Activating the Basal Plane of Defective SnS₂ Nanosheets for NH₃ Gas Sensing

Layered metal dichalcogenides (LMDs) have been acknowledged as having an efficient gas-sensing process because of their tunable electronic structure and active edge sites. However, the full operation of their sensing properties is greatly hindered by the inactive basal plane of LMD and thus could possibly be considered by deblocking the basal plane. Herein, defective SnS2 nanosheets were synthesized via a facile solvothermal process with subsequent argon plasma irradiation in just several seconds and have been exploited for NH3 gas-sensing applications. A large number of surface defects on SnS2 nanosheets were produced by plasma treatment and tailored by the irradiation time to modulate the electronic structure. It is found that SnS2 nanosheets after 4 s of Ar plasma treatment exhibit promising NH3-sensing properties including high sensitivity, superior selectivity, and promoted sensing kinetics as well as low operation temperature. A five-axe spider-web diagram was also established for the evaluation of suitable operation condition. Furthermore, density functional theory calculations were conducted to reveal the rationales behind the defect-enhanced sensing behaviors. The results suggest that the efficient NH3 detection and NH3 adsorption transient from physi- to chemisorption mechanism are dominated by the S-vacancy defects on the basal plane. This work may open up interesting horizons for rational design of the LMD-based materials with promising sensing behaviors through defect engineering.