JP2003203642A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell in which a conductive organic polymer is provided as an electrode catalyst and a polymer having proton exchange property in itself is used as its binder and, thereby, which has high output and high voltage. <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. At least one of the electrodes uses as an electrode catalyst a conductive organic polymer having oxidation-reduction function and is fixed firmly to the conductive substrate by a binder made of a proton exchanging organic polymer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to a conductive organic polymer having an oxidation-reduction function as an electrode catalyst for at least one of a cathode and an anode, which is made conductive by a binder made of a proton-exchangeable organic polymer. The present invention relates to a fuel cell having a high output and a high voltage, which is fixed to a base material.

[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 conductive ion exchange membrane sandwiched therebetween. A reducing agent (fuel) such as hydrogen is brought into contact with the surface of the anode, an oxidizing agent (oxygen) is brought into contact with the surface of the cathode, an electrochemical reaction is caused, and this reaction is utilized. Electric energy is taken out from between the pair of electrodes. As the proton-conductive ion exchange membrane, a fluororesin-based ion exchange membrane having excellent basic properties is conventionally used.
It is well known, and as an anode and a 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 dopant represented by polyacetylene, polypyrrole, polyaniline, etc., and having a redox function (redox function) is an electrode active material in a lithium secondary battery or the like. It has been attracting attention as (Patent No. 1945557
No.), a use as a conductive polymer capacitor having a rapid discharge function has also been proposed (Proceedings of the 39th Battery Symposium, p. 173 (1998), Proc. 147 (2000)).

However, the conductive organic polymer as described above has a higher energy than the inorganic oxides and metal materials such as lithium cobalt oxide (LiCoO ₂ ) and lithium, which are the electrode active materials which are 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, JP-A-61-212070).

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 characteristics thereof are as high as several mA / cm ^2. In addition to being unable to obtain the output voltage, the battery system is also complicated and 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 and the elution of the acidic liquid and the carbon monoxide poisoning at the anode are caused. However, it is an important obstacle to practical use, and practical electrode catalysts other than platinum have not yet been found.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in conventional fuel cells, and uses a conductive organic polymer as an electrode catalyst and as a binder thereof. It is an object of the present invention to provide a fuel cell having high output and high voltage by using an organic polymer having a proton exchange property.

[0009]

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 the battery, at least one of the electrodes is composed of a conductive organic polymer having a redox function as an electrode catalyst and fixed to a conductive base material with a binder made of a proton-exchangeable organic polymer. A featured fuel cell is provided.

Further, according to the present invention, at least in a fuel cell in which a cathode and an anode are arranged with an electrolyte membrane sandwiched therebetween, an oxidizing agent 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 composed of a conductive organic polymer having a redox function and an inorganic redox catalyst as an electrode catalyst, and is fixed to a conductive base material with a binder composed of a proton-exchangeable organic polymer. A fuel cell is provided.

[0011]

According to the present invention, at least one of the cathode and the anode has a redox function (redox function), and preferably, a conductive organic polymer having a dopant is used as an electrocatalyst to produce a proton. It is constituted by being fixed on a conductive base material with a binder made of an exchangeable organic polymer.

Examples of such conductive organic polymers include polyacetylene, poly-p-phenylene, polyaniline, polypyrrole, polythiophene, polyindole, poly-2,5-diaminoanthraquinone and poly (o-o-
Examples thereof include phenylenediamine), poly (quinolinium) salt, poly (isoquinolinium) salt, polypyridine, polyquinoxaline, and polyphenylquinoxaline. 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,
Examples thereof include a carboxyl group, a sulfonic acid group, a halogen group, a nitro group, a cyano group, an alkylsulfonic acid group and a dialkylamino group. These substituents are useful for adjusting the redox potential of the conductive organic polymer.

The above-mentioned dopant is preferably one having a sulfonic acid group, for example, an ionic polymer sulfonic acid such as polyvinyl sulfonic acid or phenol sulfonic acid novolak resin, or a low ionic acid such as dodecylbenzene sulfonic acid. Although a molecular weight organic sulfonic acid compound can be mentioned, among them, an ionic polymer such as the former is preferable, and a polymer sulfonic acid is particularly preferable. Here, 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 as the conductive organic polymer. 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 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 p-type, When it has a redox couple in the potential region of, the conductive organic polymer is n-type.

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 100 per electrode area.
It is in the range of 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, the 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 protonic 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)

[0023]

[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, and 0 <m ≦ 1, 0 ≦ n <1, m
+ N = 1. ) Deoxidized polyaniline powder comprising a repeating unit represented by the formula (1) is obtained.

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. The solubility of the undoped polyaniline in such an organic solvent depends on the average molecular weight and the solvent, but usually 0.5 to 100% of polyaniline is 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 undoped state is put into an aqueous polymer sulfonic acid solution which has been 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 a mixture of a conductive organic polymer and an inorganic redox catalyst is provided on at least one electrode 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.

Further, the inorganic redox catalyst may be supported by utilizing the doping reaction to the conductive polymer. That is, after the conductive organic polymer is doped with a water-soluble salt or a water-soluble acid of the anion containing the transition metal, the conductive organic polymer having the anion containing the transition metal as a dopant is used as a hydrogen gas or a reducing agent. Then, an inorganic redox catalyst composed of these transition metals can be supported on the conductive organic polymer. If necessary, the conductive organic polymer can be further supported with an inorganic redox catalyst composed of a transition metal oxide by further treating with oxygen gas or an oxidizing agent thereafter.

Of a conductive organic polymer and an inorganic redox catalyst
When using the mixture as an electrode catalyst, an inorganic redox catalyst
Is usually 0,0 with respect to 100 parts by weight of the conductive organic polymer.
It is used in the range of 1 to 30 parts by weight. Also, in the electrode area
The amount of the inorganic redox catalyst supported is usually 0.001 to
5 mg / cm²Range, but preferably 0.005
~ 1 mg / cm²Range, and particularly preferably 0.
01-0.5 mg / cm ²Is the range.

As described above, according to the present invention, by providing the electrode with the mixture of the conductive organic polymer and the inorganic redox catalyst as an electrode catalyst, compared with the case where only the conductive organic polymer is used as the electrode catalyst. As a result, a high output fuel cell can be obtained.

In the fuel cell of the present invention, at least one of the electrodes is a conductive organic polymer having the above redox function, or a mixture of this conductive organic polymer and an inorganic redox catalyst is used as an electrode catalyst. It is configured by being fixed to a conductive base material with a binder made of a proton-exchangeable organic polymer.

As the above-mentioned proton exchangeable organic polymer,
For example, Nafion (DuPont (USA), registered trademark)
A perfluorosulfonic acid resin represented by is preferably used. The perfluorosulfonic acid resin is a polymer whose polymer chain is made of perfluorohydrocarbon and has a sulfonic acid group on the side chain, if necessary, via an intermediate group, and, for example, the above Nafion ( (Registered trademark) has a structure represented by the following general formula (II).

[0035]

[Chemical 2]

In the above formula, Nafion is, for example,
It is said that m ≧ 1, n = 2, x = 5-13.5, and y = 1000.

According to the present invention, the above Nafion (registered trademark) is preferably used as the perfluorosulfonic acid resin. However, in the present invention, the proton-exchangeable organic polymer used as the binder is, as in Nafion (registered trademark), a solution that is used as a solution and forms an insoluble resin by heating, In particular, it is not limited.

That is, according to the present invention, as will be described later,
After mixing the electrode catalyst with a conductive agent as needed, this is made into a paste using a binder, coated on an appropriate conductive base material, heated and dried to render the perfluorosulfonic acid resin insoluble, The electrode catalyst is fixed on the conductive base material.

As described above, the concentration of the proton-exchangeable organic polymer in the solution of the proton-exchangeable organic polymer used as the binder is formed by applying this on a conductive substrate, heating and drying. There is no particular limitation as long as the film has high strength, but it is usually in the range of 1 to 20% by weight, preferably 5 to 10% by weight.

According to the present invention, such a binder is usually used as a solution in an amount of 50 parts by weight per 100 parts by weight of the electrode catalyst.
Used in the range of about 200 to 200 parts by weight, preferably 100
It is used in the range of up to 150 parts by weight. Therefore, the amount of the proton-exchangeable organic polymer applied to the electrode is usually 0.5 to
It is 10 mg / cm ² .

The conductive base material is not particularly limited, but a conductive porous base material such as carbon paper is preferably used.

As described above, according to the present invention, by using the proton-exchangeable organic polymer as the binder of the electrode catalyst, the electrode catalyst, the proton-exchangeable organic polymer and hydrogen,
By forming an interface with oxygen or water, that is, a so-called three-phase interface satisfactorily, it is possible to obtain a fuel cell having a high output as compared with the case where an organic polymer having no proton exchange ability is used as a binder. You can

Next, the production of the electrode used in the fuel cell according to the present invention will be described in detail. 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 and, if necessary, a conductive agent (for example, conductive carbon black powder) are mixed with a proton-exchangeable resin solution (for example, a solution such as Nafion (registered trademark)). (Fluorosulfonic acid resin solution) is stirred and mixed with a binder to form a paste, and this paste is placed on a conductive base material, for example, a conductive porous base material (for example, carbon paper manufactured by Toray Industries, Inc.). After coating and drying, a cathode is obtained.

A cathode having 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 binder comprising a conductive polyaniline powder having a polymer sulfonic acid as a dopant, an inorganic redox catalyst powder, and a proton exchange resin solution (for example, a perfluorosulfonic acid resin solution such as Nafion (registered trademark)), If necessary, a conductive agent (for example, conductive carbon black powder) is stirred and mixed to form a paste, and this paste is used as a conductive base material, for example, a conductive porous base material (for example, Toray Industries, Inc.). Coated carbon paper) 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 at a potential where a reduction peak appears. It is convenient to electrochemically reduce the cathode.

An electrolyte membrane (that is, a proton exchange membrane) is sandwiched between the thus obtained cathode and anode, and if necessary, integrally molded by hot pressing or the like to prepare an electrode for a fuel cell-proton exchange membrane. Get the zygote.

In the fuel cell according to the present invention, the electrolyte membrane is a cation exchange membrane made of a perfluorosulfonic acid resin such as that used in conventional solid polymer membrane type cells, for example, Nafion (registered trademark). Membranes are preferably used, but are not so limited. Therefore, for example, a porous membrane made of a fluororesin such as polytetrafluoroethylene impregnated with the above Nafion (registered trademark) or another ion conductive substance, or a porous membrane made of a polyolefin resin such as polyethylene or polypropylene. Alternatively, a non-woven fabric carrying the above Nafion (registered trademark) or another ion conductive substance may be used. Further, a hydrocarbon-based proton exchange polymer may be used.

In the fuel cell according to the present invention, the cathode is supplied with the oxidizing agent in the form of gas and the anode is supplied with the reducing agent in the form of gas. 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 invention is operated at temperatures above 40 ° C. The temperature 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, it is not possible to obtain a high output because the reaction speed of the conductive organic polymer is slow.On the other hand, when the operating degree is too high, deterioration or peeling of the material used may occur. is there.

[0050]

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 (4.295 mol) of aniline were charged in this order to dissolve the aniline. Separately, while cooling with ice water, distilled water 149 in a beaker
Add 434 g (4.295 mol) of 97% concentrated sulfuric acid to 3 g,
A sulfuric acid aqueous solution was prepared by mixing. This sulfuric acid aqueous solution was added to the separable flask, and the entire flask was cooled to -4 ° C in a low temperature constant temperature bath.

Then, 980 g (4.295 mol) of ammonium peroxodisulfate was added to 2293 g of distilled water in a beaker and dissolved to prepare an aqueous oxidant solution.

The entire flask was cooled in a low temperature constant temperature bath and, while maintaining the temperature of the reaction mixture at -3 ° C or lower, to the acidic aqueous solution of aniline salt under stirring, using a tubing pump, through a straight pipe adapter to the above peroxo tube. Aqueous ammonium disulfate 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. In this case as well, 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 powder of a black-green conductive polyaniline composition. 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 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 was 1.23 dl / g.

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 23,000 and the weight average molecular weight was 1600.
It was 00 (both in terms of polystyrene).

Example 1 Phenol sulfonic 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 56.4 was added for dilution, and 12.0 g of oxidatively undoped polyaniline powder was added to the obtained phenolsulfonic acid novolak resin aqueous solution, and the mixture was heated at 80 ° C. for 2 hours on a water bath, and then at room temperature. The black-brown oxidatively undoped polyaniline powder turned black green immediately after being added to the phenolsulfonic acid novolac resin aqueous solution, indicating that polyaniline was doped with the phenolsulfonic acid novolac resin. Was done.

This doped 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 conductivity was measured by the Van der Pauw method, and it was 4.1 S / cm. Carbon supporting 20% by weight of platinum (EC-2 manufactured by Electrochem, USA)
0-PTC) 80 mg and doped polyaniline powder 720 mg, 5% by weight Nafion solution (perfluorosulfonic acid resin solution, Aldrich) 1600 mg
In addition, the mixture was stirred 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. The amount of platinum supported was 0.
It was calculated to be 10 mg / cm ² . The electrode thus obtained was used as the cathode.

The electrode prepared in the same manner as described above was dipped in a 20 wt% aqueous solution of novolac phenolsulfonate resin, 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. Potato stat / galvanostat (HA manufactured by Hokuto Denko KK)
-501) and function generator (HB-
105), and a potential range of −0.2 to 0.6 V v
s. A cyclic voltammogram was obtained under the conditions of SCE and sweep speed 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.

The acid-type Nafion (registered trademark) membrane 117 is placed as a proton exchange membrane between the cathode and the anode thus produced, and a mold is used at a temperature of 130 ° C.
An electrode / proton exchange membrane assembly was prepared by hot pressing under a pressure of 3 MPa, and a single-layer fuel cell unit 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 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 0.69V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, 9.
A current of 50 A (380 mA / cm ² ) was obtained.

Comparative Example 1 80 mg of carbon supporting 20% by weight of platinum (EC-20-PTC manufactured by US Electrochem) and conductive carbon black powder (Ketjenblack EC manufactured by Akzo).
160 mg and 720 mg of the doped polyaniline powder obtained in Example 1 were added and mixed for 10 minutes while being ground with a porcelain mortar. To the obtained mixture was added 6 g of a 2.5 wt% concentration polyvinylidene fluoride dimethylformamide solution as a binder, and further,
The mixture was mixed using a mortar to obtain a paste.

This paste was applied to a 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. As a result, the amount of platinum supported is 0.10 m per electrode area.
It was calculated to be g / 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 at 80 ° C. for 15 minutes,
Dried. The electrode thus obtained was used as the cathode.

The electrode prepared in the same manner as above was immersed in a 20 wt% aqueous solution of phenolsulfonic acid novolac resin, 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. Potato stat / galvanostat (HA manufactured by Hokuto Denko KK)
-501) and function generator (HB-
105), and a potential range of −0.2 to 0.6 V v
s. A cyclic voltammogram was obtained under the conditions of SCE and sweep speed 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 nafion film (Nafion (registered trademark)) was formed between the cathode and the anode thus manufactured.
117) as a proton exchange membrane and using a mold,
An electrode / proton exchange membrane assembly was prepared by hot pressing under the conditions of a temperature of 130 ° C. and a pressure of 3 MPa, and 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 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 0.69V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, 6.
A current of 33 A (253 mA / cm ² ) was obtained.

Example 2 In the same manner as in Example 1, phenolsulfonic acid novolac
Polyaniline powder doped with black resin, platinum 20 weight
% Supported carbon (EC manufactured by US Electrochem
-20-PTC), 5% by weight Nafion (registered trademark) solution
Liquid (made by Aldrich) is stirred to form a paste.
Adjust the electrode by supporting it on a carbon paper of 8 cm square.
Made The amount of platinum carried is 0.10 m per electrode area
g / cm ²Was calculated. This electrode at 80 ℃ for 15 minutes
The electrode thus obtained was heated and dried for a period of time to serve as a cathode.

On the other hand, for the anode, polyphenylquinoxaline, which is an n-type conductive polymer, was used as a conductive polymer and prepared as follows. That is, the literature (P.
M. Hergenrother, HH Levine, J. Polymer Sci., Pa
rt A-1, 5, 1453-1466 (1967)), polyphenyl is obtained by reacting 3,4,3 ′, 4′-tetraaminobiphenyl with 1,4-bisbenzyl in m-cresol. A highly viscous solution of quinoxaline was obtained and diluted with m-cresol to give a 1% by weight solution.
Carbon black (Cabot Co., Ltd. Vulcan XC
72R) was added and the mixture was stirred with a homogenizer, and then the solvent m-cresol was distilled off in a drier 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 the above polyphenylquinoxaline were added to 890 mg of a 5% by weight Nafion (registered trademark) solution (manufactured by Aldrich Co.) and stirred 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 electrodes thus obtained were 55.
Saturated calomel electrode (S
CE) as a reference electrode and a platinum wire having a diameter of 0.5 mm as a counter electrode, and a potentiostat manufactured by Hokuto Denko KK
Galvanostat (HA-501) and function generator (HB-105) are used for potential range-
0.2-0.5V vs. SCE, pulling speed 20 mV /
A cyclic voltammogram was obtained under the condition of second. The reduction peak of polyphenylquinoxaline is 0 V vs. SC
Appeared in E.

Therefore, the potential of the potentiostat is set to 0V.
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)

[0077]

[Chemical 3]

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

An acid-type Nafion (registered trademark) film (Nafion 117) was placed as a Broton exchange film between the cathode and the anode thus produced, and a mold was used.
The electrode / broton exchange membrane assembly was prepared by hot pressing at a temperature of 130 ° C., and a single-layer fuel cell unit for testing 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 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 1000 mL / min at a humidifier temperature of 80 ° C. At first, the electromotive force (open circuit voltage) was measured without passing a current, and it was 0.73V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, 16.2
A current of A (646 mA / cm ² ) was obtained.

[0081]

As described above, in the fuel cell according to the present invention, a conductive organic polymer having a redox function is preferably combined with an inorganic redox catalyst to form an electrode catalyst,
This is fixed to a conductive base material with a binder made of a proton-exchangeable organic polymer, and an oxidizing agent is supplied as a gas to such a cathode, and a reducing agent is supplied as a gas to the anode. It exhibits electromotive force and can be discharged at high current densities, thus exhibiting high power fuel cell characteristics.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 8/10 H01M 8/10 F term (reference) 5H018 AA06 AS02 AS03 BB03 BB06 BB08 BB16 CC06 DD08 EE03 EE12 EE17 5H026 AA06 BB02 BB03 BB04 BB10 CX05 CX07 EE02 EE12 EE18

Claims (10)

[Claims] 1. A fuel cell in which a cathode and an anode are arranged with an electrolyte membrane sandwiched therebetween, an oxidant is supplied to the cathode as a gas, and a reducing agent is supplied to the anode as a gas. At least one of the electrodes is redox-reduced. A fuel cell comprising a conductive organic polymer having a function as an electrode catalyst and being fixed to a conductive base material with a binder made of a proton-exchangeable organic polymer. 2. 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 redox-reduced. A fuel cell comprising a conductive organic polymer having a function and an inorganic redox catalyst as an electrode catalyst, which is fixed to a conductive base material with a binder made of a proton-exchangeable organic polymer. . 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 dopant. 6. The fuel cell according to claim 5, wherein the dopant 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 fuel cell according to claim 1, wherein the proton-exchangeable organic polymer is a perfluorosulfonic acid resin. 9. The inorganic redox catalyst is at least one transition metal selected from platinum, palladium, ruthenium, rhodium, silver, nickel, iron, copper, cobalt and molybdenum, or an oxide thereof. The fuel cell described. 10. The fuel cell according to claim 1, wherein the oxidizing agent is oxygen and the reducing agent is hydrogen.