Preparation Of Metal Oxides And Graphene Nanocomposites By Aerogel Method And Their Gas Sensing Properties

For a long time,metal oxides SnO₂,ZnO,NiO,etc.have been widely studied as important gas sensing materials.However,pristine metal oxide-based gas sensors are difficult to meet the needs of practical applications due to high power consumption,poor selectivity and low response to some gases.At present,the sensitivity of gas sensor can be improved by constructing metal oxide matrix composite nanomaterials.In this thesis,metal oxide and graphene composite nanomaterials were constructed by aerogel method,and the noble metal Pt modification was used to further improve the gas sensitivity.The gas sensing properties of composite nanomaterials were studied by analyzing their crystal structure,microstructure and surface properties.The main research contents are as follows:（1）SnO₂/graphene nanocomposites with SnSO₄ as raw material were prepared by aerogel method.Through XRD,XPS,Raman,SEM and TEM characterization and gas sensing test,the gas sensing properties of SnO₂/graphene nanocomposites with different mass ratios were studied and compared.On this basis,the precious metal Pt was modified,and its response value to 200 ppm ethylene glycol gas reached 187 at 200°C,which showed a great improvement in gas sensitivity compared with SnO₂/graphene.（2）NiO/graphene nanocomposites were prepared by aerogel method using Ni（CH₃COO）₂·4H₂O as raw material,and the morphologic characteristics of composite nanocomposites were regulated by changing the concentration of NiO.On this basis,Pt modification was introduced into the composite system,and the gas-sensing test showed that the response value of the composite system to methanol gas at 200 ppm was 87 at the optimal operating temperature of 200°C.（3）ZnO/graphene composites were prepared by aerogel method with Zn（CH₃COO）₂·2H₂O as raw material.The effects of different ZnO contents on the gas-sensing properties of the composite nanomaterials were studied and modified by precious metal Pt.The response value of 2%Pt composite nanomaterials toward 200 ppm acetone gas is 202 at 300°C.（4）The metal oxides SnO₂and NiO were combined with graphene by one-step method,and the gas-sensing properties of different proportions SnO₂/NiO and graphene composite nanomaterials were studied and compared.The 1:1 optimal ratio of composite nanomaterials responds 311 to 200 ppm ethylene glycol at 150°C.On this basis,ZnO/NiO and graphene composite nanomaterial was prepared by ZnO instead of SnO₂,and its response value to 200 ppm acetone was 289 at 200°C.