Enhancing Built‐in Electric Field via Balancing Interfacial Atom Orbit Hybridization at Boride@Sulfide Heterostructure for Hydrogen Evolution Reaction

Exploring nonprecious metal‐based catalysts for cathodic hydrogen evolution reaction (HER) has facilitated the realization of hydrogen economy toward water electrolysis in alkaline media. However, the difficult water dissociation process for the Volmer step (H2O → H* + OH*) and the subsequent unsuitable OH* adsorption energy on nonprecious metal‐based catalysts severely reduced the kinetics of HER. Herein, the universal synthesis for a series of transition metal (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W)‐based boride@sulfide heterostructured catalysts was realized by using molten‐salt method to conduct the in situ boronization of commercial sulfides. Significantly, WB2@WS2 heterostructured catalyst exhibits excellent catalytic activity and stability for HER. Balancing interfacial atom orbit hybridization between W(d)‐B(s,p) and W(d)‐S(s,p) at WB2@WS2 heterostructured interface enhances the built‐in electric field. In situ Raman spectroscopy and density functional theory calculation results reveal that the built‐in electric field in WB2@WS2 optimizes the adsorption and desorption of OH* intermediate, favoring the enhancement of catalytic performance toward HER. Besides, the rate‐determining step over WS2, which is generally considered to be the Volmer step, was changed to the step of OH* desorption over WB2@WS2, and thus the corresponding energy barrier was decreased.