Construction of homologous cations SnO2/SnS heterojunction for ultra-sensitive NO detection

SnO₂ is an n-type wide band gap (E_g = 3.6 eV) metal oxide semiconductor (MOS) that has been widely studied, due to its low cost, non-toxicity and simple preparation process, and it has become the most important sensitive material for the preparation of gas sensors. However, the SnO₂ sensor still has some defects of high operating temperature and low response, which hinders its practical application. In this work, SnO₂/SnS composites were prepared by hydrothermally growing SnS nanoparticles on the surface of electrospun hollow SnO₂ nanotubes with high porosity. Results show that the SnO₂/SnS gas sensor based on the heterojunction has a much higher response of 375 to 50 ppm NO at 130 ℃ than that of pure SnO₂ sensor, as well as rapid response/recovery (26 s/90 s), excellent selectivity (12 times that of H₂S), repeatability and stability (225–250 to 20 ppm NO). Its enhanced sensing property may be attributed to the synergistic effect of the formation of homologous cations heterojunction and unique micro-structure of SnO₂/SnS composite, which could facilitate efficient charge transfer and provide more active sites (such as vacancy, point defects) for NO adsorption and reaction. This experiment provides a new idea for the development of SnO₂ gas sensors with excellent properties, which can meet the detection of toxic and harmful gas.