JPS5968172A - Manufacture of catalyst for oxygen electrode - Google Patents

Abstract

PURPOSE:To provide oxygen reduction catalyst having high activity and good storage performance by heat-treating in a nonoxidizing atmosphere manganese dioxide obtained by electrolysis of a mixed solution of manganese sulfate and a metal chelete compound. CONSTITUTION:0.5-1.2mol/l manganese sulfate solution and 0.5-1.2mol/l sulfuric acid containing a specified amount of cobalt phthalocyanine sulfonate are mixed. This mixed solution is electrolyzed at an anode current density of 0.7- 1.2A/dm<2> at 88-98 deg.C to obtain manganese dioxide on which cobalt phthalocyanine is deposited. This manganese dioxide is fully washed to remove free sulfuric acid, and dried, then crushed and ground with a mortar and pestle to 200-300 mesh. The power obtained is heated in a nonoxidizing atmosphere at 400-550 deg.C to manufacture a catalyst. The catalyst is kneaded with activated carbon acting as oxygen carrier, acetylene black of electric conductive material, and fluorine resin for giving water repellent property, and this mixture is spreaded on a nickel net to obtain an oxygen reduction electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing an oxygen electrode catalyst used for the positive electrode of a button-type air cell.

Conventional Structures and Problems Various materials have been studied as catalyst materials for the positive electrode of button-type air cells, and platinum, palladium, and the like are particularly often used as immersed oxygen reduction catalysts. However, these precious metal catalysts are extremely expensive, especially when used as positive electrodes in power batteries for hearing aids, calculators, etc.
Considering that it is difficult to reproduce and reuse, it is expensive and difficult to put into practical use. On the other hand, although manganese oxides such as manganese dioxide and activated carbon are effective as inexpensive oxygen reduction catalysts, they have the following drawbacks.

In other words, manganese oxide is extremely hydrophilic and gets wet with alkaline electrolyte during long-term storage.
OBJECT OF THE INVENTION The present invention solves the problems of the above-mentioned conventional examples, which were reduced to lower-grade manganese oxides with low activity and caused a decrease in oxygen reduction ability.
The purpose of this invention is to provide a manufacturing method for obtaining an oxygen electrode catalyst with excellent storage stability.

Components of the Invention That is, the present invention is a method for producing an oxygen electrode catalyst that achieves the above-mentioned object, which includes a step of electrolyzing an aqueous solution containing manganese sulfate and a metal chelate compound, and converting the manganese dioxide obtained by the electrolysis into a non-oxidizing material. This method is characterized by a step of heat treatment in an atmosphere. According to the production method of the present invention, it is possible to obtain an oxygen reduction catalyst with high activity and excellent storage stability.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows a button-type air battery using the oxygen reduction catalyst according to the present invention.
Oxygen 1 coated and integrated with nickel net 3 which is a current collector! Original electrode 4. A water-repellent film 6 and a separator 6 are inserted. Zinc 7, which is a negative electrode active material, is filled into a negative electrode container 8.

9 is a gasket), and 10 is a support paper to prevent liquid leakage. Reference numeral 11 denotes an air supply hole which is normally covered with a seal paper (not shown) to cut off the supply of oxygen and prevent self-discharge.

Next, a method for manufacturing catalyst material 2 will be described. Manganese sulfate 0
．． 5-1, 2-E/V (2 (7) water j container, o, 6
MoL, 7e ~ 1, O”Vl +7) 'bR acid IK-
A predetermined amount of cobalt phthalocyanine sulfonate was added thereto, and the electrolytic temperature was 88 to 98°C, anode current density was 0.7 to 1', 2 A//d, ♂f? Manganese dioxide is obtained by electrodeposition of cobalt phthalonanine by an order of magnitude of gas decomposition. This product is thoroughly washed to remove free sulfuric acid, dried, and then ground in a mortar to a concentration of 200 to 300 Metu/U. Next, this material was placed in a non-oxidizing atmosphere for 4
Heat treatment is performed at 00 to 550°C to obtain a catalyst. This material is mixed with activated carbon, which mainly acts as a partner for oxygen, acetylene black, which is a conductive agent, and fluororesin to impart water repellency, and then applied to a nickel net, which is a current collector. Then, an oxygen reduction electrode 4 is obtained. In addition, the catalyst material is 400~
The reason for heating to 550°C is that the manganese oxide produced has excellent oxygen reduction ability when heat treated in this temperature range.
This is because it contains γ-type Mn2O3, which has a surface state with low affinity for the electrolyte, and the fine particulate metal chelate compound electrodeposited on the surface of this manganese oxide is still in a monomer state, so it is difficult to maintain a non-oxidizing atmosphere. By performing the heat treatment inside, the metal ion at the center of the metal chelate compound is not detached, and the π electrons of the metal ion are expanded to form a conjugated double bond, resulting in polymerization. Therefore, the electron transfer and ion separation of the adsorbed oxygen molecules become favorable, and the oxygen reduction ability increases. Also, these things are Den Jf! The contact angle with f liquid is large and the wettability is extremely low. Such metal chelate compounds must be eutectoided extremely uniformly on the surface of manganese dioxide by electrodeposition.
Its catalytic activity is extremely high.

Further, although cobalt was shown as the metal at the center of the metal chelate compound in the previous example, the same effect can be obtained even when iron or nickel manganese is used. In addition to phthalocyanine, porphyrin-based metal chelate compounds, such as tetra-para-methquine phenylporphyrin cobalt, have similar effects as gyrate compounds. In addition, the amount of metal filler-1 compound added to the surface of the manganese oxide is in the range of 3 to 8 weight ratios to the manganese oxide.
It had the highest catalytic activity. Those within this range are those that maximize the synergistic effect of both. Next, regarding specific effects, Figure 2 shows the discharge characteristics when a button-type zinc-air battery of R44 size according to the IEC standard was constructed and a 100Ω constant resistance discharge was performed. The discharge characteristics after C6 storage are shown. Further, FIG. 4 shows a comparison of the polarization characteristics of the catalyst electrodes, and cathodic polarization was performed using nickel as a counter electrode. In addition, the catalyst area is 1Ca.

As the electrolyte, a KOH aqueous solution having a concentration of 30% by weight was used. In the figure, (A) is a catalyst electrode in the present invention, in which cobalt phthalocyanine is applied to manganese oxide by using a chelate compound.
The main catalyst is mixed with activated carbon, acetylene black, and a fluororesin and applied to a nickel net, and the mixture ratio is d-1: main catalyst: activated carbon: acetylene black, and a fluororesin. j finger 50:2021
It was 0:20.

(B) is another catalytic electrode in the present invention, in which tetra-para-methoxyphenyl nickel is added to manganese oxide at 3%
% by weight, and the formulation was the same as in (A).

(G) is a conventional example in which the main catalyst is manganese dioxide calcined at 500° C. as a manganese oxide, and the electrode is constructed in the same manner as in (A).

(D) is another conventional example, in which the main catalyst is one in which two weight ratios of platinum are supported on activated carbon, and the blending ratio of main catalyst: acetylene brano difluororesin is 6:20:20.

Effects of the Invention As is clear from the second results, the catalyst produced by the production method of the present invention is an inexpensive, highly storable, and highly active oxygen reduction catalyst.

[Brief explanation of the drawing]

Figure 1 shows a quadruple 4j structure constructed using the catalyst phase in the present invention.
), FIG. 3 is a diagram showing the discharge characteristics of the same battery after storage, and FIG. 4 is a diagram showing the polarization characteristics of the oxygen reduction catalyst electrode. 1... Positive electrode container, 2... Catalyst material, 3...
...Current collector, 4...Oxygen reduction catalyst electrode, 7...
...Negative lead capture. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 1 Figure 2 Poetry Ranking Shoulder (hrs)

Claims (4)

[Claims] (1) A method for producing an oxygen electrode catalyst comprising the steps of electrolyzing an aqueous solution containing manganese sulfate and a metal chelate compound, and heat-treating manganese dioxide obtained by electrolysis in a non-oxidizing atmosphere. (2) -1-compound iron, cobalt, nickel. Centered on one of the metals manganese, with 4 nitrogen atoms
A method for producing an oxygen electrode catalyst according to claim 1, which has a phthalocyanine ring or a porphyrin ring surrounded by . (3) The method for producing an oxygen electrode catalyst according to claim 1, wherein the heating temperature of the heat treatment is 400 to 650°C. (4) The method for producing an oxygen electrode catalyst according to any one of claims 1 to 3, wherein the amount of the metal chelate compound mixed with manganese dioxide is 3 to 8 weight ratios with respect to manganese dioxide.