Molybdenum-induced tuning 3d-orbital electron filling degree of CoSe2 for alkaline hydrogen and oxygen evolution reactions

The development of high-performance non-precious metal-based robust bifunctional electrocatalyst for both hydrogen evolution reaction (HER) and oxygen evolution reactions (OER) in alkaline media is es-sential for the electrochemical overall water splitting technologies. Herein, we demonstrate that the HER/OER performance of CoSe2 can be significantly enhanced by tuning the 3d-orbital electron filling degree through Mo doping. Both density functional theory (DFT) calculations and experimental results imply that the doping of Mo with higher proportion of the unoccupied d-orbital (Pun) could not only serve as the active center for water adsorption to enhance the water molecule activation, but also mod-ulate the electronic structures of Co metal center leading to the optimized adsorption strength of *H. As expected, the obtained Mo-CoSe2 exhibits a remarkable bifunctional performance with overpotential of only 85 mV for HER and 245 mV for OER to achieve the current density of 10 mA/cm2 in alkaline media. This work will provide a valuable insight to design highly efficient bifunctional electrocatalyst towards HER and OER.(c) 2022 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

In this study, the HER/OER performance of CoSe2 was significantly improved by tuning the 3d-orbital electron filling degree through Mo doping. The Mo doping with a higher proportion of the unoccupied d-orbital not only enhanced water molecule activation but also modulated the electronic structures of the Co metal center, leading to optimized adsorption strength of *H. The resulting Mo-CoSe2 exhibited remarkable bifunctional performance with low overpotentials for both HER and OER in alkaline media.