Single-Atom Tungsten Doped Nis0.5Se0.5 Nanosheets@Nanorods Heterostructures Catalyze Water Splitting Highly Active and Durable

Abstract Developing robust nonprecious electrocatalysts towards hydrogen/oxygen evolution reaction (HER/OER) is crucial for the spread of hydrogen energy industrialization. Here, we prepared a highly active and durable electrocatalyst of W single-atoms doped NiS 0.5 Se 0.5 nanosheets@NiS 0.5 Se 0.5 nanorods heterostructure (W-NiS 0.5 Se 0.5 ). The W-NiS 0.5 Se 0.5 exhibits superior catalytic activity for HER and OER with an ultralow overpotential (39, 106 mV for HER and 171, 239 mV for OER) and excellent long-term durability (500 h) at 10 and 100 mA cm − 2 , outperforming commercial precious-metal catalysts and many other reported transition-metal-based compounds. The spin state of Ni was delocalized by introducing low spin-state of W single-atom, thus increasing the electron density of Ni 2p orbital, optimizing the adsorption/desorption process of H, significantly reducing the energy barrier of the rate-determining step (O* → OOH*), finally accelerating thermodynamics and kinetics of HER/OER. This work provides a rational feasible strategy to design single-atom catalysts for water splitting and develop advanced transition metal-based electrocatalysts via regulating delocalized spin states.