Indium-doping-induced selenium vacancy engineering of layered tin diselenide for improving room-temperature sulfur dioxide gas sensing

Abstract

Layered metal dichalcogenides (LMDs) are promising gas-sensing materials due to their high specific surface area and satisfactory electrical conductivity. However, virgin LMD-based gas sensors have several performance constraints, including low sensor sensitivity and poor detection limits, which need to be addressed urgently. Cation-doping-induced vacancy engineering is an appealing route to improve the gas-sensing performance of LMDs by modulating their electronic structures and chemical properties. In this work, indium-doped tin diselenide (In–SnSe₂) nanosheets were synthesized via a one-step hydrothermal strategy, resulting in a sulfur dioxide (SO₂) sensor with improved sensitivity (4.85 ppm⁻¹) and a low detection limit (3.46 ppb). Compared with the pristine SnSe₂ sensor, the In-doped SnSe₂ sensor with a vintage doping ratio has enhanced the SO₂ response (72.45% vs. 38.66% to 5 ppm) at room temperature (25 °C). In addition, the In-doped SnSe₂ sensor shows rapid reaction time, outstanding SO₂ selectivity, as well as exceptional stability. According to experimental investigation and density functional theory (DFT) calculations, doped-In and induced-Se vacancies have opposite roles in SO₂ sensing, which yields the optimum doping ratio with the highest gas response. This study sheds light on the sensitization mechanism and promotes the development of high-performance gas sensors based on doped 2D LMDs.