Collective Synergistic Effects in High Entropy Perovskite Oxide Electrocatalysts for Enhanced Oxygen Evolution Reaction

ABSTRACT High entropy oxides (HEOs) have emerged as promising catalysts for the oxygen evolution reaction (OER) in water splitting. Herein, five elements were selected: Fe, Co, and Ni for their exceptional OER catalytic activity, alongside Cr and Mg to exploit their zero‐spin electronic configurations and cost‐effectiveness. Through a combination of systematic experiments and density functional theory (DFT) calculations, we analyzed five single‐element oxides and compared them with high‐entropy and ternary‐structured counterparts. Our findings reveal that the four key effects of high‐entropy materials collectively play an essential role in optimizing e g orbital occupancy, increasing defect density, and accelerating charge transfer, collectively enhancing activity and stability. Consequently, La(CoFeNiCrMg)O 3 exhibits an overpotential of 381 mV at 10 mA cm −2 , outperforming its counterparts while demonstrating enhanced reaction kinetics. Furthermore, a water‐splitting electrolyzer employing La(CoFeNiCrMg)O 3 as the anode and Pt/C as the cathode achieves a current density of 10 mA cm −2 at 1.68 V, highlighting its practical applicability. This work advances the fundamental understanding of the catalytic mechanisms of HEOs in the OER.