Development of Dual-Selective Chemiresistive Sensor for NH3 and NOx at Room Temperature Using MoS2/MoO2 Heterostructures

Molybdenum oxides and sulfides stand out as promising materials for chemiresistive gas sensors. In this study, we tailored MoS2/MoO2 heterostructures, adapting pyrolysis-assisted in situ sulfidation of hydrothermally grown MoO3 by tuning the concentration of the sulfur source. The MoS2 flakes adorning a MoO2 cuboid rod heterostructure represent the n-type semiconducting property, confirmed by Hall measurement. Notably, the sensor demonstrated dual selectivity toward NH3 and NOx at room temperature. To our knowledge, the dual selectivity of the MoS2/MoO2 heterostructure has not been reported previously. The heterostructure, characterized by a higher carrier concentration, displayed enhanced sensitivity, yielding responses of 10.3 and 8.4% to 10 ppm of NH3 and NOx, respectively. The lowest detection limits were 0.32 ppm for NH3 and 0.29 ppm for NOx. Furthermore, the heterostructure sensor exhibited commendable cyclic stability and device reproducibility. A long-term stability assessment over 50 days revealed that the response of the sensor remained at 98.6 and 98.4% toward NH3 and NOx, respectively. Our results show that the optimized n–n heterojunction between MoO2 and MoS2 offers superior sensitivity to NH3 and NOx at room temperature. The results could have potential for the development of dual gas sensors suitable for real-time applications.