Effect of heat treatment on surface structure and gas sensing of electrospun ZnO‐SnO ₂ composite nanofibers

Abstract ZnO‐SnO ₂ composite nanofibers with a constant Zn/Sn ratio of 0.4 have been electrospun and calcined at 650°C in ambient air, followed then by heat treatment at 350°C in either air, 5% H ₂ ‐95% N ₂ , or 15 ppm H ₂ S‐air atmosphere for comparison of gas‐sensing behaviors. The nanofibers being heat‐treated in the H ₂ S‐air atmosphere display a sensing response more than 25 times than the as‐calcined counterpart, that is, the sensing response increases from 20 to 514 against a model NO ₂ gas of 10 ppm concentration at a working temperature of 180°C. This appears to be attributable to the formation of sulfate on the nanofiber surface, which resulted in an enriched oxygen vacancy and chemisorbed oxygen near the surface for facilitating the redox reaction toward NO ₂ gas molecules. The facile heat treatment in the presence of dilute H ₂ S concentration may have opened up an alternative route for enhancing the surface‐sensitive gas‐sensor activity.