Two-dimensional black phosphorus/tin oxide heterojunctions for high-performance chemiresistive H2S sensing

Hydrogen sulfide (H2S) emission from industrial fields and bacteria decomposing of sulfur-containing organic matter poses a significant impact on human health and atmospheric environment, thus necessitating the development of a H2S sensor with high sensitivity and exclusive selectivity especially at a very low dose. Chemiresistive sensors based on traditional metal oxides were readily limited by the elevated operating temperature and severe cross-sensitivity. To overcome these obstacles, we prepared two dimensional (2D) tin oxide (SnO2) nanosheets decorated with thin black phosphorus (BP) as the sensing layer of MEMS H2S sensors. Compared with pure SnO2 counterparts, BP-SnO2 sensors demonstrated lower optimal working temperature (130 °C vs. 160 °C), higher response (8.1 vs. 4.6) and faster response/recovery speeds (39.8 s/47.4 s vs. 79 s/140 s) toward 5 ppm H2S as well as larger sensitivity (1.3/ppm vs. 0.342/ppm). In addition, favorable repeatability, long-term stability, selectivity and humidity tolerance were exhibited. Thin BP not only served as an excellent conductivity platform within the composites, but enriched the adsorption sites by constructing p-n heterojunctions and introducing more oxygen vacancy, thus separately accelerating and strengthening the gas-solid interaction. This study showcased the application superiorities of BP nanosheets in the field of gas sensing, simultaneously providing a new strategy for trace H2S sensing via the 2D heterojunctions.