Study On The Preparation And Gas Sensing Properties Of Copper Oxide Based Semiconductor Nanomaterials

With the development of social industrialization,the air pollution caused by volatile organic compounds(VOCs)has become a serious challenge,and the research work of the corresponding gas detection technology is very urgent.Semiconductor metal oxide gas sensor has been a promising gas detection technology for VOCs because of its low cost,simple preparation,excellent performance,easy to miniaturization and other advantages.In this paper,copper oxide(CuO)was selected as gas sensing material.CuO nanostructures with different morphology and exposed crystal surface were prepared by chemical precipitation-heat treatment method and hydrothermal method,and their VOCs gas sensing properties were studied.Then,CuO/WO₃ nanostructured heterojunction was prepared by hydrothermal method,and the gas sensing enhancement mechanism brought by introducing CuO into heterojunction is discussed.In the process of preparation of CuO micro-polyhedron by chemical precipitation heat treatment,firstly three kinds of cubic phase Cu₂O micro-particles with different shapes were obtained by changing the amount of precipitant and the order of heating step.After heat treatment,the monoclinic phase CuO micro-polyhedrons were obtained.It was found that among the three kinds of CuO micro-polyhedrons,CuO micro-octahedron preferentially exposed active(110)plane,and showed significant selective sensitivity to n-butanol,which is 2.4 to 50 ppm n-butanol at 235?,and it was the best one among the three kinds of CuO micro-polyhedrons.The two-dimensional CuO nanosheets prepared by hydrothermal method also showed good gas sensing performance towards n-butanol:The optimal working temperature is only 175?,and the sensitivity to 30 ppm n-butanol is 3.1,which resulted from its large specific surface area,open structure and high surface oxygen adsorption,showing the advantages of two-dimensional CuO nanomaterials in the field of VOCs gas sensing.In addition,CuO micro-polyhedrons and nanosheets showed excellent repeatability in the gas sensing process,and the baseline resistance and target gas resistance have no significant change.On the basis of CuO gas sensing research,a new type of CuO/WO₃ nanostructured heterojunction was prepared.The formation of the heterojunction was confirmed by physical properties characterization.Then the VOCs gas sensing performance was studied,compared with the pure WO₃ nanoplate.It is found that the introduction of CuO can effectively improve the gas sensing performance of WO₃ nanoplate,like improving the gas sensing selectivity to n-butanol,reducing the optimal working temperature from 280? to 120?,increasing the sensitivity to 10 ppm n-butanol from1.77 to 4.25 at 120?,and reducing the response time to 5 ppm n-butanol from 240 s to 21 s.These can be attributed to the introduction of CuO nanoparticles.On the one hand,it increased the amount of surface oxygen adsorption,which will be conducive to the occurrence of gas sensing reaction,on the other hand,the formation of P-N heterojunction broadened the depletion layer in WO₃ substrate,so that the change of resistance value before and after gas sensing reaction became larger,thus showing a higher sensitivity.