Water Oxidation by Co-Based Oxides with Molecular Properties

This chapter summarizes early and recent developments relating to the use of amorphous Co‐based oxides for water oxidation. These oxides often consist of Co ions, redox‐inactive cations (K, Na, Ca, etc.), anions that can act as proton‐accepting bases (phosphate, borate, chloride, etc.), and (layers) of water molecules. These oxide catalysts are denoted as Co catalyst (CoCat), NiCat, or MnCat, according to their respective redox‐active metal. These expressions are used irrespective of whether the material was electrodeposited as a thick film (50–3000 nm) on a planar electrode or synthesized in particle form. The CoCat function, or the mechanism of electrocatalytic water oxidation, has been studied predominantly by electrochemical methods, such as cyclic voltammetry (CV), potentiostatic polarization, and galvanostatic polarization, all of which may be utilized to construct Tafel plots. The CoCat has been thoroughly characterized by the collection of electrokinetic data.