Boosting the ORR/OER Activity of Cobalt‐Based Nano‐Catalysts by Co 3d Orbital Regulation

Abstract

AbstractThe transition metal oxides/sulfides are considered promising catalysts due to their abundant resources, facile synthesis, and reasonable electrocatalytic activity. Herein, a significantly improved intrinsic catalytic activity is achieved for constructing a Co‐based nanocrystal (Co‐S@NC) with the coordination of Co─S, Co─S─C, and Co─Nx─C. The calculational and experimental results demonstrate that the diversified chemical environment of Co‐cations induces the transition of 3d orbitals to a high spin‐state that exhibits the coexistence of Co2+ with fully occupied dπ orbitals and Co3+ with unpaired electrons in dπ orbitals. The diverse dπ orbitals occupation contributes to an elevated d‐band center of Co ions, which accelerates oxygen reduction reaction and oxygen evolution reaction electrocatalytic kinetics of the Co‐S@NC nanocrystal. Therefore, the Li–O2 batteries with Co‐S@NC as cathode catalyst exhibit 300 cycles at the current density of 500 mA g−1 with a cut‐off capacity of 1000 mAh g−1. Moreover, the ultrahigh discharge specific capacity of 34 587 mAh g−1 is obtained at a current density of 1000 mA g−1, corresponding to the energy density 949 Wh kg−1 of a prototype Li–O2 battery. The study on 3d orbital regulation of nanocrystals provides an innovative strategy for bifunctional electrocatalysts toward the practical application of metal–air batteries.