Study On Preparation And Photocatalytic Performance Of BiOBr Composite Materials

Appropriate band gap and unique layered structure make Bi OBr have the characteristic of visible light response,showing broad application prospects in the photocatalytic degradation of organic pollutants.However,the unmodified Bi OBr can only absorb part of visible light,and the recombination rate of photo-generated carriers is still relatively high compared with actual applications.Therefore,in order to further improve the photocatalytic activity of Bi OBr,Ag/Bi OBr,Zn Fe₂O₄/Bi OBr and Ag/Ag Br/Bi OBr composites were prepared and their structure,morphology,optical properties and photocatalytic performance were investigated.The main research contents of this paper are as follows:1.The solvothermal method was used to prepare nano-sheet Bi OBr,and the photoreduction precipitation method was used to prepare the Ag/Bi OBr composite photocatalyst.Through the controlled variable method,the effects of Ag NO₃dosage and the photoreduction time on the structure,morphology,optical properties and photocatalytic properties of the composites were investigated.And the photocatalytic mechanism of Ag/Bi OBr was discussed.The results indicatded that with the increase of Ag NO₃,the photocatalytic performance of Ag/Bi OBr showed a trend of first increasing and then decreasing.The sample prepared under the condition that the mass ratio of Ag NO₃/Bi OBr is 5%exhibited excellent photocatalytic performance,and the degradation rate of Rh B solution can reach 97.1%within 15 minutes,while the degradation efficiency of pure Bi OBr under the same conditions is only 68.1%.The sample prepared when the photoreduction time is 60 min has excellent photocatalytic activity,and after four cycles,the degradation efficiency of Rh B still remains above80%.Through free radical capture experiments,it was found that holes（h⁺）and superoxide radicals（·O₂^-）are the main active species in the reaction process.On this basis,the corresponding photocatalytic mechanism was proposed.2.Nanometer Zn Fe₂O₄ was prepared by solvothermal method,and then Zn Fe₂O₄/Bi OBr composites were prepared by hydrothermal method under citric acid-assisted conditions.The effects of different loadings of Zn Fe₂O₄ on the photocatalytic performance of Zn Fe₂O₄/Bi OBr were studied,and the photocatalytic mechanism was discussed.The results showed that the introduction of Zn Fe₂O₄ can not only improve the light utilization efficiency of the composites,but also reduce the recombination rate of photogenerated carriers.A proper amount of Zn Fe₂O₄ loading can effectively improve the photocatalytic activity of the composites.When the mass ratio of Zn Fe₂O₄to Bi（NO₃）₃·5H₂O is 1.2%,the prepared sample has high photocatalytic performance,and the degradation rate of Rh B solution can reach 99.8%under visible light irradiation for 60 min.3.The Ag/Ag Br/Bi OBr composites were prepared by combining solvothermal method and photoreduction method,and the photocatalytic performance of the samples were evaluated by degrading methyl orange（MO）and toluene under visible light.The results showed that the sample S2 prepared with the Ag NO₃/Bi OBr mass ratio of 49%has excellent photocatalytic performance,and the degradation rate of MO can reach90.5%in 120 min.In the experiment of photocatalytic degradation of toluene,it was found that the degradation rate of toluene by active carbon fiber（ACF）loaded with S2was up to 62%,while the degradation rate of pure ACF was only 24.5%.In addition,a Z-strctured photocatalytic mechanism of Ag/Ag Br/Bi OBr was proposed on the basis of free radical capture experiment.The improvement of the photocatalytic performance of Ag/Ag Br/Bi OBr was attributed to the two effects of Ag in the reaction system.On the one hand,the surface plasmon resonance（SPR）effect of Ag can enhance the utilization of visible light.On the other hand,Ag nanoparticles are an important medium for charge transfer in the reaction system,which effectively reduces the recombination rate of carriers.