Study On Gas Sensitive Properties Of Metal Oxide Semiconductor Based On CuO

The rapid development of industrialization and the growth of urban population have caused more and more serious air pollution.Therefore,it is necessary to develop an accurate and real-time gas detection device.Metal oxide semiconductor gas sensor has the advantages of high efficiency,reliability,low power consumption,high sensitivity and small size,and has become the best candidate for detecting poisonous,harmful,inflammable and explosive gases.As a typical p-type metal oxide semiconductor,copper oxide（CuO）has the advantages of low cost,easy manufacturing,and long life.But,due to its high initial resistance,Cuo-based composites show gas sensitive performance at the higher temperatures usually.Therefore,in the field of gas sensors,CuO is often used as a load component combined with other metal oxides to construct gas sensors.For this reason,the metal oxides gas sensors based on CuO are rarely reported.In this thesis,the metal oxide semiconductors gas-sensitive composites of ZnO/CuO,rGO-CuO and WO₃/Cu₂O/CuO based on CuO were prepared,and the relevant gas-sensitive properties of the composites were tested,and the specific research contents were as follows:A novel ZnO/CuO composite with hierarchical crystal flower/urchin-like structure was prepared by a simple hydrothermal method.In this material,CuO showed the urchin-like particles accumulated by the nano-needles,the particle diameter was about 4-5μm.Crystal flower-like ZnO accumulated by rod-like particles was uniformly distributed on the surface of CuO.This unique structure could provide the more active sites which could effectively improve the gas sensitivity of the composite.At room temperature（25°C）,when the concentration of nitrogen oxides（NO_x）was 100 ppm,the prepared ZnO/CuO composites had the better gas-sensitive properties with a response value of 14.91,a response time of only 1s,and a detection limit of 50 ppb.Graphene oxide（GO）was prepared by an improved Hummers process,and rGO coated spherical CuO gas sensitive composites（rGO-CuO）was prepared by a simple hydrothermal method.Its structure showed the morphology of the spherical CuO encased by the rGO sheets,and the spherical CuO was composed of small particles with different diameters.The rGO package greatly improved the stability of CuO.Due to the better conductivity of rGO,doping rGO could effectively reduce the initial resistance of copper oxide.At the same time,the CuO particles wrapped by rGO were closely arranged and connected with each other by rGO with low resistance to form a parallel circuit of CuO micro-gas sensor,which improved the gas sensitive property of the material.At room temperature（25°C）,the response value of rGO-CuO gas sensitive material to 100 ppm NO_x gas was as high as 54.99,the response time was only 1 s,and the detection limit was as low as 50 ppb.WO₃/Cu₂O/CuO ternary gas sensitive composite was prepared by two-step hydrothermal method.The structure of the material showed the irregular spherical particles morphology.The n-p-p ternary heterojunction was formed at the three phase interfaces.The optimum synthesis conditions were determined by adjusting the hydrothermal time,temperature and the ratio of copper source to tungsten source.The response value of the WO₃/Cu₂O/CuO gas sensitive material to 100 ppm NO_x gas reached to 17.45 at 160°C,which was 5 times of pure copper oxide,the response time was 2.5 s,the recovery time was only 4 s,and the detection limit was 5 ppm.