Design Of Bi-based Heterojunction Photocatalyst And The Study On Its Degradation Mechanism Of Antibiotics

In recent years,Bi-based photocatalytic materials have attracted the attention of researchers because of rich resources and good response to visible light,but the characteristics of the recombination of photogenerated electrons and holes limit the application of Bi-based photocatalytic materials.The construction of p-n heterojunction and morphology control are propitious to promote the separation of photogenerated electrons and holes and to improve their photocatalytic performance.In this paper,we designed and constructed a Bi OBr/BiVO₄ p-n heterojunction and a BiOCl/BiVO₄ p-n heterojunction with special structures by hydrothermal method and in-situ conversion method,respectively.The series of characterizations,as well as the photoelectrochemical and photocatalytic performance tests were used to investigate the effects of different reaction conditions on the formation,morphology and photocatalytic properties of the prepared composites.What's more,the antibiotic norfloxacin was degraded by BiOBr/BiVO₄ and BiOCl/BiVO₄ composites,and the degradation properties and mechanism were analyzed.The experimental results showed that the BiOBr/BiVO₄ composite can be formed only when CTAB and HNO3 co-existed in the preparation process.The efficiency of BiOBr/BiVO₄ p-n heterojunction photocatalytic degradation RhB has been significantly improved than that of pure BiVO₄,which is mainly attributed to the exist of internal electric field between BiOBr and BiVO₄ which can effectively inhibit the recombination of photogenerated electrons and holes.The effect of HCl concentration on the morphology and properties of BiOCl/BiVO₄ composites was also very obvious when BiOCl/BiVO₄ p-n heterojunction was prepared.Due to the combined effect of p-n heterojunction and special morphology structure,the photocatalytic properties of Bi OCl/BiVO₄ composites with structure of interlaced BiOCl nanosheets and BiVO₄ mesoporous spindles have been further improved.It can be concluded that holes play the major role in the reaction process by analysing the degradation mechanism of norfloxacin.Therefore,in order to achieve the degradation of antibiotics,not only the separation of photogenerated electrons and holes is needed,but also the photogenerated holes which possess strong oxidation ability are needed.