The O2 Reduction on Intermetallic Compounds

The search for effective electrocatalysts led to investigations of the corrosive resistance and of the reactivity for the O2 reduction of compounds of metals with other elements like boron, carbon, nitrogen, oxygen, etc. The cathode [78] of the Bacon cell represents the classical example. The porous cathodes were made by pressing and sintering mixtures of carbonyl nickel and ammonium bicarbonate. Subsequently, they were coated with a layer of lithiated nickel oxide. 

Many of the intermediate compounds are semiconductors. The conductivity may be improved by adding appropriate ions during their preparation. Solid solutions result in certain cases. Davtyan and CO workers [79] interpreted the mechanism of the oxygen electrode on semiconductors of the type L T. O by postulating the intermediate formation and dissociation of complexes of the type L —O —T —O. There designates an alkali cation and T a transition metal like Ni, Cu, Co, Mn, and x -100 gives the atomic percent of L. The chemisorption of oxygen leads to the formation of the complex  

The O2 reduction was reported [82] to occur in a potential region where the passive films are stable on Ni, NiAs, NiSi, and NiSb. The order of reactivty for the O2 reduction is Ni NiAs NiSi in acid solution, and NiS Ni NiSiJ NiSb NiAs in alkaline solution. However, the performance of these compounds is not satisfactory for their use as electrocatalysts in a practical oxygen electrode. 

Sodium tungsten bronzes of the general formula NaxW03 with 0.2 X 0.93 were stable [83] in sulfuric acid solutions even at potentials 

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