Multilayer hollow MnCo₂O₄ microsphere with oxygen vacancies as efficient electrocatalyst for oxygen evolution reaction

Highly efficient and stable electrocatalysts for oxygen evolution reaction are of technological importance in energy conversion and storage. Surface modification is one of the most promising strategies for improving the activity of such electrocatalysts. Herein, we report the multilayer hollow MnCo₂O₄ microsphere enriched with oxygen vacancies induced by the plasma-engraving technique for the first time. The defective MnCo₂O₄ microsphere exhibits an excellent catalytic activity and durability as compared to pristine MnCo₂O₄. Our electrochemical analysis, combined with first-principles calculations, reveals that the improved electrocatalytic performance is attributed mainly to abundant active sites after the plasma treatment and the effects of the introduced oxygen vacancies. The oxygen vacancy not only reduces the density of states near the Fermi level but also lowers the Co d-band center, weakening the adsorption of the intermediates. This facilitates the desorption of the adsorbates, which is necessary for oxygen evolution reaction.