Preparation And Photocatalytic Properties Of Rare Earth Doped Bismuth Fluoride Oxide Heterojunction Materials

Bismuth series compounds have been widely used in the field of environmental protection and energy due to their special outer electron configuration（6S~2）and appropriate band gap width,which can separate electron holes and exhibit good light absorption ability under light irradiation.However,the single bismuth photocatalyst has some problems such as easy recombination of photogenerated carriers and limited absorption range of visible light,so it is necessary to take some measures to inhibit the recombination of photogenerated electrons and holes and enhance the utilization rate of the spectrum so as to improve the photocatalytic performance.In this paper,the rare earth doped bismuth fluoride oxide is selected as the research object,and the rare earth doped BiOF is used as the matrix material to compound with different bismuth based semiconductor materials to construct heterojunction,so as to improve its visible light catalytic performance and show good near-infrared photocatalytic ability.The specific research contents are as follows:1.BiOF:Tm³⁺,Yb³⁺/Bi₂WO₆ composite photocatalyst was prepared by simple solvothermal method.The effect of different composite ratio of BiOF:Tm³⁺,Yb³⁺and Bi₂WO₆ on the photocatalyst performance was studied.It was found that the best photocatalytic activity was obtained when the mass ratio of BiOF:Tm³⁺,Yb³⁺and Bi₂WO₆ was 1:2.With Rhodamine B as the simulated pollutant,the degradation rate of 30min under visible light has reached 98.08%,which is more than 90%higher than that of BiOF:Tm³⁺,Yb³⁺,and nearly 30%higher than that of pure Bi₂WO₆.Under the irradiation of 980nm high power pump light source,the degradation rate of the target pollutant reaches 46.83%within 10h,which is more than 30%higher than that of a single catalyst.Some characterization methods were used to analyze the crystal phase,morphology,light absorption capacity and photocarrier recombination of the prepared materials to explore the reasons for the improvement of photocatalytic performance.Through characterization,it can be seen that BiOF:Tm³⁺,Yb³⁺/Bi₂WO₆ composite photocatalyst formed a heterojunction in the structure,which can effectively inhibit the recombination of photocarriers.At the same time,compared with the pure phase bismuth fluoride oxide,the band gap width is narrower,and the absorption range of the spectrum is obviously extended.2.BiOF:Tm³⁺,Yb³⁺/Bi₂O₂CO₃ composite photocatalyst was prepared by two-step solvothermal method,and the optimal catalytic ratio was explored by adjusting the composite ratio of BiOF:Tm³⁺,Yb³⁺and Bi₂O₂CO₃.It was found that the best photocatalytic activity was achieved when the mass ratio of BiOF:Tm³⁺,Yb³⁺and Bi₂O₂CO₃was 1:2.Under visible light,the degradation rate reached 97.68%in100min,which was more than 30%higher than that of a single catalyst.Under the irradiation of 980nm high power pump light source,the degradation rate of the target pollutant reaches 36.88%within 5h.XRD,SEM,DRS,PL and other characterization methods were used to analyze the crystal phase,morphology and optical properties of the samples.The results show that BiOF:Tm³⁺,Yb³⁺and Bi₂O₂CO₃ form heterojunction in structure,and have narrower band gap and larger specific surface area than bismuth fluoride oxide alone.The photocatalytic performance was better through multi-component synergistic effect.3.A series of rare earth doped BiOF/Bi₂MoO₆ composite photocatalysts were prepared by two-step solvothermal method.XRD,SEM,DRS,PL and other characterization methods were used to analyze the crystal phase,microstructure,light absorption capacity and photocarrier recombination,and the photocatalytic activity was evaluated by catalytic degradation of dyes under visible and near-infrared light.It was found that BiOF/Bi₂MoO₆:Tm³⁺,Yb³⁺showed the best photocatalytic activity under visible light,and the degradation rate of rhodamine B reached 96.10%after30min.BiOF:Tm³⁺,Yb³⁺/Bi₂MoO₆ composite photocatalyst had the best photocatalytic effect under near-infrared photocatalysis,and the degradation rate of rhodamine B reached 36.39%at 5h.