On the Homogeneity of a Cobalt-Based Water Oxidation Catalyst

[Image: see text] The homogeneity of molecular Co-based water oxidation catalysts (WOCs) has been a subject of debate over the last 10 years as assumed various homogeneous Co-based WOCs were found to actually form CoO(x) under operating conditions. The homogeneity of the Co(HL) (HL = N,N-bis(2,2′-bipyrid-6-yl)amine) system was investigated with cyclic voltammetry, electrochemical quartz crystal microbalance, and X-ray photoelectron spectroscopy. The obtained experimental results were compared with heterogeneous CoO(x). Although it is shown that Co(HL) interacts with the electrode during electrocatalysis, the formation of CoO(x) was not observed. Instead, a molecular deposit of Co(HL) was found to be formed on the electrode surface. This study shows that deposition of catalytic material is not necessarily linked to the decomposition of homogeneous cobalt-based water oxidation catalysts.