Preparation and gas-sensing performance of SnO2/NiO composite oxide synthesized by microwave-assisted liquid phase deposition

We synthesized SnO2/NiO composite oxides by microwave-assisted liquid phase deposition to improve their surface physico-chemical properties and gas-sensing selectivity, and we investigated how the molar ratio of Ni2+ to Sn4+ and the microwave power affected their gas-sensing performance. The microstructure, surface physico-chemical states, and morphology of the samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy, respectively. Nitrogen adsorption-desorption isotherms were used to characterize the specific surface areas of the samples. Our results showed that microwave-assisted liquid phase deposition increased the surface-adsorbed oxygen content and the specific surface area of the SnO2/NiO composite oxide from about 22 to 120 m(2)/g. When the molar ratio of Ni2+ to Sn4+ was 0.1, the gas response to 1000 ppm ethanol gas reached 84.7 at a lower working voltage of 3.5 V. However, the optimum working voltages for methanol and acetone gas were 4.5 and 4.0 V, respectively. Thus, a new method was found to improve the selectivity of the gas sensor. Moreover, at a working voltage of 4.0V, the gas response of a SnO2/NiO gas sensor synthesized by microwave-assisted liquid phase deposition with the optimum radiation power of 450W to 1000 ppm acetone gas was 49.7, twice that of a sensor synthesized by traditional liquid phase deposition. (C) 2018 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.