Unraveling eg-band modulation as an alternate strategy to enhance lattice oxygen participation and entice oxygen electrocatalytic bifunctionality via switching of active site

Abstract

Lattice oxygen participation is believed to be crucial for enhanced electrocatalytic oxygen evolution reaction activity of perovskite oxides. However, the inherent criteria of uplifted O 2p-band for lattice oxygen participation make perovskites prone to elemental leaching and, hence, structural instability. Herein, we report an alternate strategy of eg-band modulation to enhance the lattice oxygen participation rather than the usual uplift of the O 2p band. We designed a high-entropy perovskite oxide (HEPO) Ba0.33Sr0.66Co0.165Mn0.165Ti0.33Sb0.33O3 (BSCMTS), which exhibits enhanced lattice oxygen participation by virtue of modified eg-band structure despite a downshifted O 2p-band as compared to its Co and Mn only analog. A switchover of the reaction active center from the lattice oxygen site in Co-only analog to the Co/Mn metal site in BSCMTS due to the upliftment of eg-bands of Co/Mn in BSCMTS is believed to be responsible for the enhanced lattice oxygen participation. Moreover, the HEPO also shows one of the best-reported bifunctional oxygen electrocatalytic activity among the pristine perovskite systems and acts as a superior air-cathode electrocatalyst for Zn-air batteries. The study also underscores the importance of the eg-band structure rather than the usual eg-electron filling and location of the O 2p and metal d-band center in perovskite oxides for oxygen electrocatalysis.