Stabilization of a Mn-Co Oxide During Oxygen Evolution in Alkaline Media

Improving the stability of electrocatalysts for the oxygen evolution reaction (OER) through materials design has received less attention than improving their catalytic activity. We explored the effects of Mn addition to a cobalt oxide for stabilizing the catalyst by comparing single phase CoO_x and (Co_0.7Mn_0.3)O_x films electrodeposited in alkaline solution. The obtained disordered films were classified as layered oxides using X-ray absorption spectroscopy (XAS). The CoO_x films showed a constant decrease in the catalytic activity during cycling, confirmed by oxygen detection, while that of (Co_0.7Mn_0.3)O_x remained constant within error as measured by electrochemical metrics. These trends were rationalized based on XAS analysis of the metal oxidation states, which were Co^2.7+ and Mn^3.7+ in the bulk and similar near the surface of (Co_0.7Mn_0.3)O_x, before and after cycling. Thus, Mn in (Co_0.7Mn_0.3)O_x successfully stabilized the bulk catalyst material and its surface activity during OER cycling. The development of stabilization approaches is essential to extend the durability of OER catalysts.