Synergistic Interlayer and Defect Engineering in VS₂ Nanosheets toward Efficient Electrocatalytic Hydrogen Evolution Reaction

Abstract

A simple one-pot solvothermal method is reported to synthesize VS₂ nanosheets featuring rich defects and an expanded (001) interlayer spacing as large as 1.00 nm, which is a ≈74% expansion as relative to that (0.575 nm) of the pristine counterpart. The interlayer-expanded VS₂ nanosheets show extraordinary kinetic metrics for electrocatalytic hydrogen evolution reaction (HER), exhibiting a low overpotential of 43 mV at a geometric current density of 10 mA cm^-2 , a small Tafel slope of 36 mV dec^-1 , and long-term stability of 60 h without any current fading. The performance is much better than that of the pristine VS₂ with a normal interlayer spacing, and even comparable to that of the commercial Pt/C electrocatalyst. The outstanding electrocatalytic activity is attributed to the expanded interlayer distance and the generated rich defects. Increased numbers of exposed active sites and modified electronic structures are achieved, resulting in an optimal free energy of hydrogen adsorption (∆G_H ) from density functional theory calculations. This work opens up a new door for developing transition-metal dichalcogenide nanosheets as high active HER electrocatalysts by interlayer and defect engineering.