Fabrication Of Bi₂XO₆/ZnFe₂O₄（X=Mo,W） Composite Nanofibers And Their Photocatalytic Properties

Semiconductor photocatalyst can use solar light as a green energy to degrade organic pollutants through a series of oxidation-reduction reactions,so it has attracted much attention in the field of sewage treatment.Traditional photocatalytic materials,such as Ti O₂,ZnO and other wide band semiconductor Photocatalysts,can only absorb and utilize UV light.Compared with UV light,visible light has a higher proportion of solar energy（45%）.In order to make better use of sunlight,design and synthesis of highly efficient visible–light-driven photocatalystsis becoming to be the research focus.Zinc ferrite（ZnFe₂O₄）is a kind of visible light photocatalytic material with potential application because of its narrow band gap and good magnetic properties.However,its photo generated electrons and holes are easily compounded and their photocatalytic activity is still low.In order to solve this problem,the ZnFe₂O₄ based heterojunction composite nanofibers were prepared by electrostatic spinning and solvothermal technology to improve the photocatalytic activity of ZnFe₂O₄ nanomaterials.The main contents are as follows:（1）By using the electrospun ZnFe₂O₄ nanofibers as hard template and through hydrothermal method,Bi₂WO₆/ZnFe₂O₄ composite nanofibers were prepared.In our work,scanning electron microscopy,transmission electron microscopy,X-ray diffraction and differential thermal analysis,were used to characterize the as-fabricated Bi₂WO₆/ZnFe₂O₄composite nanofibers.The results revealed that Bi₂WO₆ nanosheets were successfully grown on the primary ZnFe₂O₄ nanofiber templates.The loading of Bi₂WO₆ nanosheets of Bi₂WO₆/ZnFe₂O₄ heterojunctions could be controlled by adjusting the concentration of molybdenum precursor during the solvothermal process.We carried out the experiments of the photocatalytic degradation of Rhodamine B（RB）under visible-light irradiation.The Bi₂WO₆/ZnFe₂O₄ heterojunctions exhibited a higher visible light photocatalytic activity for the degradation of RB than the pure ZnFe₂O₄ nanofibers and Bi₂WO₆ nanosheets.Photocurrent measurements further confirm that heterojunctions can promote the separation of photoelectrons and holes.The mechanism of photocatalytic degradation of RB by Bi₂WO₆/ZnFe₂O₄ was also explored through the experiments of active species capture and Mott Schottky test.Moreover,the Bi₂WO₆/ZnFe₂O₄ composite nanofibers could be easily recycled without a decrease in their photocatalytic activity due to their good magnetic separation performance and excellent chemical stability.（2）One-dimensional Bi₂MoO₆/ZnFe₂O₄ heterojunction nanofiber photocatalytic materials were obtained by hydrothermal method using electrospinning ZnFe₂O₄ nanofibers as templates and reactants.Morphological and structural tests have shown that by adjusting the concentration of the precursor solution during the solvothermal reaction,the loading of the Bi₂MoO₆ nanosheets can also be regulated,and a suitable Bi₂MoO₆/ZnFe₂O₄ heterostructure can be obtained.The photocatalytic experiment showed that Bi₂MoO₆/ZnFe₂O₄heterojunction nanofibers could mineralized RB effectively,and its photocatalytic activity was significantly higher than that of pure ZnFe₂O₄ nanofibers and pure Bi₂MoO₆ nanosheets.Photoluminescence and photocurrent experiments show that the rapid charge transfer between the heterojunction interfaces can improve the separation efficiency of photogenerated electrons and holes,which is the main reason for the increase of photocatalytic activity.Combined with the capture experiment and the results of the Mottshott test,the possible mechanism of photocatalytic degradation of RB by Bi₂MoO₆/ZnFe₂O₄ composite nanofibers was proposed.Based on the good magnetic separation properties and chemical stability of the material system,Bi₂MoO₆/ZnFe₂O₄ photocatalytic materials also have recycling performance.