Interface-Engineered SnS2/Nb-Doped TiO2 Bilayer Heterostructure for Enhanced Sensitivity to NO2 at Room Temperature

Nitrogen dioxide (NO2) is a harmful air pollutant that poses serious risks to human health and the environment. Achieving NO2 sensors with high sensitivity, selectivity, and stability at room temperature remains a significant challenge. In this work, we report a room-temperature NO2 sensor based on a SnS2/Nb-doped TiO2 bilayer heterostructure, which exhibits an ultrahigh response and excellent selectivity without the need for external heating or light activation. The sensor was fabricated via a simple hydrothermal method and an impregnation process. The SnS2/0.5% Nb-doped TiO2 bilayer heterostructure (16.7) exhibited a 227.4% increase in response at 10 ppm of NO2 compared with pristine SnS2 (5.1). It attained a response of 4.4 at a low concentration of 5 ppm of NO2 and reached an ultrahigh response of 736.5 at 100 ppm of NO2. The large specific surface area and unique layered structure of SnS2 promote gas diffusion and adsorption. The formation of the heterojunction between SnS2 and Nb-doped TiO2 facilitates the separation and transport of charge carriers and increases the density of active sites for the reactions. Furthermore, we investigated the influence of different metal electrodes on the sensor performance and calculated the corresponding variations in the Schottky barrier height to further elucidate the gas-sensing mechanism. This work offers a promising strategy for designing high-performance, low-power NO2 sensors for real-time environmental monitoring.