SiO2-templated high-entropy spinel oxides with abundant oxygen vacancies enabling lattice-oxygen-mediated oxygen evolution

Abstract

High-entropy oxides (HEOs) offer a promising platform for overcoming the activity–stability trade-off in oxygen evolution reaction (OER) catalysis. Herein, we report a SiO₂-templated strategy to construct porous spinel HEOs with tunable oxygen vacancy concentrations. The optimized HEO-350 catalyst exhibits a high specific surface area (213 m² g⁻¹) and abundant defect sites, delivering an overpotential of 267 mV at 10 mA cm⁻² and excellent durability over 100 h at 100 mA cm⁻² in alkaline media. Spectroscopic and electrochemical analyses reveal enhanced metal–oxygen electronic interactions and increased surface-active oxygen species at lower calcination temperatures. pH-dependent measurements, tetramethylammonium inhibition experiments, and in situ ATR-FTIR spectroscopy collectively indicate promoted lattice oxygen participation in the OER process. The synergistic effects of entropy stabilization and oxygen-vacancy engineering enable high intrinsic activity while preserving structural robustness. This work provides an effective route for designing defect-rich HEO electrocatalysts for efficient and durable water oxidation.