JPS61121264A - Catalitic material for electrode - Google Patents

Abstract

PURPOSE:To obtain highly activating and excellently performance electrodes by forming catalitic material used in fuel electrodes of a fuel cell from two sorts of compounds, namely, complex carbide consisting of tungsten and molybdenum, and compound of germanium, antimony, etc. CONSTITUTION:Catalitic material for electrode used in fuel electrodes of a fuel cell employing organic compounds such as methanol, formalin, etc., is prepared in such a way that two sorts of compounds, namely, complex carbides consisting of tungsten and molybdenum, W1-xMoxC(0<=X<=1), and compounds including at least one of the elements Ge, As, Se, Sn, Sb, Te, Pb, Bi, Re, and Os, are immersed, or immersed and electrolized at the same time in the solution of compound consisting of promoter elements added with carbide catalysis. Therefore, highly activating and excellently performance fuel electrodes can be obtained without the need of such rare and costly elements as platinum group to be used as catalitic material for electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electrode catalyst, and particularly to a catalyst material suitable for use in a fuel electrode of a fuel cell using an organic compound such as methanol or formalin as fuel.

[Background of the invention]

Platinum-based noble metals have been known as methanol electrode catalysts for a long time, but the disadvantage is that they are expensive because platinum is a rare element. As a substance other than platinum-based precious metals that exhibits activity as a methanol electrode catalyst, a carbide W+--xMoxC (0≦x≦0.8) consisting of tungsten and molybdenum is proposed in JP-A-58-128661.

[Purpose of the invention]

An object of the present invention is to provide an electrocatalyst material having high activity for the electrolytic oxidation of methanol, formalin, formic acid, and carbon monoxide using a catalyst based on the above-mentioned tungsten carbide/molybdenum carbide.

[Summary of the invention]

In order to increase the catalytic activity of the above-mentioned tungsten carbide/molybdenum carbide, we investigated the possibility of adding co-catalysts and added Ge, As, Se, Sn, and Sb among various elements.

It has been found that the addition of 'l'e, pb, Bi, Re and O5 improves the catalytic activity. These elements may be added alone or in combination of two or more.

The method of adding the promoter element includes immersing the carbide catalyst in a solution of a compound made of the promoter element, or electrolyzing the carbide catalyst at the same time as immersing it, mixing the compound containing the promoter element with the carbide, and adding the carbide catalyst to the carbide catalyst. It is possible to choose a method such as adding a compound consisting of the above-mentioned cocatalyst element during the process of synthesizing.

[Embodiments of the invention]

The present invention will be explained in detail below.

Example 1 Powder 2 of Wa, 4 M'o o, a Cz, a compound containing tungsten and molybdenum in an atomic ratio of 4=6
0.8 g of Teflon suspension (Daikin Industries D-1)
After adding 4 and mixing thoroughly, 10cW1! It was coated on a tansil mesh having a size of 1, and was heat-treated at 250C for 30 minutes in a kiln gas atmosphere to prepare an electrode. This electrode is 1MH2SO4+1
Electrolytic treatment was performed in mM5'nC1< solution. The conditions for the electrolytic treatment are to maintain a potential of 0.05'l reversible hydrogen electrode (the same applies hereafter) for 24 hours, during which time approximately 1rn
A current of A was flowing steadily. This current is based on the reduction reaction of tin, in which tin, which exists as tetravalent ions in the solution, is reduced to divalent or zero-valent atoms, and the latter are adsorbed as adsorbed atoms on the particle surface of the carbide powder. It is estimated to be. Number nine, which proves that tin is adsorbed.
As a result of analyzing the amount of tin contained in the two electrodes that were washed by immersing them in running water for 1 hour immediately after the electrolytic treatment and after the electrolytic treatment, the amount of tin contained in the former was 5.3 mg, and the latter was 5.3 mg.
1 mg of tin was detected.

This result means that tin is not held inside the electrode in a solution state, but is strongly adsorbed on the surface of the particles forming the electrode.

Table 1 shows the activity of the electrodes electrolytically treated in the tin-containing solution described above for electrolytic oxidation of various fuels. The electrolytic solution used in the measurement was a 50C aqueous solution containing 1MH2SO4 and IM fuel, and the current value at an electrode potential of 0.5V was measured. Note that the reference examples in Table 1 are measurement results for electrodes that were not subjected to tin adsorption treatment.

As shown in Table 1, according to the present invention, a highly active catalyst can be obtained by adding tin to a carbide catalyst.

Example 2 Ge! by the same method as in Example 1. , As, Se.

A carbide catalyst electrode was prepared by adding Sb, Te, Pb, Bi, Re, and ost. The solutions for adding the above various elements are GeO2 and H3ASO4, respectively.

HzSdO4+ 8bzOs * TeO', Pb((
1'tO4L +B1C63,Reads +0120
7 to IM H2SO4.

It was dissolved in HCl or HCto 4 at a concentration of 1mM. The methanol oxidation activity of the carbide catalyst electrode to which each of the above elements was added by electrolytic reduction treatment in the various solutions mentioned above is in the range of 15 to 20 mA, and the activity of the untreated electrode (see Table 1) The activity was improved compared to example).

Example 3 2 g of powder of Wα7M013C, a carbide containing tungsten and molybdenum in an atomic ratio of 7:3, and 0.05 g of tin dioxide powder were thoroughly mixed, and 0.8 g of Teflon suspension was added to the mixture. was added, and an electrode was prepared in the same manner as in Example 1. This electrode was held at an electrode potential of 0.05 V for 24 hours in a 1M H2SO4 solution to undergo electrolytic reduction and treatment. The methanol oxidation activity of this electrode was measured by the method described in Example 1, and a value of 18 mA was obtained. 8 m for electrodes made with conventional catalysts without the addition of tin dioxide.
It was A. According to the present invention, the catalytic disease resistance is improved by more than twice.

Example 4 80.0 g of tungstic acid, 84.7 g of ammonium molybdate and 0.3 g of potassium stannate were added to 400 portions of a 15% aqueous ammonia solution and completely dissolved by stirring at a temperature of 50 to 70 G. This solution was dried by freeze-drying to obtain a white powder. 5 g of this white powder was placed in a tubular quartz glass reaction tube, and treated with SOOR for 1 hour while flowing -carbon oxide gas at a rate of 100 - per minute to obtain a black carbide powder. X-ray diffraction analysis of this powder revealed that it was a single hexagonal WC phase.

In addition, the result of elemental analysis is W:Mo:Sn:C=0.4
: 0.6 : 0.00125:1 (atomic ratio).

2 g of the above black powder was used as a 10 crn2 electrode with a tantalum mesh as a current collector by the method described in Example 1, and the methanol oxidation current was measured to be 28 mA. The characteristics of the electrode according to the prior art without the addition of tin were 10 m, A as shown in the reference example in Table 1, and the present invention significantly improved the characteristics.

〔Effect of the invention〕

As described above, by using the electrocatalyst material according to the present invention, methanol, formalin.

Excellent performance t'#& can be obtained for electrolytically oxidizing fuels such as formic acid. Industrial applications of this electrode include fuel cells that use the above fuel as an energy source, and electrolysis industry that uses the above fuel as a depolarizing material for anodes, and its industrial value is extremely high.

Claims (1)

[Claims] 1. Composite carbide consisting of tungsten and/or molybdenum, W_1_-_xMo_xC (0≦x≦1) and Ge, As, Se, Sn, Sb, Te, Pb, Bi, R
An electrode catalyst material comprising a compound containing at least one of e, Os. 2. Ge, As, Se, Sn, Sb,
An electrode catalyst material characterized in that at least one element selected from the group of Te, Pb, Bi, Re, and Os or a compound of the above element is adsorbed and supported.