JP5540294B2 - Method for producing electrode catalyst for fuel cell - Google Patents

Description

  The present invention relates to a method for producing an electrode catalyst for a fuel cell. More specifically, an organic-inorganic hybrid fuel using a porphyrin complex such as cobalt or iron and a polyacid of a transition metal as main catalyst component materials, which can be suitably used for a polymer electrolyte fuel cell (PEFC). The present invention relates to a method for producing a battery catalyst.

In recent years, fuel cells have attracted attention as clean energy sources. Among the fuel cells, the polymer electrolyte fuel cell (PEFC), in particular, can be operated at room temperature and can be miniaturized, so it can be used for mobile devices such as laptop computers and mobile phones for automobiles, railways, and consumer use. It is expected as an energy source covering various uses and scales such as industrial cogeneration and power plants.
The polymer electrolyte fuel cell (PEFC) has higher power generation efficiency and higher current density than various fuel cells such as molten carbonate fuel cells (MCFC) and phosphoric acid fuel cells (PAFC), and has various physical properties. It is excellent.

  The polymer electrolyte fuel cell (PEFC) has a film-like ion exchange membrane of about 50 μm for moving protons (hydrogen ions) from the hydrogen electrode to the air electrode at the center. This is a fuel cell employing a membrane. A catalyst layer exists on both sides of the polymer film, a platinum catalyst and a platinum / ruthenium catalyst are used for the hydrogen electrode, and a platinum catalyst is used for the air electrode. Furthermore, the structure which improved the quantity of noble metal catalyst components, such as platinum, using the carbon-type material which has special structures, such as a graphite, is proposed (for example, refer patent document 1 thru | or patent document 3).

However, the above-mentioned fuel cell catalyst using a carbon-based material having a special structure such as graphite is a so-called platinum-based noble metal catalyst, which uses platinum as its catalyst component. Since platinum is very expensive, it has a problem that it is an obstacle to the spread of fuel cells.
In addition, when a reformed gas such as hydrocarbon or methanol is used as a fuel, the platinum-based noble metal catalyst has a problem that it reacts with carbon monoxide contained in the reformed gas and deactivates.

  From this point of view, development of a non-platinum catalyst that does not use platinum as a fuel cell catalyst component has been carried out. Instead of using platinum as a fuel cell catalyst component, N4-macrocycles such as porphyrin and phthalocyanine are used. Complexes of iron (Fe) and cobalt (Co) having a ligand have been studied. In the iron (Fe) and cobalt (Co) complexes, the active sites formed when the carbon-supported complex is heat-treated at a temperature around 600 ° C. are highly active, but the durability is low. For this reason, in order to improve durability, a catalyst using an oxide that is stable under acidic conditions as a raw material has been developed. For example, a catalyst obtained by nitriding a carbon-supported cobalt tungsten catalyst prepared by an impregnation method is disclosed. However, the oxidation-reduction starting potential (ORR starting potential) of the catalyst and the current density (linear sweep voltammetry: LSV) measured at the stationary polarization line are not sufficient as compared with the platinum-based catalyst, and the catalyst at a practical level. There is a problem that the activity and durability are not yet sufficient.

  In addition, this patent applicant discloses the following technical literature as a publication in which the literature well-known invention relevant to this invention was described.

JP 2005-19332 A JP 2008-123810 A JP 2006-058578 A

  In view of the above-described situation, the object of the present invention is to use sufficient platinum as a fuel cell electrode catalyst component, and sufficient catalytic activity and durability comparable to a so-called platinum-based noble metal fuel cell electrode catalyst. It is to manufacture an electrode catalyst having a simple, easy and low cost.

As a result of intensive studies to solve the above problems, the present inventors have obtained a fuel cell obtained by mixing a cobalt porphyrin complex, carbon (carbon), and polytungstic acid and heat-treating them in a predetermined temperature range. The inventors have found that the electrode catalyst is excellent in various physical properties such as ORR characteristics, and have completed the present invention.
The present invention is composed of the following technical matters. That is, (1) a method for producing a fuel cell electrode catalyst,
A precursor is prepared by mixing a porphyrin complex having one or more metal elements selected from cobalt, iron, nickel, chromium, and manganese as a central metal, a carbon-based material, and a polyacid having tungsten as a central metal. Process,
And a step of forming an electrode catalyst by heat-treating the precursor within a temperature range of 500 ° C. to 600 ° C. A method for producing an electrode catalyst for a fuel cell.
(2) The fuel cell according to (1), wherein 5,10,15,20-tetrakis (N-methyl-4-pyridyl) porphyrinatocobalt (II) .4 toluenesulfonate is used as the porphyrin complex. A method for producing an electrode catalyst.
(3) The method for producing an electrode catalyst for a fuel cell according to (1), wherein ammonium metatungstate is used as the polyacid.
(4) The method for producing an electrode catalyst for a fuel cell according to (1), wherein H ₃ PW ₁₂ O ₄₀ or FePW ₁₂ O ₄₀ is used as the polyacid.
(5) The method for producing an electrode catalyst for a fuel cell according to (1), wherein the carbon-based material uses at least one carbon-based fine particle selected from carbon black, carbon nanotube, carbon nanohorn, and fullerene.
(6) The method for producing an electrode catalyst for a fuel cell according to (5), wherein the carbon-based fine particles are carbon fine particles in which nitrogen atoms are introduced into carbon-carbon bond portions.

According to the method for producing a fuel cell electrode catalyst of the present invention, without using platinum as a catalyst component, an electrode catalyst component having the same catalytic activity and durability as an electrode catalyst containing platinum as an electrode catalyst component is produced. can do.
In addition, according to the method for producing an electrode catalyst for a fuel cell of the present invention, there is no initial large activity deterioration, and it has high activity and high durability as compared with a conventionally proposed non-platinum catalyst. The electrode catalyst which has can be manufactured.
Furthermore, according to the method for producing a fuel cell electrode catalyst of the present invention, an inexpensive fuel cell electrode catalyst can be provided without using platinum as a catalyst component. For example, in the present invention, by utilizing the strong affinity of polyacid for carbon, a porphyrin complex such as cobalt as a catalyst raw material can be supported on carbon without waste, and it is economical and catalyst preparation is possible. It will be very easy. At the same time, since platinum is not used as the electrode catalyst component, there is an advantage that there is no deterioration of the electrode catalyst component even when carbon monoxide is present in the fuel gas such as the reformed gas.

It is a flowchart explaining the measuring method of cyclic voltammetry (CV). It is the figure which compared the CV curve of each sample of an unheat-processed state. It is the figure which compared the CV curve of each sample which changed heat processing temperature. It is the figure which compared the CV curve heat-processed at 600 degreeC. It is the figure which compared the CV curve which changed the carbon particle. It is the figure which compared the stationary polarization curve of each sample of Example 1, Example 2, the comparative example 1, and the control example 1. FIG. A, B It is a figure which shows the result of the LSV measurement before and behind a durability test. It is a flowchart explaining the measuring method of a three-electrode measurement. The amount of catalyst applied to the disk electrode and 0.8 Vvs. It is a figure which shows the relationship with the value of the current density in RHE. It is the figure which compared the stationary polarization curve of each sample. It is an enlarged view of 0.8V vicinity of FIG. It is the figure which compared Tafel plot of each sample. It is the figure which compared the number of reaction electrons of each sample. It is the figure which compared the hydrogen peroxide generation amount of each sample. It is the figure which compared the stationary polarization curve of each sample. It is an enlarged view of 0.8V vicinity of FIG. And the heat treatment temperature ^is a diagram showing the relationship between the ratio of the value and the amount of generated hydrogen peroxide ^{Co 2+ / (Co 2+ + Co} 3+). It is a figure which shows the relationship between the ratio of the electric charge / ion radius of a metal ion, and the current density in 0.8V.

Hereinafter, embodiments of the present invention will be described in detail.
The method for producing a fuel cell electrode catalyst according to the present invention comprises a porphyrin complex having one or more metal elements selected from cobalt, iron, nickel, chromium, and manganese as a central metal, a carbon-based material, and a transition metal as a central metal. A step of preparing a precursor by mixing a polyacid (for example, polytungstic acid), and a step of preparing an electrode catalyst by heat-treating the precursor within a temperature range of 500 ° C. to 600 ° C. It is what has.

First, in the method for producing an electrode catalyst for a fuel cell of the present invention, the porphyrin complex used as the first component is a porphyrin complex having a basic structure as a structure represented by the following chemical formula. That is, it is not particularly limited as long as it has a cationic substituent at the meso position of porphyrin.
The central metal M of the porphyrin complex is most preferably cobalt, and is preferably an element such as iron, nickel, chromium, manganese, magnesium, or aluminum. For example, a cobalt porphyrin complex in which the central metal M is only cobalt may be used, or the central metal M may be a cobalt-iron porphyrin complex in which cobalt and iron are mixed at a molar ratio of 1: 0.1-1.

Specific examples of the cobalt porphyrin complex satisfying the above general formula include, for example, 5,10,15,20-tetrakis (N-methyl-4-pyridyl) porphyrinatocobalt (II) .4 toluenesulfonate (CoTMPyP.multidot. 4Tosyl), 5,10,15,20-tetrakis [4- (trimethyl) phenyl] porphyrinatocobalt (II) .4 toluenesulfonate and the like. Among the above-described cobalt porphyrin complexes, 5,10,15,20-tetrakis (N-methyl-4-pyridyl) porphyrinatocobalt (II) · 4 toluenesulfonate (CoTMPyP · 4Tosyl) is easy in structure and easy to produce. ) Is preferred.
The cobalt porphyrin complex is a water-soluble compound and can be produced by a known method. Generally, it can be produced by subjecting porphyrin sulfonic acid to a condensation reaction of pyrrole and aldehyde under acidic conditions. For example, pyridine-4-aldehyde and pyrrole are mixed at an appropriate ratio, heated in propionic acid, and then each porphyrin is purified by silica gel column chromatography and converted to N-methylpyridinium ion by methyl iodide. Can be manufactured. In addition, silica gel column chromatography can be used for the purification of the compound, and chloroform-methanol can be used for the mobile phase.

In the method for producing an electrode catalyst for a fuel cell of the present invention, the polyacid used as the second component is not particularly limited as long as it is a polyacid containing a transition metal capable of forming a polyacid. . Specifically, polyacids having a transition metal belonging to Groups 5A to 7A of the periodic table such as tungsten, molybdenum, vanadium, chromium, manganese, niobium, etc. as a central metal can be exemplified.
Among the polyacids, tungsten is particularly preferably used as a central metal, and the structure thereof is a so-called Keggin-type (general formula: XM ₁₂ O ₄₀ ⁿ⁻ , X represents a group 3B to group 5B element in the periodic table). M represents W (tungsten, n represents an integer of 3 to 7) or Dawson-type (general formula: X ₂ M ₁₈ O ₆₂ ⁶⁻ ) and M ₆ O ₁₉ ⁿ⁻ (n = 3) Represents an integer of ˜7). Specifically, for example, ammonium metatungstate (NH ₄ ) ₆ · [H ₂ W ₁₂ O ₄₀ ] · nH ₂ O, 12-tungstophosphoric acid (H ₃ [PW ₁₂ O ₄₀ ] · nH ₂ O) In addition to W ₁₂ O ₄₀ ⁴⁻ , a polyacid containing W ₁₀ O ₃₂ ⁴⁻ , PW ₁₁ O ₃₉ ⁷⁻ , SiW ₁₁ O ₃₉ ⁸⁻ , P ₂ W ₁₇ O ₆₁ ^{10− and the} like as an anion is used. be able to. Among the tungsten polyacids, 12-tungstophosphoric acid (H ₃ [PW ₁₂ O ₄₀ ] · nH ₂ O) having the highest acid resistance is most preferable from the viewpoint of acid resistance. By using this 12-tungstophosphoric acid, high activity is obtained in the produced electrode catalyst.
Further, 12-a-tungstophosphoric compound having the same structure and the ^{_{acid, H 8-n X n +}} W 12 O 24 · xH 2 O ( in particular, X = P, Si) can be used. Further, metal-exchanged polyoxotungstate M _{n / 3} PW ₁₂ O ₄₀ (M ^{n +} = Mg, Ca, Sc, Y, lanthanoid, Ti, Zr, Hf, V, in which hydrogen of this compound is substituted with another metal element. Nd, Ta, Cr, Mo, Mn, Fe, Ru, Co, Ni, Cu, Ag, Zn, Al, Ga, Sn, Bi, Se) can also be used. Among these metal exchange polyoxotungstates, FePW ₁₂ O ₄₀ is particularly preferable because high activity is obtained in the produced electrocatalyst. In addition to the above polytungstic acid, the heteropolyphosphate anion (polyoxometalate) and the central metal of this compound include various transition metals, alkali metals such as Cs, alkaline earth metals such as Mg, lanthanoids, cerium Compounds obtained by exchanging lanthanoids such as these can also be used.

In the method for producing a fuel cell electrode catalyst of the present invention, the carbon-based material used as the third component is for constituting the electrode catalyst by supporting the first component and the second component. The carbon-based material used as the third component is not particularly limited as long as it is a carbon-based material having carbon as a main component and carbon fine particles having a diameter of about 3.0 to 500 nm and having electrical conductivity. . As the carbon-based material, carbon-based materials such as carbon nanotubes, carbon nanohorns, fullerenes, and silicon nanotubes can be used as well as so-called carbon black. And it is preferable to use 1 or more types of carbon type microparticles | fine-particles chosen from carbon black, a carbon nanotube, carbon nanohorn, and fullerene as said carbon type material. Further, as the carbon-based fine particles, it is preferable to use carbon fine particles in which a nitrogen atom is introduced into a carbon-carbon bond portion. From the viewpoint of the adsorptive power of polyacids to carbon-based materials, these carbon-based materials have surface functional groups, and the surface functional groups are preferably electron-donating. For example, it is preferable that an electron-donating group having an unshared electron pair such as pyridine, pyrrole, and amino group is present.
Moreover, since the larger the surface area of the carbon-based material, the more the first component and the second component can be supported, the activity of the electrode catalyst can be improved.
Specific examples of carbon-based materials include Vulcan XC-72R, Ketjen Black, and Ketjen Black Pearl 2000, which are commonly used as supports for electrode catalysts for solid polymer fuel cells. ) And the like. Regarding various physical properties of these carbon-based materials, for example, Vulcan XC-72R has a surface area of 252 m ² / g, a particle size of 30 nm, and an electric conductivity of 4 Scm ⁻¹ , and Black Pearl (Ketjen Black Pearl 2000) is Surface area of 1475 m ² / g and particle size of 15 nm.

Next, in the method for producing an electrode catalyst for a fuel cell of the present invention, the two components of the first component porphyrin complex and the second component polyacid are used as essential catalyst components, and this is the third component carbon-based carrier. It is made to carry | support to material and it is set as the precursor of the electrode catalyst for fuel cells. As described above, in the present invention, by using the above-mentioned ternary system, the polyacid as the second component is strongly adsorbed to the carbon as the carbon material of the third component, and further fine particles of carbon by this adsorption action. It is characterized by the progress of conversion. At the same time, it is possible to introduce a polyacid and a porphyrin complex into the internal structure of carbon, which is a carbon-based material.
In other words, in the method for producing an electrode catalyst for a fuel cell of the present invention, carbon fine particles and introduction of a first component porphyrin complex as an electrode catalyst component and a second component polyacid into carbon as a carbon-based material. The catalytic activity and durability can be improved by two actions.

That is, in the precursor of the fuel cell electrode catalyst, by using tansugten polyacid (polytungstic acid) as the second component, tungsten oxide (WOx) in the polyacid penetrates into the carbon microstructure. Therefore, it is thought that further refinement of carbon is promoted.
In addition, it is considered that self-organization of the cationic porphyrin complex as the first component and the anionic polytungstic acid as the second component occurs, and the dispersion of the complex proceeds.
In the present invention, it is considered that the diffusion of protons into the carbon-based material, which is the third component due to the reduction of tungsten oxide (WOx), progresses and the interface of each component increases. As a result, the electrode catalyst activity and durability can be improved by increasing the three-phase interface of the fuel electrode catalyst component.
And since the manufacturing method of this invention does not use platinum as a catalyst component, an inexpensive catalyst for fuel cells can be provided. Further, since platinum is not used as a catalyst component, even when carbon monoxide is present in a fuel gas such as a reformed gas, the electrode catalyst component is not deteriorated at all.

In order to produce a precursor of a fuel cell electrode catalyst in which two components, a porphyrin complex of the first component and a polyacid of the second component are used as a catalyst component and supported on a third component carbon-based material as a carrier These components are mixed in a solvent and stirred for a predetermined time. The solvent to be used is not particularly limited as long as each catalyst component can be diffused and mixed and the precursor of the fuel cell electrode catalyst can be easily dried after mixing. For example, water and a water-alcohol mixture can be exemplified. As a stirring means, a stirrer can be illustrated, for example, and it stirs with a predetermined rotation speed with a stirrer.
The order of mixing each component is not particularly limited, and a method of mixing two components and then mixing the remaining one component, or a method of mixing three components simultaneously is possible. Specifically, for example, there is a method in which a porphyrin complex as a first component and a carbon-based material as a third component are mixed and then a polyacid as a second component is mixed.

After the above components are mixed and stirred, the precursor of the lower layer fuel cell electrode catalyst and the upper layer solvent are separated, and the precursor is collected and then dried. Further, the precursor is pulverized with an agate bowl or the like, and further finely divided.
The precursor has a structure in which the graphite structure of carbon, which is a carbon-based material, is expanded by the polyacid acting as a pillar, thereby facilitating the diffusion of oxygen to the active site. Conceivable.

Further, in the method for producing a fuel cell electrode catalyst according to the present invention, the precursor of the fuel cell electrode catalyst produced by mixing and stirring each of the above electrode catalyst components is heat-treated at a predetermined temperature and for a predetermined time. . By performing the heat treatment, the three-phase interface of each electrode catalyst component further increases.
The predetermined temperature at which the heat treatment is performed is preferably in the range of 500 ° C to 600 ° C. Preferably, it is 525 degreeC-585 degreeC, It is preferable to process at 550 degreeC most preferably. A treatment temperature of less than 500 ° C. is not preferable because sufficient activity and durability cannot be obtained. When the treatment temperature exceeds 600 ° C., the structure of the electrode catalyst becomes unstable, which is not preferable.

In order to perform the heat treatment, a predetermined amount of the above-mentioned fuel cell electrode catalyst precursor powder is put into a heat treatment apparatus or a heat treatment furnace. For example, put in a quartz reactor.
Then, starting from room temperature, the inert gas is purged at a predetermined flow rate for a predetermined time, and then the flow rate of the inert gas is decreased and the temperature is raised to a target temperature at a predetermined temperature increase rate for a predetermined time. Hold and heat-treat. After the heat treatment, it is allowed to cool to obtain a fuel cell electrode catalyst.

Hereinafter, the fuel cell electrode catalyst produced by the method for producing a fuel cell electrode catalyst of the present invention will be referred to as a “fuel cell electrode catalyst according to the present invention”.
The fuel cell electrode catalyst according to the present invention is particularly suitable as an electrode catalyst for a polymer electrolyte fuel cell (PEFC).

In the polymer electrolyte fuel cell (PEFC), one electrode (anode or fuel electrode) for introducing hydrogen and an opposite electrode (cathode or air electrode) for introducing oxygen are arranged via an electrolyte. It is configured by connecting a lead wire or the like to each pole.
The fuel cell electrode catalyst according to the present invention can be used as the above-mentioned anode and / or cathode electrode catalyst, but is preferably used as a catalyst on the cathode or air electrode side. Moreover, application to the direct methanol method is also possible.
The fuel cell electrode catalyst according to the present invention can be used not only as a catalyst on the cathode or air electrode side but also as a catalyst on the anode or fuel electrode side.

In order to use the fuel cell electrode catalyst according to the present invention for a fuel cell electrode, for example, a liquid in which the electrode catalyst is dispersed may be applied to an electrode (for example, a cathode or an air electrode) and dried.
Also, a so-called MEA (membrane / electrode assembly) may be formed using an electrode catalyst.

  Hereinafter, although this invention is demonstrated using an Example, this invention is not limited to this at all.

Example 1
As the porphyrin complex of the first component, 5,10,15,20-tetrakis (N-methyl-4-pyridyl) porphyrinatocobalt (II) · 4 toluenesulfonate (CoTMPyP · 4Tosyl) is used, and the second component is used. A sample of a fuel cell electrode catalyst was prepared by the following procedure using ammonium metatungstate as the polyacid and Vulcan (Vulcan XC-72R) as the third component carbonaceous material.
First, 4 mg of CoCl ₂ was mixed with 5 ml of methanol and stirred to obtain a first solution.
Moreover, 19.8 mg of H ₂ TMPyP · 4 Tosyl was mixed with 5 ml of ion-exchanged water and stirred to obtain a second solution.
Next, the first solution was added to the second solution, a few drops of 2,6-lutidine were further added, and the mixture was stirred for 2 days.
Thus, as the first component, 5,10,15,20-tetrakis (N-methyl-4-pyridyl) porphyrinatocobalt (II) .4 toluenesulfonate (CoTMPyP.4 Tosyl) which is a water-soluble complex. ) Was obtained.

Next, 46.2 mg of carbon powder (Vulcan: Vulcan XC-72R powder) was added to the CoTMPyP · 4Tosyl ion exchange water aqueous solution as the third component carbon-based material, followed by stirring for about 1 hour.
Then, as the second component, (NH ₄₎ of _{42.9mg 6 · [H 2 W 12} O 40] · nH were adjusted using _{2 O (NH 4) 6 ·} [H 2 W 12 O 40] -An nH ₂ O aqueous solution was dropped, and the mixture was further stirred for about 1 hour.
When (NH ₄ ) ₆ · [H ₂ W ₁₂ O ₄₀ ] · nH ₂ O was added, fine particles of the carbon powder were observed, and a colorless and transparent supernatant solution and carbon precipitates were formed.
The resulting precipitate was filtered, washed with about 20 ml of methanol, and dried at 120 ° C. for 12 hours. Thus, the precursor for producing an electrode catalyst was obtained.

Further, in order to heat-treat the precursor, 100 g of the powder obtained by drying was put in a quartz reactor.
Then, He was purged as an inert gas at room temperature and a flow rate of 100 ml / min for 30 minutes.
Thereafter, the flow rate of He was reduced to 20 ml / min, the temperature was raised to 550 ° C., which was the target temperature, at 10 K / min, and the heat treatment was held for 2 hours, and then allowed to cool.
Thus, an electrode catalyst was produced and used as a sample of Example 1. Under these conditions, the molar ratio of CoTMPyP to (NH ₄ ) _6. [H ₂ W ₁₂ O ₄₀ ] is 1: 1.

(Example 2)
An electrode catalyst was prepared in the same manner as in Example 1 except that 136.6 mg of Ketjen Black was used as the third component carbon-based material, and a sample of Example 2 was obtained.

(Comparative Example 1)
The second component (NH ₄ ) ₆ · [H ₂ W ₁₂ O ₄₀ ] · nH ₂ O was not used, and the amount of CoTMPyP · 4Tosyl supported on the carbon-based material was increased accordingly. Otherwise, an electrode catalyst was prepared in the same manner as in Example 1 to obtain a sample of Comparative Example 1.

(Comparative Example 2)
Instead of (NH ₄ ) ₆ · [H ₂ W ₁₂ O ₄₀ ] · nH ₂ O, which is the polyacid of the second component, NaWO ₄ · 2H ₂ O, which is a W oxide, is used. An electrode catalyst was prepared in the same manner as in Example 1 and used as a sample of Comparative Example 2.

(Comparative Example 3)
A sample of Comparative Example 3 was prepared in the same manner as Comparative Example 1 except that the precursor in an unheated state was used as it was without performing the heat treatment.

(Comparative Example 4)
A sample of Comparative Example 4 was prepared in the same manner as in Example 1 except that the precursor in an unheated state was used as it was without performing the heat treatment.

(Comparative Example 5)
In Example 1 and Comparative Example 4, after CoTMPyP was supported on carbon, (NH ₄ ) _6. [H ₂ W ₁₂ O ₄₀ ] .nH ₂ O was added (operation abbreviation; IAA). Instead, CoTMPyP and (NH ₄ ) _6. [H ₂ W ₁₂ O ₄₀ ] .nH ₂ O were self-assembled and supported on carbon (operation abbreviation; IBA). Other than that, a sample in an unheated state was prepared in the same manner as in Comparative Example 4 to obtain a sample of Comparative Example 5.

(Comparative Example 6)
An electrode catalyst was prepared in the same manner as in Example 1 except that the target temperature of the heat treatment was set to 300 ° C., and used as a sample of Comparative Example 6.

(Comparative Example 7)
An electrode catalyst was produced in the same manner as in Example 1 except that the target temperature of the heat treatment was 400 ° C., and used as a sample of Comparative Example 7.

(Comparative Example 8)
An electrode catalyst was produced in the same manner as in Example 1 except that the target temperature of the heat treatment was 800 ° C., and used as a sample of Comparative Example 8.

(Control 1)
A commercially available 20% by mass Pt / C electrocatalyst was prepared as Control Example 1.

<Measurement of characteristics>
Various characteristics of the produced carbon catalyst sample were measured as follows.

(Cyclic voltammetry)
For each sample, cyclic voltammetry (CV) measurement was performed. Specific measurement conditions were as follows.
In an argon (Ar) atmosphere and an oxygen (O ₂ ) atmosphere, cyclic voltammetry (CV) and linear sweep measurement (LSV) were performed under the conditions shown in Table 1 and according to the flowchart shown in FIG. . In the flowchart of FIG. 1, each step of S4, S8, and S15 indicates that the atmosphere is changed from argon to oxygen or from oxygen to argon.

  The CV curve was calculated | required from the difference of the measurement result of S14, and the measurement result of S17 among step S1-S17 shown to the flowchart of FIG. This is because the measurement result may not be stable in the first step.

(Comparison in unheated state)
FIG. 2 shows CV curves obtained by CV measurement for the samples of Comparative Examples 3 to 5 in the unheated state.
As can be seen from FIG. 2, there was almost no difference in the size of the CV curve between the case of Co / Vulcan in Comparative Example 3 and the case of CoW ₁₂ / Vulcan in Comparative Examples 4 and 5.
Further, although the difference between Comparative Example 4 and Comparative Example 5 is small, the CV curve of Comparative Example 4 is larger at the portion where the potential is minimum and maximum, and it is better to first support CoTMPyP on carbon. Seems good.

(Comparison by heat treatment temperature)
For each sample of CoW ₁₂ / Vulcan (Comparative Example 4 in an unheated state, Example 1 having a heat treatment temperature of 550 ° C., and Comparative Examples 6 to 8), CV curves obtained by CV measurement are shown in FIG. Shown in
As can be seen from FIG. 3, the CV curve increases as the heat treatment temperature increases, but the sample of Comparative Example 8 heat treated at 800 ° C. has a smaller CV curve than the sample of Example 1 heat treated at 550 ° C. ing.
In the CV curve of the sample of Example 1 heat-treated at 550 ° C., a redox peak peculiar to the electrochromic characteristics of WO _3-x can be seen. From this, it is considered that the polyacid of W changes to WO _3-x by heat treatment, and protons diffuse into the catalyst layer along with the oxidation and reduction, leading to an increase in the three-phase interface essential for ORR.
That is, in order to sufficiently increase the catalytic activity, the heat treatment temperature is preferably in a range including 550 ° C. (the above-described 500 ° C. to 600 ° C.), and the heat treatment temperature is too low at 300 ° C. or 400 ° C. Is too high at 800 ° C.

(Comparison of electrode catalyst heat-treated at 550 ° C)
FIG. 4 shows CV curves obtained by CV measurement for the samples of Example 1 and Comparative Example 1 heat-treated at 550 ° C.
As can be seen from FIG. 4, when heat-treated at 550 ° C., the catalyst in which CoW is supported on carbon shows a much larger CV curve than the catalyst in which Co is supported on carbon.
That is, it was found that the activity of the electrode catalyst was improved by using the second component tungsten in addition to the first component cobalt.

(Comparison due to differences in carbon particles)
Next, FIG. 5 shows CV curves obtained by CV measurement for the sample of Example 1 using Vulcan XC-72R and the sample of Example 2 using Ketjen Black.
As can be seen from FIG. 5, a larger CV curve was observed in the sample of Example 2 using Ketjen Black having a higher surface area as carbon compared to the sample of Example 1 using Vulcan XC-72R. .
That is, by using Ketjen Black, it was found that the activity of the electrode catalyst is improved because the actual surface area of the carbon particles is larger than when VulcanXC-72R is used.

(Comparison of stationary polarization curves)
Each sample of Example 1, Example 2, Comparative Example 1, and Control Example 1 was 0.2 Vvs using a three-electrode cell in a 0.5 M aqueous H ₂ SO ₄ solution saturated with oxygen at room temperature. . Activity was measured with RHE. The amount of catalyst applied to the electrode was 510 μg / cm ² and the rotation speed was 2000 rpm.
FIG. 6 shows a comparison of the steady polarization curves of the samples obtained by the measurement.

From FIG. 6, it can be seen that the Co—W catalyst has a larger current density in the high potential region than the Co catalyst. That is, it can be seen that the Co—W catalyst has a higher catalytic activity that is closer to the Pt / C catalyst of Control Example 1 than the Co catalyst.
However, the oxygen reduction start potentials of the Co catalyst and the Co—W catalyst shown in FIG. 6 are both about 0.85 Vvs. It was RHE and there was no significant difference.
That is, it was found that the current density was improved by using the second component tungsten in addition to the first component cobalt.

(Durability comparison)
Each sample of Example 1 and Comparative Example 1 was subjected to a durability test as follows.
In a 0.5 M aqueous solution of H ₂ SO ₄ saturated with oxygen, 0.2 Vvs. A 24 hour durability test was performed with RHE, and linear sweepmetry (LSV) measurement was performed under oxygen saturation before and after the durability test. The sweep speed was 5 mV / s and the rotation speed was 2000 rpm.
The measurement result of the sample of Comparative Example 1 is shown in FIG. 7A, and the measurement result of the sample of Example 1 is shown in FIG. 7B.

As can be seen from FIG. 7A, the Co catalyst of Comparative Example 1 shows a decrease in current density over the entire scanning potential after the durability test.
On the other hand, as shown in FIG. 7B, in the Co—W catalyst of Example 1, there was almost no change in current density before and after the durability test. Therefore, it was found that the durability was greatly improved.

Each sample of Example 1 and Comparative Example 1 was heat-treated at 550 ° C., but the catalyst adjusted under such heat-treatment conditions is generally more initial than the catalyst heat-treated at a high temperature of 900 ° C. High activity but low durability.
However, the catalyst of Example 1 has high activity as well as no significant initial deterioration in activity.
Thus, it was found that the Co—W catalyst prepared from CoTMPyP and ammonium metatungstate exhibits high durability and activity.

Further, with respect to the sample of Example 1, a Koutecky-Levitch plot was performed from the obtained measurement result, and the number of reaction electrons was determined from the slope of the obtained straight line.
As a result, 0.6-0.1 Vvs. RHE showed a value of 3.82-4.02. This shows that highly selective reduction from O ₂ to H ₂ O occurs.

(Comparison of hydrogen peroxide generation)
For each sample of Example 1 and Comparative Example 1, the amount of hydrogen peroxide generated was compared.
0.5Vvs. The amount of hydrogen peroxide generated was measured under RHE conditions.
As a result, Example 1 was 4.3% and Comparative Example 1 was 11.1%.
It can be seen that the amount of hydrogen peroxide generated by the Co—W catalyst of Example 1 can be reduced to about half that of the Co catalyst of Comparative Example 1.
That is, it was found that the amount of hydrogen peroxide generated can be greatly reduced by using the second component tungsten in addition to the first component cobalt.

(Difference in the raw materials of tungsten)
Carbon fine particles are not limited to Mo and W polyacids, but are commonly found in water-soluble oxides of Mo and W.
Even with a NaWO ₄ · 2H ₂ O in Comparative Example 2, fine particles of carbon after addition of NaWO 4 · _2H 2 _O were observed.
However, in this case, the adsorption of CoTMPyP to carbon, which was observed when (NH ₄ ) ₆ · [H ₂ W ₁₂ O ₄₀ ] · nH ₂ O was used, was so complete that the supernatant became transparent. The color of CoTMPyP remained in the supernatant even after the precipitation of carbon.
Thus, it can be said that ionic bonds between a cationic complex such as CoTMPyP · 4Tosyl and an anionic oxide of a metal such as Mo and W are particularly likely to occur with a polyacid of Mo and W.
That is, it can be seen that by using the transition metal polyacid which is the second component, the amount of adsorption to carbon is increased as compared with the case where the same transition metal oxide is used. As a result, the activity of the electrode catalyst can be improved.

(Example 3)
As the porphyrin complex of the first component, 5,10,15,20-tetrakis (N-methyl-4-pyridyl) porphyrinatocobalt (II) · 4 toluenesulfonate (CoTMPyP · 4Tosyl) is used, and the second component is used. Sample of fuel cell electrode catalyst by using the following procedure using tungstophosphoric acid H ₃ PW ₁₂ O ₄₀ as the polyacid and Ketjen black as the third component carbon material Was made.
First, 4.6 mg of CoCl ₂ (3.54 × 10 ⁻² mmol) was mixed with 5 ml of methanol and stirred to obtain a first solution.
Further, 20.0 mg (1.47 × 10 ⁻² mmol) of H ₂ TMPyP · 4Tosyl was mixed with 5 ml of ion-exchanged water, and stirred to obtain a second solution.
Next, the first solution was added to the second solution, a few drops of 2,6-lutidine were further added, and the mixture was stirred for 2 days.
Thus, as the first component, 5,10,15,20-tetrakis (N-methyl-4-pyridyl) porphyrinatocobalt (II) .4 toluenesulfonate (CoTMPyP.4 Tosyl) which is a water-soluble complex. ) Was obtained.

Next, 47.0 mg of carbon powder (Ketjen Black powder) was added to the CoTMPyP · 4Tosyl ion exchange water aqueous solution as the third component carbon-based material, and the mixture was stirred for about 1 hour.
Thereafter, 42.9 mg of H ₃ PW ₁₂ O ₄₀ was added as the second component. When the aqueous solution of tungstophosphoric acid was added, the carbon powder was atomized, and a colorless transparent supernatant solution and carbon precipitates were formed.
The obtained precipitate was suction filtered, dried at 120 ° C. for 12 hours, and then ground and stored in a mortar. Thus, the precursor for producing an electrode catalyst was obtained.

Furthermore, in order to heat-treat the precursor, the powder obtained by drying was put into a quartz reactor.
Then, He was purged as an inert gas at room temperature and a flow rate of 100 ml / min for 30 minutes.
Thereafter, the flow rate of He was reduced to 20 ml / min, the temperature was raised to 550 ° C., which was the target temperature, at 10 K / min, and the heat treatment was held for 2 hours, and then allowed to cool.
Thus, an electrode catalyst was produced and used as a sample of Example 3. Under this condition, the molar ratio of CoTMPyP to H ₃ PW ₁₂ O ₄₀ is 1: 1.

Example 4
An electrode catalyst was produced in the same manner as in Example 3 except that an aqueous solution of H ₄ SiW ₁₂ O ₄₀ was used as the second component, and a sample of Example 4 was obtained.

(Example 5)
In the same manner as in Example 3, an aqueous tungstophosphoric acid solution having a concentration of 0.1 mol / L was prepared. Further, an aqueous iron chloride solution having a concentration of 0.1 mol / L was prepared. And in the state which stirred the tungstophosphoric acid aqueous solution, the iron chloride aqueous solution was added and it was set as the mixed solution. Since the tungstate phosphate anion (PW ₁₂ O ₄₀ ³⁻ ) is trivalent, iron chloride having a trivalent metal cation was added in an equivalent amount to tungstophosphoric acid. Furthermore, after stirring for 2 days, the solvent was distilled off and dried while maintaining 50 to 80 ° C. to obtain Fe [PW ₁₂ O ₄₀ ].
Then, an aqueous solution of the FePW ₁₂ O ₄₀ except that used as the second component, and producing an electrode catalyst in the same manner as in Example 3, was used as a sample of Example 5.

(Example 6)
In the same manner as in Example 3, an aqueous tungstophosphoric acid solution having a concentration of 0.1 mol / L was prepared. Further, a cobalt chloride aqueous solution having a concentration of 0.1 mol / L was prepared. And in the state which stirred the tungstophosphoric acid aqueous solution, cobalt chloride aqueous solution was added and it was set as the mixed solution. Since tungstophosphate anion (PW ₁₂ O ₄₀ ³⁻ ) is trivalent, 1.5 equivalent of tungstophosphoric acid was added to cobalt chloride whose metal cation is divalent. Furthermore, after stirring for 2 days, the solvent was distilled off and dried while maintaining 50 to 80 ° C. to obtain Co ₃ [PW ₁₂ O ₄₀ ] ₂ .
Then, as a second component, other using an aqueous solution of _{Co 3 [PW 12 O 40]} 2 is to prepare an electrode catalyst in the same manner as in Example 3, was used as a sample of Example 6.

(Example 7)
An electrode catalyst was prepared in the same manner as in Example ₃ except that an aqueous solution of polyoxomolybdate H ₃ PMo ₁₂ O ₄₀ was used as the second component, and a sample of Example 7 was obtained.

(Example 8)
An electrode catalyst was prepared in the same manner as in Example 3 except that an aqueous solution of AlPW ₁₂ O ₄₀ was used as the second component, and a sample of Example 8 was obtained.

Example 9
An electrode catalyst was produced in the same manner as in Example 3 except that FeTMPyP was used as the first component, and a sample of Example 9 was obtained.

(Example 10)
An electrode catalyst was prepared in the same manner as in Example 3 except that an aqueous solution of AgPW ₁₂ O ₄₀ was used as the second component, and a sample of Example 10 was obtained.

(Control 2)
An electrode catalyst in which 50% by mass of Pt was supported on Vulcan (Vulcan XC-72R; VC), which is a carbon-based material, was prepared as Control Example 2.

<Measurement of characteristics>
Various characteristics of the produced carbon catalyst sample were measured as follows.

(Three electrode measurement)
Three-electrode measurement was performed for each sample of Examples 3 to 9 and Control Example 2. The specific measurement method and conditions were as follows.
A sample of the electrocatalyst was placed in a 15 ml tube and dispersed by ultrasonic waves for 15 minutes, and then stirred for 2 minutes with a tube mixer. This was applied to the disk electrode with an Eppendorf and dried. Further, 2.5 μl of 5 wt% Nafion solution was applied and dried.
Three-electrode measurement was performed using the disk electrode coated with the electrode catalyst thus obtained.
The cyclic voltammetry (CV) and the linear sweep measurement (LSV) in the argon (Ar) atmosphere and the oxygen (O ₂ ) atmosphere, respectively, under the conditions shown in Tables 2 and 3, and the flowchart shown in FIG. Performed according to. In the flowchart of FIG. 8, each step of S24 and S27 indicates that the atmosphere is changed from argon to oxygen or from oxygen to argon.

LSV was adjusted to 0.05-1.0 Vvs. Cathode activity was evaluated by sweeping with RHE (0.05-1.15 Vvs. RHE).
Of the steps S21~S29 shown in the flowchart of FIG. 8, the measurement results of the LSV under Ar saturated (S29) as a baseline, the measurement results of the _{O 2} saturation of a LSV (S26), and creates a steady polarization curve. From this steady polarization curve, the ORR starting potential (5 μA / cm ² or 0.2 μA / cm ² ), 0.8 Vvs. Value of current density at RHE, 0.9 Vvs. The value of current density at RHE was determined.

(Relationship between coating amount and activity)
With respect to the sample of Example 3, three-electrode measurement was performed, respectively, by changing the amount of catalyst applied to the disk electrode. As a measurement result, the applied amount of the catalyst and 0.8 Vvs. The relationship with the current density value i _{0.8V in} RHE is shown in Table 4 and FIG.

From Table 4 and FIG. 9, 0.8 Vvs. It can be seen that the value of current density at RHE increases linearly.
The current density when the coating amount was 376 μg was 206 μA / cm ⁻² . When the same measurement was performed for the 50 wt% Pt / VC catalyst of Control Example 2, when compared with the current density at 0.8 V, the catalyst of Example 3 showed 52% activity of the catalyst of Control Example 2. . Further, when compared with the same coating amount, the activity was improved as compared with the catalyst using (NH ₄ ) _6. [H ₂ W ₁₂ O ₄₀ ] and ketjen black.

(Comparison by polyacid material)
For each sample of Examples 3 to 10, the catalyst was applied to the disk electrode with a coating amount of the catalyst of 376 μg. Further, with respect to the sample of Control Example 2, the catalyst was applied to the disk electrode with the application amount of the catalyst being 10 μg. And sweep range 0.05-1.0Vvs. RHE and sweep range 1.15-0.05 Vvs. In RHE, three-electrode measurement was performed by the method described above.
Further, from the measurement results, as ORR onset potential was determined the potential when the current of 0.2 .mu.A / cm ² was passed, and a potential when the current of 5 .mu.A / cm ² was passed.

First, the sweep range 0.05-1.0 Vvs. In the case of RHE, the steady polarization curves of the respective samples are compared and shown in FIG. 10, and an enlarged view around 0.8 V in FIG. 10 is shown in FIG.
Table 5 shows a comparison between the ORR start potential of each sample, the current density at 0.8V, and the current density at 0.9V. In Table 5, ORR onset potential, after the potential when the current of 0.2 .mu.A / cm ² was passed, describes the potential when the current of 5 .mu.A / cm ² flows in the ().

From Table 5, the ORR start potential (0.2 μA / cm ² ) is 0.922 V for H ₃ PW ₁₂ O ₄₀ , 0.861 V for H ₄ SiW ₁₂ O ₄₀ , and 0.935 V for FePW ₁₂ O ₄₀ , respectively. CoPW ₁₂ O ₄₀ is _0.89V, H _{3 PMo} 12 _{O 40} is _{0.868V, AlPW} 12 _{O 40} is _{0.881V, H 3 PW 12 O 40} (FeTMPyP) is _{0.875V, AgPW} 12 _{O 40} 0. 866V was indicated. Further, 0.8 V current density _{of, FePW} 12 _{O 40} is _{^{287μA / cm 2, H 3 PW}} 12 O 40 is 207μA / cm ^2, electrode active high results. The current density of 0.9V is 8.1 μA / cm ² for FePW ₁₂ O _{40 and 5} μA / cm ² for H ₃ PW ₁₂ O ₄₀ , and high electrode activity that was not obtained with conventional electrode catalysts was obtained. Yes.

In addition, a Tafel plot was created using the measurement results of the three-electrode measurement.
Furthermore, the number of reaction electrons was determined from the ring current. Furthermore, the amount of hydrogen peroxide generated was measured.
The Tafel plot of each sample is compared and shown in FIG. 12, the number of reaction electrons of each example is compared and shown in FIG. 13, and the amount of hydrogen peroxide generated in each example is compared and shown in FIG.
Moreover, from the Tafel plot of FIG. 12, the slope of each sample, the exchange current density iex, and the intercept A on the vertical axis are compared and shown in Table 6.

From Table 6, the exchange current density of FePW ₁₂ O ₄₀ is 5.49 × 10 ⁻⁶ mA / cm ^2, which is close to the exchange current density of 7.35 × 10 ⁻⁶ mA / cm ² of 50 wt% Pt / VC. Is obtained.
Therefore, it turns out that it has higher activity than the conventional platinum alternative catalyst.
In addition, FIG. 13 shows that FePW ₁₂ O ₄₀ has approximately 4 reaction electrons and has a high 4-electron reducibility.
From FIG. 14, the hydrogen peroxide generation amount of FePW ₁₂ O ₄₀ is always around 1% regardless of the voltage, and the maximum is 1.35%, and almost no hydrogen peroxide is generated.
From these facts, a catalyst in which FePW ₁₂ O ₄₀ and cobalt porphyrin are supported on carbon is considered to be a promising catalyst for a future fuel cell non-platinum cathode electrode catalyst.

When the catalyst of Example 3 using cobalt porphyrin and the catalyst of Example 9 using iron porphyrin were compared, the current densities at 0.8 V were 206.5 μA / cm ⁻² and 49.7 μA / cm ⁻² and the ORR start voltages are 0.922V and 0.875V. That is, it can be seen that the use of cobalt porphyrin as the second component porphyrin is more active than using iron porphyrin.

Next, the sweep range 1.15-0.05 Vvs. In the case of RHE, the steady polarization curves of the respective samples are compared and shown in FIG. 15, and an enlarged view around 0.8 V in FIG. 15 is shown in FIG.
Table 7 shows a comparison between the ORR start potential of each sample, the current density at 0.8V, and the current density at 0.9V. In Table 7, ORR onset potential, after the potential when the current of 0.2 .mu.A / cm ² was passed, describes the potential when the current of 5 .mu.A / cm ² flows in the ().

From Table 7, even in this sweep range, the ORR start voltage and current density of FePW ₁₂ O ₄₀ are higher than those of the other examples, and high activity close to 50 wt% Pt / VC of Control Example 2 is obtained. I understand that.

(Difference in Co state depending on heat treatment temperature)
In the same manner as in Example 1 and Comparative Examples 6 to 8, the heat treatment temperatures were 573 K (300 ° C.), 673 K (400 ° C.), 773 K (500 ° C.), 823 K (550 ° C.), 973 K (700 ° C.), A sample of the catalyst at 1073 K (800 ° C.) was prepared.
For each of these samples, the value of the ratio Co ²⁺ / (Co ²⁺ + Co ³⁺ ) was determined by XPS measurement, and 0.5 V vs. The amount of hydrogen peroxide generated in RHE was measured.
These results are shown in FIG.

From FIG. 17, it can be seen that the value of the ratio of Co ²⁺ / (Co ²⁺ + Co ³⁺ ) increases as the heat treatment temperature increases, takes the maximum value at 823 K, and decreases further.
The amount of hydrogen peroxide generated tends to be opposite to the value of the ratio Co ²⁺ / (Co ²⁺ + Co ³⁺ ). That is, it can be seen that it contributes to the activity of Co ²⁺ ions.

(Difference due to metal ion of polyacid)
The influence of the charge / ion radius ratio (e / r) of the metal ion M ^{n +} of the polyacid on the activity was investigated.
Four measurement values were extracted from the measurement values shown in Table 5, and the charge / ion radius ratio (e / r) of metal ions M ^{n +} (Ag ⁺ , Co ²⁺ , Fe ³⁺ , Al ³⁺ ) and 0.8 V were obtained. FIG. 18 shows a plot of the relationship with current density at.
FIG. 18 indicates that polyoxotungstate acts as a moderately strong Lewis acid (mountain curve) in relation to the deprotonation energy of hydrogen ions and the acid strength order of exchange metal ions.
In addition, it promotes dimerization of cobalt porphyrin and tungsten, and due to the synergistic effect of tungstophosphoric acid containing cobalt porphyrin and exchange metal (activity increases when iron is used as exchange metal), remarkable oxygen reduction activity appears. It is thought that.
In addition, tungstophosphoric acid is considered to react with hydrogen peroxide generated at the cathode and change into a peroxo species that becomes a stronger oxidant.
This divalent cobalt porphyrin and polyoxotungstate metal ions are considered to bind to the graphite carbon via nitrogen of cobalt porphyrin due to the synergistic effect (even the protonic acid acts in the absence of metal). It is done.

Table 8 shows a comparison of the activity per unit mass of metal for FePW ₁₂ O _{40 of} Example 5 and 50 wt% Pt / VC of Control Example 2.

From Table 8, the activity at 0.8 V was 12.4% of the FePW ₁₂ O _{40 of} Example 5 being 50 wt% Pt / VC of the control example. In addition, the activity at 0.9 V was 4.5% of the 50 wt% Pt / VC of the control example of FePW ₁₂ O _{40 of} Example 5.

  The present invention is not limited to the above-described embodiments, and various other configurations can be taken without departing from the gist of the present invention.

  As described above, the present invention can produce an electrode catalyst component having the same catalytic activity and durability as an electrode catalyst containing platinum as an electrode catalyst component without using platinum as a catalyst component. It has the excellent effect of providing an inexpensive fuel cell electrode catalyst without significant deterioration in activity, so it can be used in mobile devices such as notebook computers and mobile phones, and from automobiles, railways, consumer industrial cogeneration, and power generation. It can be used in the field of fuel cells that cover various uses and scales, and has industrial applicability.

Claims (6)

A method for producing an electrode catalyst for a fuel cell, comprising:
A precursor is prepared by mixing a porphyrin complex having one or more metal elements selected from cobalt, iron, nickel, chromium, and manganese as a central metal, a carbon-based material, and a polyacid having tungsten as a central metal. Process,
And a step of forming an electrode catalyst by heat-treating the precursor within a temperature range of 500 ° C. to 600 ° C. A method for producing an electrode catalyst for a fuel cell.   2. The fuel cell electrode catalyst according to claim 1, wherein 5,10,15,20-tetrakis (N-methyl-4-pyridyl) porphyrinatocobalt (II) · 4 toluenesulfonate is used as the porphyrin complex. Production method.   The method for producing an electrode catalyst for a fuel cell according to claim 1, wherein ammonium metatungstate is used as the polyacid. The method for producing an electrode catalyst for a fuel cell according to claim 1, wherein H ₃ PW ₁₂ O ₄₀ or FePW ₁₂ O ₄₀ is used as the polyacid.   The method for producing an electrode catalyst for a fuel cell according to claim 1, wherein the carbon-based material uses one or more carbon-based fine particles selected from carbon black, carbon nanotube, carbon nanohorn, and fullerene.   The method for producing an electrode catalyst for a fuel cell according to claim 5, wherein the carbon-based fine particles are carbon fine particles in which nitrogen atoms are introduced into the carbon-carbon bond portion.

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