Selective acid leaching: a simple way to engineer cobalt oxide nanostructures for the electrochemical oxygen evolution reaction

Abstract

Developing a simple and cost-effective strategy to construct earth-abundant catalysts is in high demand for diverse applications. Herein, a general and facile strategy is developed to engineer cobalt oxide nanostructures via selective acid leaching for the electrochemical oxygen evolution reaction (OER). A leaching process is implemented to selectively remove CoMoO₄ by treating mixed Co–Mo oxides in diluted hydrochloric acid solution, resulting in the formation of sub-5 nm particles and a threefold increase in the specific surface area (up to 150 m² g⁻¹). The leached oxides exhibit superior OER activity to pristine oxides as a result of (i) a larger surface area, (ii) phase purification to expose more active Co₃O₄ species to the reactant, and (iii) faster charge transfer kinetics for the OER. This strategy can be also applied to a broader range of earth-abundant metals, where a second metal (Li, Ca, and Mg) is selectively leached out, which results in a material with a larger surface area and enhanced catalytic performance for the OER. Moreover, various metal oxides with a high surface area, such as NiO and Fe₂O₃, can be prepared via this simple synthetic method. This work will pave a new practical way for the production of high surface area catalysts for diverse applications.