present invention, and the present invention is not limited to the following examples.

1. Production of alloy catalyst (Example 1-1)
(i) First step Add 0.5 g of mesoporous silica (manufactured by Taiyo Kagaku Co., Ltd., TMPS-4R, pore volume: 0.89 cm ³ /g) as a porous material to 100 mL of water as the first solvent. was added and dispersed for 2 minutes using an ultrasonic homogenizer. To this, 0.39 g of dinitrodiammine platinum nitrate solution as a noble metal compound, 0.046 g of nickel (II) sulfate hexahydrate as a base metal compound, and 0.051 g of cobalt sulfate heptahydrate were added, and the mixture was stirred using a stirrer. Stir for 30 minutes.

(ii) Second step After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the mass of the sample was measured to calculate the mass of water, and solvent removal was continued until the mass of water was 0.22 g. Here, the pore volume of mesoporous silica is 0.89 cm ³ /g×0.5(g)=0.445 ^{cm 3} . The volume of 0.22 g of water is 0.22 cm ³ because the density of water is 0.99 g/cm ³ . Therefore, the volume of water in the sample was 0.5 times the pore volume of the mesoporous silica.

(iii) Third step Next, in the atmosphere, a reducing solution obtained by dissolving 0.34 g of sodium borohydride as a reducing agent in 4.5 mL of water (second solvent) was prepared after removing the solvent. The mixture was added to the sample and stirred vigorously. At this time, the reaction was performed at room temperature. After stirring as it was for 1 hour, the resulting mixed solution was washed by filtration, and the collected sample was vacuum dried to obtain an alloy catalyst according to Example 1-1.

(Example 1-2)
An alloy catalyst according to Example 1-2 was obtained in the same manner as in Example 1-1, except that the various materials and experimental conditions in the first to third steps were changed as shown in Table 1-1. .

(Example 1-3)
(i) First step Mesoporous silica (manufactured by Taiyo Kagaku Co., Ltd., TMPS-4R, fine Pore volume: 0.89 cm ³ /g) was added and dispersed for 2 minutes using an ultrasonic homogenizer. 0.14 g of chloroauric acid as a noble metal compound and 0.027 g of nickel (II) chloride hexahydrate as a base metal compound were added thereto, and the mixture was stirred for 30 minutes using a stirrer.

(ii) Second step After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the mass of the sample was measured to calculate the mass of the first solvent, and the solvent was continued to be removed until the mass of the first solvent reached 0.20 g. Here, the pore volume of mesoporous silica is 0.89 cm ³ /g×0.5(g)=0.445 ^{cm 3} . The volume of 0.20 g of the first solvent is 0.22 cm ³ because the density of the water/ethanol=1/1 (vol/vol) mixed solution is 0.91 g/cm ³ . Therefore, the volume of water in the sample was 0.5 times the pore volume of the mesoporous silica.

(iii) Third step Next, in an Ar atmosphere, a reducing solution obtained by dissolving 1.27 g of sodium borohydride as a reducing agent in 16.8 mL of water (second solvent) was obtained after removing the solvent. and stirred vigorously. At this time, the reaction was performed at room temperature. After stirring as it was for 1 hour, the resulting mixed solution was washed by filtration, and the collected sample was vacuum dried to obtain an alloy catalyst according to Example 1-3.

The manufacturing conditions for each of the above examples are shown in Table 1-1. In addition, in the table,
"Pt(NO ₂ ) ₂ (NH ₃ ) ₂ " is a dinitrodiammine platinum nitrate solution with a platinum concentration of 4.5 wt%.
"Pd nitrate" means palladium nitrate,
"Chloroauric acid" refers to chloroauric acid (III) acid tetrahydrate,
"Ni sulfate" refers to nickel (II) sulfate hexahydrate,
"Co sulfate" refers to cobalt (II) sulfate heptahydrate,
"Co nitrate" refers to cobalt(II) nitrate hexahydrate,
"Ni chloride" refers to nickel (II) chloride hexahydrate,
"EtOH" means ethanol,
"rt." each indicates room temperature. Note that the remaining amount of the first solvent in the second step was described as a ratio based on the pore volume of the porous material.

2. Evaluation of alloy catalyst 2.1. Particle Size of Catalyst Particles The particle size of the catalyst particles of the obtained alloy catalyst was measured using an X-ray diffraction device (XRD, manufactured by Rigaku Co., Ltd., Smart Lab). From the results of the XRD measurement, the crystallite diameter (particle diameter of the catalyst particles) was calculated using the Scherrer equation below.
Scherrer equation: D=Kλ/βcosθ
D: crystallite diameter, K: Scherrer constant (0.94), λ: X-ray wavelength of CuKα, β: half width, θ: Bragg angle

2.2. Dispersibility The dispersibility of the obtained alloy catalyst was measured by the change in particle size before and after heat treatment. The obtained alloy catalyst was vacuum-dried, and the dried sample was heat-treated at 900° C. for 20 minutes while flowing a mixed gas of 50 vol% hydrogen and 50 vol% argon at 150 mL/min. If the dispersibility is poor, the formation of coarse particles due to heat treatment is clearly confirmed, so the dispersibility was evaluated by measuring the change in particle size (increase in particle size) before and after the heat treatment. More specifically, the degree of dispersion defined by the above equation (5) was measured. If the degree of dispersion is 1.5 or less, it can be evaluated that the dispersibility is sufficiently high.

2.3. Alloying Ratio The alloying ratio of the obtained catalyst particles was measured using an X-ray diffraction device (XRD, manufactured by Rigaku Co., Ltd., Smart Lab). From the results of the XRD measurement, the alloying rate was calculated using the above-mentioned formula (3). In addition, when there are two or more types of noble metals, the calculation was performed based on the lattice constant of the noble metal containing the largest amount of substance.

2.4. Evaluation of the presence of catalyst particles inside the pores (internal support rate)
The internal support rate of the catalyst particles of the obtained alloy catalyst was evaluated using a scanning transmission electron microscope (STEM SU9000, manufactured by Hitachi High-Technologies, Inc.) and image analysis software (ImageJ). . First, images of the same field of view at different acceleration voltages were obtained by STEM observation. The accelerating voltage can be selected from values including low accelerating voltage (~1 kV), high accelerating voltage (25 to 30 kV), and an intermediate accelerating voltage (2 to 7 kV). It is preferable to include. In this example, observation was performed at 3 kV and 30 kV. Next, particle analysis of the images obtained by STEM observation was performed using image analysis software. First, the catalyst particles were subjected to edge processing, and then binarization processing was performed. The number of catalyst particles at each acceleration voltage was counted from the obtained binarized image. That is, the number of catalyst particles in a 3 kV reflection image and the number of catalyst particles in a 30 kV transmission image were counted. The internal loading rate was calculated based on these values and the above-mentioned formula (4). Here, the number of catalyst particles in the 3kV reflection image represents a in equation (4), that is, the number of catalyst particles present on the outermost surface and near the surface of the porous material, and the number of catalyst particles in the 30kV transmission image is: b in formula (4) indicates the total number of catalyst particles within the observation field. Since b also includes the number of particles present on the back side of the carrier, it was assumed that the same number of particles existed on the back side of the carrier as on the outermost surface and near the surface.

2.5. Supporting rate of catalyst particles The supporting rate of the obtained catalyst particles was measured by inductively coupled plasma emission spectrometry (ICP-AES: ICPE-9800, manufactured by Shimadzu Corporation). Note that the supporting ratio here was determined as the mass % of each metal element relative to the total mass of the alloy catalyst used as a test sample.

2.6. Standard deviation of base metal element concentration The standard deviation of base metal element concentration was measured using STEM-EDS. Specifically, SU9000 manufactured by Hitachi High Technologies was used as the STEM, and E-MAX Evolution manufactured by Horiba, Ltd. was used as the EDS. In this measurement, one test sample was observed in three different fields of view, and a total of 100 catalyst particles were randomly extracted from each field of view. The magnification during observation was 500,000 times. Next, the atomic number concentrations of noble metals and base metals were measured for each catalyst particle by EDS point analysis. Next, the standard deviation was calculated based on the base metal element concentration (atomic concentration) for each catalyst particle. Note that since the catalyst particles of Example 1-1 are ternary catalyst particles containing two types of base metal elements (Ni and Co), in Example 1-1, the standard deviation of the Co concentration was calculated.
The above results are shown in Table 1-2.

3. Results As is clear from Table 1-2, the alloy catalysts according to Examples 1-1 to 1-3 had small particle sizes and high dispersion, small variations in composition, and catalyst particles with a high alloying rate. supported on a porous material.

4. Production of alloy catalyst for polymer electrolyte fuel cells (Example 2-1)
(i) First step Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd., pore volume: 2.9 cm ³ /g) as a porous material is added to 100 mL of 1-propanol as the first solvent. 0.5 g was added and dispersed for 2 minutes using an ultrasonic homogenizer. 0.32 g of platinum acetylacetonate as a noble metal compound and 0.22 g of cobalt (III) acetylacetonate as a base metal compound were added thereto, and the mixture was stirred for 30 minutes using a stirrer.

(ii) Second step After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the mass of the sample was measured to calculate the mass of 1-propanol, and solvent removal was continued until the mass of 1-propanol reached 5.8 g. Here, the pore volume of Ketjenblack is 2.9 cm ³ /g×0.5(g)=1.45 ^{cm 3} . The volume of 5.8 g of 1-propanol is 7.25 cm ³ since the density of 1-propanol is 0.8 g/cm ³ . Therefore, the volume of 1-propanol in the sample was 5.0 times the pore volume of Ketjenblack.

(iii) Third step Next, in an Ar atmosphere, a reducing solution obtained by dissolving 0.27 g of sodium cyanoborohydride as a reducing agent in 4 mL of methanol (second solvent) was prepared after removing the solvent. The mixture was added to the sample and stirred vigorously. At this time, the reaction was carried out in an oil bath set at 75°C. After stirring for 1 hour, the resulting mixed solution was washed by filtration, and the collected sample was vacuum-dried to obtain an alloy catalyst according to Example 2-1.

(Examples 2-2 to 2-7)
The alloys according to Examples 2-2 to 2-7 were prepared in the same manner as in Example 2-1, except that the various materials and experimental conditions in the first to third steps were changed as shown in Table 2-1. I got a catalyst.

(Example 2-8)
(i) First step Ketjen Black EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd., pore volume: 2.9 cm ³ /g) as a porous material was added to 100 mL of water as the first solvent. 5 g was added and dispersed for 2 minutes using an ultrasonic homogenizer. 5.5 g of a dinitrodiammine platinum nitric acid solution having a platinum concentration of 4.5 wt% as a noble metal compound and 0.066 g of iron(III) nitrate nonahydrate as a base metal compound were added thereto, and the mixture was stirred for 30 minutes using a stirrer.

(ii) Second step After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the mass of the sample was measured to calculate the mass of water, and solvent removal was continued until the mass of water became 0.072 g. Here, the pore volume of Ketjenblack is 2.9 cm ³ /g×0.5(g)=1.45 ^{cm 3} . The volume of 0.072 g of water is 0.073 cm ^{3 because the density of water is 0.99 g/cm 3 .} Therefore, the volume of water in the sample was 0.05 times the pore volume of Ketjenblack.

(iii) Third step Next, in the air, 4.8 g of sodium borohydride as a reducing agent, a small amount (about 1 mL) of a 1.0 mol/L aqueous sodium hydroxide solution, and 32 mL of water (second solvent) ) was added. The pH of this solution was measured while stirring, and 1.0 mol/L sodium hydroxide was added until the pH reached 11.8 to obtain a reduced solution. The obtained reduced solution was added to the sample obtained after removing the solvent, and the sample was vigorously stirred. At this time, the reaction was performed at room temperature. After stirring as it was for 1 hour, the resulting mixed solution was washed by filtration, and the collected sample was vacuum dried to obtain an alloy catalyst according to Example 2-8.

(Examples 2-9 to 2-13)
The alloys according to Examples 2-9 to 2-13 were prepared in the same manner as in Example 2-8, except that the various materials and experimental conditions in the first to third steps were changed as shown in Table 2-1. I got a catalyst.

(Example 2-14)
(i) First step Ketjen Black EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd., pore volume: 2.9 cm ³ /g) as a porous material was added to 100 mL of water as the first solvent. 5 g was added and dispersed for 2 minutes using an ultrasonic homogenizer. 5.5 g of a dinitrodiammine platinum nitric acid solution having a platinum concentration of 4.5 wt% as a noble metal compound and 0.12 g of cobalt sulfate heptahydrate as a base metal compound were added thereto, and the mixture was stirred for 30 minutes using a stirrer.

(ii) Second step After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the mass of the sample was measured to calculate the mass of water, and solvent removal was continued until the mass of water became 0.015 g. Here, the pore volume of Ketjenblack is 2.9 cm ³ /g×0.5(g)=1.45 ^{cm 3} . The volume of 0.015 g of water is 0.015 cm ^{3 because the density of water is 0.99 g/cm 3 .} Therefore, the volume of water in the sample was 0.01 times the pore volume of Ketjenblack.

(iii) Third step Next, in the atmosphere, 32 mL of a reducing solution prepared by dissolving 4.8 g of sodium borohydride as a reducing agent in 32 mL of water (second solvent) was added to the sample obtained after removing the solvent. and stirred vigorously. At this time, the reaction was performed at room temperature. After stirring as it was for 1 hour, the resulting mixed solution was washed by filtration, and the collected sample was vacuum dried to obtain an alloy catalyst according to Example 2-14.

(Example 2-15)
An alloy catalyst according to Example 2-15 was obtained in the same manner as Example 2-14, except that the various materials and experimental conditions in the first to third steps were changed as shown in Table 2-1. .

(Comparative Examples 2-1 to 2-10)
The alloys according to Comparative Examples 2-1 to 2-10 were prepared in the same manner as in Example 2-1, except that the various materials and experimental conditions in the first to third steps were changed as shown in Table 2-2. I got a catalyst.

(Comparative Example 2-11)
0.5 g of Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd.) was added to 80 mL of water and dispersed for 2 minutes using an ultrasonic homogenizer. 5.5 g of a dinitrodiammine platinum nitric acid solution with a platinum concentration of 4.5 wt% and 20 mL of ethanol were added thereto, and the mixture was stirred for 12 hours in an oil bath set at 110°C. The resulting mixture was washed and collected by filtration. 100 mL of water was poured into the collected sample, 0.12 g of cobalt nitrate hexahydrate was added thereto, and the mixture was stirred for 30 minutes.

After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the weight of the sample was measured to calculate the weight of water, and solvent removal was continued until the weight of water was 0.015 g.

After removing the solvent, the sample was vacuum-dried, and the dried sample was heat-treated at 900°C for 20 minutes while flowing a mixed gas consisting of 50 vol% hydrogen and 50 vol% argon at 150 mL/min. Comparative Example 2- An alloy catalyst according to No. 11 was obtained.

(Comparative example 2-12)
0.5 g of Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd.) was added to 80 mL of water and dispersed for 2 minutes using an ultrasonic homogenizer. 5.5 g of a dinitrodiammine platinum nitric acid solution with a platinum concentration of 4.5 wt% and 20 mL of ethanol were added thereto, and the mixture was stirred for 12 hours in an oil bath set at 110°C. The resulting mixture was washed and collected by filtration. 100 mL of water was poured into the collected sample, 0.12 g of cobalt nitrate hexahydrate was added thereto, and the mixture was stirred for 30 minutes.

After stirring, an aqueous solution prepared by dissolving 4.8 g of sodium borohydride in 43 mL of water was added to this mixed solution, and the mixture was vigorously stirred. After stirring for 3 hours, the mixed solution was washed by filtration, and the collected sample was dried in vacuum, and then heat-treated at 900 ° C. for 20 minutes while flowing a mixed gas consisting of 50 vol% hydrogen + 50 vol% argon at 150 mL/min. , an alloy catalyst according to Comparative Example 2-12 was obtained.

(Comparative example 2-13)
0.5 g of Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd.) was added to 200 mL of water and dispersed for 2 minutes using an ultrasonic homogenizer. To this were added 5.5 g of dinitrodiammine platinum nitric acid solution with a platinum concentration of 4.5 wt% and 0.12 g of cobalt sulfate heptahydrate, and the mixture was stirred for 30 minutes.

After stirring, an aqueous solution prepared by dissolving 4.8 g of sodium borohydride in 60 mL of water was added to this mixed solution, and the mixture was vigorously stirred. After stirring for 3 hours, the mixed solution was washed by filtration, and the collected sample was dried in vacuum, and then heat-treated at 900 ° C. for 20 minutes while flowing a mixed gas consisting of 50 vol% hydrogen + 50 vol% argon at 150 mL/min. , an alloy catalyst according to Comparative Example 2-13 was obtained.

(Comparative example 2-14)
0.5 g of Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd.) was added to 100 mL of water, and dispersed for 2 minutes using an ultrasonic homogenizer. 5.5 g of dinitrodiammine platinum nitric acid solution with a platinum concentration of 4.5 wt% and 0.12 g of cobalt sulfate heptahydrate were added to the mixture, and the mixture was stirred for 30 minutes using a stirrer.

After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the weight of the sample was measured to calculate the weight of water, and solvent removal was continued until the weight of water was 0.15 g.
After removing the solvent, heat treatment was performed at 900° C. for 20 minutes while flowing hydrogen at a rate of 150 mL/min to obtain an alloy catalyst according to Comparative Example 2-14.

(Comparative example 2-15)
0.5 g of Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd.) was added to 200 mL of water and dispersed for 2 minutes using an ultrasonic homogenizer. To this were added 5.5 g of dinitrodiammine platinum nitric acid solution with a platinum concentration of 4.5 wt%, 0.12 g of cobalt sulfate heptahydrate, and 0.13 g of polyvinylpyrrolidone K-15, and the mixture was stirred for 30 minutes.

After stirring, an aqueous solution prepared by dissolving 4.8 g of sodium borohydride in 43 mL of water was added to this mixed solution, and the mixture was vigorously stirred. After stirring for 3 hours, the mixed solution was washed by filtration, and the collected sample was dried in vacuum, and then heat-treated at 900 ° C. for 20 minutes while flowing a mixed gas consisting of 50 vol% hydrogen + 50 vol% argon at 150 mL/min. , an alloy catalyst according to Comparative Example 2-15 was obtained.

(Comparative example 2-16)
5.5 g of dinitrodiammine platinum nitric acid solution with a platinum concentration of 4.5 wt% was added to 60 mL of tetraethylene glycol and stirred to prepare a diluted Pt solution. On the other hand, 0.12 g of cobalt sulfate heptahydrate was added to 70 mL of tetraethylene glycol and stirred to prepare a Co diluted solution.
70 mL of tetraethylene glycol was added to polyvinylpyrrolidone (PVP) and stirred to prepare a PVP solution.

The diluted Pt solution was slowly added dropwise to the PVP solution prepared above and mixed, and the mixture was stirred at room temperature in a nitrogen atmosphere for about 1 hour. A diluted Co solution was slowly added dropwise to this and mixed, and the mixture was stirred for about 1 hour in a nitrogen atmosphere. A solution of 4.8 g of sodium borohydride dissolved in 43 mL of tetraethylene glycol was added to this mixed solution, heated to 150° C., and heated under reflux for about 1 hour to simultaneously reduce Pt and Co.

The obtained reaction solution was added to 0.5 g of Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd.) dispersed in 70 mL of distilled water so that Pt was 32.3% by mass based on the powder. and stirred for 3 hours. Further, water was evaporated at 120°C and calcined at 450°C for 2 hours to obtain an alloy catalyst according to Comparative Example 2-16.

(Comparative Example 2-17)
0.5 g of Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd., pore volume: 2.9 cm ³ /g) as a porous material was added to 100 mL of water as the first solvent, and the mixture was subjected to ultrasonic waves. Dispersion was performed using a homogenizer for 2 minutes. 0.66 g of hexachloroplatinic (IV) acid hexahydrate as a noble metal compound and 0.10 g of cobalt chloride as a base metal compound were added thereto, and the mixture was stirred for 30 minutes using a stirrer.

After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the mass of the sample was measured to calculate the mass of water, and solvent removal was continued until the mass of water became 0.015 g. Here, the pore volume of Ketjenblack is 2.9 cm ³ /g×0.5(g)=1.45 ^{cm 3} . The volume of 0.015 g of water is 0.015 cm ^{3 because the density of water is 0.99 g/cm 3 .} Therefore, the volume of water in the sample was 0.01 times the pore volume of Ketjenblack.

The obtained porous material was dried at 150° C. for 16 hours under a nitrogen atmosphere, and then reduced using 5% ethylene in nitrogen at 150° C. for 5 hours to obtain the alloy catalyst according to Comparative Example 2-17. Obtained.

(Comparative example 2-18)
0.5 g of Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd., pore volume: 2.9 cm ³ /g) as a porous material was added to 100 mL of water as the first solvent, and the mixture was subjected to ultrasonic waves. Dispersion was performed using a homogenizer for 2 minutes. 0.66 g of hexachloroplatinic (IV) acid hexahydrate as a noble metal compound and 0.10 g of cobalt chloride as a base metal compound were added thereto, and the mixture was stirred for 30 minutes using a stirrer.

After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the mass of the sample was measured to calculate the mass of water, and solvent removal was continued until the mass of water became 0.015 g. Here, the pore volume of Ketjenblack is 2.9 cm ³ /g×0.5(g)=1.45 ^{cm 3} . The volume of 0.015 g of water is 0.015 cm ^{3 because the density of water is 0.99 g/cm 3 .} Therefore, the volume of water in the sample was 0.01 times the pore volume of Ketjenblack.

Thereafter, the porous material was impregnated with 391.79 ml of an aqueous solution in which 0.21 g of potassium hydroxide was dissolved, and stirred for 16 hours to precipitate noble metal elements and base metal elements as their respective hydroxides. The resulting porous material was then dried at 150°C for 16 hours under a nitrogen atmosphere, and then reduced using 5% ethylene in nitrogen at 150°C for 5 hours to form an alloy according to Comparative Example 2-18. I got a catalyst.

(Comparative Example 2-19)
0.5 g of Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd., pore volume: 2.9 cm ³ /g) as a porous material was added to 100 mL of water as the first solvent, and the mixture was subjected to ultrasonic waves. Dispersion was performed using a homogenizer for 2 minutes. 0.66 g of hexachloroplatinic (IV) acid hexahydrate as a noble metal compound and 0.10 g of cobalt chloride as a base metal compound were added thereto, and the mixture was stirred for 30 minutes using a stirrer.

After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the mass of the sample was measured to calculate the mass of water, and solvent removal was continued until the mass of water became 0.015 g. Here, the pore volume of Ketjenblack is 2.9 cm ³ /g×0.5(g)=1.45 ^{cm 3} . The volume of 0.015 g of water is 0.015 cm ^{3 because the density of water is 0.99 g/cm 3 .} Therefore, the volume of water in the sample was 0.01 times the pore volume of Ketjenblack.

Thereafter, the porous material was impregnated with 391.79 ml of an aqueous solution in which 0.21 g of potassium hydroxide was dissolved, and stirred for 16 hours to precipitate noble metal elements and base metal elements as their respective hydroxides.

Next, in an Ar atmosphere, a reducing solution in which 3.21 g of hydrazine monohydrate as a reducing agent was dissolved in 13 mL of water was poured into the obtained sample and vigorously stirred. At this time, the reaction was performed at room temperature. After stirring as it was for 1 hour, the resulting mixed solution was washed by filtration, and the collected sample was vacuum dried to obtain an alloy catalyst according to Comparative Example 2-19.

(Comparative example 2-20)
Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals Co., Ltd., pore volume: 2.9 cm ³ /g) as a porous material was added to a reduced solution in which 0.45 g of hydrazine monohydrate was dissolved in 30 mL of water. 0.5 g was added and dispersed for 2 minutes using an ultrasonic homogenizer. Next, 5.5 g of a dinitrodiammine platinum nitric acid solution with a platinum concentration of 4.5 wt% and 0.12 g of cobalt nitrate hexahydrate were added, and the mixture was stirred at room temperature for 30 minutes.

After stirring, the solvent was removed using a rotary evaporator. During solvent removal, the mass of the sample was measured to calculate the mass of water, and solvent removal was continued until the mass of water became 0.015 g. Here, the pore volume of Ketjenblack is 2.9 cm ³ /g×0.5(g)=1.45 ^{cm 3} . The volume of 0.015 g of water is 0.015 cm ^{3 because the density of water is 0.99 g/cm 3 .} Therefore, the volume of water in the sample was 0.01 times the pore volume of Ketjenblack.
Next, it was calcined at 630° C. for 5 hours in a nitrogen atmosphere to obtain an alloy catalyst according to Comparative Example 2-20.

The manufacturing conditions in each of the above Examples and Comparative Examples are shown in Tables 2-1 and 2-2. In addition, in the table, "acacPt" refers to bis(acetylacetonato)platinum (II), "Pt chloride" refers to hexachloroplatinic (IV) acid hexahydrate, and "Pt(NO ₂ ) ₂ (NH ₃ ) ₂ '' refers to a dinitrodiammine platinum nitrate solution with a platinum concentration of 4.5 wt%, ``acacCo'' refers to cobalt (III) acetylacetonate, ``Co chloride'' refers to cobalt (II) chloride, and ``Co nitrate'' is cobalt (II) nitrate hexahydrate, "Co sulfate" is cobalt (II) sulfate heptahydrate, "Fe nitrate" is iron (III) nitrate nonahydrate, "Ni nitrate" is " is nickel (II) nitrate hexahydrate, "Ti sulfate" is titanium (IV) sulfate, "EtOH" is ethanol, "1-PrOH" is 1-propanol, "2- "PrOH" is 2-propanol (isopropanol), "THF" is tetrahydrofuran, "MeOH" is methanol, "TEG" is tetraethylene glycol, "DEE" is diethyl ether, "hydrazine" indicates hydrazine monohydrate, "PVP" indicates polyvinylpyrrolidone, and "r.t." indicates room temperature, respectively. Note that the remaining amount of the first solvent in the second step was described as a ratio based on the pore volume of the porous material. Furthermore, the amount of the reducing agent was also described as a ratio based on the amount of the noble metal compound. In addition, although Comparative Examples 2-11 to 2-20 cannot simply be applied to each step of the method for manufacturing an alloy catalyst according to the present embodiment, for reference, each condition is It is described in the part that can correspond to the conditions in the method related to.

Note that in Example 2-1, since NaBH ₃ CN is used in an organic solvent, it is difficult to measure the redox potential. Therefore, Table 2-1 shows, as reference values, the values of the redox potential of NaBH ₃ CN in the aqueous solution measured in Example 2-3.

Also, for Example 2-2, LiAlH ₄ is well known as a very strong reducing agent. It is also clear that LiAlH ₄ is stronger than NaBH ₄ and its redox potential is -1.20V or less. For example, _NaBH4 can generally reduce aldehydes and ketones, but usually cannot reduce esters, amides, and carboxylic acids, whereas _LiAlH4 can reduce not only aldehydes and ketones, but also esters, carboxylic acids, and carboxylic acid salts. It is. Therefore, although it is difficult to obtain an aqueous solution of LiAlH ₄ due to its strong reducing power and it is difficult to measure it, it is clear that the redox potential of LiAlH ₄ is -1.20V or less.

5. Evaluation of alloy catalysts Particle size, dispersibility, alloying rate of catalyst particles of alloy catalysts, evaluation of existence of catalyst particles inside pores (i.e. internal loading rate), loading rate of catalyst particles, and standard deviation of base metal element concentration Regarding evaluation, see 2.1. above. The evaluation was performed by the method described in ~2.6.

6. Evaluation of polymer electrolyte fuel cells 6.1. Creation of test cell 6.1.1. Preparation of Coating Ink A Nafion solution in which Nafion (registered trademark: Nafion, persulfonic acid-based ion exchange resin) serving as an electrolyte resin was dissolved was prepared. The alloy catalyst and Nafion solution were then mixed under an argon atmosphere. Here, the mass ratio of the solid content of the electrolyte resin was 1.0 times that of the alloy catalyst. Next, after stirring the mixed solution lightly, the alloy catalyst in the mixed solution was crushed by ultrasonic waves. Next, ethanol was further added to the mixed solution to adjust the total solid content concentration of the alloy catalyst and electrolyte resin to 1.0% by mass based on the total mass of the mixture. In this way, a coating ink containing an alloy catalyst and an electrolyte resin was produced.

6.1.2. Preparation of Catalyst Layer By further adding ethanol to the coating ink, the catalyst concentration in the coating ink (concentration of fuel cell catalyst) was made 1.0% by mass with respect to the total mass of the coating ink. Here, although the type of fuel cell catalyst differs from sample to sample, the concentration of the fuel cell catalyst means the concentration of all the metal elements constituting the alloy catalyst. The same applies to the basis weight described below. Next, the spray conditions were adjusted so that the mass per unit area of the catalyst layer of the fuel cell catalyst (hereinafter referred to as "catalyst basis weight") was 0.2 mg/ ^cm2 , and the coating ink was coated with Teflon (registered trademark). ) sprayed onto the sheet. Next, a catalyst layer was prepared by performing a drying process at 120° C. for 60 minutes in an argon atmosphere. Two identical catalyst layers were produced, one serving as a cathode and the other serving as an anode.

6.1.3. Preparation of Membrane Electrode Assembly (MEA) A square electrolyte membrane with a side of 6 cm was cut out from a Nafion membrane (NR211 manufactured by DuPont). Further, each of the anode and cathode catalyst layers coated on the Teflon (registered trademark) sheet was cut into a square shape of 2.5 cm on each side using a cutter knife. The electrolyte membrane was sandwiched between the anode and cathode catalyst layers cut out in this manner so that the catalyst layers were in contact with each other across the center of the electrolyte membrane, and there was no deviation from each other. / ^cm2 for 10 minutes. This laminate was then cooled to room temperature. Next, only the Teflon (registered trademark) sheets of both the anode and cathode were carefully peeled off. Through the above steps, the anode and cathode catalyst layers were fixed to the electrolyte membrane.

Next, two square pieces of carbon paper each 2.5 cm on a side were cut out from the carbon paper (35BC manufactured by SGL Carbon Co., Ltd.) that would serve as the gas diffusion layer. Next, a laminate was produced by stacking these carbon papers so that there was no misalignment between the anode and the cathode. Then, the MEA was produced by pressing the laminate at 120° C. and 50 kg/cm ² for 10 minutes. In addition, the mass of the catalyst layer fixed on the Nafion membrane is calculated from the difference between the weight of the Teflon (registered trademark) sheet with the catalyst layer before pressing and the mass of the Teflon (registered trademark) sheet peeled off after pressing, and the composition of the catalyst layer is calculated. The basis weight of the catalyst, the basis weight of the alloy catalyst, and the basis weight of the electrolyte resin were calculated from the mass ratio of . By this method, it was confirmed that the basis weight of the catalyst was 0.2 mg/cm ² .

6.2. Power generation performance and durability evaluation Each MEA produced by the method described above was assembled into a cell, set in a fuel cell measuring device (manufactured by Toyo Technica Co., Ltd., AutoPEM), and the performance of the fuel cell was evaluated using the following procedure. .

6.2.1. Power Generation Performance Regarding the reactive gases, air was supplied to the cathode and pure hydrogen to the anode under atmospheric pressure so that the utilization rates were 40% and 70%, respectively. Further, the cell temperature was set at 80°C. Regarding the gas to be supplied, both the cathode side and the anode side are passed through distilled water kept at 65°C in a humidifier (that is, by bubbling), so that the gas is supplied with saturated water vapor corresponding to the water temperature in the humidifier. Now supplied to the cell.

Under the conditions where gas was supplied to the cell under these settings, the load was gradually increased and the initial power generation characteristics were evaluated (shown in the "Initial Performance" column in the table). The power generation characteristics were evaluated by recording the cell terminal voltage (hereinafter referred to as cell voltage) at a current density of 0.2 A/cm ² and comparing the cell voltage values as power generation characteristics.

6.2.2. Durability Subsequently, for durability evaluation, the cell terminal voltage was set to 0.6V and held for 4 seconds, then the cell terminal voltage was increased to 1.2V and held for 4 seconds, and then the cell terminal voltage was increased to 1.2V and held for 4 seconds. A durability test was carried out in which the operation of "returning the voltage between the terminals to the original 0.6 V" was considered as one cycle operation, and this cycle operation was repeated 300 times. After this durability test, the power generation performance (cell voltage at a current density of 0.2 mA/cm ² after the durability test) was measured in the same way as in the initial performance evaluation test before the durability test ("After durability" in the table). (shown in column). Subtract the cell voltage (V) after this durability test from the cell voltage before the durability test to find the cell voltage drop width △V, and divide this drop width △V by the cell voltage before the durability test to reduce the cell voltage. Durability was evaluated by calculating the ratio.
The results are shown in Table 3-1 and Table 3-2.

7. Results As is clear from Tables 3-1 and 3-2, the alloy catalysts according to Examples 2-1 to 2-15 have small particle sizes and high dispersion, have small compositional variations, and have a high alloying rate. Catalyst particles with a high carbon content are supported on a porous material, and when used as a catalyst in a polymer electrolyte fuel cell, the initial power generation performance and durability were excellent. On the other hand, the alloy catalysts according to Comparative Examples 2-1 to 2-20 have small particle diameters, high dispersion, small compositional variations, and high alloying ratio by forming catalyst particles on a porous material. I couldn't carry it. As a result, when used as a catalyst in a polymer electrolyte fuel cell, both the initial power generation performance and the power generation performance after durability were inferior, and the voltage drop rate was generally lower than that of Examples 2-1 to 2-1. It was inferior to the case where the alloy catalyst according to No.-15 was used.

Specifically, in Examples 2-2 to 2-15 in which the amount of first solvent removed was large (the amount of first solvent after drying was small), compared with the alloy catalyst according to Example 2-1. As a result, the grain size was small, the variation in composition was small, and the alloying rate was high. This tendency was more pronounced as the amount of first solvent removed was larger. This is because when the amount of first solvent removed is large, the reaction field for the reduction reaction in the third step is restricted to an area closer to the surface of the porous material, which suppresses aggregation of catalyst particles. Conceivable.

Further, in Examples 2-2, 2-7 to 2-15, the first solvent and the second solvent contain the same solvent, or the octanol/water partition coefficient of the first solvent and the second The absolute value of the difference between the solvent and the octanol/water partition coefficient is 1.2 or less. Furthermore, in Examples 2-3 to 2-15, the first solvent and the second solvent satisfy any of the relationships (i) to (iii) described above. In these Examples 2-2 to 2-15, the particle size was smaller, the variation in composition was smaller, and the alloying rate was higher than that of the alloy catalyst according to Example 2-1. In addition to the reasons mentioned above, this is because when the reducing solution is brought into contact with the porous material in the third step, the first solvent and the second solvent are quickly mixed, and the base metal compound, the noble metal compound, and the reducing agent are mixed together. It is thought that the reduction reaction progressed more easily because of the easier contact between the two.

Furthermore, in Examples 2-4 to 2-15, sodium borohydride, potassium borohydride, or lithium borohydride was used as the reducing agent. The above results revealed that these reducing agents have sufficient reducing power to simultaneously reduce noble metal compounds and base metal compounds. Note that these reducing agents are highly safe compared to stronger reducing agents. Furthermore, compared to Example 2-3 in which sodium cyanoborohydride, which has a weaker reducing power, was used, the particle size, dispersibility, compositional variation, and alloying rate tended to be improved. This is considered to be a result of the fact that during the reduction reaction in the third step, the reduction reaction proceeds in a shorter time at a higher reduction rate, so that the influence of the difference in reduction rate between the noble metal compound and the base metal compound becomes smaller.

In Examples 2-5 to 2-15, the amount of the reducing agent used was 10 times or more the total amount of noble metal elements. As a result, the particle size, dispersibility, composition variation, and alloying rate of the obtained catalyst particles tended to be improved compared to Examples 2-1 to 2-4. This is considered to be the result of the reduction reaction proceeding more uniformly due to the increased amount of reducing agent used. This tendency was observed as the amount of reducing agent used increased (eg, Examples 2-8 to 2-10, 2-14, and 2-15).

In Examples 2-7 to 2-15, dinitrodiammine platinum was used as the noble metal compound, and cobalt sulfate, cobalt nitrate, iron sulfate, iron nitrate, nickel sulfate, nickel nitrate, or titanium sulfate was used as the base metal compound. According to the HSAB rule, the combination of these compounds is such that the influence of the difference in reduction rate between the base metal compound and the noble metal compound becomes smaller. As a result, compared to other Examples 2-1 to 2-6, the particle size, dispersibility, compositional variation, and alloying rate of catalyst particles tended to be improved.

In Examples 2-8 to 2-15, the pH of the reducing solution was set to 8.0 or more and 12.0 or less. As a result, compared to other Examples 2-1 to 2-7, the particle size, dispersibility, compositional variation, and alloying rate of the catalyst particles tended to be improved. This can stabilize the reducing agent, suppressing undesired decomposition of the reducing agent and suppressing the deactivation of the reducing agent, while also preventing the stability of the reducing agent from becoming excessively high. This is thought to be the result of suppressing the reduction rate.

In Comparative Example 2-1, a catalyst was produced using only a noble metal compound without using a base metal compound. Therefore, the initial performance was lower than that of the alloy catalyst according to the example. Note that in Comparative Example 2-1, since no base metal element was used, the standard deviation of the base metal element concentration was not measured.

In Comparative Examples 2-2 to 2-5, the removal of the first solvent in the second step was insufficient, and the particle size of the resulting catalyst particles after heat treatment increased, resulting in decreased dispersibility. . This is considered to be the result that the reaction field for the reduction reaction was not sufficiently restricted in the third step. This point is supported by the fact that the porous material is insufficiently supported inside the pores. Furthermore, although the alloying rate increased, the standard deviation of the base metal element concentration also increased. Since the reducing agent itself is strong, it is thought that the alloying rate increased. However, the reaction field for the reduction reaction is not sufficiently restricted and the effect of the difference in reduction rate between noble metal compounds and base metal compounds cannot be reduced, so in many reaction fields, noble metal compounds are reduced before base metal compounds. This is thought to have made it difficult to uniformly proceed alloying on all catalyst particles. For this reason, it is thought that the composition of each catalyst particle varied and the standard deviation of the base metal element concentration became large.

In Comparative Examples 2-6 to 2-9, as a result of using relatively weak hydrazine as a reducing agent, it was difficult to obtain a sufficient alloying rate, or it was difficult to obtain a small particle size and high dispersion. there were. This is because hydrazine did not have sufficient reducing power to reduce noble metal compounds and base metal compounds at the same time, and also because the reducing power was relatively weak and the reduction rate was slow. This is thought to be because the particles formed aggregates of catalyst particles in the liquid phase before being deposited on the carrier. In addition, in Comparative Examples 2-6 to 2-8, the first solvent used had insufficient affinity with water as the second solvent, and hydrazine and noble metal compounds and base metal compounds were mixed during the reduction reaction. It was thought that one of the reasons was that there was insufficient contact with Furthermore, in Comparative Examples 2-6 to 2-9, the standard deviation of the base metal element atomic number concentration was also large. It is thought that hydrazine has insufficient reducing power and cannot reduce noble metal compounds and base metal compounds simultaneously and quickly, which is why the composition of each catalyst particle varies and the standard deviation of the base metal element concentration becomes large.

In Comparative Example 2-10, the amount of reducing agent was insufficient and the reducing power was insufficient to reduce the noble metal compound and the base metal compound, so the particle size was large, the dispersibility was poor, and the alloying rate was low. Catalyst particles with a low concentration were formed. In addition, the standard deviation of base metal element concentrations increased. Because the amount of reducing agent is not sufficient, the reducing power is insufficient, and the noble metal compound and the base metal compound cannot be reduced simultaneously and quickly, so the composition of each catalyst particle varies and the standard deviation of the base metal element concentration is large. It is thought that it has become.

Comparative Examples 2-11 and 2-12 are the results of reproduction based on a conventionally known general alloy catalyst synthesis technique in which the constituent elements constituting the catalyst particles are separately supported. In Comparative Examples 2-11 and 2-12, as a result of reducing and supporting the noble metal compound and the base metal compound separately, they were not sufficiently alloyed and the alloying rate decreased. In Comparative Example 2-11, the reduction reaction of the base metal compound must be carried out only by heat treatment, and at the same time, alloying with the noble metal compound must also proceed, so the reduction in the alloying rate was particularly remarkable. In Comparative Example 2-12, the base metal compound was reduced using a reducing agent in the liquid phase and then the alloying was progressed by heat treatment, which not only reduced the alloying rate but also improved the dispersibility. decreased. Furthermore, in Comparative Examples 2-11 and 2-12, the standard deviation of the base metal element concentration became large. In Comparative Examples 2-11 and 2-12, since the noble metal compound and the base metal compound are reduced and supported separately, it is difficult to uniformly proceed the alloying in all the catalyst particles. This is thought to be due to the variation in the composition of the base metal elements, and the standard deviation of the base metal element concentration. Furthermore, in Comparative Examples 2-11 and 2-12, unlike Examples 2-1 to 2-15, the driving force for alloying is only the heat treatment, so the noble metal component and the base metal component move on the porous material that is the carrier. However, unless thermal diffusion occurs, alloying will not proceed. Therefore, in this respect as well, it is difficult to uniformly proceed with alloying in all the catalyst particles, and it is thought that the composition of each catalyst particle varies and the standard deviation of the base metal element concentration becomes large.

Comparative Example 2-13 is the result of reproduction based on a conventionally known general alloy catalyst synthesis technique in which constituent elements constituting catalyst particles are simultaneously reduced in a liquid phase. In Comparative Example 2-13, reduction was performed in the liquid phase without removing the first solvent, and as a result, aggregation of catalyst particles could not be suppressed, resulting in a decrease in dispersibility. Furthermore, although the alloying rate increased, the standard deviation of the base metal element concentration also increased. Since the reducing agent itself is strong, it is thought that the alloying rate increased. However, the reaction field for the reduction reaction is not sufficiently restricted and the effect of the difference in reduction rate between noble metal compounds and base metal compounds cannot be reduced, so in many reaction fields, noble metal compounds are reduced before base metal compounds. This is thought to have made it difficult to uniformly proceed alloying on all catalyst particles. For this reason, it is thought that the composition of each catalyst particle varied and the standard deviation of the base metal element concentration became large.

Comparative Examples 2-14 and 2-17 are based on a conventionally known synthesis method for alloy catalysts, in which a carrier on which the constituent elements constituting catalyst particles are supported is heated, and alloying is progressed through heat treatment. This is the result of reproducing this based on the following. In Comparative Examples 2-14 and 2-17, as a result of the reduction reaction and alloying performed by heat treatment, the progress of alloying was insufficient and the alloying rate decreased. Furthermore, in Comparative Examples 2-14 and 2-17, the standard deviation of the base metal element concentration became large. In Comparative Examples 2-14 and 2-17, alloying proceeds only by heat treating the porous material on which the noble metal compound and the base metal compound are supported. A noble metal component (here, mainly a noble metal compound supported on a porous material) and a base metal component (here, mainly a base metal compound supported on a porous material) move on the porous material that is the carrier and undergo thermal diffusion. Otherwise, alloying will not proceed. Therefore, it is difficult to uniformly proceed with alloying in all the catalyst particles, and it is thought that the composition of each catalyst particle varies and the standard deviation of the base metal element concentration becomes large.

Comparative Example 2-15 is the result of reproducing this technique based on a conventionally known general fine particle dispersion technique in which fine particles are dispersed with a protective agent such as a polymer. In Comparative Example 2-15, PVP was used as a protective agent in Comparative Example 2-13 in an attempt to suppress the decrease in dispersibility. However, as a result of the catalyst particles being covered by the protective agent, it was difficult to support the porous material inside the pores, and agglomeration was likely to occur on the surface, resulting in insufficient dispersibility. Furthermore, as a result of the catalyst particles being covered with the protective agent, the power generation performance, especially the initial performance, decreased. Furthermore, although the alloying rate increased, the standard deviation of the base metal element concentration also increased. Since the reducing agent itself is strong, it is thought that the alloying rate increased. However, the reaction field for the reduction reaction is not sufficiently restricted and the effect of the difference in reduction rate between noble metal compounds and base metal compounds cannot be reduced, so in many reaction fields, noble metal compounds are reduced before base metal compounds. This is thought to have made it difficult to uniformly proceed alloying on all catalyst particles. For this reason, it is thought that the composition of each catalyst particle varied and the standard deviation of the base metal element concentration became large.

Comparative Example 2-16 is the result of reproducing the synthesis method described in Patent Document 1 by applying the conditions of the present invention. In Comparative Example 2-16, catalyst particles were synthesized using a protective agent and then supported on a porous material. As a result, the catalyst particles are covered with the protective agent, making it difficult to support them inside the pores of the porous material, and the catalyst particles are supported only on the outer surface of the porous material, resulting in agglomeration of the catalyst particles. , the dispersibility decreased. Furthermore, as a result of the catalyst particles being covered with the protective agent, the power generation performance, especially the initial performance, decreased. Furthermore, although the alloying rate increased, the standard deviation of the base metal element concentration also increased. Since the reducing agent itself is strong, it is thought that the alloying rate increased. However, in Comparative Example 2-16, the reduction reaction proceeds in the liquid phase, so the reaction field for the reduction reaction is not sufficiently restricted, and the influence of the difference in reduction rate between the noble metal compound and the base metal compound cannot be reduced. From this, it is thought that in many reaction sites, noble metal compounds were reduced before base metal compounds, making it difficult to uniformly proceed alloying on all catalyst particles. For this reason, it is thought that the composition of each catalyst particle varied and the standard deviation of the base metal element concentration became large.

Comparative Examples 2-18 and 2-19 show that in the present invention, the alkaline substance used to control the pH of the reducing solution in the third step was used for the porous material after the second step. This is a modified method. In Comparative Examples 2-18 and 2-19, a porous material is impregnated with a noble metal compound and a base metal compound, and then potassium hydroxide is used to form these hydroxides. However, when hydroxide is formed in this way, the formed hydroxide becomes a gel-like solid, so it is difficult to immobilize it inside the pores of a porous material. The dispersibility of the catalyst particles was reduced because the surface area of the included porous material was not utilized. Furthermore, in Comparative Example 2-18, the reduction reaction and alloying were performed by heat treatment, and as a result, the progress of alloying was insufficient and the alloying rate was also reduced. Furthermore, in Comparative Example 2-19, as a result of using hydrazine, which has a weak reducing power, as a reducing agent, alloying did not proceed sufficiently and the alloying rate also decreased. Furthermore, in Comparative Examples 2-18 and 2-19, the standard deviation of the base metal element concentration was large. In Comparative Examples 2-18 and 2-19, the noble metal compound and the base metal compound formed hydroxides and were not uniformly adsorbed onto the porous material. For this reason, it is thought that uniform particle formation was not performed all at once during the subsequent reduction reaction, resulting in variations in composition among the catalyst particles, resulting in an increase in the standard deviation of the base metal element atomic number concentration.

In Comparative Example 2-20, in the present invention, after fixing the noble metal compound and the base metal compound in the porous material in the second step, the method of contacting with the reducing solution in the third step was changed, and In step 2, the noble metal compound, base metal compound, and reducing agent are all immobilized on the porous material at the same time in advance. In Comparative Example 2-20, a solution containing hydrazine in advance is used as a solution to impregnate the porous material. In such cases, the reduction reaction starts from the moment hydrazine, the noble metal compound, and the base metal compound come into contact with each other in the liquid phase, and the reduction reaction field is limited to near the surface of the porous material to reduce the difference in reduction rate. As a result, dispersibility decreased. Further, as in Comparative Example 2-13, since the reduction was performed in the liquid phase, aggregation of the catalyst particles could not be suppressed, resulting in a decrease in dispersibility. Furthermore, in Comparative Example 2-20, the standard deviation of the base metal element concentration was increased. In Comparative Example 2-20, the influence of the difference in reduction rate between the noble metal compound and the base metal compound was large, and the noble metal compound was reduced before the base metal compound in many reaction sites, resulting in uniform alloying on all catalyst particles. It is thought that it was difficult to advance the process. For this reason, it is thought that the composition of each catalyst particle varied and the standard deviation of the base metal element concentration became large.

In addition, in the method according to Comparative Example 2-20, even when a stronger reducing agent is used as the reducing agent, the reduction reaction proceeds as soon as the reducing agent, the noble metal compound, and the base metal compound come into contact with each other in the liquid phase. As a result, agglomeration of catalyst particles cannot be suppressed and dispersibility deteriorates.

In addition, FIG. 1 shows a secondary electron image (left) and a transmission image (right) of the alloy catalyst according to Example 2-15 observed with a scanning transmission electron microscope at an acceleration voltage of 30 kV, and FIG. A secondary electron image (left) and a transmission image (right) of an alloy catalyst according to Comparative Example 2-9 observed with a scanning transmission electron microscope at an accelerating voltage of 30 kV are shown.

As shown in FIG. 1, in the alloy catalyst according to Example 2-15, catalyst particles were observed only sparsely in the secondary electron image (left) showing the outer surface of the alloy catalyst; In the transmission image (right) showing the internal state of the alloy catalyst, it was observed that catalyst particles with a small diameter of just under 10 nm were highly dispersed. From this, it can be seen that in the alloy catalyst according to Example 2-15, small-sized catalyst particles are highly dispersed inside the porous material.

On the other hand, as shown in Figure 2, in the alloy catalyst according to Comparative Example 2-9, even in the secondary electron image (left) that shows the appearance of the outer surface of the alloy catalyst, the inside appearance of the alloy catalyst is also shown. Also in the transmission image (right), many relatively large catalyst particles of just under 100 nm were observed. From this, in the alloy catalyst according to Comparative Example 2-9, coarse catalyst particles that are difficult to support inside the porous material adhere to the outer surface of the porous material, and It can be seen that small-sized catalyst particles are not supported.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea stated in the claims. It is understood that these also naturally fall within the technical scope of the present invention.

Claims (13)

A first step of obtaining a mixture by mixing a noble metal compound containing a noble metal element, a base metal compound containing a base metal element, a first solvent, and a porous material;
The following formula (1):

(Volume of first solvent in mixture) ≦ (pore volume of porous material) x 5 (1)

a second step of fixing the noble metal compound and the base metal compound to the porous material by removing the first solvent from the mixture until
a third step of contacting the porous material with a reducing solution containing a reducing agent having an oxidation-reduction potential of -1.20 V or less and a second solvent,
The amount of the reducing agent in the reducing solution is 5 times or more the total amount of the noble metal element,
A method for producing an alloy catalyst , wherein the pH of the reducing solution at 25° C. is 8.0 or more and 12.0 or less . In the second step, the following formula (2):

(Volume of first solvent in mixture) ≦ (pore volume of porous material) x 2 (2)

The method for producing an alloy catalyst according to claim 1, wherein the first solvent is removed from the mixture until the following is satisfied. the first solvent and the second solvent contain the same solvent, or
The production of the alloy catalyst according to claim 1 or 2, wherein the absolute value of the difference between the octanol/water partition coefficient of the first solvent and the octanol/water partition coefficient of the second solvent is 1.2 or less. Method. the first solvent contains water, and the second solvent has an octanol/water partition coefficient of 0.8 or less;
the second solvent contains water, and the first solvent has an octanol/water partition coefficient of 0.8 or less, or
The method for producing an alloy catalyst according to claim 1 or 2, wherein the first solvent and the second solvent both contain water. The reducing agent is one or two selected from the group consisting of alkali metal borohydride, transition metal borohydride, alkali metal aluminum hydride, alkali metal cyanoborohydride, and diisobutylaluminum hydride. The method for producing an alloy catalyst according to any one of claims 1 to 4, comprising the above steps. The reducing agent is lithium borohydride, sodium borohydride, potassium borohydride, lithium triethylborohydride, nickel borohydride, zinc borohydride, lithium aluminum hydride, sodium aluminum hydride, potassium aluminum hydride. , sodium bis(2-methoxyethoxy)aluminum hydride, lithium cyanoborohydride, sodium cyanoborohydride, potassium cyanoborohydride, and diisobutylaluminum hydride. A method for producing an alloy catalyst according to any one of claims 1 to 5. Production of the alloy catalyst according to any one of claims 1 to 6, wherein the reducing agent contains one or more selected from the group consisting of sodium borohydride, potassium borohydride, and lithium borohydride. Method. The method for producing an alloy catalyst according to any one of claims 1 to 7, wherein the amount of the reducing agent in the reducing solution is 10 times or more the total amount of the noble metal elements. Production of an alloy catalyst according to any one of claims 1 to 8 , wherein the pH of the reducing solution is adjusted using a base selected from the group consisting of sodium hydroxide, potassium hydroxide, and aqueous ammonia. Method. The method for producing an alloy catalyst according to any one of claims 1 to 9 , wherein the noble metal element in the noble metal compound includes one or more selected from the group consisting of platinum, gold, and palladium. The noble metal compounds include dinitrodiammineplatinum, bis(acetylacetonato)platinum, hexachloroplatinum(IV) acid, potassium hexachloroplatinate(IV), sodium hexachloroplatinate(IV) hexahydrate, and hexaammineplatinum(IV). Chloride, hexaammineplatinum (IV) hydroxide solution, tetraammineplatinum (II) dichloride, platinum (II) bromide, platinum (IV) bromide, platinum cyanide, platinum iodide, dimethyl (acetylacetonate) ) Gold (III), gold chloride, chloroauric acid, gold bromide, gold iodide, gold cyanide, potassium gold cyanide, palladium chloride, palladium iodide, palladium bromide, palladium nitrate, palladium sulfate, bis(acetyl) acetonato) palladium (II), sodium tetrachloropalladate, ammonium tetrachloropalladate, and potassium tetrachloropalladate, comprising one or more selected from the group consisting of palladium (II), sodium tetrachloropalladate, and potassium tetrachloropalladate , A method for producing the alloy catalyst described. The method for producing an alloy catalyst according to any one of claims 1 to 11 , wherein the base metal element in the base metal compound contains one or more selected from the group consisting of Co, Fe, Ni, and Ti. The base metal compounds include cobalt chloride, cobalt bromide, cobalt iodide, cobalt cyanide, cobalt thiocyanate, cobalt sulfate, cobalt nitrate, cobalt acetylacetonate, iron chloride, iron bromide, iron iodide, iron sulfate, and nitric acid. Iron, iron (III) acetylacetonate, nickel chloride, nickel bromide, nickel iodide, nickel sulfate, nickel nitrate, nickel (II) potassium cyanide, nickel (II) acetylacetonate, titanium chloride, titanium bromide, The method for producing an alloy catalyst according to any one of claims 1 to 12 , comprising one or more selected from the group consisting of titanium iodide, titanium tetraisopropoxide, and titanium sulfate.