Synergistic Effects of Pd Decoration and Substrates on the NO2 Sensing Performance of Sprayed WO3 Thin Films

The selective detection of NO2 is achieved using Pd decorated WO3 thin films deposited on glass (WO3G) and alumina (WO3A) substrates. WO3A film shows superior performance over WO3 G film in terms of sensitivity, response magnitude and response and recovery time. Lower detection limit of 2 ppm is achieved using WO3A film for which gas response was 20 % whereas for WO3 G film response was 9 %. In particular, higher gas response towards NO2 is observed for WO3A film, which is attributed to the high surface roughness and high catalytic activity of Pd causing enhanced spillover and effective diffusion of NO2.