Electrochemical studies of the oxygen evolution reaction at passive oxide covered Ni, Co and Fe electrodes in aqueous alkaline solution

Abstract

There has been an abundance of publications over the last twenty years on electrode materials proposed to be suitable catalysts for the oxygen evolution reaction (o.e.r.) in concentrated alkaline solution. Although it is generally accepted that RuO2 is the most efficient electrocatalyst towards the reaction, its cost renders prohibitive the widespread adoption of this material for commercial applications. Amongst the more cost effective materials that have been forwarded as o.e.r. anodes are, various inter-metallic alloys (often containing significant amounts of Ni, Co or Fe), electrodeposited Ni (NiOx) and Co (C03O4) oxides, and mixed oxides, including spinels (particularly nickelites, cobaltites and ferrites) and perovskites. Many of these studies have been conducted on an essentially empirical basis with little attention devoted to the details of the o.e.r. mechanistic pathway. Yet the fact is, that there remains considerable controversy in the literature regarding the latter point, even in the case of passive oxide covered poly crystalline metallic electrodes. In view of this, the present work reports a comprehensive electrochemical study on the o.e.r. at Ni, Co and Fe electrodes in aqueous alkaline solution, with particular attention being paid to the question of whether or not the reaction proceeds via a common pathway at the anodic oxide covered surfaces of these three metals.