Sustainable Oxygen Evolution Catalysis - Electrochemical Generation Of Mossbauerite Via Corrosion Engineering Of Steel

A versatile electrochemical corrosion process was used to generate green rust (GR) on a steel substrate and to transform it into the trivalent iron-only oxygen evolution catalyst mossbauerite (GR*) upon a subsequent oxidation process. Besides being scalable, cheap, and time-efficient, the demonstrated procedure is based on earth-abundant and non-hazardous materials only. Oxidation of mixed-valence Fe2+/Fe3+ GR to GR* was achieved by chemical and electrochemical processes. The latter induces less grafting of interlayer CO32-, leading to less contraction of the interlayer space and a reduction in the observable stacking disorder. The direct electrodeposition of the catalyst on a conductive substrate enabled the first systematic study of the impact of grafting on the performance of GR* in the oxygen evolution reaction (OER). The materials subjected to chemical (GR*(ChOx)) and electrochemical oxidation (GR*(ElOx)) allowed obtaining a current density of 100 mA cm(-2) at 1.82 V and 1.84 V, respectively, thus improving the electrocatalytic capabilities and outperforming the bare steel substrate operated in 1 M KOH solutions.