Highly sensitive and selective room temperature ammonia gas sensor by novel MoS2/Ce2Sn2O7 heterojunction

In this study, we report the synthesis of a MoS₂/Ce₂Sn₂O₇ composite via a simple hydrothermal method. The selectivity of the as-fabricated sensors was systematically evaluated against a range of volatile organic compounds, including ethanol, acetone, methanol, n-butanol, isopropanol, and triethanolamine. Notably, the MoS₂/Ce₂Sn₂O₇ heterojunction exhibited superior selectivity for NH₃ gas at room temperature, with the MoCe3 sample showing an impressive response of 87.3% to 100 ppm of NH₃. Furthermore, the MoCe3 sensor displayed a rapid response time of 40 s and an ultra-low detection limit of 50 ppt. The sensors demonstrated excellent repeatability, stability, and humidity resistance when exposed to NH₃, with the MoCe3 sensor particularly excelling at lower concentrations at room temperature. The MoCe3 sample also exhibited low activation energy (5 kJ/mol) and enhanced surface band bending compared to other sensors. The gas adsorption/desorption behaviors and the underlying gas sensing mechanisms were systematically explored, highlighting the transition between n-type and p-type phases. The dual-mode sensing capability of the MoS₂/Ce₂Sn₂O₇ composite, operational at both room and lower temperatures, opens up diverse applications ranging from environmental monitoring to industrial safety.