Highly Sensitive Chemiresistive H2S Detection at Subzero Temperature over the Sb-Doped SnO2@g-C3N4 Heterojunctions under UV Illumination.

Abstract

NASA has detected H2S in the persistently shadowed region of the lunar South Pole through NIR and UV/vis spectroscopy remotely, but in situ detection is generally considered to be more accurate and convincing. However, subzero temperatures in space drastically reduce chemisorbed oxygen ions for gas sensing reactions, making gas sensing at subzero temperature something that has rarely been attempted. Herein, we report an in situ semiconductor H2S gas sensor assisted by UV illumination at subzero temperature. We constructed a g-C3N4 network to wrap the porous Sb doped SnO2 microspheres to form type II heterojunctions, which facilitate the separation and transport of photoinduced charge carriers under UV irradiation. This UV-driven technique affords the gas sensor a fast response time of 14 s and a response value of 20.1 toward 2 ppm H2S at -20 °C, realizing the sensitive response of the semiconductor gas sensor at subzero temperature for the first time. Both the experimental observations and theoretical calculation results provide evidence that UV irradiation and the formation of type II heterojunctions together promote the performance at subzero temperature. This work fills the gap of semiconductor gas sensors working at subzero temperature and suggests a feasible method for deep space gas detection.