Fe‐Substituted MoO <i> _x </i> Catalysts With Lattice Distortion–Vacancy Coupling for Enhanced Alkaline Oxygen Evolution Reaction

Molybdenum oxide catalysts have been widely investigated as cost-effective electrocatalysts for water electrocatalysis due to their easily tunable electronic structures. However, their oxygen evolution reaction (OER) activities remain limited by their low electrical conductivities and electronically inactive oxidation states, thereby prompting the development of various alternative strategies. Herein, Fe-substituted MoO_x catalysts with controlled lattice distortion and oxygen vacancy concentrations are proposed. Fe-substituted MoO_x is synthesized via aerosol spray pyrolysis and subsequent postannealing to control its interfacial properties. Fe substitution induces spatial segregation from Mo, leading to the formation of a yolk-shell structure that exposes abundant active sites. Furthermore, Mo orbital hybridization improves the electronic structure and greatly enhances electrical conductivity. The optimized yolk-shell-structured FeMoO_x catalyst exhibits excellent performance at a high current density of 100 mA cm^-2, delivering a low overpotential of 294 mV and maintaining stable performance over 100 h. In situ electrochemical analyses reveal that temperature control of the charge distribution enhances oxygen intermediate adsorption and promotes OO bond formation through lattice oxygen species, thereby activating the lattice oxygen mechanism. This study provides mechanistic insights and a practical design strategy toward developing cost-effective, high-performance OER electrocatalysts based on transition-metal-modified molybdenum oxides.