CoSe/CoSe2 Mott–Schottky heterostructures embedded in porous carbon nanofibers toward efficient bifunctional catalysis in zinc–air batteries

Abstract

The exploration of highly efficient bifunctional oxygen electrocatalysts is crucial for zinc–air batteries (ZABs). Transition metal selenides with low cost and high catalytic activity have demonstrated considerable potential in the field of catalysts. Herein, a novel CoSe/CoSe2 Mott–Schottky heterostructure is embedded in a porous, N-doped carbon (PNC) nanofiber network to fabricate the CoSe/CoSe2@PNC bifunctional catalyst for ZABs. Theoretical analyses reveal that the CoSe/CoSe2 heterointerface induces a strong built-in electric field, which effectively optimizes the adsorption of oxygen intermediates and promotes bifunctional catalytic behavior. Experimental testing results demonstrate that PNC nanofiber network not only provides high electrical conductivity, but also effectively prevents the heterostructures from agglomerating during cycling. Benefitting from both aspects of advantages, the CoSe/CoSe2@PNC catalyst achieves the remarkable bifunctional activity and superior stability. Integrated with the CoSe/CoSe2@PNC air cathode, the aqueous ZAB is assembled and exhibits a peak power density of 215.13 mW cm⁻2 and a high stability during long-term cycling (400 h). Furthermore, the solid-state ZAB with flexible CoSe/CoSe2@PNC shows the superior reliability and high stability under different outside deformations. Thus, this study not only provides an effective strategy for the design of nonprecious metal–based oxygen electrocatalysts, but also promotes the development of high-performance ZABs for diverse working conditions.