Construct Z-scheme Heterojunction Based On Bi₂WO₆ For The Photocatalytic Degradation Of Ethylene

With the rapid development of industrialization,environmental pollution is becoming increasingly serious.In particular,air pollution has seriously threatened people’s healthy lives,so it is urgent to find an effective solution.Semiconductor photocatalytic technology can use solar energy to degrade pollutants in the atmosphere.Due to its advantages of safety,clean,green and environmental protection and so on,it attracts widespread concern.The key problem of semiconductor photocatalysis is finding efficient and stable photocatalyst.In this thesis,ethylene with low content in air,great harm,extremely stable and difficult to degrade is taken as an example to carry out the research.According to the principle of semiconductor photocatalytic degradation of ethylene,the Z-Scheme heterojunction photocatalytic material was constructed by combining Bi₂WO₆ nanosheet with other suitable narrow band-gap semiconductor materials.Then the photocatalytic performance and stability of the samples were systematically studied.The following is the main work in this thesis:（1）A series of composite photocatalytic materials of Co O and Bi₂WO₆ were prepared by two-step hydrothermal method.The structure and morphology of the samples were characterized by XRD,UV-vis DRS,Raman,XPS,SEM and so on,and then photocatalytic degradation of ethylene was studied.The results showed that compared with pure Co O and Bi₂WO₆,the performance of composite photocatalyst was significantly improved.When the weight ratio of Co O and Bi₂WO₆ is 40%:60%,the composite photocatalyst shows the best performance,which can fully degrade 100 ppm ethylene within 90 min.The reaction kinetic rate of the optimal sample is 46.85?10^-3?min^-1,which is 29.6 times of pure Bi₂WO₆(k=1.58?10^-3?min^-1)and 4.84 times of pure Co O(k=9.67?10^-3?min^-1).The cyclic stability test of the best sample showed that to some extent the stability of the catalyst was improved.（2）A series of composite photocatalytic materials of Cd S and Bi₂WO₆ were prepared by two-step hydrothermal method.The structure and morphology of the samples were characterized by XRD,UV-vis DRS,Raman,XPS,SEM and so on,and then photocatalytic degradation of ethylene was examined.The results showed that compared with pure Cd S and Bi₂WO₆,the performance of composite photocatalyst is significantly improved.When the weight ratio of Cd S and Bi₂WO₆ is 7%:93%,the composite photocatalyst shows the best performance,which can fully degrade 100 ppm ethylene within 15 min.The reaction kinetic rate of Bi₂WO₆ is 1.58?10^-3?min^-1,and the reaction kinetic rate of Cd S is 6.198?10^-3?min^-1.The reaction kinetic rate of the sample with the best performance is 388.963?10^-3?min^-1,which is246.17 times of pure Bi₂WO₆ and 62.756 times of pure Cd S.The cyclic test of catalyst stability showed that the stability of the composite material was significantly improved.