Study On Preparation And Properties Of Bi₂O₃/BiOBr Heterojunction Photocatalyst

The traditional TiO₂ semiconductor photocatalyst is only responded to ultraviolet light,and the catalytic efficiency is low under sunlight.Most of the bismuth-based photocatalytic materials have excellent photocatalytic activity under visible light,which can be effectively used for sunlight.So Bi-based of photocatalytic materials have important significance to be studied.Although many Bi-based photocatalytic materials have a better response to visible light,their photocatalytic activity still needs to be improved.In this thesis,Bi2O3/BiOBr heterojunction photocatalyst was prepared by partial in-situ conversion of hydrobromic acid by adding bismuth oxide.Rhodamine B was used to the target pollutant to evaluate its photocatalytic activity.In addition,the optimized process parameters of Bi₂O₃/BiOBr,and the enhancement mechanism of Bi₂O₃/BiOBr photocatalytic efficiency were explored.The results of thesis are as follows:（1）Using commercial bismuth oxide as the raw material,different ratios ofα-Bi₂O₃/BiOBr heterojunction photocatalysts were prepared by adding the amount of hydrobromic acid.Rhodamine B degradation test showed that the degradation efficiency of the A3 sample（α-Bi₂O₃:BiOBr=1:1.2）was the highest,and the degradation rate of rhodamine B was reached 89.64%within 40 minutes,which was much higher than the pure phaseα-Bi₂O₃ and BiOBr.（2）Using Bi₂O₂CO₃ as a precursor to synthesizeβ-Bi₂O₃,theβ-Bi₂O₃/BiOBr heterojunction photocatalysts with different ratios were prepared by adding the amount of hydrobromic acid.The degradation test results showed that the S3 sample（β-Bi₂O₃:BiOBr=1:1.6）had the highest degradation efficiency,and the degradation rate of rhodamine B was reached 99.85%within 25 minutes,much higher than the pure phaseβ-Bi₂O₃ and BiOBr.（3）Due to the staggered energy level structure of Bi₂O₃ and BiOBr,changes the migration path of photogenerated electrons and holes was changed by heterojunction,reducing the reorganization of electron holes and enhancing the photocatalytic activity.（4）The adsorption of the pore structure can adsorb pollutants to the photocatalyst during dark reaction.The large specific surface area was beneficial to increase the contact between pollutants and active sites during the degradation process,which improved the efficiency of the photocatalyst to degrade pollutants to a certain extent.The pore structure was utilized to physical adsorption,and the activity of the photocatalyst is enhanced by constructing a heterojunction.This combination of physical adsorption and photocatalytic degradation process greatly improved the efficiency of photocatalytic degradation.A photocatalyst with high adsorption performance was significative in the field of water pollution treatment.