JP2006190637A - Composition for electrode, electrode, composition for air electrode, air electrode for fuel cell, fuel cell, fuel cell system, and fuel cell vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for an electrode by which reduction in a quantity of platinum used can be made without impairing performance as a fuel cell. <P>SOLUTION: A compound has an oxidation and reduction cycle which works as a reducing agent at a potential lower than an oxidation reduction potential of oxygen and works as an oxidant at a potential higher than an oxidation reduction potential of hydrogen and hydrogen ion. The air electrode for the fuel cell contains as an oxidation reduction catalyst a compound such as NHPI whose standard oxidation-reduction potential is in the range of 0.00V to 1.40V. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrode composition, an electrode, a composition for an air electrode, an air electrode for a fuel cell, a fuel cell, a fuel cell system and a fuel cell vehicle, and more particularly to an electrode composition for use in a polymer electrolyte fuel cell.

Fuel cell technology is attracting attention as a means of solving the recent energy resource problems and global warming problems associated with CO ₂ emissions. A fuel cell is one in which fuel such as hydrogen, methanol, or other hydrocarbon is electrochemically oxidized in the cell, thereby converting the chemical energy of the fuel directly into electric energy and taking it out. For this reason, fuel cells are attracting attention as clean electrical energy sources because there is no generation of NO _X or SO _X due to fuel combustion in internal combustion engines such as thermal power generation and automobiles.

  There are several types of fuel cells. Among them, the polymer electrolyte fuel cell (PEFC) has attracted the most attention and is being developed. PEFC is (1) easy to start and stop due to low temperature operation, (2) high theoretical voltage and high conversion efficiency, and (3) flexible cell structure such as vertical because there is no liquid phase in the electrolyte. (4) The ion exchange membrane / electrode interface is advantageous in that a large amount of current can be taken out by controlling the three-phase interface and a high output density can be obtained.

In PEFC, protons (H ⁺ ) that have passed through the ion exchange membrane are reacted with oxygen in the air at the air electrode, and the reaction is a four-electron reduction reaction that mainly reduces oxygen to water. However, this reaction does not occur at a yield of 100 [%], and a two-electron reduction reaction of oxygen occurs as a side reaction (see Non-Patent Document 1). When a two-electron reduction reaction of oxygen occurs, active oxygen such as hydrogen peroxide is generated. In this case, since the platinum-supporting carbon used in the air electrode is oxidized by active oxygen, the carbon is consumed, and there is a possibility that the activation rate of oxygen on platinum as a catalyst decreases. On the other hand, platinum used as a catalyst has a lower electrochemical charge voltage than other metals and catalyzes a four-electron reduction reaction from around room temperature to the fuel cell electrochemical reaction, that is, oxygen to water. Is the only metal that can. However, exposure to a high potential or high temperature in the start / stop operation may increase the platinum particle size and decrease the catalytic activity.

  In PEFC, a Nafion (registered trademark) membrane, which is a perfluorosulfonic acid cation exchange membrane, is generally used. Since this membrane is acidic, PEFC cannot be established without using chemically stable noble metals. In addition, since the 4-electron reduction reaction reduces oxygen at the highest potential, the catalyst used here needs to be an oxidizing agent having a strong oxidizing power. For these reasons, it is difficult to replace platinum as a catalyst.

  However, platinum is expensive, and the current fuel cell system requires 1 [g] of platinum per 1 [kW]. For this reason, assuming that the output of an automobile with a displacement of 2000 cc is 100 [kW] and equivalent fuel cell automobiles (FCV) are converted into an example, 100 [g] of platinum is required per FCV and costs high ( (Refer nonpatent literature 2.). As described above, it is important to reduce the amount of platinum used for the electrode or to develop an alternative catalyst for platinum.

Therefore, a catalyst using a cobalt salen compound instead of platinum has been proposed (see Patent Document 1). Further, a catalyst using tungsten carbide has been proposed (see Patent Document 2).
JP 2000-251906 A (page 4) JP 2003-117398 A (2nd page, FIG. 1) New Energy and Industrial Technology Development Organization Subcontractor, Graduate School of Engineering, Kyoto University, “2001 Results Report, Research and Development of Solid Polymer Fuel Cells, Research on Degradation Factors of Polymer Electrolyte Fuel Cells, Basics on Degradation Factors Research (1) Electrode catalyst / electrolyte interface degradation factors ", March 2002, p.27 Supervised by Kenichiro Ota and one other, “Development and Materials for Fuel Cell Vehicles”, CMC Publishing Co., Ltd., December 2002, p.21

  However, since the activity of a catalyst using a cobalt salen compound is reduced in an acidic medium, the electrolyte membrane must be changed from a cation exchange membrane such as a Nafion (registered trademark) membrane to an anion exchange membrane. Further, tungsten carbide has not yet reached a level exceeding the performance of platinum, and it is difficult to use it as a four-electron reduction reaction catalyst instead of platinum.

  The present invention has been made to solve the above problems, and the electrode composition according to the first invention works as a reducing agent at a potential lower than the oxidation-reduction potential of oxygen, and also contains hydrogen and hydrogen ions. The gist is to contain, as an oxygen reduction catalyst, a compound having a redox cycle that acts as an oxidant at a potential higher than the redox potential.

  Moreover, the electrode which is 2nd invention makes it a summary to have at least any one among the composition for electrodes which concerns on the said 1st invention.

  Furthermore, the composition for air electrodes which is 3rd invention makes it a summary to have at least any one among the compositions for electrodes which concerns on the said 1st invention.

  In addition, a fuel cell air electrode according to a fourth aspect of the invention is characterized by having the air electrode composition according to the third aspect of the invention.

  The gist of a fuel cell according to a fifth aspect of the invention is that it includes the electrode electrode according to the second aspect of the invention or the air electrode for a fuel cell according to the fourth aspect of the invention.

  The gist of a fuel cell system according to a sixth aspect of the invention is that it includes the fuel cell according to the fifth aspect of the invention.

  The gist of a fuel cell vehicle according to a seventh aspect is that the fuel cell system according to the sixth aspect is mounted.

According to the first invention, the compound acts as a reducing agent at a potential lower than the oxidation-reduction potential of oxygen and, after being oxidized, reversibly as an oxidizing agent at a potential higher than the oxidation-reduction potential of hydrogen and hydrogen ions. work. At that time, a four-electron reduction reaction in which proton (H ⁺ ) and molecular oxygen (O ₂ ) are reacted to reduce to water is promoted. Thus, since this compound functions as a four-electron reduction reaction catalyst that promotes the reduction of oxygen, the amount of platinum used in the electrode composition can be reduced. In addition, this compound acts as a redox catalyst by repeating the redox cycle and can be used as a catalyst many times, so that the amount of catalyst used can be further reduced.

  According to the second aspect of the invention, since the electrode composition includes the redox catalyst, the redox catalyst activates the reaction of the electrode, and the amount of platinum used can be reduced.

  According to 3rd invention, since it has the composition for electrodes containing a redox catalyst, the composition for air electrodes which can accelerate | stimulate 4 electron reduction reaction of oxygen in an air electrode is obtained.

  According to the fourth aspect of the invention, since the air electrode composition including the oxidation-reduction catalyst is included, the 4-electron reduction reaction of oxygen at the air electrode is promoted, and the amount of platinum used can be reduced.

  According to the fifth invention, since the redox catalyst is included, the fuel cell reaction is promoted, and the amount of platinum used can be reduced.

  According to the sixth invention, it is possible to maintain the performance of the fuel cell system even if the amount of platinum used is reduced.

  According to the seventh invention, it is possible to obtain a fuel cell vehicle in which the amount of platinum used is reduced.

  DESCRIPTION OF EMBODIMENTS Hereinafter, details of an electrode composition, an electrode, an air electrode electrode composition, a fuel cell air electrode, a fuel cell, a fuel cell system, and a fuel cell vehicle according to the present invention will be described based on embodiments.

  First, an embodiment of an electrode composition according to the present invention will be described. The electrode composition according to the present embodiment has a redox cycle that acts as a reducing agent at a potential lower than the oxidation-reduction potential of oxygen and acts as an oxidizing agent at a potential higher than the oxidation-reduction potential of hydrogen and hydrogen ions. It is characterized by containing the compound which has as an oxygen reduction catalyst.

  In a solid polymer electrolyte fuel cell, a reaction represented by the following formula proceeds.

Negative _{^{(anode): H 2 → 2H + +}} 2e - E 0 = 0.00 [V] ··· Equation (1)
Positive electrode (air electrode): O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O E ₀ = 1.23 [V] .. Formula (2)
At the fuel electrode, a fuel gas containing hydrogen is supplied, the reaction of formula (1) proceeds, and hydrogen ions are generated. Hydrogen ions are hydrated by the water contained in the solid polymer electrolyte membrane and move through the solid polymer membrane to reach the air electrode. At the air electrode, the transferred hydrogen ions react with oxygen in the oxidizing gas supplied to the positive electrode, and the reaction of formula (2) proceeds to produce water. At this time, an electromotive force is generated by electrons generated at the fuel electrode moving to the air electrode via the external circuit. Note that E ₀ is represented by a normal oxidation-reduction potential (Normal Hydrogen Electrode; NHE).

  In such a redox reaction that occurs at the air electrode, water as a final product is generated by a four-electron reduction reaction of oxygen shown in Formula (2). It is also known that hydrogen peroxide is generated by a two-electron reduction reaction of oxygen in addition to the reaction of formula (2) when the potential is low or when impurities are attached to platinum as a catalyst. .

O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O ₂ E ₀ = 0.68 [V] (3)
Since PEFC uses platinum as an electrode catalyst, the reaction of the formula (2) as a main reaction and the reaction of the formula (3) as a side reaction proceed simultaneously as a competitive reaction. And it is thought that hydrogen peroxide generated in the formula (3) disappears by the reactions shown in the following formulas (4) to (6).

H ₂ O ₂ + H ₂ → 2H ₂ O Formula (4)
H ₂ O ₂ + 2H ⁺ + 2e ⁻ → 2H ₂ O E ₀ = 1.77 [V] (5)
2H ₂ O ₂ → 2H ₂ O + O ₂ Formula (6)
Formula (4) shows a reaction in which hydrogen peroxide receives hydrogen ions and electrons at the air electrode and is reduced to water. Formula (5) shows a reaction in which hydrogen peroxide is reduced to water by H ₂ crossing the membrane from the fuel electrode to the air electrode. Formula (6) shows a reaction in which two molecules of hydrogen peroxide react to generate water and oxygen. In formula (6), one hydrogen peroxide acts as an oxidizing agent, and the other hydrogen peroxide acts as a reducing agent to generate water and oxygen as shown in formula (7) shown below.

^{_{H 2 O 2 → O 2 +}} 2H + + 2e - E 0 = 0.68 [V] ··· Equation (7)
As shown in the above formulas (5) and (7), hydrogen peroxide acts as an oxidant for substances having a higher oxidation-reduction potential than hydrogen peroxide, while the oxidation-reduction potential is higher than that of hydrogen peroxide. It is known to work as a reducing agent for substances with a low content.

Here, the formula (4) is the sum of the elementary reaction represented by the formula (5) and the elementary reaction represented by the formula (1). Formula (6) is the sum of the elementary reaction shown by Formula (5) and the elementary reaction shown by Formula (7). Thermodynamically, a substance with a high redox potential acts as an oxidizing agent, and a substance with a low redox potential acts as a reducing agent. Basically, the reaction proceeds when ΔE _{0 of the} entire system is a positive value. However, since E ₀ of each substance represents the average value of each substance, and the actual oxidation-reduction potential has a certain range, even a negative value of about ΔE ₀ = −0.15 [V] does not react. May progress.

  As shown in the above formula (2), the standard redox potential of oxygen is 1.23 [V], and the hydrogen or proton standard redox potential is 0.00 [V]. For this reason, in the positive electrode, oxygen acts as an oxidizing agent for hydrogen, and the reaction of the above formula (2) or formula (3) proceeds. The standard redox potential of hydrogen peroxide generated by the reaction of the formula (3) is 1.77 [V] as shown in the formula (4) when acting as an oxidant, and the standard redox potential of hydrogen. Higher than. For this reason, hydrogen peroxide acts as an oxidizing agent for hydrogen, and the reaction of the above formula (4) or formula (5) proceeds. Since the standard oxidation-reduction potential when hydrogen peroxide acts as a reducing agent is 0.68 [V], water and oxygen are generated by the reaction of two molecules of hydrogen peroxide according to the above formula (6). To do.

  The platinum-supported carbon used in the positive electrode is oxidized by the hydrogen peroxide generated at the positive electrode, so that the carbon is consumed and the performance of the fuel cell gradually deteriorates. The oxygen activation rate on the platinum Decreases. In addition, the generation of hydrogen peroxide increases with the deterioration of platinum. Therefore, in the electrode composition, a compound having a redox cycle that acts as a reducing agent at a potential lower than the redox potential of oxygen and acts as an oxidizing agent at a potential higher than the standard redox potential of hydrogen and hydrogen ions. In this case, this compound acts as a reducing agent at a potential lower than the standard oxidation-reduction potential of oxygen when it is first reduced, so that oxygen promotes the four-electron reduction reaction represented by formula (2). . In so doing, the compound is oxidized. After this compound is oxidized and becomes an oxidized form, this compound receives hydrogen ions and electrons from the positive electrode, and becomes a reduced form again.

Thus, this compound works reversibly as a redox catalyst by repeating the redox cycle. Since the compound functions as a four-electron reduction reaction catalyst that promotes the reduction of oxygen by the reversible redox cycle of the compound, proton (H ⁺ ) and molecular oxygen (O ₂ ) are reacted to form water. This promotes the four-electron reduction reaction that reduces to Thus, since this compound functions as a four-electron reduction reaction catalyst that promotes the reduction of oxygen, the amount of platinum used in the electrode composition can be reduced. In addition, this compound acts as a redox catalyst by repeating the redox cycle and can be used as a catalyst many times, so that the amount of catalyst used can be further reduced.

  Specifically, the standard redox potential of this compound is preferably in the range of 0.00 [V] to 1.40 [V] (vs. NHE). In this case, the reduction of oxygen is promoted and acts as an oxidant for hydrogen and hydrogen ions. The standard redox potential of the compound is more preferably in the range of 0.68 [V] to 1.00 [V]. Furthermore, it is more preferable if the oxidized form and reduced form of this compound are relatively stable compounds. In addition, since the actual oxidation-reduction potential (Real Hydrogen Electrode; RHE) of each compound changes according to various conditions such as pH and temperature, it is preferable to use those in a range corresponding to the conditions. However, considering the poisoning of platinum used for the electrode, the compound used for the electrode composition according to the present embodiment is an organic compound composed only of carbon, hydrogen, oxygen, and nitrogen. preferable.

The above compound has the following general formula (I)

In the formula, R1 and R2 are preferably the same or different arbitrary substituents, and X is an oxygen atom or a hydroxyl group. In this general formula (I), R1 and R2 are each a kind of substituent selected from the group consisting of an alkyl group, an aryl group, an alkoxy group and a substituent containing a hydrogen atom, and R1 and R2 are an alkyl group or an alkoxy group. In this case, an alkyl group or an alkoxyl group partially substituted with an arbitrary group, an unsaturated alkyl group or an alkoxy group may be used, and these groups may be chain, cyclic or branched, R1 and R2 may contain oxygen and nitrogen atoms. When R1 and R2 are aryl groups, they may be aryl groups partially substituted with any group, and may contain oxygen and nitrogen atoms. In the general formula (I), R1 and R2 are more preferably bonded to each other to form a double bond, an aromatic ring, or a non-aromatic ring in order to promote oxygen activation.

Further, this compound has the following general formula (II)

(Wherein ring Y1 represents a imide compound having a double bond or any one of aromatic or non-aromatic 5- to 12-membered rings). By using a composition containing an imide compound for an air electrode of a fuel cell, oxygen activation is promoted, and further, there is a catalytic effect that promotes oxygen reduction even at room temperature and normal pressure.

The above compound formula is represented by the following general formula (III)

(Wherein R3 and R4 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a cycloalkyl group, a hydroxyl group, an alkoxyl group, a carboxyl group, an alkoxycarbonyl group, or an acyl group. X represents oxygen. In terms of chemical stability and catalytic activity, an atom or a hydroxyl group is preferred. N is an integer of 1 to 3).

  In the compound represented by the general formula (III), the halogen atom in the substituents R3 and R4 includes iodine, bromine, chlorine and fluorine. Examples of the alkyl group include straight chain having about 1 to 10 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, heptyl, octyl and decyl groups. Branched alkyl groups are included. Preferred alkyl groups include, for example, lower alkyl groups having about 1 to 6 carbon atoms, particularly about 1 to 4 carbon atoms.

  Aryl groups include phenyl groups, naphthyl groups, and the like, and cycloalkyl groups include cyclopentyl, cyclohexyl, cyclooctyl groups, and the like. The alkoxy group includes, for example, about 1 to 10 carbon atoms such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, t-butoxy, pentyloxy and hexyloxy groups, preferably about 1 to 6 carbon atoms, particularly carbon. A lower alkoxy group of about 1 to 4 is included.

  In the alkoxycarbonyl group, for example, the carbon number of the alkoxy moiety such as methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, t-butoxycarbonyl, pentyloxycarbonyl, hexyloxycarbonyl group and the like is 1 About 10 to 10 alkoxycarbonyl groups are included. Preferred alkoxycarbonyl groups include lower alkoxycarbonyl groups having about 1 to 6, particularly about 1 to 4 carbon atoms in the alkoxy moiety.

  Examples of the acyl group include acyl groups having about 1 to 6 carbon atoms such as formyl, acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl, and pivaloyl groups.

  The substituents R3 and R4 may be the same or different. In the compound represented by the general formula (III), R3 and R4 may be bonded to each other to form a double bond, an aromatic ring, or a non-aromatic ring. Among them, the aromatic ring or the non-aromatic ring preferably forms any one of 5 to 12-membered rings, more preferably about 6 to 10-membered rings. Although it may be a condensed heterocyclic ring, it is preferably a hydrocarbon ring.

  Examples of such a ring include a non-aromatic hydrocarbon ring such as a cycloalkane ring typified by a cyclohexane ring, a cycloalkene ring typified by a cyclohexene ring, and a bridged hydrocarbon represented by a 5-norbornene ring. Non-aromatic bridged rings such as rings, aromatic rings such as benzene rings and naphthalene rings are included. In addition, these rings may have a substituent.

Preferred imide compounds include compounds represented by the following formulas (IVa) to (IVf).

(Wherein R3 to R6 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group, a hydroxyl group, an alkoxyl group, a carboxyl group, an alkoxycarbonyl group, an acyl group, a nitro group, a cyano group or an amino group, n represents an integer of 1 to 3).

  Here, in the substituents R3 to R6, the alkyl group includes an alkyl group similar to the alkyl group exemplified above, particularly an alkyl group having about 1 to 6 carbon atoms. Examples of the alkoxy group include the same alkoxy groups as described above, particularly lower alkoxy groups having about 1 to 4 carbon atoms. The alkoxycarbonyl group includes the same alkoxycarbonyl group as described above, particularly those having an alkoxy moiety having 1 to 1 carbon atoms. About 4 lower alkoxycarbonyl groups are included. Examples of the acyl group include the same acyl groups as described above, particularly those having about 1 to 6 carbon atoms, and examples of the halogen atom include fluorine, chlorine, and bromine atoms. ~ R6 is usually a hydrogen atom, a lower alkyl group having about 1 to 4 carbon atoms, a carboxyl group, a nitro group, or a halogen atom in many cases.

  In the compound represented by the general formula (III), X represents an oxygen atom or a hydroxyl group, and n is usually about 1 to 3, preferably 1 or 2. Moreover, the compound shown by the said general formula (III) can be used 1 type, or 2 or more types in oxygen reduction reaction.

  Examples of the acid anhydride corresponding to the compound represented by the general formula (III) include saturated or unsaturated aliphatic dicarboxylic acid anhydrides such as succinic anhydride and maleic anhydride, tetrahydrophthalic anhydride, and hexahydro anhydride. Saturated or unsaturated non-aromatic cyclic polyvalent carboxylic acid anhydrides such as phthalic acid (1,2-cyclohexanedicarboxylic acid anhydride), 1,2,3,4-cyclohexanetetracarboxylic acid 1,2-anhydride ( Alicyclic polyhydric carboxylic acid anhydrides), heptic anhydride, hymic anhydride, etc., bridged cyclic polyhydric carboxylic anhydrides (alicyclic polycarboxylic anhydrides), phthalic anhydride, tetrabromophthalic anhydride , Tetrachlorophthalic anhydride, nitrophthalic anhydride, trimellitic anhydride, methylcyclohexeric carboxylic anhydride, pyromellitic anhydride, melittic anhydride, , 8; include aromatic polycarboxylic acid anhydrides such as 4,5-naphthalene tetracarboxylic dianhydride.

  Further, as preferred imide compounds, for example, N-hydroxysuccinimide, N-hydroxymaleic imide, N-hydroxyhexahydrophthalimide, N, N'-dihydroxycyclohexanetetracarboxylic imide, N-hydroxyphthalic acid Imido, N-hydroxytetrabromophthalimide, N-hydroxytetrachlorophthalimide, N-hydroxyhetic acid imide, N-hydroxyhymic acid imide, N-hydroxytrimellitic acid imide, N, N'-dihydroxypyro Mellitic acid imide and N, N′-dihydroxynaphthalenetetracarboxylic imide are exemplified. Among them, a preferable compound is an alicyclic polycarboxylic acid anhydride, and particularly an N-hydroxyimide compound derived from an aromatic polycarboxylic acid anhydride, such as N-hydroxyphthalic acid imide.

In addition, as the imide compound, a conventional imidization reaction, for example, a corresponding acid anhydride and hydroxylamine (NH ₂ OH) are reacted to open a ring of an acid anhydride, and then ring-close and imidize. Can be prepared.

  Here, FIG. 1 shows an oxidation reduction potential (ORP) when oxygen, active oxygen, hydrogen or the like acts as an oxidizing agent or a reducing agent. The right column of this figure shows the oxidation half reaction formula of the reducing agent, and the left column shows the reduction half reaction formula of the oxidizing agent. The vertical axis shows the standard oxidation-reduction potential, and it becomes higher as it goes up. That is, it is shown that it is hard to be oxidized as it is located above. In addition, the numerical value shown in the parenthesis after the half reaction formula is a standard oxidation-reduction potential of a compound that acts as an oxidizing agent or a reducing agent. Since the oxidation-reduction potential is affected by pH and temperature, FIG. 1 shows the standard oxidation-reduction potential measured using a standard hydrogen electrode (NHE).

  FIG. 2 shows the redox mechanism of the compound contained in the electrode composition in the present embodiment. Here, as a representative example of the above compound, N-hydroxyphthalimide (abbreviated as NHPI) is shown as an example, and an oxygen activation mechanism, an oxygen reduction mechanism, and a reaction with protons are shown. When NHPI is oxidized, it becomes PINO (phthalimide-N-oxyl). NHPI and PINO have an oxidation-reduction potential of 1.34 [V] as shown in the following formulas (8) and (9).

NHPI → PINO + H ⁺ + e ⁻ E ₀ = 1.34 [V] (8)
PINO + H ⁺ + e ⁻ → NHPI E ₀ = 1.34 [V] (9)
The reaction represented by the above formula (2) is a complex reaction composed of a plurality of elementary reactions represented by the following formulas (10) to (14).

NHPI + O ₂ → PINO + · OOH Formula (10)
NHPI + · OOH → PINO + H ₂ O ₂ Formula (11)
NHPI + H ₂ O ₂ → PINO + H ₂ O + · OH Formula (12)
NHPI + .OH → PINO + H ₂ O Formula (13)
4PINO + 4H ⁺ + 4e ⁻ → 4NHPI (14)
The oxygen molecule in the air is called triplet oxygen, and the ground state is a triplet radical molecule. As shown in the formula (10), hydrogen is easily extracted from the N-hydroxyl group of NHPI at room temperature and normal pressure, It produces PINO and peroxy radicals (.OOH). The peroxy radical has a high reduction potential of 1.50 [V] and flies to the active species more than oxygen. Therefore, as shown in the formula (11), hydrogen is extracted from other NHPI.

  Further, as shown in the following formula (15), the peroxy radical is hydrogen peroxide.

OOH + H ⁺ + e ⁻ → H ₂ O ₂ E ₀ = 1.50 [V] (15)
Although hydrogen peroxide is not a radical, it is reactive, has a high reduction potential of 1.77 [V], and is a species that is more active than oxygen. Therefore, as shown in formula (12), hydrogen is more hydrogen than other NHPIs. Pull out an atom. Hydrogen peroxide from which hydrogen has been extracted generates water and hydroxy radicals (.OH) as shown in the following formula (16).

H ₂ O ₂ + H ⁺ + e ⁻ → H ₂ O + · OH (16)
Since this hydroxy radical is a species that does not have a large reduction potential of 2.85 [V] and is active, it draws hydrogen from NHPI as shown in formula (13) to generate PINO and water. As described above, the four-electron reduction of oxygen proceeds by the elementary reactions of the formulas (10) to (13), and four molecules of PINO are generated. PINO is also a species that has been activated, and as shown in Equation (14), it receives electrons (e ⁻ ) from the positive electrode of the fuel cell together with protons and is regenerated into NHPI.

For reference, the oxidation-reduction potential of NHPI was measured using glassy carbon as the working electrode, platinum as the counter electrode, a saturated calomel electrode (SCE) as the reference electrode, and 1 [M] sulfuric acid as the electrolyte. A cyclic voltammogram of NHPI measured under these conditions is shown in FIG. In this condition (SCE), the oxidation-reduction potential of NHPI exists in the vicinity of 1.10 [V]. In FIG. 1, the claims and the specification, the following formula ( 17) The display is corrected to the standard potential E ⁰ (NHE) by the equation shown in 17).

E ⁰ (NHE) = E (SCE) +0.24 [V] (17)
When corrected to NHE, the oxidation-reduction potential of NHPI is around 1.34 [V]. With this potential, the oxidation-reduction potential of NHPI is slightly higher than the oxidation-reduction potential of oxygen, but it is a level that sufficiently acts as a reducing agent for oxygen, and NHPI is a compound that functions reversibly as an oxidizing agent or a reducing agent. NHPI has been shown to be a compound having a redox cycle that acts as an oxidant at a potential higher than the redox potential of hydrogen and hydrogen ions. Thus, NHPI has a 4-electron reduction function of oxygen in terms of potential, and NHPI continues to function as an oxygen reduction catalyst over a long period of time. These four-electron reduction reactions of oxygen occur at room temperature and normal pressure, and exhibit low temperature activity superior to that of platinum. Therefore, it is possible to reduce the amount of platinum used in the electrode catalyst of a fuel cell.

Further, the compound represented by the general formula (II) has the following general formula (V) having a 6-membered N-substituted cyclic imide skeleton.

(In the formula, X represents an oxygen atom or a hydroxyl group. R1 to R6 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a cycloalkyl group, a hydroxyl group, an alkoxy group, a carboxyl group, a substituted oxy group) Represents a carbonyl group, an acyl group or an acyloxy group, and at least two of R1 to R6 may be bonded to each other to form a double bond or an aromatic or non-aromatic ring. At least one of them may have an N-substituted cyclic imide group). In the N-substituted cyclic imide skeleton, both the 5-membered ring and the 6-membered ring are hydrolyzed as shown in the following formula (18) and the following formula (19), but the 6-membered ring is more hydrolyzed than the 5-membered ring. Slow and highly resistant to hydrolysis.

For this reason, when the compound having an N-substituted cyclic imide skeleton is a 6-membered cyclic imide, it can be used many times as a redox catalyst, so that the amount of catalyst used can be further reduced.

  The alkyl group includes, for example, a straight chain having about 1 to 10 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, heptyl, octyl and decyl groups. And a branched alkyl group. Preferred is a lower alkyl group having about 1 to 6 carbon atoms, more preferably about 1 to 4 carbon atoms.

  In addition, examples of the aryl group include a phenyl group and a naphthyl group, and examples of the cycloalkyl group include a cyclopentyl, cyclohexyl, and cyclooctyl groups. Examples of the alkoxy group include about 1 to 10 carbon atoms, preferably about 1 to 6 carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, t-butoxy, pentyloxy, and hexyloxy groups, and more preferably about 1 to 6 carbon atoms. Is a lower alkoxy group having about 1 to 4 carbon atoms.

  As the alkoxycarbonyl group, for example, the carbon number of the alkoxy moiety such as methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, t-butoxycarbonyl, pentyloxycarbonyl, hexyloxycarbonyl group and the like is 1 About 10 to 10 alkoxycarbonyl groups. A lower alkoxycarbonyl group having preferably about 1 to 6 carbon atoms, more preferably about 1 to 4 carbon atoms, is preferable.

  Examples of the acyl group include acyl groups having about 1 to 6 carbon atoms such as formyl, acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl, and pivaloyl groups.

  In the compound represented by the general formula (V), at least two of R1 to R6 may be bonded to each other to form a double bond, an aromatic ring, or a non-aromatic ring. Among them, the aromatic ring or the non-aromatic ring preferably forms any one of 5 to 12-membered rings, more preferably about 6 to 10-membered rings. It may be a heterocycle or a fused heterocycle. Examples of such a ring include a non-aromatic hydrocarbon ring such as a cycloalkane ring typified by a cyclohexane ring, a cycloalkene ring such as a cyclohexene ring, and a bridged hydrocarbon ring typified by a 5-norbornene ring. And aromatic rings such as non-aromatic bridged rings, benzene rings, and naphthalene rings. In addition, these rings may have a substituent.

  Next, FIG. 4 shows examples of other compounds contained in the electrode composition in the present embodiment, and shows the redox mechanism of the compounds. Here, as a representative example of the compound represented by the general formula (V), N-hydroxyglutaric acid imide (NHGI), in which R1 to R6 are all hydrogen atoms and has a reversible redox cycle, Activation mechanism, oxygen reduction mechanism, and reaction with protons. When NHGI is oxidized, it becomes glutaric imide N-oxyl (GINO). NHGI and GINO have an oxidation-reduction potential of 1.39 [V] as shown in the following equations (20) and (21).

_{^{NHGI → GINO + H + + e}} - E 0 = 1.39 [V] ··· formula (20)
GINO + H ⁺ + e ⁻ → NHGI E ₀ = 1.39 [V] (21)
The reaction represented by the above formula (2) is a complex reaction composed of a plurality of elementary reactions represented by the following formulas (22) to (26).

NHGI + O ₂ → GINO + · OOH Formula (22)
NHGI + · OOH → GINO + H ₂ O ₂ Formula (23)
NHGI + H ₂ O ₂ → GINO + H ₂ O + · OH Formula (24)
NHGI + .OH → GINO + H ₂ O Formula (25)
4PINO + 4H ⁺ + 4e ⁻ → 4GINO (formula 26)
The oxygen molecule in the air is called triplet oxygen, and the ground state is a triplet radical molecule. As shown in the formula (22), hydrogen is easily extracted from the N-hydroxyl group of NHGI at room temperature and normal pressure, GINO and peroxy radical (.OOH) are generated. The peroxy radical has a high reduction potential of 1.50 [V] and flies to the active species more than oxygen. Therefore, hydrogen is extracted from other NHGI as shown in the equation (23).

  In addition, as shown in the following formula (27), the peroxy radical is hydrogen peroxide.

OOH + H ⁺ + e ⁻ → H ₂ O ₂ E ₀ = 1.50 [V] (27)
Although hydrogen peroxide is not a radical, it is reactive, has a high reduction potential of 1.77 [V], and is a species that is more active than oxygen. Therefore, as shown in formula (24), hydrogen is more hydrogen than other NHGI. Pull out an atom. Hydrogen peroxide from which hydrogen has been extracted generates water and hydroxy radicals (.OH) as shown in the following formula (28).

H ₂ O ₂ + H ⁺ + e ⁻ → H ₂ O + · OH Formula (28)
Since this hydroxy radical is a species that does not have a large reduction potential of 2.85 [V] and is active, it draws hydrogen from NHGI and generates GINO and water as shown in formula (22). As described above, the four-electron reduction of oxygen proceeds by the elementary reactions of the formulas (22) to (25), and four molecules of GINO are generated. GINO is also a species that has been actively activated, and as shown in Equation (26), it receives electrons (e ⁻ ) from the positive electrode of the fuel cell in cooperation with protons and is regenerated into NHGI.

  In addition, when the redox potential of NHGI was measured in 1 [M] sulfuric acid aqueous solution by SCE, a cyclic voltammogram almost similar to FIG. 3 was obtained, and the redox potential of NHGI under this condition was around 1.15 [V]. Exists. When corrected to NHE, it is 1.39 [V]. Due to this potential, the oxidation-reduction potential of NHGI is slightly higher than the oxidation-reduction potential of oxygen, but it is a level that sufficiently acts as a reducing agent. NHGI is a compound that functions reversibly as an oxidizing agent or a reducing agent, and hydrogen and It is shown that the compound has a redox cycle that acts as an oxidant at a potential higher than the redox potential of hydrogen ions. Thus, NHGI has a 4-electron reduction function of oxygen in terms of potential, and NHGI continues to function as an oxygen reduction catalyst for a long time. These four-electron reduction reactions of oxygen occur at room temperature and normal pressure, and exhibit low temperature activity superior to that of platinum. Therefore, it is possible to reduce the amount of platinum used in the electrode catalyst of a fuel cell. NHGI is a 6-membered cyclic imide, and has a slower hydrolysis and higher hydrolysis resistance than a 5-membered ring. For this reason, when the compound having an N-substituted cyclic imide skeleton is a 6-membered cyclic imide, it can be used as a redox catalyst for a longer period of time, so that the amount of catalyst used can be further reduced. .

In addition, the compound represented by the general formula (V) is preferably represented by the following general formula (VIa) or (VIb) from the viewpoints of stability and durability of the compound.

(Wherein R7 to R12 are the same or different and each represents a hydrogen atom, an alkyl group, a hydroxyl group, an alkoxyl group, a carboxyl group, an alkoxycarbonyl group, an acyl group, a nitro group, a cyano group, or an amino group). A compound is preferred.

  Furthermore, the compound represented by the general formula (V), (VIa) or (VIb) is N-hydroxyglutaric acid imide, N-hydroxy-1,8-naphthalenedicarboxylic imide, N-hydroxy-1,8-decalin. Dicarboxylic acid imide, N, N′-dihydroxy-1,8; 4,5-naphthalene tetracarboxylic acid imide, N, N′-dihydroxy-1,8; 4,5-decalin tetracarboxylic acid imide and N, N ′ , N ″ -trihydroxyisocyanuric acid is preferably at least one imide compound (6-membered imide ring) selected from the group consisting of.

Further, the compound represented by the general formula (I) is represented by the following general formula (VII)

(Wherein R13 and R14 are an alkyl group or an alkyl group partially substituted with an arbitrary group, and R13 and R14 may be chain, cyclic or branched. R13 and R14 are bonded to each other. It may form a ring and may contain oxygen and nitrogen atoms). When the compound represented by the general formula (VII) is used, the redox potential is low and the oxygen reduction reaction is further promoted. In the compound represented by the general formula (VII), examples of the substituents R13 and R14 include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, Examples thereof include a linear or branched alkyl group having about 1 to 10 carbon atoms such as a decyl group. Preferred is a lower alkyl group having about 1 to 6 carbon atoms, more preferably about 1 to 4 carbon atoms.

Further, the compound represented by the general formula (VII) is represented by the following general formula (VIII)

(Wherein R13 to R16 are an alkyl group or an alkyl group partially substituted with an arbitrary group, and R13 to R16 may be a chain, a ring, or a branch. Also, R13 and R14 Or R15 and R16 may be bonded to each other to form a ring, which may contain oxygen and nitrogen atoms). In the compound represented by the general formula (VII), examples of the substituents R13 to R16 include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, Examples thereof include a linear or branched alkyl group having about 1 to 10 carbon atoms such as a decyl group. Preferred is a lower alkyl group having about 1 to 6 carbon atoms, more preferably about 1 to 4 carbon atoms.

Further, the compound represented by the general formula (VIII) is represented by the following general formula (IX)

In the formula, ring Y2 is preferably a compound represented by R13 and R14 which are bonded to form either a 5-membered ring or a 6-membered ring. Examples of such a ring include, for example, a non-aromatic hydrocarbon ring such as a cycloalkane ring typified by a cyclohexane ring, a cycloalkene ring typified by a cyclohexene ring, and a bridged type typified by a 5-norbornene ring. Non-aromatic bridged rings such as hydrocarbon rings, aromatic rings such as benzene rings and naphthalene rings are included. In addition, these rings may have a substituent.

Further, the compound represented by the general formula (IX) is represented by the following general formula (X)

(Wherein, Z is a kind of substitution selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some groups may be chain, cyclic, or branched, And may contain oxygen and nitrogen atoms, and when Z is an aryl group, it may be an aryl group partially substituted with any group, and may contain oxygen and nitrogen atoms). It is preferable that Since the compound represented by the general formula (X) is hardly hydrolyzed, it can be used for a long time when used as a redox catalyst, and the amount of the catalyst used can be further reduced.

  In the substituent Z, the alkyl group includes an alkyl group having about 1 to 6 carbon atoms among the same alkyl groups as those described above, and examples of the aryl group include a phenyl group and a naltyl group. As the alkoxy group, an alkoxy group having about 1 to 6 carbon atoms is particularly included among the same alkoxy groups as the above alkyl group, and examples of the carboxyl group include a carboxyl group having about 1 to 4 carbon atoms. As the alkoxycarbonyl group, for example, the carbon number of the alkoxy moiety such as methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, t-butoxycarbonyl, pentyloxycarbonyl, hexyloxycarbonyl group and the like is 1 About 10 to 10 alkoxycarbonyl groups. A lower alkoxycarbonyl group having preferably about 1 to 6 carbon atoms, more preferably about 1 to 4 carbon atoms, is preferable.

  One example of the compound represented by the general formula (X) is TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl). Examples of compounds represented by TEMPO and general formula (X) are shown in FIG. TEMPO shown in FIG. 5 (i) is an N-hydroxyimide derivative having a reversible redox cycle, and ultimately reduces oxygen to water.

In addition, the compound represented by the general formula (IX) is represented by the following general formula (XI)

(Wherein, Z is a kind of substitution selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some groups may be chain, cyclic, or branched, And may contain oxygen and nitrogen atoms, and when Z is an aryl group, it may be an aryl group partially substituted with any group, and may contain oxygen and nitrogen atoms). The compound represented by the general formula (IX) may be represented by the following general formula (XII):

(Wherein, Z is a kind of substitution selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some groups may be chain, cyclic, or branched, And may contain oxygen and nitrogen atoms, and when Z is an aryl group, it may be an aryl group partially substituted with any group, and may contain oxygen and nitrogen atoms). It may be. Since these compounds are also difficult to hydrolyze like the compounds represented by the general formula (X), they can be used for a long time when used as a redox catalyst, and the amount of catalyst used can be further reduced. Become. When the compound is represented by general formula (XI) or general formula (XII), the same substituents as those of the compound represented by general formula (X) can be used.

  Examples of compounds represented by general formula (XI) and general formula (XII) are shown in FIGS. Examples of compounds represented by the general formula (XI) and the general formula (XII) include PROXYL (2,2,5,5-tetramethylpyrrolidine-1-oxyl) and DOXYL (4,4-dimethyloxazolidine-3- Oxyl). These compounds also have a reversible redox cycle similar to TEMPO and reduce oxygen to water.

  FIG. 9 shows a redox mechanism in another example of a compound contained in the electrode composition in the present embodiment. Here, as a representative example of the above compound, TEMPO is taken as an example to show an oxygen activation mechanism and an oxygen reduction mechanism. TEMPO is oxidized and reduced by the elementary reactions shown in the following formulas (29) and (30), and its oxidation-reduction potential is 0.81 [V].

_{^{TEMPO → TEMPO + + e - E}} 0 = 0.81 [V] ··· formula (29)
TEMPO ⁺ + e ⁻ → TEMPO E ₀ = 0.81 [V] (30)
The oxygen reduction mechanism is a complex reaction composed of a plurality of elementary reactions represented by the following formulas (31) to (36).

TEMPO + O ₂ → TEMPO ⁺ + O ₂ ⁻ (31)
O ₂ ⁻ + H ⁺ → HOO... (32)
TEMPO + · OOH + H ⁺ → TEMPO ⁺ + H ₂ O ₂ Formula (33)
TEMPO + H ₂ O ₂ + H ⁺ → TEMPO ⁺ + H ₂ O + · OH Formula (34)
TEMPO + .OH + H ⁺ → TEMPO ⁺ + H ₂ O Formula (35)
4TEMPO ⁺ + 4e ⁻ → 4TEMPO Expression (36)
Oxygen molecules in the air are called triplet oxygen, and the ground state is a triplet radical molecule. As shown in formula (31), electrons are exchanged between TEMPO and oxygen at room temperature and pressure. And forms a charge transfer complex (charge transfer complex = CT complex). At this time, since the nitrogen atom of TEMPO is quaternized to N ⁺ , TEMPO becomes TEMPO ⁺ and oxygen is activated in the form of superoxide (O ₂ ⁻ ). The activated superoxide rapidly reacts with hydrogen ions to generate peroxy radicals (.OOH). The peroxy radical has a high reduction potential of 1.50 [V] and flies to the active species more than oxygen. Therefore, hydrogen peroxide is generated by the reaction shown in Formula (33). Although hydrogen peroxide is not a radical, it is reactive in the presence of a catalyst, has a reduction potential of 1.77 [V], and is a species that has been activated more than oxygen. It receives electrons from TEMPO and generates water and hydroxy radicals (.OH). TEMPO is activated to TEMPO ⁺ .

The generated hydroxy radical has a large reduction potential of 2.85 [V] and, of course, is a species that is actively flying, and therefore receives electrons from another TEMPO as shown in formula (35) to generate water. As a result of the elementary reactions shown in the equations (31) to (35), the four-electron reduction of oxygen proceeds and four molecules of TEMPO ⁺ are generated. TEMPO ^{+ is} also a species that has been activated. As shown in Equation (36), electrons (e ⁻ ) are received from the positive electrode of the fuel cell and regenerated into TEMPO.

  In addition, when the redox potential of TEMPO was measured in 1 [M] sulfuric acid aqueous solution by SCE, the cyclic voltammogram shown in FIG. 10 was obtained, and the redox potential of TEMPO in this condition was around 0.57 [V]. To do. When corrected to NHE, it is 0.81 [V]. Due to this potential, the redox potential of TEMPO is slightly higher than the redox potential of oxygen, but at a level that sufficiently acts as a reducing agent. TEMPO is a compound that functions reversibly as an oxidizing agent or a reducing agent, and hydrogen and It is shown that the compound has a redox cycle that acts as an oxidant at a potential higher than the redox potential of hydrogen ions. Thus, TEMPO has a 4-electron reduction function of oxygen in terms of potential, and TEMPO continues to function as an oxygen reduction catalyst for a long time. These four-electron reduction reactions of oxygen occur at room temperature and normal pressure, and exhibit low temperature activity superior to that of platinum. Therefore, it is possible to reduce the amount of platinum used in the electrode catalyst of a fuel cell. Moreover, since TEMPO does not hydrolyze, it can be used for a long time when used as a redox catalyst, and the amount of catalyst used can be further reduced.

  When the above compound is added as a redox catalyst, it is added in such a range that the concentration of the oxygen reducing catalyst present in the platinum-supported carbon film formed after the drying treatment is 0.001 to 30 [wt%]. It is preferable. If it is 0.001 [wt%] or less, it is considered that the effect of the oxygen reduction catalyst is not sufficiently exhibited. If it is 30 [wt%] or more, the power generation performance decreases due to catalyst poisoning, the ion conductivity decreases, and the film strength changes. Influence, induction of new side reaction, etc. are considered, which is not preferable. Further, when added, it is important that this compound is uniformly dispersed in the platinum-supported carbon. For this reason, the solvent in which the compound is dispersed can be water or an organic solvent as long as it increases the solubility of the compound, and may be a mixed solution of water and an organic solvent.

  Although the compounds shown above have a sufficient function as an oxygen reduction catalyst even when used alone, if necessary, such as increasing the reaction rate, a co-catalyst that assists the exchange of electrons with other electrodes may be used in combination. Also good. Applicable materials include lanthanoid elements, V (vanadium), Mo (molybdenum), W (tungsten), Fe (iron), Ru (ruthenium), Co (cobalt), Rh (rhodium), Ni (nickel), Cu (Copper), Ag (silver), Ir (iridium), Pd (palladium), Pt (platinum), Au (gold), or an oxide, organic acid salt, inorganic acid salt containing these elements, It is possible to use at least one selected from the group consisting of halides, complexes, heteropolyacids and heteropolyacid salts, or a combination of two or more.

  The electrode composition according to the embodiment of the present invention is used in such a manner that the above compound is supported on a carrier. When applied as an electrode for a fuel cell, it is preferable to use conductive carbon black such as acetylene black or nanostructure carbon typified by carbon nanotube as a carrier. As a method for impregnating the carrier, a solution obtained by dissolving the above compound in a solvent is poured onto the carrier, the catalyst is adsorbed on carbon, and then the carbon is filtered and dried.

Thus, in the electrode composition according to the embodiment of the present invention, it acts as a reducing agent at a potential lower than the oxidation-reduction potential of oxygen, and the oxidizing agent at a potential higher than the oxidation-reduction potential of hydrogen and hydrogen ions. By containing a compound having a redox cycle that acts as an oxygen reduction catalyst, this compound acts as a reducing agent at a potential lower than the redox potential of oxygen, and after being oxidized, the redox potential of hydrogen and hydrogen ions It works reversibly as an oxidant at higher potentials. At that time, a four-electron reduction reaction in which proton (H ⁺ ) and molecular oxygen (O ₂ ) are reacted to reduce to water is promoted. Thus, since this compound functions as a four-electron reduction reaction catalyst that promotes the reduction of oxygen, the amount of platinum used in the electrode composition can be reduced. In addition, this compound acts as a redox catalyst by repeating the redox cycle and can be used as a catalyst many times, so that the amount of catalyst used can be further reduced.

  Hereinafter, although the electrode composition which concerns on this invention is demonstrated more concretely by Example 1- Example 20 and Comparative Example 1- Comparative Example 4, the scope of the present invention is not limited to these. These examples are for examining the effectiveness of the electrode composition according to the present invention, and show examples of electrode compositions prepared with different raw materials.

Tables 1 and 2 show the compounds used and their redox potentials. Here, the oxidation-reduction potential of the compound used in each example was measured using glassy carbon as a working electrode, platinum as a counter electrode, a saturated calomel electrode (SCE) as a reference electrode, and 1 [M] sulfuric acid as an electrolyte. . In order to match the redox potential of each substance, the obtained value was corrected to the standard potential E ⁰ (NHE) by the formula shown in the following formula (37).

E ⁰ (NHE) = E (SCE) +0.24 [V] Expression (37)

Each sample was prepared by the following method.

<Preparation of sample>
Example 1
As platinum-supporting carbon, 20 wt% Pt / Vulcan XC-72 manufactured by Cabot was used. First, a 0.5 [mM] NHPI aqueous solution as an oxygen reduction catalyst was added to platinum-supporting carbon and stirred sufficiently, and then allowed to stand for 12 [hours] to impregnate platinum-supporting carbon with NHPI. Thereafter, the platinum-supported carbon impregnated with NHPI was recovered by filtration to obtain an electrode composition. Next, the obtained electrode composition was applied to one surface on the air electrode side of the Nafion (registered trademark) film so as to be 1 [mg / cm ² ], and platinum-supported carbon not impregnated with NHPI Was applied to the other surface on the fuel electrode side so as to be 1 [mg / cm ² ] to produce a membrane-electrode assembly (MEA). Then, the formed MEA was incorporated into a single cell and used for evaluation as a single cell for PEFC. In addition, in order to evaluate the electrode of this invention and the composition for electrodes, the single cell was adjusted so that it might become a 5 [cm < ² >] single cell. Further, a Nafion (registered trademark) 117 membrane (thickness: 175 [μm]) manufactured by DuPont was used as the polymer solid electrolyte membrane used for MEA.

(Example 2)
As an oxygen reduction catalyst, a 0.5 [mM] N-hydroxymaleimide aqueous solution was used in place of the NHPI aqueous solution, and the same treatment as in Example 1 was carried out as Example 2.

(Example 3)
As an oxygen reduction catalyst, a 0.5 [mM] N-hydroxysuccinimide aqueous solution was used instead of the NHPI aqueous solution, and the same treatment as in Example 1 was carried out as Example 3.

Example 4
As an oxygen reduction catalyst, an aqueous solution of 0.5 [mM] N-hydroxytrimellitic acid imide was used instead of the NHPI aqueous solution, and the same treatment as in Example 1 was performed as Example 4.

(Example 5)
As an oxygen reduction catalyst, a 0.5 [mM] N, N′-dihydroxypyromellitic imide aqueous solution was used in place of the NHPI aqueous solution and treated in the same manner as in Example 1 to give Example 5.

(Example 6)
As an oxygen reduction catalyst, a 0.5 [mM] N-hydroxyglutarimide (NHGI) aqueous solution was used instead of the NHPI aqueous solution, and the same treatment as in Example 1 was carried out as Example 2.

(Example 7)
An example in which a 0.5 [mM] N-hydroxy-1,8-naphthalenedicarboxylic imide (NHNDI) aqueous solution was used as the oxygen reduction catalyst in place of the NHPI aqueous solution and the same treatment as in Example 1 was performed. It was set to 7.

(Example 8)
An example in which a 0.5 [mM] N-hydroxy-1,8-decalindicarboxylic acid imide (NFDI) aqueous solution was used as the oxygen reduction catalyst instead of the NHPI aqueous solution and the same treatment as in Example 1 was performed. It was set to 8.

Example 9
As an oxygen reduction catalyst, 0.5 [mM] N, N′-dihydroxy-1,8; 4,5-naphthalenetetracarboxylic imide (NHNTI) aqueous solution was used instead of NHPI aqueous solution, and the same as in Example 1 The treated sample was designated as Example 9.

(Example 10)
As an oxygen reduction catalyst, 0.5 [mM] N, N′-dihydroxy-1,8; 4,5-decalintetracarboxylic imide (NHDTI) aqueous solution was used instead of the NHPI aqueous solution, and the same as in Example 1 was used. The treated sample was designated as Example 5.

(Example 11)
As the oxygen reduction catalyst, a 0.5 [mM] N, N ′, N ″ -trihydroxyisocyanuric acid (THICA) aqueous solution was used instead of the NHPI aqueous solution, and the same treatment as in Example 1 was performed. Example 11 was used.

(Example 12)
As an oxygen reduction catalyst, a TEMPO aqueous solution of 0.5 [mM] shown in FIG. 5 (i) was used instead of the NHPI aqueous solution, and Example 12 was subjected to the same treatment as in Example 1.

(Example 13)
As an oxygen reduction catalyst, an aqueous solution of 0.5 [mM] 4-hydroxy-TEMPO shown in FIG. 5 (ii) was used instead of the NHPI aqueous solution, and the same treatment as in Example 1 was performed as Example 13. .

(Example 14)
As an oxygen reduction catalyst, an aqueous solution of 0.5 [mM] 4-carboxy-TEMPO shown in FIG. 5 (iii) was used instead of the NHPI aqueous solution, and the same treatment as in Example 1 was carried out as Example 14. .

(Example 15)
As an oxygen reduction catalyst, the same treatment as in Example 1 was performed using a 0.5 [mM] 3-carbamoyl-PROXYL aqueous solution shown in FIG. .

(Example 16)
As the oxygen reduction catalyst, a 0.5 [mM] 3-carboxy-PROXYL aqueous solution shown in FIG. 6 (xiv) was used in place of the NHPI aqueous solution, and the same treatment as in Example 1 was carried out as Example 16. .

(Example 17)
Example 1 A 0.5 [mM] 3-carbamoyl-2,2,5,5-tetramethylpyrrolin-1-yloxy aqueous solution shown in FIG. 6 (xv) was used as the oxygen reduction catalyst instead of the NHPI aqueous solution. Example 17 was subjected to the same treatment as in Example 17.

(Example 18)
As an oxygen reduction catalyst, a 0.5 [mM] 3-di-t-butyl nitroxide aqueous solution shown in FIG. 6 (xx) was used in place of the NHPI aqueous solution, and the same treatment as in Example 1 was performed. It was.

(Comparative Example 1)
The platinum-supported carbon used in Example 1 was not impregnated with NHPI and was designated as Comparative Example 1. That is, MEA is formed by applying platinum-supported carbon so that the fuel electrode side and the air electrode side of the Nafion (registered trademark) membrane are 1 [mg / cm ² ], respectively, and the formed MEA is placed in a single cell. Built and used for evaluation.

(Comparative Example 2)
Comparative Example 2 was obtained by using 25 wt% Pt / Vulcan XC-72 as the platinum-supporting carbon and performing the same treatment as Comparative Example 1.

(Comparative Example 3)
Comparative Example 3 was obtained by using 30 wt% Pt / Vulcan XC-72 as the platinum-supporting carbon and performing the same treatment as Comparative Example 1.

  Here, the single cell incorporating the MEA obtained by the above method was evaluated by the following power generation test.

<Power generation test>
A single cell maintained at a temperature of 70 [° C] with hydrogen gas (atmospheric pressure) humidified at 70 [° C] at the fuel electrode and oxygen gas (atmospheric pressure) humidified at 70 [° C] at the air electrode. And held for 5 minutes in an open circuit state. Thereafter, a gas having a flow rate of 300 [dm ³ / min] was passed through the single cell, the open circuit voltage was measured, and the change in oxygen overvoltage was measured. Further, a current-potential curve was measured while flowing a gas having a flow rate of 300 [dm ³ / min] through the single cell. As for the power generation characteristics, superiority or inferiority was determined based on the potential when a current of 1 [mA / cm ² ] was passed.

The initial values of the current-potential curves of Example 1 and Comparative Example 1 are shown in FIG. Tables 3 to 5 show the open circuit voltages in Examples 1 to 18 and Comparative Examples 1 to 3, and the results of the power generation test.

  When the open circuit voltage was compared between Example 1 and Comparative Example 1, the open circuit voltage of Example 1 was about 10% higher. This was thought to be because the oxygen overvoltage decreased and the reaction of the air electrode was activated and oxygen reduction was promoted. This phenomenon was observed not only in Example 1 but also in any of Examples 1 to 18 in which an oxygen reduction catalyst was added, and 5 to 10 [ %] Became higher.

In the power generation test, the voltage when power was generated at a current density of 1 [mA / cm ³ ] was used as a guide. In Example 1, the voltage when power was generated at a current density of 1 [mA / cm ³ ] was 0.6 [V] or more, and it was found that a sufficient voltage was obtained. Also. From the comparison between Example 1 and Comparative Example 1, it is considered that Example 1 to which NHPI is added has a higher circuit voltage at the time of discharge, the reaction of the air electrode is activated, and oxygen reduction is promoted. It was. Further, when Comparative Example 3 using 30 wt% Pt / Vulcan XC-72 and Example 1 were compared, the circuit voltage at the time of discharge in Example 1 slightly decreased compared to Comparative Example 3 carrying a large amount of platinum. However, compared with Comparative Example 2 using 25 wt% Pt / Vulcan XC-72, Example 1 exceeded the circuit voltage during discharge. From these results, it was suggested that the amount of platinum added can be reduced by adding NHPI.

  Further, from the results of Examples 1 to 18, even when a compound different from NHPI was used as the catalyst as the oxygen reduction catalyst, the four-electron reduction reaction of oxygen at the air electrode was promoted, and the amount of platinum added could be reduced. It was suggested that there is. Note that THICA used in Example 11 is effective as an oxygen reduction catalyst because of its small molecular weight and trifunctionality, and the open circuit voltage and discharge voltage were higher than those of the other examples.

Next, FIG. 12 shows the initial value of the current-potential curve and the power generation state when a fuel cell was fabricated in Example 1 in which platinum-supported carbon was impregnated with NHPI as an oxygen reduction catalyst and Comparative Example 1 with only platinum-supported carbon. The criteria for superiority or inferiority are shown. As shown in FIG. 12, when NHPI, which is an oxygen reduction catalyst, is impregnated in platinum-supported carbon, the voltage when power is generated at a current density of 1 [mA / cm ³ ] is compared to the case of platinum-supported carbon alone. It was found that a high voltage could be obtained.

  In each of Examples 1 to 18, a method of impregnating platinum-supported carbon with an oxygen reduction catalyst as an aqueous solution of 0.5 [mM] was performed, but the concentration of the aqueous solution of the oxygen reduction catalyst is not particularly limited. Absent. When used, it is important that this compound is uniformly dispersed in the platinum-supported carbon. Here, water is used as a solvent, but an organic solvent can be used as needed as long as the solvent increases the solubility of the oxygen reduction catalyst. The concentration of the oxygen reduction catalyst present in the platinum-supported carbon formed after the drying treatment is preferably in the range of 0.001 to 30 [wt%]. If it is 0.001 [wt%] or less, it is considered that the effect of the oxygen reduction catalyst is not sufficiently exhibited. If it is 30 [wt%] or more, the power generation performance decreases due to catalyst poisoning, the ionic conductivity decreases, and the film strength changes. It is not preferable because of the influence of the above and the induction of a new side reaction.

<Stability test>
Regarding the stability of the compound, each compound was dissolved in 0.5 [M] sulfuric acid at a concentration of 1.0 [mM], and then maintained at 80 [° C.], and the disappearance state of the compound was determined by liquid chromatography. Quantified.

  FIG. 12 shows a graph of the results of the stability test of NHPI and TEMPO. As shown in FIG. 12, NHPI was hydrolyzed by the reaction shown in FIG. 13 (a), so the concentration decreased over time, and the NHPI concentration after 96 hours was reduced to about 0.6 [mM]. On the other hand, the concentration of TEMPO hardly changed even after 96 hours. As shown in FIGS. 13B and 13C, the PROXYL compound, the TEMPO compound, and the DTBN do not show the hydrolysis seen in the imide compound, and the disappearance amount of the compound is less than that of the imide compound. I understood.

<Single cell accelerated durability test>
An open circuit standing test at a cell temperature of 90 [° C.] was performed, and OCV (open circuit voltage) was monitored to examine the durability of the single cell by adding a compound to the electrode. Hydrogen gas humidified to 30 [%] was supplied to the fuel electrode and oxygen gas humidified to 30 [%] was supplied to the air electrode at a flow rate of 500 [ml / min], and the OCV was measured with the gas flowing. .

(Example 19)
TEC10E50E manufactured by Tanaka Kikinzoku was used as the platinum-supporting carbon, and 5 wt% Nafion (registered trademark) solution manufactured by DuPont was used as the electrolyte binder. After the platinum-supporting carbon was sufficiently moistened with water, an electrolyte binder was added, and isopropyl alcohol was added to disperse the platinum-supporting carbon and the electrolyte binder in isopropyl alcohol. Thereafter, the mixture was mixed for 3 hours with a homogenizer and homogenized, and then defoamed to obtain a catalyst ink. Thereafter, the catalyst ink was applied to a Teflon (registered trademark) sheet so that the platinum amount was 0.4 [mg / cm ³ ] to obtain a catalyst sheet A.

Similarly, TEC10E50E made by Tanaka Kikinzoku as platinum-supported carbon and 5 wt% Nafion (registered trademark) solution made by DuPont as electrolyte binder were used. wt%] NHPI and isopropyl alcohol were added to disperse platinum-supported carbon, electrolyte binder and NHPI in isopropyl alcohol. Thereafter, the mixture was mixed for 3 hours with a homogenizer and homogenized, and then defoamed to obtain a catalyst ink. Thereafter, the catalyst ink was applied to a Teflon (registered trademark) sheet so that the platinum amount was 0.4 [mg / cm ³ ] to obtain a catalyst sheet B.

The catalyst sheet A is arranged on the air electrode side of the Nafion (registered trademark) 211 membrane, the catalyst sheet B is arranged on the fuel electrode side, and hot pressing is performed at 2 [MPa], 132 [° C.], 10 [min] for the catalyst sheet A, Each B was transferred to a Nafion (registered trademark) 211 membrane to form an electrode catalyst layer, thereby obtaining a CCM (catalyst coated membrane). CCM was sandwiched between gas diffusion layers, and then sandwiched between a separator and a current collector plate to produce a single cell with a catalyst area of 5 × 5 [cm ² ].

(Example 20)
A catalyst sheet A produced in the same manner as in Example 19 is disposed on the anode side (fuel electrode side) of the Nafion (registered trademark) 211 membrane, and the catalyst sheet B is disposed on the cathode side (air electrode side). The catalyst sheets A and B were each hot-pressed at 132 [° C.] and 10 [minutes] to transfer to a Nafion (registered trademark) 211 film to form an electrode catalyst layer to obtain a CCM (catalyst coated membrane). CCM was sandwiched between gas diffusion layers, and then sandwiched between a separator and a current collector plate to produce a single cell with a catalyst area of 5 × 5 [cm ² ].

(Comparative Example 4)
TEC10E50E manufactured by Tanaka Kikinzoku was used as the platinum-supporting carbon, and 5 wt% Nafion (registered trademark) solution manufactured by DuPont was used as the electrolyte binder. After the platinum-supporting carbon was sufficiently moistened with water, an electrolyte binder was added, and isopropyl alcohol was added to disperse the platinum-supporting carbon and the electrolyte binder in isopropyl alcohol. Thereafter, the mixture was mixed for 3 hours with a homogenizer and homogenized, and then defoamed to obtain a catalyst ink. Thereafter, the catalyst ink was applied to a Teflon (registered trademark) sheet so that the amount of platinum was 0.4 [mg / cm ³ ] to prepare two catalyst sheets.

The catalyst sheet is arranged on the fuel electrode side and the air electrode side of the Nafion (registered trademark) 211 membrane, respectively, and hot pressed at 2 [MPa], 132 [° C.], 10 [minutes] to form the catalyst sheet Nafion (registered trademark) The film was transferred to a 211 membrane to form an electrode catalyst layer, and CCM (catalyst coated membrane) was obtained. CCM was sandwiched between gas diffusion layers, and then sandwiched between a separator and a current collector plate to produce a single cell with a catalyst area of 5 × 5 [cm ² ].

  FIG. 14 shows the results of the single cell accelerated durability test. In any of Example 19, Example 20, and Comparative Example 4, the OCV was about 0.95 [V] after the start of the test, and the OCV decreased to about 0.9 [V] after 5 hours. In Comparative Example 4 in which NHPI was not added to the electrode catalyst layer, the OCV decreased after 18 hours from the start of the test, and although not shown in FIG. On the other hand, in Example 19 in which NHPI was added to the fuel electrode side, the OCV was maintained at about 0.9 [V] until 29 hours passed, and power generation continued until 80 hours. In Example 20 in which NHPI was added to the air electrode side, the OCV was maintained at about 0.9 [V] until 22 hours passed, and power generation continued until 50 hours. Thus, the durability of the single cell was improved by adding NHPI to the electrode catalyst layer. This is because NHPI acts as a redox catalyst by repeating the redox cycle, and by removing the redox cycle, intermediate organisms such as hydrogen peroxide generated at the electrode are removed, and this phenomenon improves the durability time. It is thought that it was connected. This effect was more noticeable in Example 19 in which NHPI was added to the fuel electrode side. Thus, the combined use of the compound having a redox cycle and platinum improves the power generation durability time.

  In addition, in Example 19 and Example 20, NHPI was added so that it might become 1.8 [wt%], However, The addition amount of NHPI is not specifically limited. In addition, any compound having an oxidation-reduction action is not limited to NHPI, and other compounds can be used. When used, it is important that this compound is uniformly dispersed in the platinum-supported carbon. Here, isopropyl alcohol is used as a solvent for dispersing the compound. However, the solvent is not limited to isopropyl alcohol as long as it increases the solubility of the oxygen reduction catalyst, and other organic solvents can be used. The concentration of the oxygen reduction catalyst present in the platinum-supported carbon formed after the drying treatment is preferably in the range of 0.001 to 30 [wt%]. If it is 0.001 [wt%] or less, it is considered that the effect of the oxygen reduction catalyst is not sufficiently exhibited. If it is 30 [wt%] or more, the power generation performance decreases due to catalyst poisoning, the ionic conductivity decreases, and the film strength changes. It is not preferable because of the influence of the above and the induction of a new side reaction.

  As described above, in the PEFC type fuel cell, by using the electrode composition containing the above compound together with platinum, the amount of platinum used in the electrode composition can be reduced in the electrode composition and the electrode. I found it possible. It was also found that this compound acts as a redox catalyst by repeating the redox cycle and can be used as a catalyst many times, so that the amount of catalyst used can be further reduced.

  In addition, in the electrode containing the composition for electrodes of this invention, it becomes possible to reduce the usage-amount of platinum.

  Furthermore, the air electrode electrode composition having the electrode composition of the present invention or the air electrode electrode having the air electrode electrode composition of the present invention can be used as a fuel cell air electrode. In this case, even in the electrode reaction at the air electrode, the reaction between protons and oxygen is promoted, and the amount of platinum used can be reduced.

  In addition, the electrode composition according to the present invention can be used as an electrolyte membrane of a polymer electrolyte fuel cell. In this case, the fuel type is not limited as long as it is a fuel cell using a proton conductive polymer electrolyte membrane, and is not limited to the type of fuel, but is a hydrogen type solid polymer fuel cell, a direct methanol type solid polymer fuel cell, a direct hydrocarbon type. It can be used for any fuel cell such as a solid polymer fuel cell.

  Furthermore, the fuel cell according to the present invention can be used in a fuel cell system using a proton conductive polymer electrolyte membrane, and its application is not limited to a fuel cell vehicle, It can be applied to generation power generation systems, fuel cell home appliances, fuel cell portable devices, and fuel cell transport devices.

  As mentioned above, although the form of this Embodiment was demonstrated, it should not be understood that the description and drawing which make a part of indication of said Embodiment limit this invention. From this disclosure, various alternative embodiments, examples, and operational techniques will be apparent to those skilled in the art.

It is explanatory drawing which shows the oxidation-reduction potential when oxygen, active oxygen, hydrogen, etc. work as an oxidizing agent or a reducing agent. It is a schematic diagram showing the oxygen reduction mechanism in the fuel cell positive electrode of NHPI. It is a cyclic voltammogram in the electrode reaction of NHPI. It is a schematic diagram showing the oxygen reduction mechanism in the fuel cell positive electrode of NHGI. It is an example of the compound contained in the composition for electrodes. It is another example of the compound contained in the composition for electrodes. It is another example of the compound contained in the composition for electrodes. It is another example of the compound contained in the composition for electrodes. It is a schematic diagram showing the oxygen reduction mechanism in the fuel cell positive electrode of TEMPO. It is a cyclic voltammogram in the electrode reaction of TEMPO. It is a schematic diagram showing the initial value of the electric current-potential curve when the fuel cell is produced using the single cell obtained in Example 1 and Comparative Example 1, and the criterion for determining the power generation state superiority. It is a graph showing the result of the stability test of NHPI and NHGI. (A) Reaction formula showing that NHPI is hydrolyzed. (B) It is a figure which shows that PROXYL does not hydrolyze. (C) It is a figure which shows that TEMPO does not hydrolyze. It is a graph showing the result of a single cell accelerated durability test.

Claims (32)

  A compound having a redox cycle that acts as a reducing agent at a potential lower than the oxidation-reduction potential of oxygen and has an oxidation-reduction cycle that acts as an oxidizing agent at a potential higher than the oxidation-reduction potential of hydrogen and hydrogen ions is contained as an oxygen reduction catalyst. An electrode composition.   2. The electrode composition according to claim 1, wherein the standard oxidation-reduction potential of the compound is in the range of 0.00 [V] to 1.40 [V].   2. The electrode composition according to claim 1, wherein the standard redox potential of the compound is in the range of 0.68 [V] to 1.00 [V]. The compound has the following general formula (I)

(Wherein R1 and R2 represent the same or different arbitrary substituents, and X represents an oxygen atom or a hydroxyl group). The composition for electrodes described in the item.   In the general formula (I), R1 and R2 are each a kind of substituent selected from the group consisting of an alkyl group, an aryl group, an alkoxy group and a substituent containing a hydrogen atom, and R1 and R2 are an alkyl group or an alkoxy group. In this case, an alkyl group or an alkoxyl group partially substituted with an arbitrary group, an unsaturated alkyl group or an alkoxy group may be used, and these groups may be chain, cyclic or branched, R1 and R2 may contain oxygen and nitrogen atoms, and when R1 and R2 are aryl groups, they may be aryl groups partially substituted with any group, and may contain oxygen and nitrogen atoms. The electrode composition according to claim 4, wherein the composition is an electrode composition.   6. The electrode according to claim 4 or 5, wherein, in the general formula (I), R1 and R2 are bonded to each other to form a double bond, an aromatic ring, or a non-aromatic ring. Composition. The compound has the following general formula (II)

(Wherein ring Y1 represents a imide compound having a double bond or any one of aromatic or non-aromatic 5- to 12-membered rings). The electrode composition according to claim 6. The compound represented by the general formula (II) is represented by the following general formula (III):

(Wherein R3 and R4 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a cycloalkyl group, a hydroxyl group, an alkoxyl group, a carboxyl group, an alkoxycarbonyl group, or an acyl group. X represents oxygen. The composition for an electrode according to claim 7, which is an imide compound represented by an atom or a hydroxyl group, wherein n represents an integer of 1 to 3.   9. The electrode composition according to claim 8, wherein in the general formula (III), R3 and R4 are bonded to each other to form a double bond, an aromatic ring, or a non-aromatic ring.   In the general formula (III), R3 and R4 are bonded to each other to form any one of aromatic or non-aromatic 5- to 12-membered rings. The composition for electrodes according to 9.   In the general formula (III), R3 and R4 are bonded to each other to form at least one selected from the group consisting of a cycloalkane, a cycloalkene, a bridged hydrocarbon ring, an aromatic ring, and a substituent thereof. The composition for an electrode according to any one of claims 8 to 10, wherein the composition is an electrode composition. The compounds represented by the general formula (III) are represented by the following formulas (IVa) to (IVf):

(Wherein R3 to R6 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group, a hydroxyl group, an alkoxyl group, a carboxyl group, an alkoxycarbonyl group, an acyl group, a nitro group, a cyano group or an amino group, The electrode composition according to any one of claims 8 to 11, wherein n represents an imide compound represented by the following formula:   The compound represented by the general formula (III) includes N-hydroxysuccinimide, N-hydroxymaleimide, N-hydroxyhexahydrophthalimide, N, N′-dihydroxycyclohexanetetracarboxylic imide, N-hydroxyphthalimide, N-hydroxytetrabromophthalimide, N-hydroxytetrachlorophthalimide, N-hydroxyheptimide, N-hydroxyhymic imide, N-hydroxytrimellitic imide, N, N'-dihydroxypyromellit The electrode according to any one of claims 8 to 12, which is at least one imide compound selected from the group consisting of acid imides and N, N'-dihydroxynaphthalenetetracarboxylic imides. Composition. The compound represented by the general formula (II) is represented by the following general formula (V):

(In the formula, X represents an oxygen atom or a hydroxyl group. R1 to R6 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a cycloalkyl group, a hydroxyl group, an alkoxy group, a carboxyl group, a substituted oxy group) Represents a carbonyl group, an acyl group or an acyloxy group, and at least two of R1 to R6 may be bonded to each other to form a double bond or an aromatic or non-aromatic ring. 8. The electrode composition according to claim 7, wherein at least one of the compounds may have an N-substituted cyclic imide group. The compound represented by the general formula (V) is represented by the following formula (VIa) or (VIb)

(Wherein R7 to R12 are the same or different and each represents a hydrogen atom, an alkyl group, a hydroxyl group, an alkoxyl group, a carboxyl group, an alkoxycarbonyl group, an acyl group, a nitro group, a cyano group, or an amino group). The composition for an electrode according to claim 14, which is a compound.   The compound represented by the general formula (V), (VIa), or (VIb) is N-hydroxyglutarimide, N-hydroxy-1,8-naphthalenedicarboxylic imide, N-hydroxy-1,8-decalin. Dicarboxylic acid imide, N, N′-dihydroxy-1,8; 4,5-naphthalene tetracarboxylic acid imide, N, N′-dihydroxy-1,8; 4,5-decalin tetracarboxylic acid imide and N, N ′ The electrode composition according to claim 15, which is at least one imide compound selected from the group consisting of N, N ″ -trihydroxyisocyanuric acid. The compound represented by the general formula (I) is represented by the following general formula (VII)

(Wherein R13 and R14 are an alkyl group or an alkyl group partially substituted with an arbitrary group, and R13 and R14 may be chain, cyclic or branched. R13 and R14 are bonded to each other. The composition for an electrode according to claim 6, wherein the composition is a compound represented by the formula: which may form a ring and may contain oxygen and nitrogen atoms. The compound represented by the general formula (VII) is represented by the following general formula (VIII)

(Wherein R13 to R16 are an alkyl group or an alkyl group partially substituted with an arbitrary group, and R13 to R16 may be a chain, a ring, or a branch. Also, R13 and R14 Or R15 and R16 may be bonded to each other to form a ring, and oxygen and nitrogen atoms may be contained.) The composition for an electrode according to claim 17, object. The compound represented by the general formula (VIII) is represented by the following general formula (IX)

The ring Y2 is a compound represented by the formula: wherein R13 and R14 are bonded to form either a 5-membered ring or a 6-membered ring. Electrode composition. The compound represented by the general formula (IX) is represented by the following general formula (X):

(Wherein, Z is a kind of substitution selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some groups may be chain, cyclic, or branched, And may contain oxygen and nitrogen atoms, and when Z is an aryl group, it may be an aryl group partially substituted with any group, and may contain oxygen and nitrogen atoms). The electrode composition according to claim 19, wherein the composition is an electrode composition. The compound represented by the general formula (IX) is represented by the following general formula (XI)

(Wherein, Z is a kind of substitution selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some groups may be chain, cyclic, or branched, And may contain oxygen and nitrogen atoms, and when Z is an aryl group, it may be an aryl group partially substituted with any group, and may contain oxygen and nitrogen atoms). The electrode composition according to claim 19, wherein the composition is an electrode composition. The compound represented by the general formula (IX) is represented by the following general formula (XII)

(Wherein, Z is a kind of substitution selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some groups may be chain, cyclic, or branched, And may contain oxygen and nitrogen atoms, and when Z is an aryl group, it may be an aryl group partially substituted with any group, and may contain oxygen and nitrogen atoms). The electrode composition according to claim 19, wherein the composition is an electrode composition.   The electrode composition according to any one of claims 1 to 22, further comprising a promoter that promotes oxidation of the compound.   The cocatalyst is an element selected from lanthanoid elements, V, Mo, W, Fe, Ru, Co, Rh, Ni, Cu, Ag, Ir, Pd, Pt and Au, or an oxide containing these elements, organic 24. The electrode composition according to claim 23, which is at least one selected from the group consisting of acid salts, inorganic acid salts, halides, complexes, heteropolyacids, and heteropolyacid salts.   25. The electrode composition according to claim 23 or 24, wherein conductive carbon or nanostructure carbon is used as a carrier supporting the compound and the promoter.   The electrode composition according to claim 25, wherein the conductive carbon is acetylene black, and the nanostructure carbon is a carbon nanotube.   27. An electrode comprising at least one of the electrode compositions according to any one of claims 1 to 26.   An air electrode composition comprising at least one of the electrode compositions according to any one of claims 1 to 26.   An air electrode for a fuel cell comprising the air electrode composition according to claim 28.   A fuel cell comprising the electrode according to claim 27 or the air electrode for a fuel cell according to claim 29.   A fuel cell system comprising the fuel cell according to claim 30.   32. A fuel cell vehicle on which the fuel cell system according to claim 31 is mounted.

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