Overall Water Splitting on The NiS/NiS2 Heterostructures Featuring Self-Equilibrium Orbital Occupancy

Abstract

Efficient electrochemical overall water splitting requires bi-functional catalysts that work for both hydrogen and oxygen evolution reactions (HER/OER). A heterostructure is thus proposed to maintain its optimal interactions with H/O-containing intermediates. A so-called "orbital occupancy self-equilibrium" strategy is employed theoretically and experimentally to design such bi-functional catalysts, namely the incorporation of the V species into a NiS/NiS2 heterostructure. Owing to the variable valences of both Ni and V species, the electrons are controllably reoriented over the interfacial VSNi bond. The as-generated dynamic and self-equilibrium of the electron environment modify an optimal adsorption harmony toward various H/O-containing intermediates on this heterointerface, enhancing intrinsic activity and reaction kinetics for the HER, the OER, and overall water splitting. This V-NiS/NiS2 catalyst exhibits an overpotential of only 94 and 220 mV at a current density of 10 mV cm(-2) for the HER and the OER, respectively. This proposed strategy is expected to be workable for other catalysts with variable metal valences and provide insights for an agile interfacial electron allocation on heterostructure catalysts.