Strain Engineering of High-Entropy Oxides Enriches Highly Active Lattice Oxygen for Electrocatalytic Water Oxidation

Developing novel high-entropy oxide electrocatalysts for oxygen evolution is a promising strategy to accelerate the alkaline water electrolysis kinetics by optimizing the reaction paths. Herein, we demonstrate a high-strain senary (FeCoNiCrMnCu)₃O₄ electrocatalyst with remarkably increased highly active lattice oxygen, which follows the lattice-oxygen-mediated mechanism instead of the traditional adsorbate-evolution mechanism for oxygen evolution reaction (OER). A supersmall overpotential of 241.4 mV is required to obtain 10 mA cm^–2 and a considerable current retention rate of 94.9% is attained after continuously operating for 72 h. The oxygen diffusion coefficient is 1.97 × 10^–14 cm² s^–1, 5.6 times larger than the (FeCoNi)₃O₄, ensuring the rapid replenishment during water oxidation. The OER activity surpasses those of most of the reported spinel oxide electrocatalysts. More impressively, the assembled anion exchange membrane water electrolyzer can deliver an industrial-level current density of 1.0 A cm^–2 under the cell voltage of 1.79 V, exhibiting an attractive application potential.