Ce3+-Induced metal vacancies engineering of NiSe2 with needle-like structure for alkaline hydrogen evolution

Abstract

The weak water dissociation ability and hydrogen adsorption of bulk NiSe2 inhibits their HER performance under alkaline conditions. Most work focused on tuning the electron structure and activity of Se sites, the role of Ni atoms in HER process is commonly ignored. In this work, we developed a Ce3+ induced strategy to introduce Ni cationic vacancies (VNi) on NiSe2 and simultaneously regulate its morphology to form hierarchical needle-like structure. The unique nanostructure provides more exposed active sites and facilitates mass and charge transfer. After the introduction of VNi, Ni2+ (t2g6eg2) in NiSe2 can be partially converted to Ni3+ (t2g6eg1) with optimal eg1 electron configuration, which improves the water dissociation barrier and facilitate the fast electron transfer during HER process. The Ni3+ also increases the charge density around the Se atom to improve H adsorption energy on Se sites, thus improving the alkaline HER activity.