Highly selective and sensitive CH4 gas sensors based on flame-spray-made Cr-doped SnO2 particulate films

Abstract

In this research, flame-spray-made 0–2 wt% Cr-doped SnO2 nanoparticles were synthesized and methodically studied for specific detection of methane (CH4) for the first time. From characterizations using X-ray diffraction, X-ray photoelectron spectroscopy, scanning/transmission electron microscopy and nitrogen adsorption, Cr was found to form substitutional solid solution in 5–20 nm nanoparticles with tetragonal SnO2 structure. In addition, grain and particle sizes decreased while surface area increases considerably with increasing Cr content. The sensing films prepared by spin coating technique were evaluated towards various flammable and toxic gases in dry air at 200–400 °C. Gas–sensing data evidently showed that the SnO2layer with the optimum Cr-doping level of 0.5 wt% offered a remarkable response of ˜1268 with a decent response time of ˜3.9 s to 1 vol% CH4at the optimum working temperature of 350 °C. In addition, the optimal Cr-doped SnO2sensor gave high CH4 selectivity against H2, C2H2, NO2, NO, N2O, CO, NH3, SO2, C2H5OH, C3H6O and H2O. Therefore, the flame-spray-made Cr-doped SnO2material is an attractive choice for selective and sensitive detection of CH4.