Study Of Methanol Sensors Based On Semiconductor Oxide SnO₂

With the development of the Internet of Things,the role of gas sensors,which are devices used in modern science and technology to prevent early gas leaks,is gradually coming to the fore,playing an important role in everyday life and industrial production.Gas sensors have the advantages of being low-cost and easy to manufacture,thus generating interest in research on gas sensors.Scholars have classified gas sensors.Depending on the operating principle,gas sensors are classified as semiconductor oxide type,optical type,solid electrolyte type,etc.Semiconductor oxide gas sensors are used to detect organic volatile gases such as methanol,ethanol,formaldehyde,acetone,and xylene.Among them,methanol gas can cause itching of the skin and loss of vision in the light of exposure,or poisoning,coma,and other adverse symptoms,endangering personal health.Therefore,it is essential to monitor the level of methanol gas in the environment.In this thesis,tin dioxide(SnO₂)gas-sensing elements were prepared by hydrothermal method,supplemented by doping with silver(Ag)and copper(Cu)elements to modify SnO₂,and the prepared methanol sensors were characterized and gas-sensing performance tested with the aid of SEM and gas-sensing test systems to investigate the effects of Cu doping and Ag and Cu double doping on improving the methanol gas-sensing performance of the sensors.Finally,the mechanism of sensor performance improvement is elaborated and the best performing sensor devices are evaluated by combining the sensing mechanism and test data.The specific research content and results of this thesis are summarised below.(1)Fabrication and gas-sensing performance study of SnO₂methanol sensors based on Cu element doping.Firstly,the Cu/SnO₂-based methanol sensor was prepared by hydrothermal method and the gas-sensing performance of the sensor was tested.The gas-sensing performance tests showed that the 2.0 at%Cu/SnO₂-based methanol sensor performed best,with a response value of 2.37 for 100 ppm methanol gas at the optimum operating temperature(275°C)and a response time of about 6 s.Finally,the sensing mechanism analysis showed that the Cu element doping may have contributed to the conversion of adsorbed oxygen and the interaction between methanol gas molecules and the free oxygen anion The Cu doping may have a catalytic effect on the conversion of adsorbed oxygen and the interaction between methanol gas molecules and free oxygen anions,thus enhancing the methanol gas-sensing of the sensor.(2)Fabrication and performance study of SnO₂ methanol sensors based on Ag-Cu doping.To investigate the significance of the double doping of Ag and Cu elements on improving the gas-sensing performance of methanol sensors,we analyzed the methanol gas-sensing performance of the double-doped SnO₂-based sensors by doping a quantitative amount of Ag elements on top of the 2.0 at%Cu/SnO₂sensors.Previous experiments showed that the 2.0 at%Cu/SnO₂-based methanol sensor performed best,so the molar ratio of Ag to Cu was varied based on the 2.0 at%Cu element doping to investigate the gas-sensing performance of the methanol sensor made with different Ag and Cu molar ratios.The test results show that the methanol sensor of sample C(Ag:Cu=3:2)has a response value of 1.83 for 100 ppm methanol gas,with a response time of about 7 s and the best performance in its group.The main reason for the improved performance is that the pore structure on the gas sensing element acts as a good diffuser for the methanol molecules,allowing them to interact with more adsorbed oxygen,thus improving the gas sensing performance of the methanol sensor.