Preparation Of Ag/sno₂ Film By Electrodeposition And Its Response To H₂ And H₂s

SnO2 is a kind of resistance semiconductor sensor and has good stability and response to several gases, and has been widely used in many fields such as environment, safety and energy.A conventional three-electrode cell was used for the preparation of SnO2 thin film in SnCl2 and natrium citricum aqueous solution by using Model 273 electrochemical system. ITO glass was as a substrate (working electrode), platinum as the counter electrode and a saturated calomel electrode (SCE) as the reference electrode. Sn was oxidized at high temperature and the SnO2 thin film was further doped with Ag by electrodeposition in AgNO3 (aq) followed by a sintering process.The morphology and the crystal structure of SnO2 and Ag/SnO2 were characterized by SEM and XRD. The influences of voltage, time, oxidation temperature and time on the thin film was studied. The crystal Ag/SnO2 prepared is homogeneous and porous with crystal size about hundreds of nanometer and suitable to be used as gas sensors. The optimized conditions for preparation Ag/SnO2 thin film are followings:SnCl2 concentration is 7.0 g/L, voltage and time of electrodeposition Sn are-1.0 V and 5400 s, oxidation temperature and time are 600℃and 10 h respectively. AgNO3 concentration is 5.0 g/L, voltage and time of electrodeposition Ag are-1.4 V and 600 s; sintering temperature and time are 200℃and 30 min.The sensitivity of Ag/SnO2 film to H2 and H2S is tested with self-made detection device. Doping Ag can effectively improve the sensitivity of SnO2. Undoped SnO2 has no response to H2 at room temperature while the sensitivity of Ag/SnO2 to 2000μg/g H2 is 12. The temperature of the highest sensitivity and the lowest detection limit of undoped SnO2 are 300℃and 100-200μg/g to H2, and 250℃and 20μg/g to H2S. And the temperature of the highest sensitivity and the lowest detection limit of Ag/SnO2 are 175℃and 50μg/g to H2, and 125℃and 1μg/g to H2S. The sensitivity of Ag/SnO2 sensor to H2 and H2S has a linear relationship with gas concentrations, possible for quantitative analysis.