S vacancies in 2D SnS2 accelerating hydrogen evolution reaction

Abstract

Precise manipulation of atomic defects is essential for modulating the intrinsic properties of two-dimensional (2D) materials. In this study, sulfur (S) atoms are accurately knocked out in the 2D basal plane of pure tin disulfide (SnS2). By varying the annealing temperatures (250–350°C), SnS2 with different S vacancy concentrations (Vs−SnS2) can be obtained. When SnS2 is annealed at 350°C for 5 h, the S vacancies in the forms of single S atom and double S atoms could reach up to 30.5%. The Vs−SnS2 is tested in the microelectrocatalytic hydrogen evolution reaction (HER). Vs−SnS2 with S vacancies of 30.5% generates superior catalytic performance, with a Tafel slope of 74 mV dec−1 and onset potential of 141 mV. The mechanism has been proposed. First, computation confirms that the absence of S atoms prompts surface charge modulation and enhances electronic conductivity. In addition, the under-coordinated Sn atoms adjacent to S vacancy introduce the lattice distortion and charge density redistribution, which are beneficial to hydrogen binding in HER. In short, accurate knockout of specific atoms by controlling the annealing temperature is a promising strategy to explore structure-dependent properties of various 2D materials.