Study On The Preparation And Photocatalytic Performance Of Modified Bi₄O₅Br₂

Currently,the research about water quality mainly focuses on the removal and solutions of microbial pollution,heavy metal pollution,organic pollution and related risks.Semiconductor photocatalysis is considered as a potential remediation technology,and has become a research hotspot in the field of semiconductor materials in recent years.Among many semiconductor materials,the search for high-efficiency photocatalysts that can respond under visible light is an upsurge.BiOX（X=Cl,Br,I）photocatalyst has attracted people’s attention due to its unique optical and electrical properties.Among the oxyhalide materials with rich bismuth,Bi₄O₅Br₂has been widely studied due to its high chemical stability,large specific surface area,and excellent absorbance.In this work,the lamellar Bi₄O₅Br₂materials were successfully prepared by solvothermal method.In addition,pure Bi₄O₅Br₂was modified by two methods:doping with metal ions and constructing heterogeneous interfaces.The main research contents are as following:（1）Fe³⁺/Bi₄O₅Br₂and Cr³⁺/Bi₄O₅Br₂were synthesized by solvothermal method,respectively.The influence of different doping concentration of Fe³⁺and Cr³⁺ions on the photocatalytic performance of Bi₄O₅Br₂were studied.The materials were characterized by XRD,XPS,SEM,UV-vis-DRS and other testing techniques.The reasons for the improvement of Bi₄O₅Br₂photocatalytic performance were suitably analyzed.Under visible light irradiation,the degradation rate of Rh B is used to evaluate the photocatalytic performance of Fe³⁺/Bi₄O₅Br₂and Cr³⁺/Bi₄O₅Br₂.The results show that the degradation efficiency of 2wt%Fe³⁺/Bi₄O₅Br₂and 1wt%Cr³⁺/Bi₄O₅Br₂for Rh B is significantly higher 24.7%and 29.9%than that of Bi₄O₅Br₂,respectively.The reason for the improvement of photocatalytic performance is that Fe³⁺and Cr³⁺participate in the oxidation reaction with h⁺,and the recombination of photo-generated e^-/h⁺pairs is effectively inhibited.Finally,with MB and MO as the target pollutants,the best photocatalyst among all samples were applied to test with different dyes to explore their photodegradation ability for different organic pollutants.The results show that2wt%Fe³⁺/Bi₄O₅Br₂and 1wt%Cr³⁺/Bi₄O₅Br₂both showed positive effects on the degradation of the two pollutants.The results of free radical capture experiments show that the main active species affecting the efficiency of Rh B degradation by 2wt%Fe/Bi₄O₅Br₂and 1wt%Cr/Bi₄O₅Br₂photocatalysts are·OH.（2）The MoS₂were synthesized by one-step hydrothermal method,and MoS₂/Bi₄O₅Br₂compounds were prepared by the ultrasonic-assisted method.The samples were characterized by XRD,XPS,BET,TEM/HRTEM,UV-vis-DRS and other test methods.The results showed that the heterojunction was formed between MoS₂and Bi₄O₅Br₂.The MoS₂/Bi₄O₅Br₂compounds broaden the light absorption range of Bi₄O₅Br₂,and increase the specific surface area and pore size.The formation of heterojunction regulates the energy band structure of composite materials,and inhibits the recombination of photogenerated e^-/h⁺.Under visible light irradiation,the photocatalytic activity of MoS₂/Bi₄O₅Br₂compounds on Rh B,MB and MO dyes were investigated.The results show that the degradation rate of 2wt%MoS₂/Bi₄O₅Br₂reaches 98.7%within 20 min for Rh B,which is about 1.8 times than that of pure Bi₄O₅Br₂.The photocatalytic activity is significantly improved.At the same time,it also showed good photocatalytic performance for MB and MO.The results of free radical capture experiments show that the·OH and·O₂^-play important roles in the process of Rh B degradation by 2wt%MoS₂/Bi₄O₅Br₂photocatalyst,among which,the·OH has a relatively large influence.