JPH0119625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an air electrode used in air cells, fuel cells, etc., and more specifically to a method for manufacturing an air electrode having excellent polarization characteristics.

Conventionally, air electrodes used in air cells, fuel cells, etc. are made by impregnating a carbon material such as carbon black or activated carbon with an aqueous solution of transition metal nitrate, followed by heat treatment, and further reduction as necessary. This method was manufactured by attaching a metal or metal oxide as a catalyst to the surface of the catalyst, but it had the following drawbacks.

Platinum, palladium, rhodium, and the like exhibit good performance as air electrode catalysts, but they are all expensive and increase the cost of air electrodes.

Relatively inexpensive metals such as iron, cobalt, nickel, and copper have low catalytic ability as they are, so they cannot be expected to serve as catalysts for air electrodes.

In addition, coordination polymer compounds of transition metals are inexpensive and abundant, and there are attempts to use them as air electrode catalysts due to their ability to decompose hydrogen peroxide and their semiconductor properties, but they are not suitable for general solvents. Since it is insoluble, it is difficult to uniformly adhere to the carbon body. For this purpose, finely ground transition metal coordination polymers are dispersed in a solution, impregnated into the pores on the surface of the carbon body using ultrasonic waves, and dried. The reality is that it is difficult to obtain the performance as an air electrode.

Therefore, the present inventors have finally completed the present invention as a result of various studies on a method for uniformly attaching an inexpensive and abundant transition metal coordination polymer compound to a carbon body as a catalyst. A carbon body is separately impregnated with a solution containing transition metal ions and a solution of a low molecular weight polydentate ligand having two or more chelate coordination groups, and an insoluble coordination polymer compound of a transition metal is attached to the carbon body. The gist of the present invention is a method for manufacturing an air electrode characterized by the following characteristics.

In the present invention, transition metal ions are adsorbed by impregnating the surface and pores of the carbon body with a solution containing transition metal ions, and low molecular weight polydentate coordination groups having two or more chelate coordination groups are used. By immersing the carbon body in the child solution, the insoluble coordination polymer compound of the transition metal is stoichiometrically adhered uniformly to the surface of the carbon body and its pores, and it is presumed that the polarization characteristics are improved.

The present invention will be explained below.

Examples of carbon bodies used in the present invention include carbon blacks such as furnace black, channel black, and thermal black, wood, charcoal, coconut shell charcoal, palm kernel charcoal, coal, petroleum residue, synthetic resin,
Examples include one or a mixture of two or more of activated carbon and graphite made using organic waste, etc., and are formed into a certain shape by extrusion molding, injection molding, pressure molding, etc. as necessary.

Transition metal salts include chromium, manganese, iron,
Water-soluble salts of cobalt, nickel, copper, zinc, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, tungsten, iridium, etc. can be used, and considering cost and availability,
In particular, water-soluble salts of iron, nickel, cobalt, and copper can be preferably used.

Examples of low molecular weight polydentate ligands having two or more chelate coordinating groups include dimercaptomaleic acid, dimercaptomaleic acid monoamide, 2,5-dihydroxyterephthalaldehyde, 2,5-dihydroterephthalaldehyde oxime, and dihydroxyphenate. Nadine, rubeanic acid, naphthazarine, etc. can be used.

When manufacturing an air electrode, the carbon material is immersed in an aqueous solution of a transition metal salt or a solution of a low molecular weight polydentate ligand having two or more chelate coordination groups, and after air drying, it is immersed in the remaining solution. This results in an air electrode of .

The amount of transition metal insoluble coordination polymer in the air electrode obtained by the production method of the present invention is 0.1 to 5
% by weight is desirable; if it is less than 0.1% by weight, the performance as a catalyst may not be expected;
With the above conditions, the performance as a catalyst may no longer be expected.

Hereinafter, the present invention will be explained in more detail with reference to Examples. In the Examples, "parts" indicate "parts by weight."

Example 1 10 parts of coconut shell activated carbon with a particle size of 0.1 to 1μ, particle size of 0.1 to 1μ
10 parts of 0.5 μ graphite and 5 parts of thermoplastic resin (vinyl chloride resin) were mixed and extruded to make a round bar with a diameter of 10 mm, and then heated to 200°C to decompose the thermoplastic resin and create a carbon body. .

This carbon body is immersed in a 5% copper sulfate aqueous solution, taken out, and air-dried at room temperature. Next, by immersing the carbon body in an alcoholic solution of 2% dihydroxyphenazine, an air electrode having a copper-containing polymer complex uniformly adhered to the carbon body was obtained.

Example 2 The carbon body of Example 1 is immersed in a 5% iron sulfate aqueous solution, taken out and air-dried. Next, by immersing the carbon body in a 2% dithioxamide ethanol aqueous solution, an air electrode having a copper-containing polymer complex uniformly adhered to the carbon body was obtained.

Comparative Example 1 The carbon body of Example 1 was impregnated with a 5% aqueous copper sulfate solution and air-dried at room temperature. Next, by immersing it in a 2% alcohol solution of δ-oxyquinoline,
An air electrode was obtained in which a copper complex salt of δ-oxyquinoline was attached to a carbon body.

Comparative Example 2 The carbon body of Example 1 was impregnated with a 5% aqueous copper sulfate solution and air-dried at room temperature. Next, while passing the air
It was heated at 200°C for 6 hours to obtain an air electrode with copper oxide attached to the carbon body.

Comparative Example 3 The carbon body of Example 1 was immersed in a 5% iron sulfate aqueous solution, taken out, and air-dried. Next, an air electrode having an iron complex attached to the carbon body was obtained by immersing it in a 2% thioxamide ethanol aqueous solution.

Comparative Example 4 An iron-containing coordination polymer synthesized from an alcoholic solution of dithiooxamide and an aqueous iron sulfate solution was finely dispersed in alcohol, and the carbon body of Example 1 was impregnated with ultrasonic waves to obtain an air electrode.

The polarization characteristics of the air electrodes of Examples 1 and 2 and Comparative Examples 1 to 4 are shown in FIGS. 1 and 2.

As described above, the air electrode obtained by the manufacturing method of the present invention has excellent polarization characteristics.

[Brief explanation of drawings]

Figure 1 shows the polarization curves of the air electrodes obtained in Example 1 and Comparative Examples 1 and 2, and Figure 2 shows the polarization curves of the air electrodes obtained in Example 2 and Comparative Examples 3 and 4. ,
~ indicates the polarization curves of the air electrodes obtained in Example 1, Comparative Example 1, Comparative Example 2, Example 2, Comparative Example 3, and Comparative Example 4 in order, and the vertical axis is the current density (mA/cm ² ) ,
The horizontal axis shows the potential (V/SCE).

Claims (1)

[Claims] 1 A carbon body is separately impregnated with a solution containing a transition metal ion and a solution of a low molecular weight polydentate ligand having two or more chelate coordination groups, and an insoluble coordination polymer compound of a transition metal is impregnated into the carbon body. A method for manufacturing an air electrode, characterized in that the air electrode is adhered to the air electrode.