Edge Sites with Unsaturated Coordination on Core–Shell Mn₃O₄@Mn_xCo_{3− x}O₄ Nanostructures for Electrocatalytic Water Oxidation

Transition-metal oxides are extensively investigated as efficient electrocatalysts for the oxygen evolution reaction (OER). However, large-scale applications remain challenging due to their moderate catalytic activity. Optimized regulation of surface states can lead to improvement of catalytic properties. Here, the design of Mn@Co_xMn_{3− x}O₄ nanoparticles with abundant edge sites via a simple seed-mediated growth strategy is described. The unsaturated coordination generated on the edge sites of Co_xMn_{3− x}O₄ shells makes a positive contribution to the surface-structure tailoring. Density functional theory calculations indicate that the edge sites with unsaturated coordination exhibit intense affinity for OH⁻ in the alkaline electrolyte, which greatly enhances the electrochemical OER performance of the catalysts. The resulting Mn@Co_xMn_{3− x}O₄ catalysts yield a current density of 10 mA cm⁻² at an overpotential of 246 mV and a relatively low Tafel slope of 46 mV dec⁻¹. The successful synthesis of these metal oxides nanoparticles with edge sites may pave a new path for rationally fabricating efficient OER catalysts.