Design Of Superior NO₂ Gas Sensing Material And Their Gas Sensing Mechanism Research

As the precursor of PM_2.5,photochemical smog and acid rain,N02 has serious effect on human being,building and ecosystem.It is urgent to develop a gas sensor towards low concentration NO₂ at low temperature with rapid response and recovery,which is beneficial to saving energy and reduce the harm from NO₂ emission.There are two kinds of gas sensing material:metal oxide semiconductor exhibited rapid detection toward a few hundred ppb concentration NO₂ at a high temperature that prevent their practical application;the other material?carbon,conductive polymer,metal-organic complex?had a fast response and the slower recovery need be overcome in their application.In this paper,the morphology and composite were utilized to improved ZnO's NO₂ gas sensing performance;a low temperature NO₂ gas sensor could be built by the synthesis of metal-thiourea complex.The main contents are summarized as follow:?1?ZnO with four different morphologies was synthesized by hydrothermal methods.These characterizations?XRD,SEM,TEM and FT-IR?proved ZnO with four morphologies was R-ZnO,P-ZnO,F-r-ZnO and F-p-ZnO,respectively.Their NO₂ gas sensing test showed the relationship?F-p-ZnO>F-r-ZnO>P-ZnO>R-ZnO?.These results?UV-Vis DRS,PL and XPS?found that a narrow band gap and abundant defects result in F-p-ZnO with a good NO₂ gas sensing performance.A simple method was used to prepare ZnO/RGO through the mixing of ZnO solution and GO solution.The NO₂ sensing test showed ZnO/RGO has a weaker NO₂ sensing performance after recombination of ZnO and GO resulting from a lower defect of ZnO/RGO.?2?Through the optimization of metal ion,copper salt and the mole ratio of copper salt and thiourea,a metal-thiourea complex could be synthesized by the mixing of copper salt solution and thiourea solution.After the centrifugation and drying-in vacuum,a composition and morphology with Cu?TU?C1·0.5H₂O could be characterized by SEM,TEM,XRD,EDS,FT-IR and Raman technologies.Its gas sensing test showed the metal-thiourea complex could detect 0.1?10 ppm NO₂ at 60? with a response/recovery time less than 200 s;its NO₂ gas sensing performance could be further improved by selecting a reasonable heat-treatment temperature.The Hall effecting and XPS indicated the metal-thiourea complex have three properties?good proton conductivity,abundant hydroxyl oxygen and hydration oxygen,sensitive redox property?,which reaults in the good NO₂ performance of the complex and give a meaningful inspiration beneficial to the design of superior NO₂ gas sensing material.