Sulfur vacancy tuning in SnS2/Ti3C2Tx heterojunctions for enhanced room-temperature NH3 sensing

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/Ti3C2Tx composites with S vacancies are prepared by the hydrothermal process in which the introduction of a high concentration of CH4N2S promotes the formation of S vacancies. Compared with SnS2, the optimized SnS2-Ti3C2Tx composites exhibit a response of 71.5% to 300 ppm NH3, enhancement of 90%, as well as excellent reproducibility, long-term stability, and selectivity. During NH3 sensing, SnS2 with S vacancies not only provides more active sites for NH3 adsorption but also exhibits a modified electronic structure of SnS2 with improved NH3 adsorption. Ti3C2Tx, with high electrical conductivity, provides electron-transfer channels. The interfacial heterojunction facilitates charge transport and provides abundant active sites for NH3 adsorption. The results suggest significant potential for designing two-dimensional materials with tunable sensing properties through defect and heterojunction engineering.