Sulfur vacancy tuning in SnS₂/Ti₃C₂T_xheterojunctions for enhanced room-temperature NH₃sensing

Ammonia (NH₃) gas sensors play an essential role in agricultural production, industrial manufacturing, human health protection and environmental monitoring. However, development of the room-temperature NH₃-sensing materials with sensitive response remains challenging. In this work, SnS₂/Ti₃C₂T_xcomposites with S vacancies are prepared by a hydrothermal process, in which the introduction of a high concentration of CH₄N₂S promotes the formation of S vacancies. Compared with SnS₂, the optimized SnS₂-Ti₃C₂T_xcomposites exhibit a response of 71.5% to 300 ppm NH₃, enhancement of 90%, as well as excellent reproducibility, long-term stability, and selectivity. During NH₃sensing, SnS₂with S vacancies not only provides more active sites for NH₃adsorption but also exhibits a modified electronic structure of SnS₂with improved NH₃adsorption. Ti₃C₂T_x, with high electrical conductivity, provides electron-transfer channels. The interfacial heterojunction facilitates charge transport and provides abundant active sites for NH₃adsorption. The results suggest significant potential for designing two-dimensional materials with tunable sensing properties through defect and heterojunction engineering.