Electrochemical oxygen reduction on oxide catalysts

Abstract

The process of oxygen electroreduction and adsorption in alkaline medium on nickel and cobalt oxides has been studied by the potentiodynamic and the disc-ring electrode methods. The oxide films were formed on the surface of metal specimens by thermal or electrochemical oxidation.After oxidation, the surface was examined by X-ray diffraction and electron diffraction. It was found that, depending on the oxidation conditions, simple or complex oxides are formed on the surface of metal specimens. Nickel and Cobalt oxide films obtained by thermal oxidation at t ° ⩽300°C are more active than pure metals. The oxides of spinel structure Co 3 O 4 and NiCo 2 O 4 have an optimum activity. It is shown that oxygen adsorbed during the heat treatment of the specimens accelerates the process of the molecular oxygen reduction. On the oxides of spinel structure the oxygen reduction reaction proceeds to OH − , whereas on simple nickel oxides the final product of oxygen reduction is HO − 2 .