Gas-Sensing Properties Of SnO₂ Gas Sensing Material Prepared By Sol-Gel Method To Severial Toxic Gases And The Study Of In Situ Drifts

With the development of industrial society, more and more attention has been focused on the detection of toxic gases in the environment. Metal oxide semiconductor?MOS? gas sensor has advantages of high sensitivity, good stability, low cost, and so on. These advantages can make it be used as detection of toxic gases.Diffuse-reflectance Fourier-transform infrared spectroscopy technology?DRIFTS? is widely used to research the reactions of gases on gas sensing films, and it can be used to analyze the mechanism of reaction between tested gases and gas sensing materials.In this paper, First, SnO₂ nanoparticles were prepared by sol-gel method. Second, the gas-sensing properties of the SnO₂ gas sensor to severial toxic gases including diethyl ether, methylene Chloride, trichloromethane and carbon tetrachloride were tested.Finally, the reaction processes of these four kinds of toxic gases with SnO₂ film were studied by DRIFTS. The results are described as follows:?1? The SnO₂ powders prepared by sol-gel method are spherical particles with average diameter of approximately 10²0 nm, and the specific surface area?BET? is51.68 m2/g.?2? The SnO₂ gas sensor was prepared by screen printing technology. The gas-sensing properties of SnO₂ gas sensor to 1²00 ppm diethyl ether were tested. The results showed that the SnO₂ gas sensor of diethyl ether had good gas-sensitive performance, the optimum temperature was 380 ?, and the response to the detection limit of 1 ppm was2.19. Moreover, the reaction processes of diethyl ether with SnO₂ film was studied by DRIFTS at 350, 380 and 400? respectively. This indicated that diethyl ether first adsorption on the SnO₂ film in state of moleculars, then generate ethyl?CH₃CH₂??, ethoxy?CH₃CH₂O??, CH₃CH₂OH, HCHO, CH₃ CHO, C₂H₄, and the final products were H₂O and CO₂.?3? The gas-sensing properties of SnO₂ gas sensor to methylene chloride were tested.The results indicated that the SnO₂ gas sensor of methylene chloride has good gas-sensitive performance, the optimum temperature was 350 ?, and at this temperature the response to the detection limit of 1 ppm was 1.10. The reaction processes of methylene chloride on SnO₂ film was studied by DRIFTS at 300, 350 and 380?,respectively. The results showed that methylene chloride molecules first adsorption on the surface of SnO₂ film in the state of moleculars, then, the molecules generated to phosgene,HCl and HCOO?, and the final products were COCl₂, Cl₂, H₂O and CO₂.?4? The gas-sensing properties of SnO₂ gas sensor to chloroform were tested. The results showed that SnO₂ gas sensor had a good performance to chloroform, the best working temperature was 380 ?, and the detection limit of chloroform was 1ppm, the corresponding response was 1.10. The reaction processes of chloroform with SnO₂ film was studied by DRIFTS at 350, 380 and 400 ? respectively. This results indicated that chloroform molecules first adsorbed on the surface of SnO₂ film, and then generated to HCH?, phosgene and HCl, then, HCH? would be further oxidized into CO₃^2-, and COCl₂,H₂O, CO₂ and Cl₂ were the final products.?5? The gas-sensing properties of SnO₂ gas sensor to tetrachloromethane were tested,and the reaction processes of tetrachloromethane with SnO₂ film was studied by DRIFTS at 280, 300 and 350 ?, respectively. The results showed that the response to the detection limit was 1 ppm of 1.15, and the optimum working temperature was 300 ?.Tetrachloromethane initially adsorbed on the surface of SnO₂ film in the state of moleculars, and then generated to phosgene, CO₃^2- and CO, The CO₃^2- could be further oxidized to CO₂ and phosgene partly oxidized CO₂ and Cl₂.