JP2002203570A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide fuel cell which has high output and high voltage by making a conductive organic polymer an electrode catalyst. SOLUTION: The fuel cell is provided with a cathode and an anode on both sides of an electrolyte, and an oxidizer in gaseous state is supplied to the cathode, and a reducing agent in gaseous state is supplied to the anode. A conductive organic polymer having oxidization reduction capability is made to have in at least one of the electrodes as an electrode catalyst of the fuel cell. Using an inorganic oxidization reduction catalyst together with the conductive organic polymer as the electrode catalyst can obtain the fuel cell having much higher output power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell having a high output in which at least one of a cathode and an anode contains a conductive organic polymer having a redox function as an electrode catalyst.

[0002]

2. Description of the Related Art In recent years, a solid electrolyte / electrode structure is formed by disposing an anode and a cathode with a solid polymer electrolyte interposed therebetween, and a unit cell is formed by interposing this with a separator.
A fuel cell in which a plurality of such 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 distributed power source for homes, and the like because of its features of cleanness and high efficiency.

More specifically, such a polymer electrolyte fuel cell has, as a basic configuration, a pair of electrodes of an anode and a cathode each having an electrode catalyst, with a proton conductive ion exchange membrane interposed therebetween. The surface of the anode is brought into contact with a reducing agent (fuel) such as hydrogen, and the surface of the cathode is brought into contact with an oxidizing agent (oxygen) to cause an electrochemical reaction. Electric energy is extracted from between the pair of electrodes. As the proton-conducting ion exchange membrane, as a fluororesin-based ion exchange membrane having excellent basic characteristics,
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 such as polyacetylene, polypyrrole, or polyaniline and having an oxidation-reduction function (redox function) is used as an electrode active material in a lithium secondary battery or the like. (Japanese Patent No. 1845557)
No.), a use as a conductive polymer capacitor having a rapid discharge function has also been proposed (Proceedings of the 39th Symposium on Battery, p. 173 (1998), Proceedings of the 67th Annual Meeting of the Institute of Electrical Chemistry, Japan 147 (2000)).

[0005] However, the above-mentioned conductive organic polymer has higher energy than inorganic oxides and metal materials such as lithium cobalt oxide (LiCoO ₂ ) and lithium which are currently in practical use as electrode active materials. Low density.
Therefore, in order to compensate for 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 an electrolytic solution in contact with the conductive organic polymer. Thus, an attempt to use a battery like a fuel cell has been proposed (JP-A-59-60967, JP-A-61-124070).

However, according to these batteries, since both the oxidizing agent and the reducing agent are supplied as a solution, the diffusion of the active material to the electrode is slow, and the discharge characteristics thereof are about several mA / cm ² . In addition to obtaining a high output voltage, the battery system is complicated and impractical.

On the other hand, as described above, the conventional polymer electrolyte fuel cell uses platinum as an electrode catalyst, so that the cost is high, and the elution of an acidic liquid, the poisoning of carbon monoxide at the anode, etc. However, this is an important obstacle to practical application, and no practical electrode catalyst other than platinum has been found yet.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in a conventional fuel cell, and has a high output and a high voltage using a conductive organic polymer as an electrode catalyst. An object is to provide a fuel cell.

[0009]

According to the present invention, a cathode and an anode are provided with an electrolyte membrane interposed therebetween, and an oxidant is supplied to the cathode as a gas and a reducing agent is supplied as a gas to the anode. In a battery, at least one electrode
There is provided a fuel cell comprising a conductive organic polymer having a redox function as an electrode catalyst.

Further, according to the present invention, in a fuel cell in which a cathode and an anode are provided with an electrolyte membrane interposed therebetween, an oxidizing agent is supplied to the cathode as a gas, and a reducing agent is supplied to the anode as a gas. A fuel cell is provided, wherein one electrode has a mixture of a conductive organic polymer having a redox function and an inorganic redox catalyst as an electrode catalyst.

[0011]

According to the present invention, at least one of a cathode and an anode has an oxidation-reduction function (redox function), and preferably has a conductive organic polymer having a dopant as an electrode catalyst. .

Examples of such a conductive organic polymer 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,
Examples thereof include a carboxyl group, a sulfonic group, a halogen group, a nitro group, a cyano group, an alkylsulfonic group, and a dialkylamino group. These substituents are useful for adjusting the oxidation-reduction potential of the conductive organic polymer.

The dopant is preferably one having a sulfonic acid group. Examples of the dopant include ionic polymer sulfonic acids such as polyvinyl sulfonic acid and phenol sulfonic acid novolak resin, and low dopants such as dodecyl benzene sulfonic acid. Examples thereof include a molecular weight organic sulfonic acid compound, and among them, an ionic polymer such as the former, particularly a polymer sulfonic acid is preferable.

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

In the present invention, as the conductive organic polymer, among those described above, those which release protons in an oxidation reaction and consume protons in a reduction reaction are particularly preferable. As polyaniline, polyalkylaniline, polyindole,
Like poly (o-phenylenediamine), polypyridine, polyquinoxaline, polyphenylquinoxaline, etc.
Examples thereof include a conductive organic polymer having a nitrogen atom in the molecule.

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

Generally, a conductive organic polymer is p-type and n-type.
In order to determine which type is used, it is already known that, for example, a conductive organic polymer powder is formed into a disk, electrodes are attached at two places, and a temperature difference is applied to the electrodes. It is sufficient to check the positive or negative of the potential of the electrode on the low temperature side when is given. That is, when a positive potential appears at the low-temperature side electrode, the conductive organic polymer is p-type. Conversely, when a negative potential appears at the low-temperature side electrode, the conductive organic polymer becomes p-type. n
Type. As another method, a cyclic voltammogram of the conductive organic polymer is measured, and when the conductive organic polymer has a redox pair in a positive potential region with respect to SCE, the conductive organic polymer is p-type and negative. When the conductive organic polymer has an oxidation-reduction pair in the potential region of n, 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 oxidation-reduction 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 is usually 0.5 to 100 per electrode area.
mg / cm ² .

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

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

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

[0023]

Embedded image

(Wherein, m and n represent the mole fractions of the quinone diimine structural unit and the phenylenediamine structural unit in the repeating unit, respectively; 0 <m ≦ 1, 0 ≦ n <1, m
+ N = 1. To obtain an oxidized and undoped polyaniline powder comprising a repeating unit represented by the formula (1).

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, for example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide,
Dissolves in organic solvents such as dimethylsulfoxide, 1,3-dimethyl-2-imidazolidinone, and sulfolane. The solubility of the polyaniline in the undoped state in such an organic solvent depends on its average molecular weight and the solvent, but usually 0.5 to 100% of the polyaniline is dissolved to obtain a 1 to 30% by weight solution. be able to. In particular, this undoped polyaniline exhibits high solubility in N-methyl-2-pyrrolidone, and usually 20 to 100% of the 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 the polyaniline. That is, by reducing, m can be reduced and n can be increased. Conversely, if oxidized, m can be increased and n can be reduced. When the quinone diimine structural unit in the polyaniline is reduced by the reduction of the polyaniline, the solubility of the polyaniline in the organic solvent is increased. Also,
The viscosity of the solution is lower than before the reduction. For the reduction of such solvent-soluble polyaniline, for example, N 2
-Soluble 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. For example, mild silver oxide is preferable. Used.
If necessary, potassium permanganate, potassium dichromate, or the like can be used.

Next, the above-mentioned oxidized and undoped polyaniline powder is put into an aqueous solution of a polymer sulfonic acid which has been converted into an acid form with a strongly acidic cation exchange resin, and heated for several hours, whereby the polyaniline is doped with the polymer sulfonic acid. After that, the doped polyaniline powder is filtered, washed, and then dried in vacuum,
Conductive polyaniline powder using 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 included in at least one electrode as an electrode catalyst, the inorganic redox catalyst may be a catalytic hydrogenation catalyst or an oxygen autocatalyst. At least one transition metal selected from platinum, palladium, ruthenium, rhodium, silver, nickel, iron, copper, cobalt and molybdenum and / or an oxide thereof known as an oxidation catalyst can be used. Such an inorganic oxidation-reduction catalyst may be mixed with the conductive organic polymer powder as a fine powder as it is, or the conductive organic polymer powder may be dispersed in an aqueous solution of a water-soluble salt of the transition metal and stirred. After mixing, the above-mentioned transition metal salt may be converted to a metal or oxide by performing a reduction or oxidation treatment.

The reaction between the conductive organic polymer and the inorganic redox catalyst
When the mixture is used as an electrode catalyst, an inorganic redox catalyst
Is usually 0.1 part by weight based on 100 parts by weight of the conductive organic polymer.
It is used in the range of 1 to 30 parts by weight. Also, the electrode area
The loading amount of the inorganic oxidation-reduction catalyst is usually 0.001 to 0.001.
5mg / cm^TwoBut preferably 0.005.
~ 1mg / cm^TwoAnd particularly preferably, 0.
01-0.5mg / cm ^TwoRange.

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

Next, the production of the electrode used in the fuel cell according to the present invention will be described. A cathode using a conductive organic polymer as an electrode catalyst is produced, for example, as follows. That is, a conductive agent (for example, a conductive polyaniline powder having a polymer sulfonic acid as a dopant)
After mixing with conductive carbon black powder), this is made into a paste using a solution of a binder (for example, polyvinylidene fluoride resin or polytetrafluoroethylene resin),
This paste is applied to a conductive porous substrate (for example, Toray Industries, Inc.)
Coated on a carbon paper), dried and then treated with the conductive porous substrate thus treated with a proton exchange resin solution (for example, perfluorosulfonic acid manufactured by DuPont such as Nafion (registered trademark)). (Resin solution) is applied and dried to obtain a 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 is mixed with an inorganic redox catalyst powder, and if necessary, a conductive agent (for example, conductive carbon black powder) is mixed with the mixed powder. A paste is formed using a solution of an agent (for example, polyvinylidene fluoride resin or polytetrafluoroethylene resin), and the paste is applied on a conductive porous substrate (for example, carbon paper manufactured by Toray Industries, Inc.) and dried. Then, a proton exchange resin solution (for example, a perfluorosulfonic acid resin solution manufactured by DuPont such as Nafion (registered trademark)) is applied to the conductive porous base material thus treated,
Dry to obtain the cathode.

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

An electrolyte membrane (ie, a proton exchange membrane) is sandwiched between the thus obtained cathode and anode, and if necessary, is integrally formed by hot pressing or the like to form a fuel cell electrode-proton exchange membrane. Obtain a conjugate.

In the fuel cell according to the present invention, the electrolyte membrane is a cation exchange membrane made of a perfluorosulfonic acid resin as used in conventional solid polymer membrane type batteries, for example, Nafion (registered trademark). Is preferably used, but is not limited thereto. Therefore, for example, a porous film made of a fluororesin such as polytetrafluoroethylene impregnated with the above-mentioned Nafion or another ion conductive material, or a porous film or a nonwoven fabric made of a polyolefin resin such as polyethylene or polypropylene, What carried Nafion or another ion conductive substance may be used.

In the fuel cell according to the present invention, the oxidant 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 an oxidizing agent, and hydrogen gas is used as a reducing agent. In addition, as a reducing agent,
Methanol, dimethyl ether and the like can also be used.

[0038] The fuel cell according to the invention is operated at a temperature above 40 ° C. It is appropriately selected depending on the conductive organic polymer and the electrolyte membrane used, but is preferably in the range of 50 to 120 ° C, and particularly preferably in the range of 60 to 100 ° C. When the operating temperature is too low, a high output cannot be obtained because the reaction rate of the conductive organic polymer is slow.On the other hand, when the operating temperature is too high, there is a possibility that deterioration or peeling of the material used may occur. is there.

[0039]

The present invention will be described below with reference to examples together with 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) 6000 g of distilled water was placed 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 aniline. Separately, while cooling with ice water, distilled water 149 in a beaker was used.
434 g (4.295 mol) of 97% concentrated sulfuric acid was added to 3 g,
By mixing, an aqueous sulfuric acid solution was prepared. 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, 980 g (4.295 mol) of ammonium peroxodisulfate was added to 2293 g of distilled water in a beaker and dissolved to prepare an oxidizing agent aqueous 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, the peroxo acid was added to the acidic aqueous solution of the aniline salt from the straight tube adapter using a tubing pump while stirring. An aqueous solution of ammonium disulfate was gradually added dropwise at a rate of 1 mL / min or less. Initially, the colorless and transparent solution turned from green-blue to black-green as the polymerization proceeded, and then a black-green powder was deposited.

Although the temperature of the reaction mixture rises during the precipitation of the powder, the temperature in the reaction system must be kept at 0 ° C. or lower, preferably -3 ° C. or lower, in order to obtain a high molecular weight polyaniline. It is important to keep it low. After the powder deposition, the dropping rate of the aqueous solution of ammonium peroxodisulfate may be slightly increased, for example, to about 8 mL / min. However, also in this case, it is necessary to adjust the dropping speed so as to keep the temperature at −3 ° C. or lower while monitoring the temperature of the reaction mixture. So it took seven hours,
After the addition of the aqueous solution of ammonium peroxodisulfate was completed, stirring was continued at a temperature of −3 ° C. or lower for another hour.

The obtained powder was separated by filtration, 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 is 13mm in diameter,
A disk having a thickness of 700 μm was press-molded, and its conductivity was measured by the van der Pauw method.
S / cm.

(Production of Polyaniline Soluble in Organic Solvent by Dedoping of Conductive Polyaniline Composition (Polyaniline in Oxidative Dedoped State)) 350 g of the doped conductive polyaniline composition powder was placed in 4 L of 2N ammonia water. In addition, rotation speed 5
The mixture was stirred at 000 rpm for 5 hours. The mixture turned from black green to bluish purple.

The powder was filtered off with a Buchner funnel and 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. Thereafter, the powder was vacuum-dried at room temperature for 10 hours to obtain 280 g of black-brown undoped polyaniline (oxidized and undoped polyaniline) powder.

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

This polyaniline had a solubility of 1% or less in dimethyl sulfoxide and dimethylformamide. It did not substantially dissolve in tetrahydrofuran, pyridine, 80% aqueous acetic acid, 60% aqueous formic acid and acetonitrile.

Further, the polyaniline soluble in the undoped organic solvent 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
00 (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 Company) to obtain an aqueous solution of an acid type polyvinyl sulfonic acid. Next, this was concentrated using a rotary evaporator, and then dried under vacuum to obtain syrupy polyvinyl sulfonic acid. 12.5 g of this polyvinyl sulfonic acid was dissolved in 70.8 g of ion-exchanged water to prepare a 15% by weight aqueous solution of polyvinyl sulfonic acid.

10 g of the oxidized and undoped polyaniline powder obtained in Reference Example 1 was added to this aqueous solution of polyvinyl sulfonic acid, heated to 70 ° C. in a hot water bath, and kept for 130 minutes to dope polyaniline with polyvinyl sulfonic acid. The doped polyaniline was filtered by suction, washed with methanol, and then dried under vacuum at 50 ° C. for 4 hours to obtain an electric conductivity of 11.5 S / c having polyvinyl sulfonic acid as a dopant.
m of conductive polyaniline powder (15.2 g) was obtained.

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

Separately, 0.27 g of polyvinylidene fluoride resin (Kyner manufactured by Kureha Chemical Industry Co., Ltd.) was dissolved in 10.53 g of N, N-dimethylformamide to prepare a 2.5% by weight solution. A mixture of the conductive polyaniline powder and the carbon black powder was added, and further mixed using a mortar to obtain a paste. This paste was applied to a 5.8 cm square carbon paper (TGP-H-90, Toray Industries, Ltd., film thickness 260 μm), and heated to 80 ° C. in a hot air circulating drier.
For 60 minutes and dried. Next, a 5% by weight Nafion solution (manufactured by Aldrich) was applied onto the carbon paper treated in this manner, heated and dried at 80 ° C. for 15 minutes, and the electrode thus obtained was used as a cathode. Was.

The above electrode was immersed in a 15% by weight aqueous solution of polyvinyl sulfonic acid, a saturated calomel electrode (SCE) was used as a reference electrode, and a 0.5 mm diameter platinum wire was used as a counter electrode. Using a galvanostat (HA-501) and a function generator (HB-105), the potential range is -0.2 to 0.5.
A cyclic voltammogram was obtained under the conditions of V vs. SCE and a sweep speed of 20 mV / sec. The oxidation peak of polyaniline appeared at 0.5 V vs. SCE, and the reduction peak of polyaniline appeared at -0.1 V vs. SCE. Therefore, the potential of the potentiostat is fixed at -0.1V,
Reduced electrochemically for 30 minutes. The electrode thus obtained was used as an anode.

An acid-type Nafion membrane (Nafion (registered trademark) 117 manufactured by DuPont) was placed as a proton exchange membrane between the thus prepared cathode and anode, and the temperature was 130 ° C. and the pressure was 3 MPa using a mold. Under the conditions described above, an electrode-proton exchange membrane assembly was prepared by hot pressing,
A single-layer fuel cell for testing was assembled.

The fuel cell was assembled in a fuel cell evaluation apparatus (manufactured by Toyo Technica Co., Ltd.), the cell temperature was set to 70 ° C., and oxygen gas was supplied to the cathode at a humidifier temperature of 70 ° C. at a rate of 500 mL / min. Hydrogen gas was supplied to the anode at a humidifier temperature of 80 ° C. at a rate of 500 mL / min.
Therefore, first, only the electromotive force (open circuit voltage) was measured without flowing a current, and it was 0.50 V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, 0.73 A
(29 mA / cm ² ) was obtained.

Comparative Example 1 An anode and a cathode were produced in the same manner as in Example 1. The above-mentioned anode and cathode were incorporated in a two-tank type acrylic resin cell provided at the center with Nafion 117 as a diaphragm. Next, a reducing agent and an oxidizing agent in a liquid state were poured into the anode cell and the cathode cell, respectively. As a reducing agent, a 1N aqueous hydrochloric acid solution containing 0.42% by weight of stannous chloride (SnCl ₂ ) was used. As an oxidizing agent, ferric chloride (FeC
l ₃ ) 1N hydrochloric acid aqueous solution containing 0.61% by weight was used. Stannous chloride (SnCl ₂ ) and ferric chloride (FeCl ₃ )
Are 0.07V vs. standard electrode potential, respectively. NHE
(Standard hydrogen electrode) and 0.77 V vs. 0.77 V. NHE.
The battery configured in this way corresponds to the battery in Example 1 using a liquid reducing agent and an oxidizing agent instead of the hydrogen gas (reducing agent) and the oxygen gas (oxidizing agent).

The anode and the cathode were connected to a battery charging / discharging device (HJ-201B manufactured by Hokuto Denko KK), and 1 mA / c
A constant current discharge was performed at m ² , and a discharge curve was recorded by a recorder connected to a battery charge / discharge device.

The electromotive force of this battery was 0.4 V at first, but immediately began to drop, and after several minutes, it became 0.3 V, and continued to drop thereafter. After 8 hours, the electromotive force was 0 V. It became. When the constant current discharge was stopped, the voltage recovered to 0.5V. Thereafter, the current density was increased to 5 mA / cm ² , but the voltage immediately dropped, and the capacity was drastically reduced.

Example 2 Polyaniline powder in oxidized and undoped state obtained in Reference Example 1.
8 g of carbon having 0.4% of conductive carbon black powder (Ketjen Black EC manufactured by Akzo) and 20% by weight of platinum supported thereon (EC-20 manufactured by Electrochem, USA)
-PTC) was added and mixed with a mortar made of porcelain for 10 minutes while grinding until uniform.

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

A 5.8 cm square carbon paper (TGP-H-90 manufactured by Toray Industries, Inc .;
m) and heated and dried at 80 ° C. for 60 minutes in a hot air circulating drier. Next, a 5% by weight Nafion solution (manufactured by Aldrich) 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.

Next, the oxidized and undoped polyaniline powder obtained in Reference Example 1 was added to a methanol solution of hydrazine monohydrate, and the mixture was stirred and reduced for 8 hours. The obtained reaction product was filtered off with a suction bottle and a suction bottle, washed with methanol, and dried in a vacuum dryer at 70 ° C. for 5 hours. Thus, a polyaniline powder in a reduced undoped state was obtained.

A carbon (manufactured by Electrochem Co., USA) in which 1.8 g of the reduced undoped polyaniline powder and 0.4 g of a conductive carbon black powder (Ketjen Black EC manufactured by Akzo Co., Ltd.) and 20% by weight of platinum are supported. EC-
(20-PTC) was added and mixed with a mortar made of porcelain for 10 minutes until uniform.

Separately, 0.27 g of polyvinylidene fluoride resin (Kyner manufactured by Kureha Chemical Industry Co., Ltd.) was dissolved in 10.53 g of N, N-dimethylformamide to prepare a 2.5% by weight solution, and the above solution was prepared. Add a mixture of polyaniline powder and carbon black powder in a reduced undoped state,
The mixture was mixed using a mortar to obtain a paste. This paste is applied to 5.8 cm square carbon paper (TGP manufactured by Toray Industries, Inc.).
-H-90, film thickness 260 μm), and heated and dried at 80 ° C. for 60 minutes in a hot air circulating drier. Next, a 5% by weight Nafion solution (manufactured by Aldrich) was applied onto the carbon paper thus treated,
After heating and drying for minutes, the electrode thus obtained was used as an anode.

An acid-type Nafion membrane (Nafion (registered trademark) 117 manufactured by DuPont) was placed as a proton exchange membrane between the thus prepared cathode and anode.
Using a mold, at a temperature of 130 ° C. and a pressure of 3 MPa,
An electrode-proton exchange membrane assembly was prepared by hot pressing, and a single-layer fuel cell for testing was assembled.

The fuel cell was assembled in a fuel cell evaluation apparatus (manufactured by Toyo Technica Co., Ltd.), the cell temperature was set to 70 ° C., and oxygen gas was supplied to the cathode at a humidifier temperature of 70 ° C. at a rate of 500 mL / min. Hydrogen gas was supplied to the anode at a humidifier temperature of 80 ° C. at a rate of 500 mL / min.
Therefore, first, only the electromotive force (open circuit voltage) was measured without flowing a current, and it was 0.60 V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, 0.85 A
(34 mA / cm ² ).

Example 3 To 43.6 g of a phenolsulfonic acid novolak resin aqueous solution (manufactured by Konishi Chemical Industry Co., Ltd., free acid type, solid content: 45.9%, weight average molecular weight: 22,000 (GPC method, standard sodium polystyrene sulfonate)) 56.4 g of ion-exchanged water was added to dilute the solution, and 12.0 g of the oxidized and undoped polyaniline powder was added to the obtained aqueous solution of phenolsulfonic acid novolak resin, followed by heating in a water bath at 80 ° C. for 2 hours.
Left at room temperature overnight. The black-brown oxidized and undoped polyaniline powder turned black-green immediately after being added to the aqueous phenolsulfonic acid novolak resin solution, indicating that polyaniline was doped with the phenolsulfonic acid novolak resin.

The operation of filtering the doped polyaniline powder by suction filtration using a Nutsche, dispersing in methanol, stirring and washing was repeated three times.
Vacuum dried at 0 ° C. for 5 hours. The thus obtained doped polyaniline powder was formed into a disk shape using a tablet press, and the conductivity was measured by the van der Pauw method. As a result, it was 4.1 S / cm.

80 mg of carbon (EC-20-PTC, manufactured by Electrochem, USA) supporting 20% by weight of platinum and 160 mg of conductive carbon black powder (Ketjen Black EC, manufactured by Akzo) are mixed with 720 mg of the above-mentioned doped polyaniline powder. , And mixed for 10 minutes until uniform using a mortar made of porcelain. 6 g of a 2.5% by weight solution of polyvinylidene fluoride in dimethylformamide was added to the obtained mixture, and the mixture was further mixed using a mortar to obtain a paste.

A 5.8 cm square carbon paper (TGP-H-90 manufactured by Toray Industries, Inc .;
m) coated on top, heated and dried at 80 ° C. for 60 minutes,
An electrode was prepared. The weight gain was about 234 mg. Thereby, the supported amount of platinum was 0.10 mg per electrode area.
/ Cm ² . A 5% by weight Nafion solution (manufactured by Aldrich) 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.

The electrode prepared in the same manner as above was immersed in a 20% by weight aqueous solution of phenolsulfonic acid novolak resin, and 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. Hokuto Denko Co., Ltd. potentiostat / galvanostat (HA
-501) and function generator (HB-
105), a potential range of -0.2 to 0.6 V vs. S
A cyclic voltammogram was obtained under the conditions of CE and a sweep speed of 20 mV / sec. The oxidation peak of polyaniline is 0.5
V vs. SCE, and a reduction peak of polyaniline appeared at -0.1 V vs. 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 membrane (Nafion (registered trademark) 117 manufactured by DuPont) was placed between the cathode and the anode prepared as described above as a proton exchange membrane, and a mold was used at a temperature of 130 ° C. and a pressure of 3 MPa. The electrode / proton exchange membrane assembly was prepared by hot pressing under the conditions of
A single-layer fuel cell for testing was assembled.

The fuel cell was assembled in a fuel cell evaluation apparatus (manufactured by Toyo Technica Co., Ltd.), the cell temperature was set to 70 ° C., and oxygen gas was supplied to the cathode at a humidifier temperature of 70 ° C. at a rate of 500 mL / min. Hydrogen gas was supplied to the anode at a humidifier temperature of 80 ° C. at a rate of 500 mL / min.
Therefore, first, only the electromotive force (open circuit voltage) was measured without flowing a current, and it was 0.69 V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, 6.33 A
(253 mA / cm ² ).

Examples 4 to 12 and Comparative Example 2 In Example 3, instead of carbon supporting 20% by weight of platinum, carbon supporting 10% by weight of palladium, carbon supporting 5% by weight of ruthenium, Anode and cathode were prepared in the same manner as in Example 3, except that carbon containing 5% by weight of rhodium and various transition metals and oxides thereof were used together with a conductive organic polymer as shown in Table 1. Was prepared, an electrode-proton exchange membrane assembly was prepared using this electrode, and a single-layer fuel cell for testing was assembled. Urushibara Nickel is described in "Synthetic Organic Chemistry" Vol. 32, No. 11, pp. 951-958 (197
Prepared according to 4).

An acid-type Nafion membrane (Nafion (registered trademark) 117 manufactured by DuPont) is placed as a proton exchange membrane between the cathode and the anode prepared as described above, and a mold is used 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,
A single-layer fuel cell for testing was assembled.

The fuel cell was assembled in a fuel cell evaluation apparatus (manufactured by Toyo Technica Co., Ltd.), the cell temperature was set to 70 ° C., and oxygen gas was supplied to the cathode at a humidifier temperature of 70 ° C. at a rate of 500 mL / min. Hydrogen gas was supplied to the anode at a humidifier temperature of 80 ° C. at a rate of 500 mL / min.
Therefore, first, only the electromotive force (open circuit voltage) was measured without passing a current. Next, a load was applied to the fuel cell, and a voltage of 0.4 was applied.
The current value at V was measured. Table 1 shows the results.

For comparison, a result in the case of using a lead powder and a lead oxide powder which are neither a catalytic hydrogenation catalyst nor an oxygen autoxidation catalyst in place of the above-mentioned inorganic redox catalyst is shown as Comparative Example 2.

[0079]

[Table 1]

Example 13 In exactly the same manner as in Example 3, boraniline powder doped with phenolsulfonic acid novolak resin, platinum 20
A mixture consisting of carbon (wt.%) Supported carbon (EC-20-PTC manufactured by Electrochem, USA), conductive carbon black powder (Ketjen Black EC manufactured by Akzo) and polyvinylidene fluoride was coated on a 5.8 cm square carbon paper. To prepare an electrode. The amount of supported platinum was calculated to be 0.10 mg / cm ² per electrode area. 5% by weight on the carbon paper thus treated
Apply Nafion solution (Aldrich) and apply at 80 ° C
And dried for 15 minutes. The electrode thus obtained was used as a cathode.

On the other hand, the anode is a conductive polymer,
Chemistry Letters, 153-154 (1988).
Polypyridine, which is a type conductive polymer, was prepared, and was prepared as follows using this. That is, platinum 20% by weight
Loaded with carbon (Electrochem Corporation EC-2
(0-PTC) 44 mg and conductive carbon black powder (Ketjen Black EC manufactured by Akzo Co., Ltd.) 80 mg were added to polypyridine 400 mg, and mixed in a porcelain mortar for 10 minutes until uniform. To the mixture thus obtained was added 2.1 g of a 2.5% strength by weight polyvinylidene fluoride solution in dimethylformamide.
The mixture was mixed using a mortar to make a paste.

A 5.8 cm square carbon paper (TPG-H-90 manufactured by Toray Industries, Inc .;
m) coated on top, heated and dried at 80 ° C. for 60 minutes,
An electrode was prepared. A 5% by weight Nafion solution (manufactured by Aldrich) was applied onto the carbon paper thus treated, and heated and dried at 80 ° C. for 15 minutes.

The electrode thus obtained was used in an amount of 20% by weight.
Phenolsulfonic acid novolak resin aqueous solution, using a saturated calomel electrode (SCE) as a reference electrode, a 0.5 mm diameter platinum wire as a counter electrode, and a potentiostat / galvanostat (HA) manufactured by Hokuto Denko Corporation.
-501) and function generator (HB-
105) using a potential range of -0.2 to 0.5 V vs. S
A cyclic voltammogram was obtained under the conditions of CE and a sweep speed of 20 mV / sec. The reduction peak of polypyridine is -0.
2V 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 -0.0.
2V vs. The polypyridine was electrochemically reduced on SCE. This allows polypyridine to
Electrons and protons are injected into this under acidic conditions, and the formula (II)

[0085]

Embedded image

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

An acid-type naphthion membrane (Nafion 117 manufactured by DuPont) was placed as a proton exchange membrane between the cathode and the anode thus produced, and a mold was used.
An electrode / proton exchange membrane assembly was prepared by hot pressing at a temperature of 130 ° C., and a single-layer fuel cell for testing was assembled.

The fuel cell was assembled in a fuel cell evaluation apparatus (manufactured by Toyo Technica Co., Ltd.), the cell temperature was set to 70 ° C., and oxygen gas was supplied to the cathode at a humidifier temperature of 70 ° C. at a rate of 500 mL / min. Hydrogen gas was supplied to the anode at a humidifier temperature of 80 ° C. at a rate of 1000 mL / min. At first, when only the electromotive force (open circuit voltage) was measured without flowing a current, it was 0.78 V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, 7.82 A (3
A current of 13 mA / cm ² ) was obtained.

Example 14 Indole was chemically oxidized and polymerized using ammonium peroxodisulfate as an oxidizing agent in an aqueous solution of a phenolsulfonic acid novolak resin to obtain a conductive material composed of a phenolsulfonic acid novolak resin and polyindole partially doped with sulfuric acid. A conductive polymer powder was obtained. This was suction-filtered with a Nutsche, stirred and washed in methanol, and then dried at 50 ° C. for 5 hours.
Vacuum dried for hours. The obtained powder was press-formed using a tablet press to obtain a disc having a diameter of 13 mm and a thickness of 720 μm. The conductivity of the disk was measured by the van der Pauw method and found to be 1.2 × 10 ⁻¹ S / cm.

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

A 5.8 cm square carbon paper (TCP-H-90, manufactured by Toray Industries, Inc .;
m) coated on top, heated and dried at 80 ° C. for 60 minutes,
An electrode was prepared. A 5% by weight Nafion solution (manufactured by Aldrich) 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 a conductive polymer,
It was prepared as follows using polyphenylquinoxaline, which is an n-type conductive polymer. That is, PM Hergenro
ther, HH Levine, J. Polymer Sci., Part A-1, 5,
1453-1466 (1967) A high viscosity solution of polyphenylquinoxaline was obtained by reacting 3,4,3 ′, 4′-tetraaminobiphenyl with 1,4-bisbenzyl in m-cresol, This was diluted with m-cresol and then poured into methanol to obtain a powder of polyphenylquinoxaline. This was suction-filtered by Nutsche and vacuum-dried at 60 ° C.

Next, carbon (EC-20-PTC manufactured by Electrochem Corp., USA) supporting 20% by weight of platinum was used.
0 mg and 80 mg of conductive carbon black powder (Ketjen Black EC, manufactured by Akzo) were added to 435 mg of the above-mentioned polyphenylquinoxaline, and mixed in a porcelain mortar for 10 minutes until uniform. To the mixture thus obtained was added 2.1 g of a 2.5% by weight solution of polyvinylidene fluoride in dimethylformamide.
The mixture was mixed using a mortar to make a paste.

The paste was coated with 5.8 cm square carbon paper (TGP-H-90, manufactured by Toray Industries, Inc., film thickness 260 μm).
m) coated on top, heated and dried at 80 ° C. for 60 minutes,
An electrode was prepared. A 5% by weight Nafion solution (manufactured by Aldrich) was applied onto the carbon paper thus treated, and heated and dried at 80 ° C. for 15 minutes. The electrode thus obtained was immersed in a 20% by weight aqueous solution of phenolsulfonic acid novolak resin, and a saturated calomel electrode (SCE) was used as a reference electrode, and a 0.5 mm-diameter platinum wire was used as a counter electrode. Potentiometer / carbanostat (HA-501) and function generator (HB-105) manufactured by K.K. SCE, sweep speed 20mV /
A cyclic voltammogram was obtained under the condition of seconds. The reduction peak of polyphenylquinoxaline is −0.10 V v
s. Although 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 -0.0.
10V vs. 10V. The polyphenylquinoxaline was electrochemically reduced, immobilized on SCE. As a result, polyphenylquinoxaline is injected with electrons and protons under acidic conditions, and the compound of formula (III)

[0096]

Embedded image

It is presumed that the structure as described above has been reached. The electrode thus obtained was used as an anode.

A fermentation-type naphthion membrane (Nafion 117 manufactured by DuPont) was placed as a broton exchange membrane between the thus prepared cathode and anode, and a mold was used.
An electrode / broton exchange membrane assembly was prepared by hot pressing at a temperature of 130 ° C., and a single-layer fuel cell for testing was assembled.

The fuel cell was assembled in a fuel cell evaluation apparatus (manufactured by Toyo Technica Co., Ltd.), the cell temperature was set to 70 ° C., and oxygen gas was supplied to the cathode at a humidifier temperature of 70 ° C. at a rate of 500 mL / min. Hydrogen gas was supplied to the anode at a rate of 1000 mL / min at a humidifier temperature of 80 ° C. At first, when only the electromotive force (open circuit voltage) was measured without flowing a current, it was 1.20 V. Next, when a load was applied to the fuel cell, when the voltage was 0.4 V, 24.6 A (9
A current of 84 mA / cm ² ) was obtained.

[0100]

As described above, the fuel cell according to the present invention has a conductive organic polymer having an oxidation-reduction function as an electrode catalyst, supplies an oxidizing agent to the cathode as a gas, and supplies the reducing agent to the anode. Since it is supplied by gas, it shows a high electromotive force,
It can be discharged at a high current density, thus exhibiting high output fuel cell characteristics. Further, by using an inorganic oxidation-reduction catalyst together with a conductive organic polymer as an electrode catalyst, a fuel cell with higher output can be obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 31/26 B01J 31/26 M 31/28 31/28 M 31/34 31/34 MH01M 8/10 H01M 8/10 (72) Inventor Kuniaki Ishibashi 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 4G069 AA03 BA22A BA22B BB02A BB02B BB04A BB04B BC31A BC31B BC32A BC32B BC59A BC59B BC66A BC66A BC66B BC67B BC68A BC68B BC70A BC70B BC71A BC71B BC72A BC72B BC75A BC75B BE13A BE16A BE16B BE22A BE22B BE37A BE37B CC32 EA07 5H018 AA06 AS02 AS03 EE02 EE03 EE12 EE16 EE17 5H026 AA06

Claims (9)

[Claims] A fuel cell in which a cathode and an anode are provided with an electrolyte membrane interposed therebetween, an oxidant is supplied to the cathode as a gas, and a reducing agent is supplied to the anode as a gas. A fuel cell comprising a conductive organic polymer having a reducing function as an electrode catalyst. 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 method according to claim 1, wherein the conductive organic polymer is polypyridine, polyindole or polyphenylquinoxaline.
Or the fuel cell according to 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 a polyvinyl sulfonic acid or a phenol sulfonic acid novolak resin. 8. The method according to claim 2, wherein 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 as described. 9. The fuel cell according to claim 1, wherein the oxidizing agent is oxygen and the reducing agent is hydrogen.