Study On Preparation And Photocatalytic Activity Of BiOBr/TiO₂ Heterojunction Nanocomposites

Currently,as the most widely used semiconductor photocatalyst,TiO₂ can only absorb ultraviolet light??<400nm?due to the large band gap?3.2 eV?,leading to the low utilization efficiency of solar energy because the component of the ultraviolet light in sunlight is only 3% to 5%.In addition,quantum efficiency is lowered sharply by the rapid recombination of photoelectrons and holes,which further suppress its photocatalytic activity.Therefore,it is of great interest to search and develop new high-efficiency catalysts or to modify TiO₂ in order to extend light response scope from UV to visible region and improve the generation and separation of photoelectrons and holes.In this study,using P25 and 10 mol/L NaOH solution as raw material,titanate nanobelts were synthesized by hydrothermal reaction for 48 h in the condition of 180? and soaking treatment in HCl solution.Then the secondary hydrothermal reaction was carried on in a certain concentration of sulphuric acid solution to etch the nanobelts,The effects of the acid etching process on the material crystal structure,morphology,specific surface area and photocatalytic degradation of methyl orange were investigated.An efficient visible-light-responsive BiOBr/TiO₂ heterojunction nanocomposite was fabricated successfully using in-situ depositing technique at room temperature by introducing BiOBr onto the surface of TiO₂ nanobelts pre-prepared by hydrothermal reaction and etched with H2SO4.The obtained particles were characterized by the means of XRD,SEM,TEM,XPS,UV-Vis DRS and PL.Taking the 20 mg/L Rh.B solution as the goal pollutant,the photocatalytic activity under visible-light irradiation of BiOBr/TiO₂ heterojunction nanocomposites with different mass ratios of?m?BiOBr?/m?TiO₂??were disscussed inorder to achieve the the best photocatalytic properties.The results showed that the characteristic diffraction peaks of the TiO₂ nanobelts etched with acid were stronger,indicating a better crystallinity,and its surface became more rough,providing greater specific surface area and more active sites for photocatalysis.The experiment results showed that the TiO₂ nanobelts etched with acid showed relatively better photocatalytic activity,BiOBr/TiO₂-1.0 was proved the optimal mass ratio,and recycling experiment proved that the photocatalyst had a good stability.At the same time,a possible mechanism of photocatalytic enhancement was proposed.