Study On Preparation And Photocatalytic Properties Of PDPB/TiO₂

As a photocatalyst,TiO₂has the advantages of high chemical stability,non-toxic and harmless,high photoelectric conversion efficiency,low cost and high activity,so it is widely used in the degradation of organic pollutants.However,the transfer rate of photogenerated electrons and hole pairs is slow,and the recombination rate is high,which leads to low quantum efficiency and reaction conversion rate of photocatalysis,which usually can only use ultraviolet light,and the utilization rate of light is too low,which limits the application of TiO₂.In this paper,PDPB/TiO₂ composites were successfully prepared by in-situ growth method.The problems such as low visible light utilization of TiO₂ and electron-hole commutation recombination were improved,and the photocatalytic activity of TiO₂ was improved.The structure and composition of the photocatalyst were characterized by X-ray diffraction（XRD）analysis,Fourier transform infrared spectroscopy（FT-IR）analysis,N₂ adsorption-desorption analysis and X-ray photoelectron spectroscopy（XPS）analysis.The morphology of the photocatalyst was observed by scanning electron microscope（SEM）and transmission electron microscope（TEM）.The optical properties of the photocatalysts were studied by ultraviolet-visible absorption spectroscopy（UV-Vis/DRS）.The photodegradation experiments were carried out with rhodamine B（RhB）as the target pollutant and PDPB/TiO₂ composite as the photocatalyst.When the visible light irradiation time is 50 min,the reaction rate constant of 20 wt.%PDPB/TiO₂ is0.0768 min^-1,which is 5.2 and 10.2 times higher than that of PDPB and TiO₂,respectively.The PDPB/TiO₂ photocatalyst was tested for 4 times,and it was found that the photocatalytic activity of the photocatalyst was stable.The mechanism of RhB degradation by PDPB/TiO₂ photocatalyst under visible light was studied by fluorescence spectrum,photoresponse current,electrochemical impedance analysis and active species capture experiment.It is found that the reason why the photocatalytic activity of PDPB/TiO₂ is higher than that of pure PDPB and TiO₂ is that PDPB and TiO₂ form Z-scheme heterojunction and effectively improve the efficiency of electron and hole separation.·O₂^-and h⁺_VB are the main active substances in the photodegradation system of PDPB/TiO₂,and·OH plays an auxiliary role in the process of photodegradation.In order to obtain more active photocatalyst,TiO₂ was modified by PDPB and Ag co-doping,and PDPB/Ag-TiO₂ ternary composites were prepared.The experimental results of degradation of RhB under visible light show that the degradation rate constant of PDPB/Ag-TiO₂-2 after 40min is 1.6 times that of 20 wt.%PDPB/TiO₂.It can be concluded that the photocatalytic activity of PDPB/Ag-TiO₂ ternary composites is better than that of binary composites PDPB/TiO₂ to some extent.Four times of photocatalytic cycle experiments on PDPB/Ag-TiO₂-2 photocatalyst show that it has stable photocatalytic activity and shows a broad application prospect.