Edge Sites with Unsaturated Coordination on Core–Shell Mn₃O₄@Mn_xCo_3−xO₄ 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−xO₄ 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−xO₄ 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−xO₄ 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.