Controllable Synthesis Of Basic Bismuth Nitrate/Bismuth Oxyhalide Photocatalyst And Its Photocatalytic Performance

Photocatalytic technology is currently one of the main methods to control environmental pollution and solve the energy crisis.Developing effective photocatalysts has been one of the most pivotal issues to be resolved for practical application of photocatalysis technology.Since pristine or single-component semiconductors as photocatalysts have shortcomings of fast recombination of photogenerated charge carriers and limited light absorption,various strategies have been employed to improve their photocatalytic performance.At present,the regulation of morphology and construction of heterojunction are considered as one of the most effective methods.In this paper,the composites BiOBr/[Bi₆O₅（OH）₃]（NO₃）₅·3H₂O（labeled as BiOBr/BBN-5N）,BiOBr/[Bi₆O₆（OH）₂]（NO₃）₄·2H₂O（noted as BiOBr/BBN-4N）and Bi₄O₅I₂/Bi₄O₅Br₂（denoted as BOI/BOB）were synthesized through co-precipitation method at room temperature and hydrothermal method,respectively,and their photocatalytic properties were studied.The research was summarized as follows:（1）Using Bi（NO₃）₃·5H₂O and KBr as raw materials,BiOBr/BBN-5N were prepared by using a facile co-precipitation method at room temperature,which exhibited enhanced photocatalytic activity for the degradation of malachite green and tetracycline under visible light illuminatio as compared to pure BiOBr and BBN.The structure and property characterization indicate that BBN in the composites could not only restrict the recombination of the photogenerated carriers but also benefit for the formation of highly dispersed flower-like BiOBr.Similar phenomena could be observed for the composite BiOBr/BBN-4N.Based on the above findings,through removing BBN in the composites BBN-5N/BiOBr with nitric acid solution(HNO₃,0.5 mol·L^-1),the remaining flower-like BiOBr exhibited better photocatalytic activity than sheetlike BiOBr obtained by adding excessive KBr into Bi（NO₃）₃·5H₂O solution.Therefore,this work sheds light on the preparation of photocatalysts with controlled morphology.（2）The composite BiOI/BBN-5N was further modified by hydrothermal method,and the p H value of the solution was adjusted by ammonia water and the ratio of I/Bi was adjusted to obtain pure Bi₄O₅I₂（denoted as BOI-A）.Based on this,the ratio of I/Bi in the composite BiOI-BiOBr/BBN-5N was fixed,the amount of KBr was adjusted and the same method was used to obtain the compound Bi₄O₅I₂/Bi₄O₅Br₂（labeled as BOI/BOB-w-x-y-z,where w is the molar ratio of Br/Bi,x is the p H of the solution,y is the hydrothermal temperature（℃）,and z is the hydrothermal time（h））.The results showed that the composite BOI/BOB-0.125-8-160-12（when w=0.125,x=8,y=160 and z=12）is better than that of other composites,which is mainly due to the construction of its Z-Scheme heterojunction.