Oxygen Evolution Reaction Electrocatalysis on Cobalt(oxy)hydroxide: Role of Fe Impurities

Abstract

In this work, we present extensive electronic structure simulations on the oxygen evolution reaction (OER) mechanism and the influence of Fe substitution in cobalt(oxy)hydroxide under OER conditions. The study employs cluster models with an explicit treatment of the electrochemical potential via charges, an inclusion of the pH via protonation/deprotonation, and an implicit treatment of solvation. Our results suggest that early oxidation of Fe(III) to Fe(IV) promotes the electrophilic character in the reaction center, reducing the proton affinity of the surface-bound hydroxyl moieties. Computed energy profiles with explicit inclusion of the electrochemical potential imply that the Fe center of the Fe–OH site after its deprotonation acts as the active center for water nucleophilic attack. For the pristine cobalt(oxy)hydroxide system, Co(IV) promotes the efficient formation of an active O radical intermediate followed by intramolecular O–O coupling under OER conditions. In a detailed study of different computational approaches, it is demonstrated that the explicit inclusion of the electrochemical potential and pH within a constant-potential approach yields improved models that better reproduce experimental findings for the OER mechanism.