Gas Sensing Properties Of SnO₂ Based Materials Prepared By Hydrothermal Method To Several Toxic Gases And The Study Of In Situ Diffuse-Reflectance Infrared-Fourier Transform Spectroscopy

Metal oxide semiconductor（MOS） has attracted much attention due to its advantages of low cost, high sensitivity, short response and recovery time. In situ diffuse-reflectance Fourier-transform infrared spectroscopy（in situ DRIFTS） can be used to simulate the real gas-solid interface reaction process and provide strong evidence for researching gas-sensing mechanism. In this study, first, SnO₂/rGO and SnO₂ gas-sensing materials were synthesized by hydrothermal method. Second, SnO₂/rGO and SnO₂ gas sensors were prepared by screen printing technique, and then their sensitivities to diethyl ether, tetrachloroethylene, acrylonitrile, acetonitrile, ethylamine and trichloroethylene were studied. Finally, the adsorption and reaction processes of these six toxic gases on SnO₂/rGO and SnO₂ gas-sensing films were studied by in situ DRIFTS. The main conclusions are as follows:（1） The crystal structure of SnO₂ in SnO₂ and SnO₂/ rGO gas-sensing materials synthesized by hydrothermal method is rutile structure; the specific surface area of the former is 143.702 m²/g, and the latter is 187 m²/g.（2） The optimum working temperature of SnO₂/rGO and SnO₂ gas-sensing materials to diethyl ether is 380 oC, and the detection concentration limit is 1ppm. Under the best working temperature, the sensitivity of SnO₂/rGO is higher and its response and recovery time is shorter compared to SnO₂. The in situ DRIFTS results show that CH₃CH₂·, CH₃CH₂O·, CH₃CH₂ OH, HCHO, CH₃ CHO, C₂H₄, H₂ O, and CO₂ were formed on the SnO₂/rGO and SnO₂ gas-sensing films.（3） The optimum working temperature of SnO₂/rGO gas-sensing material to tetrachloroethylene is 350 oC, while the sensitivity of SnO₂ is increased with the temperature increase; the detection concentration limit is 1ppm. At 350 oC, the sensitivity of SnO₂/rGO to tetrachloroethylene is higher than that of SnO₂, the response and recovery time of SnO₂/rGO is shorter than that of SnO₂. In situ DRIFTS results show that TCAC, COCl₂, Cl₂ and CO₂ were formed on the SnO₂/rGO and SnO₂ gas-sensing films.（4） The optimum working temperature of SnO₂/rGO gas-sensing material to acrylonitrile is 380 oC, while the sensitivity of SnO₂ is increased with the temperature increase; the detection concentration limit is 5ppm. At 380 oC, the sensitivity of SnO₂/rGO to acrylonitrile is higher than that of SnO₂, the response and recovery time of SnO₂/rGO is shoter than SnO₂. In situ DRIFTS results show that CH₂=CH-CONH₂, CH₂=CHCOOH,-NCO, NH₃, N₂, H₂ O, and CO₂ were formed on the SnO₂/rGO and SnO₂ gas-sensing films.（5） The optimum working temperature of SnO₂/rGO gas-sensing materials to acetonitrile is 380 oC, while the sensitivity of SnO₂ is increased with the temperature increase; the detection concentration limit is 1ppm. At 380 oC, the sensitivity of SnO₂/rGO to acetonitrile is higher than that of SnO₂, the response and recovery time of SnO₂/rGO is shoter than that of SnO₂. In situ DRIFTS results show that CH₃ O, CH₂ CNH, CHOO, HCN, H₂ O, and CO₂ were formed on the SnO₂/rGO and SnO₂ gas-sensing films.（6） The sensitivity of SnO₂/rGO and SnO₂ gas-sensing materials increased with the increase of temperature from room temperature to 400 oC, the detection concentration limit is 1ppm. At 400 oC, the sensitivity of SnO₂/rGO to ethylamine is higher and its response and recovery time is shorter compared to SnO₂. In situ DRIFTS results show that CH₃ CN, CH₃ O, H₂ O and CO₂ were formed on the SnO₂/rGO and SnO₂ gas-sensing films.（7） The optimum working temperature of SnO₂/rGO gas-sensing materials to trichloroethylene is 300 oC, and the detection concentration limit is 5ppm. At 300 oC, the sensitivity of SnO₂/rGO to trichloroethylene is higher and its response and recovery time is shorter compared to SnO₂. In situ DRIFTS results show that DCAC、CH₂ClCOO-、COCl₂、HCl、CO₂、CO、H₂O、Cl₂ were formed on the SnO₂/rGO gas-sensing films.