Sustainable oxygen evolution catalysis – electrochemical generation of mössbauerite via corrosion engineering of steel

Abstract

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 mössbauerite (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.