Engineering B‐Site Configurational Entropy in Perovskite Oxides for Enhanced Alkaline Oxygen Evolution Reaction

High‐entropy composition design offers an effective approach to overcome the sluggish oxygen evolution reaction (OER) kinetics of lanthanum‐based perovskite oxides. By incorporating a wider variety of metal cations into the B‐site sublattice, the configurational entropy increases accordingly. Following this high‐entropy compositional strategy, low‐entropy LaCoO 3 , medium‐entropy La(FeCoNi)O 3 , and high‐entropy La(MnFeCoNiCu)O 3 were successfully synthesized via a facile sol–gel combustion method. The construction of the high‐entropy perovskite oxide (HEPO) was found to substantially alter the morphology, crystal structure, and electronic environment, leading to reduced particle size, modulated B‐site metal valence states, and enriched oxygen vacancies. These modifications collectively induce synergistic effects among multiple B‐site metal active sites and promote the participation of lattice oxygen through the introduction of surface oxygen defects, thereby activating the oxygen‐mediated (LOM) pathway of OER. Remarkably, the as‐prepared HEPO exhibited superior OER performance in alkaline media, achieving a low overpotential of 303 mV at 10 mA cm −2 , a small Tafel slope of 43 mV dec −1 , and excellent stability over 100 h of continuous operation. This work provides valuable insights into the role of B‐site configurational entropy in perovskite oxides and highlights the potential of high‐entropy design strategies for developing advanced OER electrocatalysts.