Optimizing d‐Orbital Electronic Configuration via Metal–Metal Oxide Core–Shell Charge Donation for Boosting Reversible Oxygen Electrocatalysis

Abstract Tuning the d‐orbital electronic configuration of active sites to achieve well‐optimized adsorption strength of oxygen‐containing intermediates toward reversible oxygen electrocatalysis is desirable for efficient rechargeable Zn‐Air batteries but extremely challenging. Herein, this work proposes to construct a Co@Co3O4 core–shell structure to regulate the d‐orbital electronic configuration of Co3O4 for the enhanced bifunctional oxygen electrocatalysis. Theoretical calculations first evidence that electron donation from Co core to Co3O4 shell could downshift the d‐band center and simultaneously weak spin state of Co3O4, result in the well‐optimized adsorption strength of oxygen‐containing intermediates on Co3O4, thus contributing a favor way for oxygen reduction/evolution reaction (ORR/OER) bifunctional catalysis. As a proof‐of‐concept, the Co@Co3O4 embedded in Co, N co‐doped porous carbon derived from thickness controlled 2D metal‐organic‐framework is designed to realize the structure of computational prediction and further improve the performance. The optimized 15Co@Co3O4/PNC catalyst exhibits the superior bifunctional oxygen electrocatalytic activity with a small potential gap of 0.69 V and a peak power density of 158.5 mW cm−2 in ZABs. Moreover, DFT calculations shows that the more oxygen vacancies on Co3O4 contribute too strong adsorption of oxygen intermediates which limit the bifunctional electrocatalysis, while electron donation in the core–shell structure can alleviate the negative effect and maintain superior bifunctional overpotential.