Construction Of BiOBr Homojunction Photocatalyst And Its Visible Light Degradation Of Tetracycline

So far,oxygen reduction reaction（ORR）plays a crucial role in the photocatalytic process,which can produce a large amounts of reactive oxygen species（ROS）on the premise of having enough electrons.It is well known that ROS include superoxide radicals（·O₂^-）and hydroxyl radicals（·OH）.Both have strong oxidizability and can react with organic pollutants rapidly,efficiently degrading them into small molecules and even mineralizing them into CO₂ or H₂O.Due to the easy recombination of photogenerated electrons and holes,the single BiOBr material cannot provide sufficient electrons for the ORR in the system,resulting in insufficient ORR and less·O₂^-as well as·OH generated in the system,which affects the photocatalytic activity of the material.In order to maximize the rate of ORR,we propose to construct BiOBr-P/BiOBr-F（BPF-1/1）homojunction.The photocatalysts were systematically characterized by various analysis and testing methods,and the reaction mechanism of the system was investigated.The research progress achieved in this paper is as follows:（1）BPF-1/1 homojunction photocatalyst was prepared by in-situ synthesis.XRD,FTIR,SEM,TEM and other characterization results indicated that BPF-1/1homojunction had been constructed,which presented interlaced structure.XPS and DFT confirmed the formation of internal electric field in BPF-1/1 homojunction and the flow of electrons from BiOBr-F to BiOBr-P.（2）Taking tetracycline（TC）as the target pollutant,the photocatalytic activities of BiOBr-P,BiOBr-F,BPF-1/2,BPF-2/1,BPF-4/1 and BPF-1/1 homojunctions were evaluated.The TC degradation rate by BPF-1/1 homojunction reached 97.80%within120 min,and the experimental results proved that BPF-1/1 homojunction had the best photocatalytic activity.The control variable method was adopted to change the single experimental conditions,and it was found that the most suitable reaction conditions for the reaction were p H=7,the amount of catalyst added was 0.50 g/L,the light intensity was set to 500 W,and the initial concentration of TC was set to 0.02 g/L.Through cycling experiments and XRD characterization before and after the material reaction,the TC degradation efficiency by BPF-1/1 homojunction still reached 96.90% after four cycle experiments,which only decreased by 0.90%,and the structure of BPF-1/1homojunction did not change,suggesting that the catalyst has good recyclability and stability.（3）The BPF-1/1 homojunction could effectively shorten the channel of electron transfer and accelerate the separation of carriers as verified by EIS,transient photocurrent response and PL.Meanwhile,the quantification of·O₂^-,·OH and H₂O₂showed that BPF-1/1 homojunction could accelerate the ORR to generate more·O₂^-and·OH than individual materials.In addition,the GC-MS technique was used to analyze the intermediates of TC degradation process and detect the toxicity index of the intermediates,and the results demonstrated that the BPF-1/1 homojunction photocatalytic degradation of TC is not harmful to the environment.Therefore,the construction of homojunctions is conducive to more electrons participating in ORR,generating a large number of active species and accelerating the efficiency of photocatalytic degradation of TC.