Modulation of Phase Transition in Cobalt Selenide with Simultaneous Construction of Heterojunctions for Highly‐Efficient Oxygen Electrocatalysis in Zinc–Air Battery

Abstract

AbstractPhase transformation of cobalt selenide (CoSe2) can effectively modulate its intrinsic electrocatalytic activity. However, enhancing electroconductivity and catalytic activity/stability of CoSe2 still remains challenging. Heterostructure engineering may be feasible to optimize interfacial properties to promote the kinetics of oxygen electrocatalysis on a CoSe2‐based catalyst. Herein, a heterostructure consisting of CoSe2 and cobalt nitride (CoN) embedded in a hollow carbon cage is designed via a simultaneous phase/interface engineering strategy. Notably, the phase transition of orthorhombic‐CoSe2 to cubic‐CoSe2 (c‐CoSe2) accompanied by in situ CoN formation is realized to build the c‐CoSe2/CoN heterointerface, which exhibits excellent/highly stable activities for oxygen reduction/evolution reactions (ORR/OER). Notably, heterostructure can modulate the local coordination environment and increase Co‐Se/N bond lengths. Theoretical calculations show that Co‐site (c‐CoSe2) with an electronic state near Fermi energy level is the main active site for ORR/OER.Energetical tailoring of the d‐orbital electronic structure of the Co atom of c‐CoSe2 in heterostructure by in situ CoN incorporation lowers thermodynamic barriers for ORR/OER. Attractively, a zinc‐air battery with a c‐CoSe2‐CoN cathode displays excellent cycling stability (250 h) and charge/discharge voltage loss (0.953/0.96 V). It highlights that heterointerface engineering provides an option for modulating the bifunctional activity of metal selenides with controlled phase transformation.