The Improved Covalent Coupling Induced by Bi Cations in CoBiSex Nanosheet Arrays for Stable Water Electrolysis

Transition metal selenides (TMSes) with high electrical conductivity, easily regulated morphological structure, and unique electronic structure have been explored as promising electrocatalysts for electrolytic water, while the lower intrinsic electrocatalytic capability has limited their wide application. Herein, we obtained CoSe nanosheet arrays with Bi cations incorporation (CoBiSe_x nanosheet arrays) driven by spinel oxides. Compared with spinel oxides, the low electronegativity of Se in CoBiSe_x nanosheet arrays leads to a portion of Co²⁺ in the low spin states (t_2g⁶e_g¹) due to the high covalent interaction between Co and Se, which can facilitate charge transfer. Density functional theory (DFT) calculation results further identify the redistribution of electron density from Se to Co, intensifying the adsorption of OOH* during the electrolytic water process with a 140 h robust catalytic performance. This work offers a unique strategy for exploring TMSe materials and their potential applications in the electrolytic water process.