On the Homogeneity of a Cobalt-Based Water Oxidation Catalyst

Abstract

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 _<i>x</i> under operating conditions. The homogeneity of the Co(H<b>L</b>) (H<b>L</b> = <i>N</i>,<i>N</i>-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 _<i>x</i> . Although it is shown that Co(H<b>L</b>) interacts with the electrode during electrocatalysis, the formation of CoO _<i>x</i> was not observed. Instead, a molecular deposit of Co(H<b>L</b>) 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.