JPH0766816B2 - Method for manufacturing gas diffusion type composite electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a gas diffusion type composite used for a fuel cell, a metal / air battery, a carbon dioxide electrolytic reduction electrode, a gas sensor, a humidity sensor and the like. The present invention relates to a method for manufacturing an electrode.

(Prior art) Fuel cell, metal / air cell, carbon dioxide electrolytic reduction electrode,
As the main body of the porous structure of the gas diffusion type composite electrode used for the gas sensor, the humidity sensor, etc., nickel tungstic acid having a low gas oxidation-reduction overvoltage, tungsten carbide coated with palladium or cobalt, oxide having a perovskite type structure, Containing nickel, silver, platinum, palladium, etc. as a catalyst and supporting these catalysts on a conductive powder such as activated carbon powder, and a binder having a relatively low film-forming property such as polytetrafluoroethylene Further, a material in which a conductive base material such as a metal porous body, a carbon porous body, or a carbon fiber nonwoven fabric is integrated is used. However, such a composition comprising a catalyst, a conductive powder and a binder contains a large amount of the conductive powder and uses a binder having a low film-forming property, so that it is extremely brittle and cracks do not occur. In addition to the drawback that the electrode life is short and the electrode life is shortened, there is a drawback that the catalyst is lost. In addition, such a composition has a drawback that it is difficult to form a thin film because of poor molding processability, and that it is difficult to control the pore size, so that the electrolyte is liable to leak when used as an electrode. was there.

(Problems to be Solved by the Invention) The present inventor uses a conductive polymer formed by electrolytic polymerization of an electropolymerizable aromatic compound and / or a heterocyclic compound without using a conductive powder. It has been found that the above-mentioned various drawbacks of the conventional gas diffusion type composite electrode can be improved by the present invention, and the present invention has been made. The present invention provides a gas diffusion type composite electrode having a long electrode life and no loss of catalyst. A manufacturing method is provided.

[Structure of Invention]

(Means for Solving the Problems) The present invention provides the above-mentioned conductivity of a composite material in which a coating material prepared by dissolving or dispersing an organometallic complex in a resin solution is applied onto a conductive substrate and dried to form a resin member. A method for producing a gas diffusion type thin film composite electrode, characterized in that an electropolymerizable aromatic compound or heterocyclic compound is electropolymerized on a substrate, and then the conductive substrate is removed.

Examples of the resin used in the present invention include fluororesins such as polytetrafluoroethylene, silicone resins,
Examples include sulfur-based resins such as polysulfone, vinyl-based resins, olefin-based resins, and phenol-based resins.

Examples of the organometallic complex used as the catalyst of the gas diffusion type composite electrode in the present invention include phthalocyanine, naphthalocyanine, porphyrin, phenatoporphyrin, biscyclopentadienyl, carbonyl, hydride, carbene, carbine, acetylacetone complex salt, salicylamine chelate. , Salicylaldehyde complex salt, ethylenediaminetetraacetic acid salt, glycine chelate, ferrocene, etc., or these atoms or substituents such as halogen atom, nitro group, sulfone group, sulfonate group, alkyl group, allyl group, hydroxyl group, carboxyl group, etc. Of the introduced derivatives, platinum, iron, cobalt, nickel, copper, palladium,
It is a complex of a metal such as molybdenum.

Further, in order to improve the effective utilization rate of the catalyst, it is desirable to use one of these organometallic complexes which is soluble in the same solvent as the resin member used, for example, a combination of the organometallic complex, the solvent and the resin. As for acetylacetone complex salt, a combination of acetone solvent, polyvinyl halogen compound and / or polystyrene resin,
For salicylamine chelate, dimethylformamide and / or pyridine solvent, polyvinyl alcohol and / or pyridine solvent, polyvinyl alcohol and / or polyacetylene and / or polyvinyl halide resin combination, salicylaldehyde complex salt, chloroform solvent, polyvinyl solvent Acetate and / or polyvinyl sulfoxide resin combination, for ferrocene, benzene solvent, polyvinyl acetate and / or polystyrene resin combination, porphyrin, sulfonate derivative such as phthalocyanine, for carboxyl derivative, dimethylformamide or dimethylsulfoxide solvent, polyvinyl Alcohol and / or polyvinyl halide and / or polyacrylo Tolyl-butadiene-styrene and (or) polyacrylonitrile and (or) can be exemplified polyacetylene resin or the like, but is not limited thereto.

The resin member composed of the organometallic complex and the resin must have a property of permeating the gas used in the gas diffusion type composite electrode according to the present invention. For example, when the gas is oxygen, the oxygen permeability coefficient of the resin member is 1 × 10 ^-15 {cm ³ (STP) cm · cm ^-2 s ^-1 (cmHg) ^-1 } or more,
Preferably 1 × 10 ^-10 {cm ³ (STP) cm · cm ^-2 s ^-1 (cmH
g) ^-1 } or more.

In the present invention, the conductive base material used as the electrode for electrolytic polymerization includes metal materials such as platinum, nickel, copper, silver, gold and palladium, and carbonaceous materials such as glassy carbon, as well as indium trioxide. It is possible to use a transparent electrode (ITO glass or the like) vapor-deposited with. The shape of the conductive base material is not particularly limited, and linear, plate-like, rod-like, spherical, mesh-like, paper-like, cloth-like and the like can be used.

In the present invention, the composite material comprises the above resin member and a conductive base material. As the composite material, the above organometallic complex and resin are used as an ether solvent such as tetrahydrofuran, an amine solvent such as diaminodiphenylmethane, a ketone solvent such as acetone and methyl ethyl ketone, an aromatic solvent such as phenol, toluene and xylene, and cyclohexene. The coating agent obtained by dissolving (including melt-dissolving) or dispersing in a suitable organic solvent such as the aliphatic compound solvent is applied onto the conductive base material and dried.

On the conductive base material of the composite material thus obtained, the electropolymerizable aromatic compound and / or heterocyclic compound are electropolymerized. Examples of the electropolymerizable aromatic compound or heterocyclic compound include azulene, pyrene, triphenylene, aniline, pyrrole, thiophene, 3-methylthiophene, furan, piperazine and isothianaphthene.

Conductivity of the composite material is improved by putting the composite material together with a counter electrode into a solution consisting of these electrolytically polymerizable aromatic compound and / or heterocyclic compound, an electrolyte for applying electric current, and an organic solvent and applying electric current. On the substrate,
That is, on the portion of the conductive base material covered with the resin member,
If there is a part not covered with the resin member in the resin member or on the conductive base material, electrolytic polymerization occurs on the part not covered with the resin member, and the polymer is deposited. (Grow). The electrolytic polymerization may be performed at least on the portion of the conductive base material covered with the resin member and only in the resin member. From the viewpoint of the efficiency of polymer formation by electrolytic polymerization, the resin on the conductive base material may be used. It is preferable to cover the part not covered with the member with a peelable or non-releasable insulating material and then carry out the electropolymerization.

As the cations constituting the electrolyte, alkali metal ions, alkaline earth metal ions, quaternary alkylammonium ions, quaternary alkylphosphonium ions, quaternary alkylphosphonium ions,
There are alkylarsenium ions, quaternary sulfonium ions, or their substitution products, and the anions include sulfonate ions, nitrate ions, perchlorate ions, carboxylate ions, tetrafluoroborate ions,
There are hexafluorophosphate ions or their substitution products. Among the electrolytes composed of these cations and anions, tetrabutylammonium perchlorate, tetraethylammonium perchlorate, tetrabutylammonium tetrafluoroborate, sodium tetrafluoroborate, etc. are particularly preferred in terms of solubility in organic solvents. Is preferably used. Organic solvents used in electrolytic polymerization include nitriles such as acetonitrile, benzyl nitrile and benzonitrile, amides such as dimethylformamide, dimethylacetamide and N-methylacetamide, ethylenediamine, hexamethylphosphoramide and pyridine. Amines, tetrahydrofuran, dioxane, ethers such as 1,2-dimethoxyethane, carboxylic acids such as acetic acid and acetic anhydride, alcohols such as methanol and ethanol, sulfur compounds such as dimethyl sulfoxide, sulfolane and dimethyl sulfone, propylene carbonate, Nitromethane, methylene chloride, acetone, etc. can be used. Considering the ionization coefficient, it is preferable to use methanol, ethanol, acetonitrile, dimethylformamide, dimethylsulfoxide, tetrahydrofuran, propylene carbonate, nitromethane among these organic solvents.

The amount of electricity applied during electrolytic polymerization is usually 0.1 to 100 C / cm ² ,
If the amount of electricity is set to 1 to 10 C / cm ² , the surface of the polymer deposited (grown) by electrolytic polymerization can be made smooth, and a gas diffusion type composite electrode with high conductivity can be obtained. In this way, electrolytic polymerization is performed, the conductive base material is removed, and a gas diffusion type composite electrode is obtained. Further, by removing the conductive base material, it is possible to further reduce the weight and the film thickness, and it is possible to easily perform processing such as molding.

(Function) In the present invention, the conductive base material functions as an electrode during electrolytic polymerization.

In the gas diffusion type composite electrode obtained by the present invention, the organometallic complex acts as a catalyst, and the polymer deposited (grown) by electrolytic polymerization acts as conductivity in the electrode body.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples. In the examples, “part” means “part by weight”.

Example 1. A dispersion obtained by dispersing 25 parts of cobalt phthalocyanine in 250 parts of a solution consisting of 50 parts of polysulfone and 200 parts of dimethylformamide was coated on ITO glass and dried at 120 ° C. for 2 hours to form a composite material. Obtained. Using the obtained composite material as an electrode and a platinum plate as a counter electrode, in a solution containing an electrolyte consisting of 100 parts of acetonitrile, 0.7 part of pyrrole and 3.5 parts of tetrabutylammonium perchlorate, the energization amount was 3 C / cm ² . Electropolymerization was performed until the temperature reached, then ITO glass was peeled off, thoroughly washed with acetonitrile, and dried at 80 ° C for 5 hours to obtain a thin-film electrode with a thickness of 20 µm. The obtained electrode contained 3% by weight of polypyrrole.

Using the electrode thus obtained, a 1N aqueous solution of potassium hydroxide was used as the electrolytic solution, and a platinum plate was used as the counter electrode. The oxygen gas pressure was 1 atm, and the oxygen gas supply rate was 100 atm.
When an oxygen half-cell was assembled with the set current density of 0.1 mA / cm ^{2 at} ml / min and the electrode potential was measured, the electrode potential was −0.39.
It was V. The electrode potential did not change and the electrolyte did not leak even after 1000 hours had elapsed since the start of measurement. At this time, an Hg / HgO electrode was used as the reference electrode.

Comparative Example 1. A dispersion obtained by dispersing 25 parts of cobalt phthalocyanine and 2.25 parts of carbon black in 250 parts of a solution consisting of 50 parts of polysulfone and 200 parts of dimethylformamide was applied on an ITO glass to give a dry film thickness of 20 μm. Applied to
After drying at 120 ° C for 2 hours, the ITO glass was peeled off to obtain a thin film electrode. An oxygen half-cell was tried to be assembled using the obtained electrode in the same manner as in Example 1, but the electrode potential was −1.0 V or less, and it was found that the oxygen half-cell was not practical.

Comparative Example 2. A dispersion obtained by dispersing 25 parts of cobalt phthalocyanine and 50 parts of carbon black in 250 parts of a solution consisting of 50 parts of polysulfone and 200 parts of dimethylformamide was applied on an ITO glass to give a dry film thickness of 20 μm. Applied to
After drying at 120 ° C for 2 hours, the ITO glass was peeled off to obtain a thin film electrode. Using the obtained electrode, an oxygen half-cell was assembled in the same manner as in Example 1 and the electrode potential was measured. The electrode potential was -0.39 V. However, 100 hours after the start of measurement, the electrolyte solution was also discharged. This occurred and the electrode potential became -1.0V.

Example 2 A mixed solution obtained by dissolving 5 parts of sodium cobalt phthalocyanine trisulfonate in 100 parts of a solution consisting of 10 parts of polyacrylonitrile butadiene styrene and 90 parts of dimethylformamide was applied on ITO glass, and then at 100 ° C. Two
After drying for an hour, a composite material was obtained. Using the obtained composite material as an electrode, using a platinum plate as a counter electrode, and using a thin film electrode obtained by compounding polypyrrole in the same manner as in Example 1, an oxygen half-cell was prepared in the same manner as in Example 1. When assembled and measured the electrode potential, the electrode potential improved to -0.24V.

〔The invention's effect〕

According to the present invention, a gas diffusion type composite electrode having a long electrode life and no loss of catalyst can be obtained.

Further, by removing the conductive base material, the weight and the thickness can be further reduced, and the processing such as molding can be performed more easily.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G01N 27/333

Claims (1)

[Claims] 1. A composite material in which a resin member is formed by coating a coating solution prepared by dissolving or dispersing an organometallic complex in a resin solution on a conductive base material, and electrolytically polymerizing the composite material on the conductive base material. A method for producing a gas diffusion type thin film composite electrode, which comprises electrolytically polymerizing an aromatic compound or a heterocyclic compound, and then removing the conductive base material.