Synthesis, characterization and sensing properties of nano-SnO2supported on SBA-15 as highly sensitive semiconductor gas sensors

Abstract

Nanocrystalline SnO2/SBA-15 composites have been successfully synthesized by wet impregnation of SnCl2 using mesoporous structured silica SBA-15 as the sensor support and subsequent calcination at 700 °C. The results of small-angle XRD and nitrogen adsorption–desorption isotherms demonstrate that the hexagonal structure of SBA-15 in SnO2/SBA-15 is well maintained after impregnation. Wide-angle XRD and SEM show the formation of nanosized SnO2clusters, and O2-TPD reveals the increase of the amount of surface-adsorbed oxygen compared with that of pure SnO2. The sensors made of SnO2/SBA-15 composites display great enhancement of gas sensitivities, and the sensitivity to 1000 ppm of H2 reached as high as 1400, which is almost 40 times more sensitive than that of a pure SnO2 sensor. O2-TPD, TPR and XPS results reveal for the first time that the increase of the amount of surface-adsorbed oxygen species plays an important role in increasing the sensitivity of such a composite gas-sensing system. The optimum temperature where the sensitivity has its maximum value also shifts to lower temperature compared with that of pure SnO2 sensor. This finding provides a simple way to improve the sensing properties of metal oxide gas sensors with the aid of mesoporous materials as the sensor support.