  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 effect of Mn addition to a cobalt oxide for
stabilizing the catalyst by comparing Na-containing CoOx and (Co0.7Mn0.3)Ox
films electrodeposited in alkaline solution. The obtained disordered films were
classified as layered oxides using X-ray absorption spectroscopy (XAS). The
CoOx films showed a constant decrease in the catalytic activity during cycling,
confirmed by oxygen detection, while that of (Co0.7Mn0.3)Ox slightly increased
as measured by electrochemical metrics. These trends were rationalized based on
XAS analysis of the metal oxidation states, which were Co2.8+ and Mn3.7+ near
the surface after cycling. Thus, adding Mn to CoOx successfully stabilized the
catalyst material and its activity during OER cycling. The development of
stabilization approaches is essential to extend the durability of OER
catalysts.
