Construction Of Bi₁₂O₁₇Br₂-based Composites By Mechanical Assisted Synthesis For Photocatalytic Removal Of Antibiotics

Since the 1980s,the domestic economical society has undergone enormous progress,but lead to the nonnegligible environmental problems.As a typical environmental problem,the water pollution caused by the unreasonable discharge of antibiotic wastewater has been concerned by social communities.In this context,photocatalysis technology as an efficient and environmental water pollutant control method has gradually attracted attention.In the field of photocatalysis,the design of environmental-friendly materials with excellent catalytic performance and simple synthesis method has become a crucial link.Bismuth oxybromide(Bi OBr),as a photocatalytic semiconductor,it has become a hotspot of research attributed to the high photo-generated carrier separation efficiency,but its further development is limited by inherent vacancy such as high photogenerated electron-hole recombination efficiency and insufficient photoresponse ability.In the previous research,the modified methods of bismuth-rich strategy,defect engineering and construction of heterojunctions could be used to effectively improve the photoelectric properties of the catalysts for enhancing corresponding degradation activity.However,catalyst modification process has disadvantages such as high energy consumption,long time-consuming,multiple processing and low yield.Therefore,ultrathin Bi₁₂O₁₇Br₂ nanosheets were prepared by mechanical assisted synthesis method in this study.Furthermore,in order to further enhance the light absorption performance of Bi₁₂O₁₇Br₂ ultrathin nanosheets and improve the transport rate of photogenerated carriers,carbon polymer dots(CPDs)and disulfide molybdenum(MoS₂)were used to modify the surface of Bi₁₂O₁₇Br₂ ultrathin nanosheets.With a series of characterizations,the composition structure and light absorption characteristics of the semiconductor materials were analyzed.Finally,the visible light degradation activity of catalysts for the target pollutants was analyzed.Moreover,electron spin resonance,band structure and free radical capture experiments of catalysts were summarized to clarify the possible mechanism of the photocatalytic reaction.1.Oxygen-rich defects Bi₁₂O₁₇Br₂ ultrathin nanosheets were successfully constructed by mechanically assisted synthesis method.A series of characterizations were used to analyze the morphology and oxygen defect concentration of the oxygen-rich defects Bi₁₂O₁₇Br₂ ultrathin nanosheets and bulk Bi₁₂O₁₇Br₂.According to the analysis,the distance of photogenerated electrons from the inside of the material to the surface was greatly reduced by the ultrathin nanostructure;at the same time,the electron-hole separation efficiency of the oxygen-rich defect Bi₁₂O₁₇Br₂ ultrathin nanosheets was significantly enhanced by the higher oxygen defect concentration.Compared with the bulk Bi₁₂O₁₇Br₂,the oxygen-rich defect Bi₁₂O₁₇Br₂ ultrathin nanosheets showed improved photodegradation activity for ciprofloxacin(CIP).Finally,the possible photocatalytic mechanism of Bi₁₂O₁₇Br₂ ultrathin nanosheets was purposed by the electron spin resonance,band structure and free radical trapping experiments.2.CPDs were introduced by mechanical synthesis to modify the Bi₁₂O₁₇Br₂ultrathin nanosheets for preparing the CPDs/Bi₁₂O₁₇Br₂ composites.A series of characterizations were used to analyze the morphology and light absorption performance of the CPDs/Bi₁₂O₁₇Br₂ composites.Compared with the Bi₁₂O₁₇Br₂ultrathin nanosheets,the CPDs/Bi₁₂O₁₇Br₂ composites exhibited better CIP degradation activity.The introduction of CPDs can not only act as an adsorption activation center,but also serve as an electron transport medium to improve the efficiency of photoelectron migration.In addition,compared with the Bi₁₂O₁₇Br₂ ultrathin nanosheets,the CPDs/Bi₁₂O₁₇Br₂ composites have a larger specific surface area,which can provide sufficient reaction area for target pollutants and photogenerated electrons.In conclusion,the possible photocatalytic mechanism of the CPDs/Bi₁₂O₁₇Br₂composites was proposed by spin resonance,band structure and free radical trapping test results.3.MoS₂/Bi₁₂O₁₇Br₂ composites were successfully prepared by the mechanically assisted synthesis method.Under visible light irradiation,the MoS₂/Bi₁₂O₁₇Br₂composites showed better degradation performance compared with the Bi₁₂O₁₇Br₂ultrathin nanosheets,The UV-vis diffuse reflectance spectra showed that the introduction of MoS₂ significantly improved the light absorption performance of the MoS₂/Bi₁₂O₁₇Br₂ composites.In addition,electrochemical impedance spectroscopy showed that MoS₂/Bi₁₂O₁₇Br₂ composites possessed low photoinduced electron-hole recombination efficiency.Consequently,the possible photocatalytic mechanism of MoS₂/Bi₁₂O₁₇Br₂ composites was deduced by the electron spin resonance,band structure and free radical trapping test results.