Study On Hydrogen Sulfide Sensor Based On Three-Dimensional SnO₂ Nanocomposites

Since the 21st century,with the vigorous development of the technology of Internet of everything,the human demand for all kinds of sensor devices in industrial production and daily life has been increasing sharply.Gas sensors have received widespread attention and research by virtue of their important position in chemical production,medical and health care,atmospheric monitoring,human health and other fields.Hydrogen sulfide（H₂S）,a colorless and highly toxic gas with a rotten egg smell,is widely present in crude oil exploratory wells,petroleum refineries,sewerage systems,digesters and landfills,etc.Because of its corrosive effects on equipment in industrial production,and human health hazards such as respiratory system stimulation at low concentrations and fainting and death at high concentrations,real-time monitoring of H₂S is particularly important.Among H₂S sensors,SnO₂ semiconductor sensors are popular because of their low cost,high sensitivity,compact size,and high mechanical stability,but these sensors have the characteristics of high operating temperature,poor selectivity,and high power consumption.In this dissertation,the specific surface area is increased by changing the morphology of the material,and the operating temperature of the SnO₂ semiconductor sensor is reduced by doping,which greatly improves the material de selectivity and response:（1）SnO₂ nanoflowers were prepared by hydrothermal method,and a series of CuO-SnO₂ nanoflower composites were prepared by impregnation with different proportions of CuO nanoparticles;secondly,the composites were applied to heated flat electrodes by brush coating method,and a series of CuO-SnO₂ gas sensors were successfully developed;thereafter,the materials were characterized by SEM,EDS,TEM,XRD,XPS and other characterization means for material characterization,it was found that the nanoflowers-like structure brought a larger specific surface area and gas diffusion and adsorption channels;subsequently,gas-sensitive detection of H₂S gas at different temperatures and concentrations was performed,and it was found that the doping of nano-CuO particles greatly enhanced the gas-sensitive performance,and the sensitivity of the 50 ppm H₂S:10 mol%CuO-SnO₂（10CS）sensor was increased the most The sensitivity of 5 mol%CuO-SnO₂（5CS）and 15 mol%CuO-SnO₂（15CS）also reached 4168.3 and 6955.2,respectively,and not only that,it was found that the doping of CuO also brought about a reduction in operating temperature,with the optimal operating temperature for pure SnO₂sensors being 200.Finally,combining characterization and gas-sensitivity analysis,we analyzed that the doping of CuO increased the specific surface area of the composite material,bringing more electron concentration and oxygen vacancy concentration,forming heterojunctions to bring about resistance drop and generating Cu S metal to bring about sensitization effect,thus reducing the sensitivity in terms of The formation of heterojunction brings resistance drop and generation of Cu S metal brings sensitization effect,thus improving the gas-sensitive performance of the sensor in terms of both lowering the operating temperature and increasing sensitivity.The 10CS high sensitivity H₂S sensor and 5CS low operating temperature sensor were successfully prepared.（2）On the basis of the already prepared SnO₂ nanoflowers,Pt nanoparticles were doped into SnO₂ nanoflowers to make composites by the impregnation precipitation method using chloroplatinic acid hexahydrate as the platinum（Pt）source,and 1.5wt%Pt-SnO₂（1.5PS）and 3wt%Pt-SnO₂（3PS）were successfully developed,which were characterized by SEM,EDS,TEM,XRD,and XPS and other characterization means to probe the Pt particle doping,and it was found that the composite nanoflower-like structures possess numerous gas channels and excellent specific surface area.Subsequently,after gas sensitivity testing,it was found that with the doping of Pt,the sensitivity of Pt-SnO₂ sensors was greatly improved when detecting 50 ppm H₂S gas,with the sensitivity of 1.5PS sensors reaching 754.7 and 3PS sensors reaching 7092.7,16and 111 times that of pure SnO₂ sensors,respectively,and the optimal operating temperature of the sensors was also reduced from 200℃to 150℃;Finally,after gas-sensitive mechanism analysis,we believe that the doping of Pt brings about the Schottky barrier and overflow effect,increasing the electron concentration and the number of oxygen vacancies on the surface of SnO₂,greatly increasing the resistance drop while also increasing the rate of oxidation and reduction reactions.