Engineering Oxygen Vacancies in (FeCrCoMnZn)3O4-δ High Entropy Spinel Oxides Through Altering Fabrication Atmosphere for High-Performance Rechargeable Zinc-Air Batteries

High entropy oxides (HEOs) offer great potential as catalysts for oxygen electrocatalytic reactions in alkaline environments. Herein, a novel synthesis approach to prepare (FeCrCoMnZn)(3)O4-delta high entropy spinel oxide in a vacuum atmosphere, with the primary objective of introducing oxygen vacancies into the crystal structure, is presented. As compared to the air-synthesized counterpart, the (FeCrCoMnZn)(3)O4-delta with abundant oxygen vacancies demonstrates a low (better) bifunctional (BI) index of 0.89 V in alkaline media, indicating enhanced electrocatalytic oxygen catalytic activity. Importantly, (FeCrCoMnZn)(3)O4-delta demonstrates outstanding long-term electrochemical and structural stability. When utilized as electrocatalysts in the air cathode of Zn-air batteries, the vacuum atmosphere synthesized (FeCrCoMnZn)(3)O4-delta catalysts outperform the samples treated in an air atmosphere, displaying superior peak power density, specific capacity, and cycling stability. These findings provide compelling evidence that manipulating the synthesis atmosphere of multi-component oxides can serve as a novel approach to tailor their electrochemical performance.