The Synthesis Of Two-dimensional Bismuth Tungstate Photocatalyst And The Study Of Photocatalytic Performance

The two-dimensional material has many advantages such as porosity,specific surface area,good crystallinity,multiple surface active sites,rich host guest selectivity and fast electron separation efficiency.This unique surface structure characteristic is conducive to the improvement of photocatalytic performance in the photocatalytic reaction system.Bi₂WO₆ is a sandwich layered structure composed of[WO₄]^2-layer and[Bi₂O₂]²⁺layer,and the band gap is about 2.7 eV,The layered characteristics are easier to form two-dimensional nanoscale structures in the process of preparation,and the narrower band gaps have the ability to absorb visible light,so Bi₂WO₆ is widely applied in the fields of photocatalysis.In this paper,two dimensional bismuth tungstate nanosheets and their composites with controllable thickness and composition were synthesized.The effects of thickness and composition of nanosheets on photocatalytic properties were studied,and their mechanism was preliminarily studied.This paper includes the following parts.?1?The two-dimensional Bi₂WO₆ nanosheets were prepared by hydrothermal synthesis.Then Bi₂WO₆ was used as carrier,TAA as sulfur source,and Bi₂S₃/Bi₂WO₆?BWS?structure was synthesized by ion-exchange method.The band gap value of Bi₂S₃ is 1.3 eV,which can effectively absorb the sunlight.In the composite materrial,the Bi₂S₃ nanoparticles are evenly dispersed on the surface of Bi₂WO₆,and the crystallinity and morphology of Bi₂WO₆ are not changed.By studying the photocatalytic degradation of RhB by BWS,it is found that the photocatalytic degradation efficiency of BWS-2 is nearly 2 times higher than that of BWO.In addition,through experiments the free radical trapping have proved that the most important active groups in the process of catalytic degradation of superoxide radical?·O₂^-??2?The two-dimensional Bi₂WO₆ nanoscale was prepared by hydrothermal method,and the ultrathin two-dimensional Bi₂WO₆ nanostructures with different thickness were synthesized by regulating the concentration of the front body.With the decrease of the precursor concentration,the thickness of the sample decreased from 27 nm to 16 nm.As the thickness of the sample thinned,the specific surface area increased and the active site increased.Through photocatalytic reduction of Cr???,the properties of Bi₂WO₆ nanosheets with different thicknesses were studied.It is found that BWO-3 nanosheets have the best ability of photocatalytic reduction of Cr???,and the oxygen vacancies?OVs?play an important role in the process of photoreduction Cr???.?3?The two-dimensional Bi₂WO₆ nanoscale was prepared by hydrothermal method.By using NaOH solution to adjust the pH value of the precursor to synthesize Bi₂WO₆ nanoscale,the morphology of Bi₂WO₆ nanostructures will change with the change of pH value.When the pH value is less than or equal to 6,Bi₂WO₆ maintains a good nano-structure.What's more,with the increase of pH,the surface area and pore size accordingly increase,which improves improve the surface activity of the sample,thereby affecting the catalytic performance of the catalyst.When the pH value of the solution is more than 6,the Bi₂WO₆ nanoscale will have a certain agglomeration,which affects the photocatalytic activity.Through photocatalytic reduction of Cr???,the properties of Bi₂WO₆ synthesized from different pH were studied.It is found that it can reach 98.4%in the condition of the pH of the current flooding solution being equal to six and irradiated at 120 min,which is more capable of reducing Cr???than other samples.