Ca‐rich‐surface core‐shell spherical LaCo <i> _x </i> Fe _1‐ <i> _x </i> O ₃ perovskite: Enhanced lattice oxygen mechanism in oxygen evolution

Abstract The oxygen evolution reaction (OER) plays a crucial role in renewable energy technologies, such as metal‐air batteries and water splitting. However, the reaction is hindered by slow kinetics, necessitating highly active and stable catalysts. Here, we synthesized a Ca‐rich‐surface core‐shell spherical LaCaCoFe perovskite oxide through a spray combustion method. Density functional theory calculations demonstrate that Ca‐doping in LaCo x Fe 1‐ x O 3 perovskite oxide significantly promotes the formation of oxygen vacancies, which can trigger the lattice oxygen mechanism to enhance OER catalysis. This is confirmed by the increased pH dependence of the OER overpotential after Ca doping. As a result, the spherical LaCaCoFe perovskite oxide exhibits an overpotential of 320 mV and a remarkably low Tafel slope of 63.1 mV/dec, indicating excellent OER kinetics. Additionally, it demonstrates long‐term catalytic stability for over 150 h. This work offers new opportunities for the design and synthesis of perovskite oxide‐based OER electrocatalysts.