Low Temperature HCHO Detection by SnO(2)/TiO(2)@Au and SnO(2)/TiO(2)@Pt: Understanding by In-Situ DRIFT Spectroscopy

In this work we analyze the effectiveness of decoration of nanocrystalline SnO(2)/TiO(2) composites with gold nanoparticles (Au NPs) and platinum nanoparticles (Pt NPs) in enhancing gas sensor properties in low-temperature HCHO detection. Nanocrystalline SnO(2)/TiO(2) composites were synthesized by a chemical precipitation method with following modification with Pt and Au NPs by the impregnation method. The nanocomposites were characterized by TEM, XRD, Raman and FTIR spectroscopy, DRIFTS, XPS, TPR-H(2) methods. In HCHO detection, the modification of SnO(2) with TiO(2) leads to a shift in the optimal temperature from 150 to 100 °C. Further modification of SnO(2)/TiO(2) nanocomposites with Au NPs increases the sensor signal at T = 100 °C, while modification with Pt NPs gives rise to the appearance of sensor responses at T = 25 °C and 50 °C. At 200 °C nanocomposites exhibited high selectivity toward formaldehyde within the sub-ppm concentration range among different VOCs. The influence of Pt and Au NPs on surface reactivity of SnO(2)/TiO(2) composite and enhancement of the sensor response toward HCHO was studied by DRIFT spectroscopy and explained by the chemical and electronic sensitization mechanisms.