Electrochemical Synthesis and Investigation of Stoichiometric, Phase-Pure CoSb₂O₆ and MnSb₂O₆ Electrodes for the Oxygen Evolution Reaction in Acidic Media

The electrochemical oxidation of water to oxygen gas is the primary counter reaction to the formation of hydrogen gas via water splitting. In acidic media, the only well-established and active oxygen evolution catalysts are expensive noble metal oxides such as IrOx and RuOx, necessitating the development of practical oxygen evolution catalysts that are stable in acidic media. In this study, we prepared stoichiometric, phase-pure CoSb2O6 and MnSb2O6 electrodes using electrochemical synthesis and investigated their ability to oxidize water in 0.5 M H2SO4 (pH 0.3). In addition, their stabilities during the oxygen evolution reaction (OER) were carefully examined by comparing their morphologies, crystallinities, compositions, and surface compositions before and after the OER. The chlorine evolution reaction on CoSb2O6 and MnSb2O6 in acidic media was also examined so that their performances can be compared with previously reported non-stoichiometric CoSb2O6 and MnSb2O6 electrodes. The electrochemical properties and stabilities of stoichiometric, phase-pure CoSb2O6 and MnSb2O6 reported in this study can provide useful insights into the development and understanding of acid-stable, non-noble metal oxide-based OER catalysts.