Molecular Nature of Electrodeposits in Electrochemical Water Oxidation

The molecular nature and the structure of the real catalyst are matters of serious concern in homogeneous catalysis. Catalyst transformation in molecular water oxidation catalysis (WOC) is usually linked to catalyst decomposition with the generation of nanostructured materials. This is mainly due to the operational conditions that are conducive for the formation of metal oxides (MO_x), which have a strong affinity for adsorbing onto the electrodes’ surfaces. Recently, the exhibition of the molecular nature of the electrodeposits rather than MO_x is a breakthrough in the field of WOC, suggesting that deposits in electrocatalysis are not constrained to metal oxides/hydroxides after molecular catalyst decomposition. Therefore, several points should be considered before deciding whether the deposits are aggregates of a molecular structure or simple metal oxides formed due to the decomposition of the original structure. Thus, the aim of this perspective is to showcase the examples of homogeneous WOCs where metal–organic species are electrodeposited instead of metal oxide-based catalysts. The transformation of heterogenized molecular catalysts for WO into a more electroactive form while preserving their molecular identity, is also discussed. This summary provides an overview of the molecular nature of electrodeposits, how to identify their presence and decide about their nature.