On the Homogeneity of a Cobalt-Based Water Oxidation Catalyst

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 CoOx 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 CoOx.
Although it is shown that Co­(HL) interacts with the electrode
during electrocatalysis, the formation of CoOx 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.