Highly selective ammonia detection by SnS2 nanosheets functionalized Ti3C2Tx

• The self-activated SnS 2 gas sensor functionalized with Ti 3 C 2 T x was prepared by the hydrothermal method. • The NH 3 -sensing response and selectivity of SnS 2 at room temperature could be enhanced by combined with Ti 3 C 2 T x . • The enhanced NH 3 sensing response and selectivity mechanism of SnS 2 /Ti 3 C 2 T x composite were discussed. SnS 2 is very promising for next-generation gas sensors due to the abundant edge-exposed sites, large surface-to-volume ratio, and high charge carrier mobility. However, SnS 2 suffers from low response and poor selectivity in gas sensing. In this paper, the self-activated SnS 2 gas sensor functionalized with Ti 3 C 2 T x is designed and fabricated to monitor NH 3 at room temperature (RT) in daily life. The response of SnS 2 and Ti 3 C 2 T x composites to 500 ppm NH 3 is about 86.35 % at RT, which is enhanced by 43.82 % and 38.33 % in comparison with pure SnS 2 and Ti 3 C 2 T x , respectively. The SnS 2 -functionalized Ti 3 C 2 T x micropatterns show high selectivity to NH 3 and a low detection limit of 143 ppt. Density-functional theory (DFT) calculations reveal that the SnS 2 /Ti 3 C 2 T x heterojunction provide the additional active sites for NH 3 adsorption, enhancing the absorption and diffusion capabilities of NH 3 . In addition, the remarkable metallic conductivity of Ti 3 C 2 T x MXene ensures efficient electron transfer to improve the sensing characteristics.