Preparation,modification And Gas-sensing Properties Of WO₃ Materials

In recent years,gas sensors have been widely used in environmental protection,air quality control,toxic gas detection and other fields.The semiconductor metal oxide gas sensor has become one of the most comprehensive applied gas sensors because of its unique advantages.However,these sensors show a low response to low concentration gas at ppb level.Therefore,it is of great significance to enhance the performance of the gas sensor and improve its response to low concentration gas.In this thesis,sheet-like WO3 materials were prepared by microwave hydrothermal method and calcination method.Moreover,the response and the response/recovery time of the materials to ppb level NO₂ were improved by doping Sb and Fe elements respectively.In addition,the gas sensing mechanism based on Sb and Fe doped WO3 materials was systematically studied.In the experiment,taking the response of the materials to 1000 ppb NO₂ as an optimization index,orthogonal experiments were carried out.Based on the results of the orthogonal experiments,the optimization synthetic process was achieved by single factor experiments.At the operating temperature of 200℃,the detection limit of the sheet-like WO₃ materials is 20 ppb,and its response to 100 ppb NO₂ can reach 1.0,and the response/recovery time is24/32 s.In order to further improve the gas sensing properties of the materials,the sheet-like WO₃ materials prepared by the optimized process were modified by doping Sb and Fe.According to the analysis of experimental results,the gas response increases to 1.5 under100 ppb NO₂ when Sb doping content is 5%.The response/recovery time can reach 9/19 s,showing excellent response and recovery ability.When Fe doping content is 3%,the gas response is up to 2.3 under 100 ppb NO₂,which greatly improves its response to low concentration gas.According to the results of phase characterization,compared with undoped WO₃ materials,the doping of Sb and Fe makes the lattice slightly deformed and forms more defects and active sites on the surface of materials.Moreover,the doping of the two elements makes the sample contain more oxygen vacancies,which increases the adsorption sites of gas and improves the gas sensing properties of the material.The material shows a good response to low concentration NO₂,which provides a new strategy for the design of high-performance gas sensors,and can be applied in tail gas treatment,environmental monitoring,smart home and other fields.