Effect of MoO3 doping and grain size on SnO2-enhancement of sensitivity and selectivity for CO and H2 gas sensing

MoO3-doped SnO2 nano-particles were prepared using sol–gel method with 0.1 molar solutions of SnCl4·5H2O and MoO3 with different doping concentration from 5.03×10−4 to 5.04×10−3 mol. The average grain size varies from 12 to 80 nm obtained by varying calcination temperature from 300 to 900 °C. Thick film samples, of about 25 μm thickness, were tested for CO and H2 in the concentration range of 15–1000 ppm in ambient air. The samples exhibit selective response to CO and H2 at 140 and 240 °C, respectively. The sensitivity increases with doping concentration for H2, whereas, for CO, it increases rapidly till the doping concentration of 2.01×10−3 mol and then reaches to saturation. The observed maximum sensitivity factor for CO at 2.01×10−3 mol doping is ∼30, whereas for H2, it is ∼10 at 5.04×10−3 mol doping. The response and recovery time is ∼5 and 10 s respectively.