JP2003203641A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell having high output and high voltage in which a conductive organic polymer is used as an electrode catalyst and, further, for example, a low cost proton exchange membrane of which polymer chain is made of hydrocarbon is used as an electrolyte membrane. <P>SOLUTION: This is a fuel cell in which a cathode and an anode are provided interposing an electrolyte membrane and an oxidizer is supplied to this cathode by gas and a reducing agent is supplied to this anode by gas. A conductive organic polymer having oxidation-reduction function is provided at least at one of the electrodes and the polymer chain is made of a hydrocarbon skeleton that may contain one or more of different kind of atoms selected from N, S, O and F (provided that a polymer chain made of perfluoro-hydrocarbon is excluded), and the proton exchange membrane is made of a polymer having an acid radical. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to at least a fuel cell in which a cathode and an anode are arranged with an electrolyte membrane sandwiched therebetween, an oxidant is supplied as a gas to the cathode, and a reducing agent is supplied as a gas to the anode. One of the electrodes is provided with a conductive organic polymer having a redox function as an electrode catalyst, and as the electrolyte membrane, a proton exchange membrane made of an inexpensive resin-based polymer is used. The present invention relates to a fuel cell having high output.

[0002]

2. Description of the Related Art In recent years, a solid polymer electrolyte is sandwiched between an anode and a cathode to form a solid electrolyte / electrode structure, which is sandwiched between separators to form a unit cell.
A fuel cell in which a plurality of these unit cells are stacked and electrically connected in series has been developed. This fuel cell has attracted attention as a power source for electric vehicles, a dispersed power source for household use, and the like, because of its cleanness and high efficiency.

More specifically, such a polymer electrolyte fuel cell has, as its basic structure, a pair of electrodes, an anode and a cathode, each having an electrode catalyst, with a proton exchange membrane sandwiched therebetween. Then, a reducing agent (fuel) such as hydrogen is brought into contact with the surface of the anode, and an oxidizing agent (oxygen) is brought into contact with the surface of the cathode to cause an electrochemical reaction. It extracts electrical energy from the electrodes.

Heretofore, as the proton exchange membrane, it is well known that an ion exchange membrane made of a perfluorosulfonic acid polymer known as Nafion (registered trademark) has excellent basic characteristics. ,
As the anode and the cathode, a carbon sheet supporting platinum as an electrode catalyst is widely known.

On the other hand, for example, a conductive organic polymer having a dovant represented by polyacetylene, polypyrrole, polyaniline, etc., and having a redox function is an electrode active material in a lithium secondary battery or the like. (Patent No. 1845557) and its use as a conductive polymer capacitor having a rapid discharge function has been proposed (39th Annual Meeting of the Battery Symposium, Proceedings, p. 173 (1998), Proceedings of the 67th Annual Meeting of the Electrochemical Society, p. 147 (2000)).

However, the conductive organic polymer as described above has a higher energy than an inorganic oxide or a metal material such as lithium cobalt oxide (LiCoO ₂ ) or lithium which is an electrode active material which is currently in practical use. Low density.
Therefore, in order to supplement the low energy density of such a conductive organic polymer, a conductive organic polymer is used as an electrode catalyst, and an oxidizing agent or a reducing agent is dissolved in the electrolytic solution in contact with this conductive organic polymer. Then, an attempt to use the cell as a fuel cell has been proposed (JP-A-59-60967 and JP-A-61-214070).

However, according to these batteries, since the oxidizing agent and the reducing agent are both supplied as a solution, the diffusion of the active material into the electrodes is slow, and the discharge characteristic thereof is about several mA / cm ² . In addition to being unable to obtain a high output voltage, the battery system is also complicated, making it impractical.

On the other hand, as described above, the conventional polymer electrolyte fuel cell uses platinum as the electrode catalyst, so that the cost is high, the elution of the acidic liquid, the carbon monoxide scratching at the anode, etc. However, it is an important obstacle to practical use, and practical electrode catalysts other than platinum have not yet been found.

As a proton exchange membrane, as mentioned above, a perfluorosulfonic acid polymer membrane is said to be useful in terms of acid resistance, oxidation resistance, heat resistance, etc. However, this polymer is Since it is extremely expensive, in a fuel cell that uses a large amount of a proton exchange membrane, this is a factor that significantly increases the manufacturing cost. Thus, conventionally, a fuel cell that uses a low-cost and high-performance proton exchange membrane has been strongly demanded. Has been done.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in conventional fuel cells, in which a conductive organic polymer is used as an electrode catalyst, and
For example, an object of the present invention is to provide a fuel cell having a high output and a high voltage, which uses an inexpensive proton exchange membrane having a polymer chain of hydrocarbon as an electrolyte membrane.

[0011]

According to the present invention, a fuel is provided in which a cathode and an anode are arranged with an electrolyte membrane sandwiched therebetween, an oxidant is supplied as a gas to the cathode, and a reducing agent is supplied as a gas to the anode. In a battery, at least one electrode,
A conductive organic polymer having a redox function is used as an electrode catalyst, and the polymer chain is composed of a hydrocarbon skeleton which may contain one or more kinds of heteroatoms selected from N, S, O and F. (However, a polymer chain made of perfluorohydrocarbon is excluded.) And a proton exchange membrane made of a polymer having an acid group are provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, at least one of a cathode and an anode has a redox function, and preferably a conductive organic polymer having a dovant is used as an electrode catalyst. .

Examples of such conductive organic polymers include polyacetylene, poly-p-phenylene, polyaniline, polypyrrole, polythiophene, polyindole, poly-2,5-diaminoanthraquinone, poly (o).
-Phenylenediamine), poly (quinolinium) salt, poly (isoquinolinium) salt, polypyridine, polyquinoxaline, polyphenylquinoxaline and the like. These conductive organic polymers may have various substituents. Specific examples of such a substituent include, for example, an alkyl group, a hydroxyl group, an alkoxyl group, an amino group, a carboxyl group, a sulfonic acid group, a halogen group, a nitro group, a cyano group, an alkylsulfonic acid group and a dialkylamino group. be able to. These substituents are useful for adjusting the redox potential of the conductive organic polymer.

The above-mentioned dopant preferably has a sulfonic acid group, for example, an ionic polymer sulfonic acid such as polypinyl sulfonic acid or phenol sulfonic acid novolac resin, or dodecylbenzene sulfonic acid. The low molecular weight organic sulfonic acid compound can be mentioned. Among them, the former ionic polymer, in particular, a polymer sulfonic acid is preferable. Here, according to the present invention, the polymer sulfonic acid means a polymer having a sulfonic acid group in the molecule.

However, in the present invention, a self-doping type conductive organic polymer such as sulfonated polyaniline having a sulfonic acid group in the molecule is also included in the conductive organic polymer having a dopant.

In the present invention, among the above-mentioned conductive organic polymers, those which release a proton in an oxidation reaction and consume a proton in a reduction reaction are preferable among the above-mentioned conductive organic polymers. As, polyaniline, polyalkylaniline, polyindole,
Like poly (o-phenylenediamine), polypyridine, polyquinoxaline, polyphenylquinoxaline, etc.,
A conductive organic polymer having a nitrogen atom in the molecule can be mentioned.

In the present invention, the same conductive organic polymer may be provided as an electrode catalyst on both the cathode and the anode, or different conductive organic polymers may be provided as electrode catalysts. However, according to the present invention, it is preferable to use a p-type conductive organic polymer for the cathode and an n-type conductive organic polymer for the anode in order to obtain a higher voltage. Among the conductive organic polymers described above, the p-type ones are polyaniline, polyalkylaniline and polyindole, and the n-type ones are
These are poly (o-phenylenediamine), polypyridine, polyquinoxaline and polyphenylquinoxaline.

In general, some conductive organic polymers are p-type and n-type.
As already known, for example, a conductive organic polymer powder is molded into a disk, electrodes are attached to the two locations, and a temperature difference is applied to the electrodes. It suffices to check the positive / negative of the potential of the electrode on the low temperature side when the voltage is given. That is, when a positive potential appears at the low temperature side electrode, the conductive organic polymer is p-type, and conversely, when a negative potential appears at the low temperature side electrode, the conductive organic polymer becomes n
It is a type. Alternatively, as another method, the cyclic organic voltammogram of the conductive organic polymer is measured, and when the conductive organic polymer has a redox couple in a positive potential region with respect to SCE, the conductive organic polymer is a p-type. , The conductive organic polymer is n-type when it has a redox couple in the negative potential region.

Further, according to the present invention, only one electrode may have a conductive organic polymer as an electrode catalyst, and the other electrode may use a conventional platinum catalyst. Further, according to the present invention, at least one of the cathode and the anode may have a mixture of a conductive organic polymer and an inorganic redox catalyst as an electrode catalyst.

As described above, when the conductive organic polymer is used as an electrode catalyst, the amount used is not particularly limited, but usually 0.5 to 10 per electrode area.
It is in the range of 0 mg / cm ² .

The conductive organic polymer as described above can be obtained by a known method. A conductive polyaniline having polymer sulfonic acid as a dopant will be described as an example.

According to the method described in JP-A-3-28229, conductive polyaniline (conductive polyaniline composition) doped with the above-mentioned protonic acid is prepared by chemically oxidatively polymerizing aniline with an oxidizing agent in the presence of a protic acid. Substance) powder, which is dedoped in an appropriate alkaline aqueous solution, for example, ammonia water, and the powder obtained is filtered and dried to obtain polyaniline which is soluble in an organic solvent in the undoped state, that is, oxidized. An undoped polyaniline powder can be obtained.

More specifically, aniline is reacted with an oxidizing agent such as ammonium peroxodisulfate in the presence of a suitable protic acid such as hydrochloric acid in a suitable solvent such as water or methanol for precipitation. By filtering the powder, a conductive polyaniline composition doped with the above-mentioned protonic acid is obtained. This powder is then, for example,
The conductive polyaniline composition is neutralized (ie, dedoped) by addition to an aqueous solution of an alkaline substance such as ammonia to give a compound of general formula (I)

[0024]

[Chemical 1]

(In the formula, m and n represent the mole fractions of the quinonediimine structural unit and the phenylenediamine structural unit in the repeating unit, respectively, 0 <m ≦ 1, 0 ≦ n <1, m
+ N = 1. ) The polyaniline powder in the oxidatively dedoped state consisting of the repeating unit represented by

The undoped polyaniline thus obtained has a high molecular weight and is soluble in various organic solvents. Usually in N-methylpyrrolidone at 30 ° C
Has an intrinsic viscosity [η] of 0.40 dL / g or more, and is, for example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide,
It is dissolved in an organic solvent such as dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone and sulfolane. Although the solubility of the undoped polyaniline in such an organic solvent depends on the average molecular weight and the solvent, 0.5 to 100% of polyaniline is usually dissolved to obtain a solution having a concentration of 1 to 30% by weight. be able to. In particular, this undoped polyaniline exhibits high solubility in N-methyl-2-pyrrolidone, and usually 20 to 100% of polyaniline dissolves to obtain a 3 to 30% by weight solution.

In the undoped polyaniline, the values of m and n can be adjusted by oxidizing or reducing polyaniline. That is, by reducing, m can be reduced and n can be increased. On the contrary, if oxidized, m can be increased and n can be decreased. The reduction of the quinonediimine structural unit in the polyaniline due to the reduction of the polyaniline enhances the solubility of the polyaniline in organic solvents. Also,
The viscosity of the solution is lower than that before the reduction. For the reduction of such solvent-soluble polyaniline, for example, N 2
-Dissolves in methyl-2-pyrrolidone, but N-methyl-
Phenylhydrazine is most preferably used because it does not reduce 2-pyrrolidone.

On the other hand, the oxidizing agent used for oxidizing the solvent-soluble polyaniline is not particularly limited as long as it can oxidize the phenylenediamine structural unit, but for example, mild silver oxide is preferable. Used.
If necessary, potassium permanganate, potassium dichromate, etc. can also be used.

Then, the polyaniline powder in the oxidatively dedoped state is put into an aqueous polymer sulfonic acid solution which is acidified with a strongly acidic cation exchange resin, and the polyaniline is doped with the polymer sulfonic acid by heating for several hours. After that, the polyaniline powder in the doped state is filtered, washed, and then vacuum dried,
A conductive polyaniline powder having polymer sulfonic acid as a dopant can be obtained.

As described above, when at least one of the electrodes is provided with a mixture of a conductive organic polymer and an inorganic redox catalyst as an electrode catalyst, the inorganic redox catalyst may be a catalytic hydrogenation catalyst or an oxygen autocatalyst. It is possible to use at least one transition metal selected from platinum, palladium, ruthenium, rhodium, silver, nickel, iron, copper, cobalt and molybdenum and / or an oxide thereof, which is known as an oxidation catalyst. Such an inorganic redox catalyst may be mixed as it is as a fine powder with the conductive organic polymer powder, or the conductive organic polymer powder may be dispersed in an aqueous solution of a water-soluble salt of the above transition metal and stirred. After mixing, reduction or oxidation treatment may be performed to convert the above transition metal salt into a metal or an oxide.

In addition, a water-soluble acid or salt of an anion containing the above transition metal is used to support the anion containing the transition metal by doping into the conductive organic polymer, and the anion containing the transition metal is used as a dopant. After obtaining the organic polymer, this can be reduced with hydrogen gas or a reducing agent to carry the inorganic redox catalyst composed of the above transition metal in the conductive organic polymer. Further, if necessary, by oxidizing the conductive organic polymer carrying the inorganic redox catalyst composed of the above transition metal with oxygen gas or an oxidizing agent, the inorganic oxidation composed of the transition metal oxide is carried out. The reduction catalyst can be supported in the conductive organic polymer.

When a mixture of a conductive organic polymer and an inorganic redox catalyst is used as an electrode catalyst, the inorganic redox catalyst is usually added to 100 parts by weight of the conductive organic polymer.
It is used in the range of 0.1 to 30 parts by weight. The amount of the inorganic redox catalyst supported on the electrode area is usually 0.0
The range is from 01 to 5 mg / cm ² , but preferably,
In the range of 0.005~1mg / cm ^2, particularly preferably in the range of 0.01 to 0.5 / cm ^2.

As described above, according to the present invention, a mixture of a conductive organic polymer and an inorganic redox catalyst is provided in an electrode as an electrode catalyst, so that a conductive organic polymer alone is used as an electrode catalyst. As a result, a much higher output fuel cell can be obtained.

Next, the proton exchange membrane used as the electrolyte membrane in the fuel cell according to the present invention will be described.

Conventionally, in a fuel cell using a platinum catalyst, an expensive perfluorosulfonic acid polymer membrane such as Nafion (registered trademark) membrane has been used as a proton exchange membrane for the following reason (DS. Wat
kins, Fuel Cell Systems, Ch.11, 493-530 (1993), Pl
enum Press, New York). That is, it is said that the inside of a fuel cell using platinum as an electrode catalyst and a proton exchange membrane based on a hydrocarbon polymer as an electrolyte membrane deteriorates the proton exchange membrane by a mechanism including the following steps. There is.

Step 1: H ₂ → 2H. Step 2: H. + O ₂ (diffuses in the proton exchange membrane) → HO ₂ Step 3: HO ₂ + H. → H ₂ O ₂ (proton It can diffuse into the exchange membrane.) Step 4: H ₂ O ₂ + M ²⁺ (Fe ²⁺ and Cu ²⁺ are always present in the membrane) + H ⁺ → M ³⁺ + H ₂ O + HO. step _{5: HO · + H 2 O} 2 → H 2 O + HO 2 · ( to attack the proton exchange membrane.)

According to such a mechanism, a series of reactions are
At the anode, it is initiated by the dissociation reaction of hydrogen molecules with a platinum catalyst. The hydrogen atoms generated by the dissociation of hydrogen molecules react with oxygen molecules that have diffused from the cathode side in the proton exchange membrane to generate HO ₂ .radicals.
The HO ₂ · radical reacts with a hydrogen atom existing in the vicinity of the anode to generate hydrogen peroxide. This hydrogen peroxide decomposes in the presence of iron ions and copper ions, which are often present in the proton exchange membrane, to generate hydroxyl radicals HO. The combination of hydrogen peroxide and divalent iron ions is well known as a "Fenton's reagent" as a reagent for generating hydroxyl radicals. This hydroxyl radical further reacts with hydrogen peroxide to generate HO ₂ · radical, which attacks the proton exchange membrane based on the hydrocarbon polymer,
Deteriorate.

In the above-mentioned document, an experiment in which the amount of sulfur derived from sulfonic acid groups in the thickness direction of the membrane cross section was quantified in the case where a polystyrene sulfonic acid membrane was used as a proton exchange membrane based on a hydrocarbon polymer. Results are shown. According to it, on the cathode side of the proton exchange membrane,
Although the amount of sulfur does not change, on the anode side, the amount of sulfur decreases to 1/3 or less of the original amount. This fact indicates that, on the anode side, hydrogen is dissociated by the action of the platinum catalyst to generate hydrogen atoms on the anode side, which leads to the deterioration of the proton exchange membrane based on the hydrocarbon polymer. Supports the mechanism.

As described above, in a fuel cell using a platinum catalyst, deterioration of a proton exchange membrane based on a hydrocarbon polymer cannot be avoided due to a series of reactions starting from hydrogen dissociation by platinum. Nafion (registered trademark), which is an expensive perfluorosulfonic acid polymer membrane, is widely used as a proton exchange membrane.

However, in the fuel cell of the present invention, unlike the above-mentioned conventional fuel cell, the catalyst is not platinum but a conductive organic polymer having a redox function, so that the proton exchange membrane as described above is used. Therefore, according to the present invention, it is possible to use, as a proton exchange membrane, an inexpensive, easily available, polymer-based proton exchange membrane in a preferable case. Combined with the fact that no catalyst is required, it is possible to realize a significant cost reduction of the fuel cell, which is expected to accelerate the speed of commercialization of the fuel cell.

In the fuel cell according to the present invention, the electrolyte membrane is composed of a hydrocarbon skeleton in which the polymer chain may contain one or more kinds of heteroatoms selected from N, S, O and F (provided that the polymer skeleton is a Except for polymer chains made of fluorohydrocarbon), and a proton exchange membrane made of a polymer having an acid group.

As described above, according to the present invention, the electrolyte membrane has a polymer chain having a hydrocarbon skeleton which may contain one or more kinds of heteroatoms selected from the above N, S, O and F. And an acid group-containing polymer, and further 10 ⁻⁶ S / in an atmosphere of room temperature (25 ° C.) and relative humidity of 50%.
It is not particularly limited as long as it has a proton conductivity of cm or more and is insoluble in water.

Then, the following can be mentioned as an example of such a polymer.

(1) A polymer having a polymer chain composed of hydrocarbon and having a sulfonic acid group as an acid group

Specific examples of such a polymer include a polymer obtained by (co) polymerizing a vinyl monomer having a sulfonic acid group, and more specifically,
For example, polystyrene sulfonic acid, styrene sulfonic acid / divinylbenzene copolymer, allyl sulfonic acid (co)
Examples thereof include polymers, vinyl sulfonic acid (co) polymers, 2-acrylamide / 2-methylsulfonic acid copolymers, and the like.

Further, by sulfonation of a polymer having a hydrocarbon polymer chain, a polymer having a hydrocarbon polymer chain and a sulfonic acid group as an acid group can be obtained. it can. Examples of such a polymer include a sulfonated product of a styrene / divinylbenzene copolymer.

(2) A polymer having a hydrocarbon polymer chain and having a phosphoric acid group, a phosphonic acid group or a phosphinic acid group as an acid group.

Such a polymer can be preferably obtained by (co) polymerizing a vinyl monomer having a phosphoric acid group, a phosphonic acid group or a phosphinic acid group. As the vinyl monomer having a phosphate group, for example, 2
-Methacryloyloxyethyl phosphate, methacryloyl tetra (oxyethylene) phosphate, methacryloyl penta (oxypropylene) phosphate, 4
-Styryl methoxy butyl phosphate etc. can be mentioned.

Examples of the vinyl monomer having a phosphonic acid group include 4- (2-styrylmethoxyethyl) phenylphosphonic acid, 4- (styrylmethoxy) butylphosphonic acid and styrylmethylphosphonic acid.

Examples of vinyl monomers having a phosphinic acid group include 4- (2-styrylmethoxyethyl) phenylphosphinic acid and 4- (styrylmethoxy).
Examples thereof include butylphosphinic acid and styrylmethylphosphinic acid.

Along with the vinyl monomer having a phosphoric acid group, a phosphonic acid group or a phosphinic acid group, a polyfunctional vinyl monomer having an acid group can be used. As such a polyfunctional vinyl monomer, for example, bis (methacryloyloxyethyl) phosphate, bis {5- (methacryloyloxyethyloxycarbonyl) pentyl}
Mention may be made of phosphoric acid diesters such as phosphates. As the polyfunctional vinyl monomer, a vinyl monomer having no phosphoric acid group, phosphonic acid group or phosphinic acid group can also be used.

The above-mentioned vinyl monomer or polyfunctional vinyl monomer having a phosphoric acid group, a phosphonic acid group or a phosphinic acid group usually has a phosphoric acid group, a phosphonic acid group or a phosphinic acid group. Copolymerized with a non-vinyl monomer,
The polymer has a polymer chain composed of a hydrocarbon and also has a phosphoric acid group, a phosphonic acid group or a phosphinic acid group as an acid group. Examples of vinyl monomers having no such phosphoric acid group, phosphonic acid group or phosphinic acid group include vinyl monomers such as styrene, vinyl sulfonic acid, sodium styrene sulfonate, vinyl ethers such as ethyl vinyl ether. , Butyl acrylate,
Acrylic monomers such as methoxyethyl acrylate, 2-ethylhexyl methacrylate, acrylic acid, N,
Examples thereof include acrylamides such as N-dimethylaminopropyl acrylamide and 2-acrylamido-2-methylpropane sulfonic acid.

The (co) polymerization of the various vinyl monomers described above is usually carried out by thermal polymerization or photopolymerization.

(3) Examples of the phenol resin having a sulfonic acid group include a phenol sulfonic acid novolak resin and a sulfonated product of a phenol resin.

(4) As the sulfonated product of the conjugated diene polymer, for example, a partially sulfonated product of polybutadiene or polyisoprene can be cited.

In addition to the above, for example, (5) a copolymer of a fluorine-containing monomer (for example, tetrafluoroethylene) and a monomer having a sulfonic acid group, (6) polyether ether ketone or poly Sulfonated product of ether sulfone, (7) Sulfonated product or sulfoalkylated product of polybenzimidazole, acid-doped complex of polybenzimidazole, (8) Sulfonated product of polyphenylquinoxaline, (9) Poly (4-phenoxybenzoyl) Examples thereof include sulfonated compounds of -1,4-phenylene).

Here, (co) polymer means homopolymerization or copolymerization, and (co) polymer means homopolymer or copolymer.

Further, according to the present invention, in the electrolyte membrane, the polymer is a fluororesin such as polytetrafluoroethylene,
It may be a substantially non-porous film supported in the pores of a porous film made of a polyolefin resin such as polyethylene or polypropylene.

Next, the production of electrodes used in the fuel cell according to the present invention will be described. The cathode using a conductive organic polymer as an electrode catalyst is manufactured, for example, as follows. That is, a conductive polyaniline powder having a polymer sulfonic acid as a dopant is added with a conductive agent (eg,
Conductive carbon black powder), and then made into a paste by using a solution of a binder (for example, polypyridinyl fluoride resin or polytetrafluoroethylene resin),
This paste is used as a conductive porous substrate (for example, Toray Co., Ltd.)
Carbon paper), dried, and then treated with a conductive porous substrate treated in this manner as a proton-exchangeable resin solution (for example, a perfluorosulfonic acid polymer solution such as Nafion (registered trademark)). Apply, dry,
Get the cathode.

A cathode using a mixture of a conductive organic polymer and an inorganic redox catalyst as an electrode catalyst is produced, for example, as follows. That is, a conductive polyaniline powder having a polymer sulfonic acid as a dopant and an inorganic redox catalyst powder are mixed, and if necessary, a conductive agent (for example, conductive carbon black powder) is mixed and then bound. A paste of a solution of an agent (for example, polyvinylidene fluoride resin or polytetrafluoroethylene resin) is used, and the paste is applied on a conductive porous substrate (for example, carbon paper manufactured by Toray Industries, Inc.) and dried. After that, a proton-exchangeable resin solution (for example, a perfluorosulfonic acid polymer solution such as Nafion (registered trademark)) is applied to the conductive porous substrate thus treated and dried to obtain a cathode.

The anode can be obtained by reducing the cathode. The reduction method is not particularly limited. For example, although the cathode may be chemically reduced, as a preferred example, a cyclic voltammogram is measured in the polymer sulfonic acid aqueous solution using an appropriate reference electrode, and the potential at which the reduction peak appears is obtained. It is convenient to electrochemically reduce the cathode.

The above-obtained cathode and anode sandwich the electrolyte membrane (that is, the proton exchange membrane), and if necessary, they are integrally molded by hot pressing or the like to form an electrode-proton for a fuel cell-proton. Obtain an exchange membrane conjugate.

In the fuel cell according to the present invention, the oxidizing agent is supplied as a gas to the cathode and the reducing agent is supplied as a gas to the anode. Here, according to the present invention, preferably,
Oxygen gas or air is used as the oxidizing agent, and hydrogen gas is used as the reducing agent. Also, as a reducing agent,
It is also possible to use methanol, dimethyl ether, or the like.

The fuel cell according to the present invention is operated at a temperature of 40 ° C. or higher. It is appropriately selected depending on the conductive organic polymer and the electrolyte membrane used, but the range of 50 to 120 ° C is preferable, and the range of 60 to 100 ° C is particularly preferable. When the operating temperature is too low, a high output cannot be obtained because the reaction speed of the conductive organic polymer is slow.On the other hand, when the operating temperature is too high, deterioration or peeling of the material used occurs. There is a risk.

[0065]

EXAMPLES The present invention will be described below with reference to examples and reference examples, but the present invention is not limited to these examples.

Reference Example 1 (Preparation of Conductive Polyaniline Composition by Oxidative Polymerization of Aniline) Distilled water 6000 g, 3 g in a 10 L separable flask equipped with a stirrer, a thermometer and a straight pipe adapter.
360 mL of 6% hydrochloric acid and 400 g of aniline (4.295)
Mol) was charged in this order to dissolve the aniline.
Separately, while cooling with ice water, distilled water in a beaker 14
To 93 g, 434 g (4.295 mol) of 97% concentrated sulfuric acid was added and mixed to prepare a sulfuric acid aqueous solution. This aqueous sulfuric acid solution was added to the separable flask, and the entire flask was cooled to -4 ° C in a low temperature constant temperature bath. Next, in a beaker, 2293 g of distilled water was added with 98% ammonium peroxodisulfate.
0 g (4.295 mol) was added and dissolved to prepare an oxidizing agent aqueous solution.

The entire flask was cooled in a low temperature constant temperature bath, while maintaining the temperature of the reaction mixture at -3 ° C or lower, while stirring, to an acidic aqueous solution of aniline salt, using a tyuping pump, a straight pipe adapter was used to remove the above. Aqueous ammonium peroxodisulfate solution was gradually added dropwise at a rate of 1 mL / min or less. First, the colorless and transparent solution changed from green-blue to black-green as the polymerization proceeded, and then a black-green powder precipitated.

A temperature rise is observed in the reaction mixture during the precipitation of the powder, and in this case also, in order to obtain a high molecular weight polyaniline, the temperature in the reaction system is 0 ° C. or lower, preferably −3 ° C. or lower. It is essential to keep After the powder is deposited, the dropping rate of the aqueous ammonium peroxodisulfate solution may be slightly increased, for example, about 8 mL / min. However, also in this case, it is necessary to monitor the temperature of the reaction mixture and adjust the dropping rate so as to maintain the temperature at −3 ° C. or lower. It took 7 hours,
After the dropwise addition of the aqueous ammonium peroxodisulfate solution was completed, stirring was continued for an additional hour at a temperature of -3 ° C or lower.

The obtained powder was filtered, washed with water, washed with acetone, and vacuum dried at room temperature to obtain 430 g of a black-green conductive polyaniline composition powder. This has a diameter of 13 mm,
It was pressed into a disk having a thickness of 700 μm, and its conductivity was measured by the van der Pauw method.
It was S / cm.

(Production of Polyaniline Soluble in Organic Solvent by Dedoping of Conductive Polyaniline Composition (Polyaniline in Oxidized and Undoped State)) 350 g of the above doped conductive polyaniline composition powder was added to 4 L of 2N ammonia water. In addition, the rotation speed is 5 with an auto homomixer
The mixture was stirred at 000 rpm for 5 hours. The mixture changed from black green to blue purple.

The powder was filtered off with a Buchner funnel, washed repeatedly with distilled water while stirring in a beaker until the filtrate became neutral, and then washed with acetone until the filtrate became colorless. did. Then, the powder was vacuum dried at room temperature for 10 hours to obtain 280 g of black-brown dedoped polyaniline (oxidized and undoped polyaniline) powder.

This polyaniline was soluble in N-methyl-2-pyrrolidone and had a solubility of 8 g (7.4%) in 100 g of the same solvent. Also, the intrinsic viscosity [η] measured at 30 ° C. using this as a solvent is 1.23 dL / g
Met.

The polyaniline had a solubility of 1% or less in dimethyl sulfoxide and dimethylformamide. It was substantially insoluble in tetrahydrofuran, pyridine, 80% acetic acid aqueous solution, 60% formic acid aqueous solution and acetonitrile.

Further, the polyaniline soluble in the organic solvent in the undoped state was subjected to GPC measurement using a GPC column for N-methyl-2-pyrrolidone. As a result, the number average molecular weight was H23000 and the weight average molecular weight was 16
It was 0000 (both in terms of polystyrene).

Example 1 Sodium polyvinyl sulfonate (manufactured by Aldrich)
Was treated with a strongly acidic cation exchange resin (Dowex 50WX12 manufactured by Dow Chemical Co., Ltd.) to obtain an aqueous solution of acid type polyvinyl sulfonic acid. Next, this was concentrated using a rotary evaporator and then vacuum dried to obtain starch syrup-shaped polyvinyl sulfonic acid. Dissolving 12.5 g of this polyvinyl sulfonic acid in 70.8 g of ion-exchanged water,
An aqueous solution of polyvinyl sulfonic acid having a concentration of 15% by weight was prepared.

10 g of the oxidatively dedoped polyaniline powder obtained in Reference Example 1 was added to this polyvinylsulfonic acid aqueous solution, and the mixture was heated to 70 ° C. in an oil bath and kept for 130 minutes to dope the polyaniline with polyvinylsulfonic acid. The doped polyaniline is suction filtered, washed with methanol, and then vacuum-dried at 50 ° C. for 4 hours to obtain polyvinyl sulfonic acid as a dopant having an electric conductivity of 11.5 S /
15.2 g of conductive polyaniline powder having a size of cm was obtained.

To 2 g of this conductive polyaniline powder, 0.4 g of conductive carbon black powder (Ketjen Black EC manufactured by Akzo Co., Ltd.) was added and mixed in a porcelain mortar for 10 minutes until uniform.

Separately, 0.27 g of polyvinylidene fluoride resin (Kina, manufactured by Kureha Chemical Industry Co., Ltd.) was dissolved in 10.53 g of N, N-dimethylformamide to obtain 2.5% by weight.
A solution was prepared, a mixture of the above-mentioned conductive polyaniline powder and carbon black powder was added thereto, and further mixed using a mortar to obtain a paste. 5.8 this paste
cm square carbon paper (TGP-H- manufactured by Toray Industries, Inc.)
90, a film thickness of 260 μm) and heated and dried at 80 ° C. for 60 minutes in a hot air circulation dryer. Next, a 5% by weight Nafion (registered trademark) solution (manufactured by Aldrich Co.) was applied onto the carbon paper thus treated,
The thus obtained electrode was used as a cathode after heating and drying at 15 ° C. for 15 minutes.

The above electrode was soaked in a 15 wt% polyvinyl sulfonic acid aqueous solution, a saturated calomel electrode (SCE) was used as a reference electrode, and a platinum wire having a diameter of 0.5 mm was used as a counter electrode, and a potentiostat manufactured by Hokuto Denko KK was used. / Using galvanostat (HA-501) and function generator (HB-105), potential range -0.2 to
0.5V vs. A cyclic volchmogram was obtained under the conditions of SCE and a sweep rate of 20 mV / sec. The oxidation peak of polyaniline is 0.5 V vs. In SCE, the reduction peak of polyaniline was -0.1 V vs. Appeared in SCE. Therefore, the potential of the potentiostat is -0.1V.
And then electrochemically reduced for 30 minutes. The electrode thus obtained was used as an anode.

The electrolyte membrane (proton exchange membrane) was prepared as follows. 2-Methacryloyloxyethyl phosphate / bis (methacryloyloxyethyl) diphosphate (65/35) mixture (light ester P-1M manufactured by Kyoeisha Chemical Co., Ltd.) 50% by weight and butyl acrylate 50% by weight monomer mixture 0.5 parts by weight of benzyl dimethyl ketal (Irgacure 651 manufactured by Ciba-Geigy) was dissolved in 100 parts by weight.

An ultrahigh molecular weight polyethylene resin porous membrane T1 (Nitto Denko Corp.) having a thickness of 25 μm, a porosity of 40% and an average pore diameter of 0.10 μm was used as it was without dilution.
(Manufactured) and then impregnated.

This porous film was sandwiched from both sides with a polyester release film to block oxygen, and a high pressure mercury lamp (UB021-1B-13 manufactured by Eye Graphic Co., Ltd.) was used at an energy of 1.5 J / cm ² . Light irradiation was performed.
In this way, the pores of the porous film were filled with the 2-methacryloyloxyethyl phosphate / bis (methacryloyloxyethyl) diphosphate copolymer, and the thickness was 3
A proton conductive composite membrane composed of a non-porous film having a thickness of 5 μm was obtained.

This proton-conductive composite membrane was placed at a temperature of 25.
After exposure to an atmosphere adjusted to 50 ° C. and a relative humidity of 50% for 24 hours, the proton conductivity was measured and found to be 2.1 × 1.
It was 0 ^-3 S / cm. The tensile strength of this proton conductive composite membrane was 87 MPa.

The above proton-conductive composite membrane is placed as a proton exchange membrane between the cathode and the anode, and an electrode-proton exchange membrane bonding is carried out by hot pressing under conditions of a temperature of 130 ° C. and a pressure of 3 MPa using a mold. The body was prepared and a single-layer fuel cell unit for test having an effective electrode area of 25 cm ² was assembled.

This fuel cell was incorporated into a fuel cell evaluation device (manufactured by Toyo Technica Co., Ltd.) and the cell temperature was 70 ° C.
Then, oxygen gas was supplied to the cathode at a rate of 500 mL / min at a humidifier temperature of 70 ° C., and hydrogen gas was supplied to the anode at a rate of 500 mL / min at a humidifier temperature of 80 ° C. The gas pressure was 0.1 MPa for both oxygen and hydrogen. Therefore, first, when only the electromotive force (open circuit voltage) was measured without passing a current, it was 0.52V. Next, when a load was applied to the fuel cell, a current of 0.23 A (9.2 mA / cm ² ) was obtained when the voltage was 0.4 V.

Example 2 1.8 g of the polyaniline powder in the oxidatively dedoped state obtained in Reference Example 1 was loaded with 20% by weight of platinum together with 0.4 g of conductive carbon black powder (Ketjen Black EC manufactured by Akzo). Carbon (EC made by US Electrochem
-20-PTC) 0.2 g, and using a porcelain mortar,
With rubbing, mix for 10 minutes until uniform.

Separately, 0.27 g of polyvinylidene fluoride resin (Kainer manufactured by Kureha Chemical Industry Co., Ltd.) was dissolved in 10.53 g of N, N-dimethylformamide to prepare a 2.5 wt% solution, and the above solution was prepared. A mixture of polyaniline powder in the oxidatively dedoped state and conductive carbon black powder was added and further mixed using a mortar to obtain a paste.

This paste was applied to carbon paper of 5.8 cm square (TGP-H-90 manufactured by Toray Industries, Inc., film thickness 260 μm).
m) was coated on the above, and heated and dried at 80 ° C. for 60 minutes in a hot air circulation dryer. Next, a 5% by weight Nafion (registered trademark) solution (manufactured by Aldrich) was applied onto the carbon paper treated in this way, and heated at 80 ° C. for 15 minutes,
The electrode thus obtained was dried and used as a cathode.

Next, the oxidatively undoped polyaniline powder obtained in Reference Example 1 was added to a methanol solution of hydrazine monohydrate and stirred for 8 hours for reduction. The obtained reaction product was filtered with a Nutsche and a suction bottle, washed with methanol, and then dried in a vacuum dryer at 70 ° C. for 5 hours. In this way, polyaniline powder in a reduced dedoped state was obtained.

To 1.8 g of this reduced dedoped polyaniline powder, 0.4 g of conductive carbon black powder (Ketjen Black EC manufactured by Akzo Co.) and 20 g of platinum were added.
Carbon supported by weight% (E produced by Electrochem, USA
C-20-PTC) (0.2 g) was added, and the mixture was mixed with a porcelain mortar for 10 minutes while rubbing until uniform.

Separately, 0.27 g of polyvinylidene fluoride resin (Kina, manufactured by Kureha Chemical Industry Co., Ltd.) was dissolved in 10.53 g of N, N-dimethylformamide to obtain 2.5% by weight.
A solution is prepared, and a mixture of the reduced type undoped polyaniline powder and carbon black powder is added thereto,
Furthermore, it mixed using a mortar and it was set as the paste. 5.8 cm square carbon paper (Toray Industries, Inc.)
Manufactured by TGP-H-90, film thickness: 260 μm), and heated and dried at 80 ° C. for 60 minutes in a hot air circulation dryer.

Next, a 5% by weight Nafion (registered trademark) solution (manufactured by Aldrich Co.) was applied onto the carbon paper treated in this way, and heated and dried at 80 ° C. for 15 minutes to obtain the thus obtained product. The obtained electrode was used as an anode.

The proton-conducting composite membrane obtained in Example 1 was placed as a proton exchange membrane between the cathode and the anode thus produced, and a mold was used at a temperature of 130.
An electrode-proton exchange membrane assembly was prepared by hot pressing under conditions of ° C and a pressure of 3 MPa to assemble a single-layer fuel battery cell for testing.

This fuel cell was incorporated into a fuel cell evaluation apparatus (manufactured by Toyo Technica Co., Ltd.), the cell temperature was 70 ° C., and the oxygen gas was supplied to the cathode at a rate of 500 mL / min at a humidifier temperature of 70 ° C. Hydrogen gas was supplied to the anode at a rate of 500 mL / min at a humidifier temperature of 80 ° C.
Therefore, first, when only the electromotive force (open circuit voltage) was measured without passing a current, it was 0.59V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V,
A current of 81 A (32 mA / cm ² ) was obtained.

Example 3 Phenolsulfonic acid novolak resin aqueous solution (manufactured by Konishi Chemical Industry Co., Ltd., free acid type, solid content 45.9%, weight average molecular weight 22000 (GPC method, sodium polystyrene sulfonate standard) 43.6 g Ion-exchanged water 56.4g
Was added to dilute. 12.0 g of the polyaniline powder in the oxidatively dedoped state was added to the obtained phenolsulfonic acid novolak resin aqueous solution, and the mixture was heated in a hot water bath at 80 ° C. for 2 hours and then left overnight at room temperature. The black-brown oxidatively undoped polyaniline powder turned black green immediately after being added to the phenolsulfonic acid novolak resin aqueous solution, indicating that the polyaniline was doped with the phenolsulfonic acid novolac resin.

The dope-state polyaniline powder was collected by suction filtration using a Nutsche filter, dispersed in methanol, stirred and washed three times, and then collected by filtration.
It was vacuum dried at 0 ° C. for 5 hours. The dope-state polyaniline powder thus obtained was molded into a disk shape with a tablet molding machine, and the electric conductivity was measured by the Van der Bau method to be 4.1 S / cm.

80 mg of carbon supporting 20% by weight of platinum (EC-20-PTC manufactured by Electrochem Co., USA) and 160 mg of conductive carbon black powder (Ketjenblack EC manufactured by Akzo Co.) were added to the above-mentioned doped polyaniline powder 720 mg. In addition, while mashing with a porcelain mortar, mixed for 10 minutes until uniform. To the obtained mixture, 6 g of a 2.5% by weight concentration polyvinylidene fluoride dimethylformamide solution was added, and further mixed using a mortar to obtain a paste.

This paste was applied to carbon paper of 5.8 cm square (TGP-H-90 manufactured by Toray Industries, Inc., film thickness 260 μm).
m), and heat at 80 ° C. for 60 minutes and dry,
An electrode was prepared. The weight gain was about 234 mg. From this, the amount of platinum supported is 0.10 mg per electrode area.
It was calculated to be / cm ² . A 5% by weight Nafion (registered trademark) solution (manufactured by Aldrich) was applied onto the carbon paper treated in this way, and heated and dried at 80 ° C. for 15 minutes. The electrode thus obtained was used as the cathode.

The electrode prepared in the same manner as above was dipped in a 20% by weight aqueous solution of phenol sulfonic acid novolac resin, the Amewa calomel electrode (SCE) was used as a reference electrode, and a platinum wire having a diameter of 0.5 mm was used as a counter electrode. , Hokuto Denko's Potentiostat / Lubanostat (HA-
501) and a function generator (HB-1)
05), and a potential range of −0.2 to 0.6 V vs.
A cyclic volchmogram was obtained under the conditions of SCE and a sweep rate of 20 mV / sec. The oxidation peak of polyaniline is 0.5 V vs. In SCE, the reduction peak of polyaniline was -0.1 V vs. Appeared in SCE. Therefore, the potential of the potentiostat was fixed at -0.1 V and electrochemical reduction was performed. The electrode thus obtained was used as an anode.

An acid type styrene / divinylbenzene copolymer sulfonated membrane was placed as a proton exchange membrane between the cathode and the anode thus prepared, and a mold was used to heat the membrane at a temperature of 130 ° C. and a pressure of 3 MPa. Under the conditions described above, an electrode / proton exchange membrane assembly was prepared by hot pressing, and a single-layer fuel battery cell for testing was assembled.

This fuel cell was incorporated into a fuel cell evaluation device (manufactured by Toyo Technica Co., Ltd.), the cell temperature was 70 ° C., and oxygen gas was supplied to the cathode at a rate of 500 mL / min at a humidifier temperature of 70 ° C. Hydrogen gas was supplied to the anode at a rate of 500 mL / min at a humidifier temperature of 80 ° C.
Therefore, first, when only the electromotive force (open circuit voltage) was measured without passing a current, it was 0.64V. Next, when a load was applied to the fuel cell and the voltage was 0.4 V, 4.
A current of 56 A (182 mA / cm ² ) was obtained.

Under this condition, continuous operation was carried out for 100 hours. As a fuel cell characteristic, a current value of 4.33 A (173 mA / cm ² ) was obtained at a voltage of 0.4 V. As described above, the characteristics of the fuel cell hardly changed even after 100 hours.

Comparative Example 1 Platinum 20 wt% supported carbon 360 manufactured by Electrochem
mg and carbon black (Cabot Vulcan XC
72R) 72 mg was weighed and added to 2.5 g of a 1.9 wt% polyvinylidene fluoride resin / N, N-dimethylformamide solution and mixed using a mortar to prepare a catalyst paste. This paste was used to make 5.8 cm square carbon paper (TGP-H-90 manufactured by Toray Industries, Inc., film thickness 260).
(2 μm) was applied onto two sheets, and heated and dried at 80 ° C. for 60 minutes in a hot air circulation dryer. The amounts of platinum carried on the two obtained electrodes were 0.69 mg / cm ² and 0.6, respectively.
It was ² mg / cm ² .

The same acid type styrene / divinylbenzene copolymer sulfonated membrane as used in Example 3 was used as a proton exchange membrane, sandwiched between the above two platinum catalyst-supporting carbon electrodes, and a die was used. The electrode-proton exchange membrane assembly was prepared by hot pressing under the conditions of a temperature of 130 ° C. and a pressure of MPa, and a test single-layer fuel battery cell having an effective electrode area of 25 cm ² was assembled.

This fuel cell was incorporated into a fuel cell evaluation device (manufactured by Toyo Technica Co., Ltd.), the cell temperature was 70 ° C., and oxygen gas was supplied to the cathode at a rate of 500 mL / min at a humidifier temperature of 70 ° C. Hydrogen gas was supplied to the anode at a rate of 500 mL / min at a humidifier temperature of 80 ° C.
The gas pressure was 0.1 MPa for both oxygen and hydrogen. Therefore, first, when only the electromotive force (open circuit voltage) was measured without passing a current, it was 0.92V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, 18.8
A large current of A (752 mA / cm ² ) was obtained. When continuous operation was performed under these conditions, the characteristics of the fuel cell for 100 hours were that the current value was 1.3 when the voltage was 0.4V.
It was 2 A (53 mA / cm ² ) and showed a very large reduction.

Example 4 In exactly the same manner as in Example 3, polyaniline powder doped with phenol sulfonate novolak resin, platinum 20.
A mixture of carbon (EC-20-PTC manufactured by Electrochem, USA), conductive carbon black powder (Ketjenblack EC manufactured by Akzo), and polyvinylidene fluoride was loaded on a 5.8 cm square carbon paper. To prepare an electrode. The amount of platinum supported was calculated to be 0.10 mg / cm ² per electrode area. 5% by weight on carbon paper treated in this way
A Nafion (registered trademark) solution (manufactured by Aldrich) was applied, and heated and dried at 80 ° C for 15 minutes. The electrode thus obtained was used as the cathode.

On the other hand, the anode is made of a conductive polymer.
As described in Chemistry Letters, pp. 153-154 (1988), an n-type conductive polymer polypyridine is prepared,
Using this, it prepared as follows.

That is, 44 m of carbon supporting 20% by weight of platinum (EC-20-PTC manufactured by Electrochem, USA)
g and 80 mg of conductive carbon black powder (Ketjenblack EC manufactured by Akzo Co., Ltd.) were added to 400 mg of polypyridine, and the mixture was ground in a porcelain mortar and mixed for 10 minutes until uniform. To the mixture thus obtained, 2.1 g of a 2.5% by weight concentration polyvinylidene fluoride resin in dimethylformamide solution was added, and further mixed using a mortar to form a paste.

This paste was applied to carbon paper of 5.8 cm square (TGP-H-90 manufactured by Toray Industries, Inc., film thickness 260 μm).
m), and heat at 80 ° C. for 60 minutes and dry,
An electrode was prepared. A 5% by weight Nafion (registered trademark) solution (manufactured by Aldrich) was applied onto the carbon paper treated in this way, and heated and dried at 80 ° C. for 15 minutes.

20% by weight of the electrode thus obtained
Of Phenolsulfonic acid novolac resin aqueous solution, and using a saturated calomel electrode (SCE) as a reference electrode and a platinum wire having a diameter of 0.5 mm as a counter electrode, a potentiostat / galvanostat (HA) manufactured by Hokuto Denko KK
-501) and function generator (HB-
105), and a potential range of −0.2 to 0.5 V v
s. A cyclic voltammogram was obtained under the conditions of SCE and sweep speed of 20 mV / sec. The reduction peak of polypyridine is -02V vs. Although it appeared in SCE, no oxidation peak was observed in the positive potential region. This indicates that polypyridine is an n-type conductive polymer. ． Therefore, the potential of the potentiostat is set to -0.2 V vs. The polypyridine was immobilized electrochemically on SCE. As a result, polypyridine has the formula (II)

[0111]

[Chemical 2]

It is presumed that the structure shown in FIG. The electrode thus obtained was used as an anode.

An acid type proton exchange membrane was prepared by casting from a toluene solution of a partially sulfonated polyisoprene.

The above-mentioned proton exchange membrane is placed as an electrolyte membrane between the cathode and the anode produced as described above, and an electrode / proton exchange membrane assembly is prepared by hot pressing at a temperature of 130 ° C. using a mold. Then, a single-layer fuel battery cell for test was assembled.

This fuel cell was incorporated into a fuel cell evaluation apparatus (manufactured by Toyo Technica Co., Ltd.), the cell temperature was 70 ° C., and oxygen gas was supplied to the cathode at a rate of 500 mL / min at a humidifier temperature of 70 ° C. Hydrogen debris was supplied to the anode at a rate of 1000 mL / min at a humidifier temperature of 80 ° C. At first, the electromotive force (open circuit voltage) was measured without flowing a current, and it was 0.72V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, it was 5.54.
A current of A (222 mA / cm ² ) was obtained.

Example 14 In a phenol sulfonic acid novolac resin aqueous solution, ammonium peroxodisulfate was used as an oxidizing agent to chemically oxidize indole to form a phenol sulfonic acid novolac resin and polyindole in which part of sulfuric acid was topped. A high-polymer powder was obtained. This is suction filtered with a nutsche, stirred and washed in methanol, and then at 5O 0 C for 5
Vacuum dried for hours. The obtained powder was pressure-molded with a tablet molding machine to obtain a disk having a diameter of 13 mm and a thickness of 720 μm. When the electric conductivity of this disk was measured by the Van der Pauw method, it was 1.2 × 10 ^-1 S / cm.

Next, carbon supporting 20% by weight of platinum (EC-20-PTC manufactured by US Electrochem) 44
and 80 mg of conductive carbon black powder (Ketjen Black EC manufactured by Akzo) are added to the above polyindole 42.
In addition to 0 mg, while mashing in a porcelain mortar, mix for 10 minutes until uniform. To the mixture thus obtained, 2.1 g of a dimethylformamide solution of poly (vinylidene fluoride) having a concentration of 2.5% by weight was added, and further mixed using a mortar to obtain a paste.

This paste was applied to carbon paper of 5.8 cm square (TGP-H-90 manufactured by Toray Industries, Inc., film thickness 260 μm).
m), and heat at 80 ° C. for 60 minutes and dry,
The electrode was prepared. A 5% by weight Nafion (registered trademark) solution (manufactured by Aldrich Co.) was applied onto the carbon paper thus treated, and heated and dried at 80 ° C. for 15 minutes. The electrode thus obtained was used as a cathode.

On the other hand, the anode is made of a conductive polymer.
It was prepared as follows using polyphenylquinoxaline, which is an n-type conductive polymer. That is, PM Hergenrot
her, HH Levine, J. Polymer Sci., Part A-1, 5, 145
3-1466 (1967), in m-cresol,
3,4,3 ', 4'-tetraaminobiphenyl and 1,4
-By reacting with bisbenzyl, a highly viscous solution of polyphenylquinoxaline was obtained, which was diluted with m-cresol to give a 1% by weight solution. Carbon black (Valcan XC72R manufactured by Cabot Corp.) was added to this solution, and the mixture was stirred with a homogenizer, and then the solvent m-cresol was distilled off in a dryer as it was to form a thin polyphenylquinoxaline film on the carbon surface.

Next, carbon supporting 20% by weight of platinum (EC-20-PTC manufactured by US Electrochem) 4
0 mg and 500 mg of carbon having a polyphenylquinoxaline film on the surface were ground in a porcelain mortar and mixed for 10 minutes until uniform. To the mixture thus obtained, 2.1 g of a polyvinylidene fluoride dimethylformamide solution having a concentration of 2.5% by weight was added, and further mixed using a mortar to obtain a paste.

This paste was applied to carbon paper of 5.8 cm square (TGP-H-90 manufactured by Toray Industries, Inc., film thickness 260 μm).
m), and heat at 80 ° C. for 60 minutes and dry,
An electrode was prepared. A 5% by weight Nafion (registered trademark) solution (manufactured by Aldrich) was applied onto the carbon paper treated in this way, and heated and dried at 80 ° C. for 15 minutes.

20% by weight of the electrode thus obtained
Phenol sulfonate / carbanostat (HA) manufactured by Hokuto Denko Co., Ltd. using a saturated calomel electrode (SCE) as a reference electrode and a platinum wire having a diameter of 0.5 mm as a counter electrode.
-501) and function generator (HB-
105), and a potential range of −0.2 to 0.5 V v
s. A cyclic voltammogram was obtained under the conditions of SCE and a drawing speed of 20 mV / sec. The reduction peak of polyphenylquinoxaline is -0.10 V vs. Although it appeared in SCE, no oxidation peak was observed in the positive potential region.
This indicates that polyphenylquinoxaline is an n-type conductive polymer.

Therefore, the potential of the potentiostat is set to −
0.10 V vs. The polyphenylquinoxaline was immobilized electrochemically on SCE. As a result, the polyphenylquinoxaline is injected with electrons and protons under acidic conditions, resulting in formula (III)

[0124]

[Chemical 3]

It is presumed that such a structure was reached. The electrode thus obtained was used as an anode.

The sulfonated product of polybenzimidazole was dissolved in N, N-dimethylacetamide, cast and dried, and the acid-type proton exchange membrane obtained was used as an electrolyte membrane. The electrode / proton exchange membrane assembly was prepared by hot pressing at a temperature of 130 ° C. by placing it between the anode and a mold, and assembling a single-layer fuel cell for testing.

This fuel cell was incorporated into a fuel cell evaluation device (manufactured by Toyo Technica Co., Ltd.), the cell temperature was set to 70 ° C., and oxygen gas was supplied to the cathode at a rate of 500 mL / min at a humidifier temperature of 70 ° C. Hydrogen gas was supplied to the anode at a rate of 1000 mL / min at a humidifier temperature of 80 ° C. At first, the electromotive force (open circuit voltage) was measured without applying a current, and it was 1.20V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, 22.5
A current of A (900 mA / cm ² ) was obtained.

[0128]

INDUSTRIAL APPLICABILITY As described above, the fuel cell according to the present invention has a conductive organic polymer having a redox function as an electrode catalyst, exhibits a high electromotive force, and can be discharged at a high current density. Thus, it exhibits high output fuel cell characteristics. Furthermore, by using an inorganic redox catalyst together with a conductive organic polymer as an electrode catalyst, a fuel cell with even higher output can be obtained.

Furthermore, according to the present invention, in the fuel cell, since the catalyst is a conductive organic polymer having a redox function, the catalyst is not attacked by oxygen radicals, and thus the electrolyte membrane is expensive. It is possible to use a cheap and easily available proton exchange membrane, for example, a proton exchange membrane in which the polymer chain is a hydrocarbon, instead of such a perfluorosulfonic acid polymer membrane, so that the cost of the fuel cell can be significantly reduced. You can

Continued front page    F-term (reference) 5H018 AA06 AS01 BB01 BB03 BB06                       BB08 BB12 BB13 BB17 CC06                       DD06 DD08 EE02 EE03 EE08                       EE17 EE18 EE19                 5H026 AA06 CX05 EE02 EE18 EE19

Claims (15)

[Claims] 1. A fuel cell in which a cathode and an anode are disposed with an electrolyte membrane sandwiched therebetween, an oxidant is supplied as a gas to the cathode, and a reducing agent is supplied as a gas to the anode, and at least one electrode is oxidized. A conductive organic polymer having a reducing function is used as an electrode catalyst, and the polymer chain is composed of a hydrocarbon skeleton which may contain one or more kinds of heteroatoms selected from N, S, O and F ( However, a fuel cell comprising a proton exchange membrane made of a polymer having an acid group, excluding a polymer chain made of perfluorohydrocarbon.). 2. The fuel cell according to claim 1, wherein the electrode catalyst comprises a mixture of a conductive organic polymer and an inorganic redox catalyst. 3. The fuel cell according to claim 1, wherein the conductive organic polymer is polyaniline or polyalkylaniline. 4. The conductive organic polymer is polypyridine, polyindole or polyphenylquinoxaline.
Or the fuel cell according to item 2. 5. The fuel cell according to claim 1, wherein the conductive organic polymer contains a dovant. 6. The fuel cell according to claim 5, wherein the dovant is a polymer sulfonic acid. 7. The fuel cell according to claim 6, wherein the polymer sulfonic acid is polyvinyl sulfonic acid or phenol sulfonic acid novolac resin. 8. The inorganic redox catalyst is at least one transition metal selected from platinum, barium, ruthenium, rhodium, silver, nickel, iron, copper, cobalt and molybdenum, or an oxide thereof. The fuel cell described. 9. The fuel cell according to claim 1, wherein the proton exchange membrane has a polymer chain made of a hydrocarbon and a polymer having a sulfonic acid group as an acid group. 10. The polymer according to claim 1, wherein the proton exchange membrane has a polymer chain made of a hydrocarbon and also has a phosphoric acid group, a phosphonic acid group or a phosphinic acid group as an acid group.
The fuel cell described in 1. 11. The fuel cell according to claim 9, wherein the proton exchange membrane is made of a polymer obtained by polymerizing a vinyl monomer having a sulfonic acid group. 12. The fuel cell according to claim 10, wherein the proton exchange membrane is made of a polymer obtained by polymerizing a vinyl monomer having a phosphoric acid group, a phosphonic acid group or a phosphinic acid group in its side chain. 13. The fuel cell according to claim 1, wherein the proton exchange membrane is made of a sulfonated product of a styrene / divinylbenzene copolymer. 14. The fuel cell according to claim 1, wherein the proton exchange membrane is made of a sulfonated product of polyisoprene. 15. The fuel cell according to claim 1, wherein the proton exchange membrane is made of a sulfonated product of polybenzimidazole.