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 (CoBiSex nanosheet arrays) driven by spinel oxides. Compared with spinel oxides, the low electronegativity of Se in CoBiSex nanosheet arrays leads to a portion of Co2+ in the low spin states (t2g6eg1) 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.