Synergistic Rolesof Crystal Symmetry and Jahn–TellerDistortion for Enhanced Oxygen Evolution Reactivity in High-EntropyOxides

High-entropy oxides (HEOs) offer a vast and largely unexplored design space for electrocatalysis. However, the effect of complex lattice chemistry in governing catalytic activity remains unclear. In this work, we demonstrated a strategy in which manipulating the Jahn-Teller (J-T) distortion is effective in optimizing the oxygen evolution reaction (OER) activity of the lanthanum-based high-entropy perovskite oxides (PHEO). By tailoring the B-site cation chemistries in the perovskite lattice, we stabilized lanthanum-based HEOs with three distinct crystallographic symmetries and directly correlated the observed phase evolution with the degree of J-T distortions. Combined experimental characterization and theoretical calculations reveal that J-T distortion lifts the degeneracy of the eg orbitals, thereby facilitating favorable adsorption energetics of oxygen-containing intermediates and surface electron transfer. As a result, the optimized HEO catalyst renders a low overpotential of 338 mV at 10 mA cm-2 with decent durability over 50 h. This work establishes crystal symmetry and J-T distortion engineering as a powerful and physically meaningful platform for manipulating catalytic functions in high-entropy oxides.