Synthesis Of BiOBr-based Materials Via Mechanical Ball Milling For Enhanced Photocatalytic Organic Pollutants Removal

At present,environmental pollution has seriously affected China's economic development and the daily lives of the people.Among the pollution problems,the water pollution problem caused by industrial wastewater and domestic wastewater is even more serious.Photocatalysis technology can directly convert solar energy into chemical energy and has been extensively applied to water pollution treatment due to its environmental friendliness,reusability,and mild reaction conditions.Photocatalyst is the main body of photocatalysis technology.Designing and constructing efficient and stable photocatalyst is the most important part in the research of photocatalysis technology.Bismuth oxybromide?BiOBr?photocatalyst has been widely used in the field of environmental photocatalysis due to its excellent photocatalytic performance and good stability.However,BiOBr has the defects of weak absorption ability of visible light and easy recombination of photogenerated carriers.In order to solve the above problems,the photocatalytic performance of BiOBr is improved through morphology control and construction of composite photocatalysts,and the photocatalytic activity of degrading organic pollutants is also explored.Firstly,the paper innovatively proposed the construction of BiOBr ultrathin nanosheets via an ionic liquid assissted mechanical ball milling method.Meanwhile,other suitable materials were selected to combine with BiOBr.Secondly,the composition,morphology,and optical properties of materials were explored through a series of characterizations.Finally,the appropriate target pollutants were selected to investigate the photocatalytic degradation performance of as-prepared photocatalysts and the possible reaction mechanism was also proposed.The specific research contents of this article are as follows:1.BiOBr-IL ultrathin nanosheets material was successfully prepared in the presence of ionic liquid([C₁₆mim]Br)serving as the bromine source via a mechanical ball milling method under normal temperature and pressure conditions.The crystal structure,morphology,and optical property of BiOBr-IL ultrathin nanosheets were explored through a series of characterizations.Compared with BiOBr nanoplates synthesized by using inorganic salt?KBr?as the bromine source and BiOBr nanosheets synthesized by hydrothermal method,respectively,the ultrathin structure of BiOBr-ILnanosheets greatly shortened the diffusion distance of photogenerated carriers and effectively inhibited the recombination of photogenerated carriers.Moreover,BiOBr-IL ultrathin nanosheets showed optimal activity in the photocatalytic degradation of organic pollutants,such as:bisphenol A?BPA?,tetracycline?TC?and rhodamine B?RhB?.The results of free radical capturing experiments and XPS valence spectra confirmed that superoxide radicals and holes are the main active species in the photocatalytic process.2.MoS₂/BiOBr flower-like composite photocatalyst was synthesized in situ by mechanical ball milling.After the introduction of MoS₂,the visible light absorption capacity and specific surface area of BiOBr material was also significantly increased.The photocatalytic degradation experiments showed that the MoS₂/BiOBr composite exhibited higher photocatalytic activity for the degradation of TC than pure BiOBr under visible light irradiation,and the activity was best when the MoS₂ introduction amount is 1.0 wt%.The results of photoelectrochemical analysis confirmed that the introduction of MoS₂ promoted the separation and transfer of photogenerated carriers and effectively inhibited their recombination.The results of ESR,free radical capturing experiments and XPS valence spectra confirmed that superoxide radicals and holes are the main active species in the photocatalytic process.3.CQDs modified BiOBr?CQDs/BiOBr?composites flower-like photocatalyst was synthesized in situ by mechanical ball milling.With TC as the target pollutant,CQDs/BiOBr composites exhibited higher photocatalytic activity than BiOBr under visible light irradiation.Among these CQDs/BiOBr composites,5.0 wt%CQDs/BiOBr has the optimal photocatalytic degradation activity,which can degrade76%TC in 120 minutes.The improvement of photocatalytic performance can be attributed to the introduction of CQDs,which can increase the light absorption capacity of the material in the visible light region and increase the specific surface area of the materials.In addition,introducing CQDs to modify BiOBr can improve the efficiency of photogenerated carrier separation and transfer,and inhibit carrier recombination.The results of ESR,free radical capturing experiments and XPS valence spectra showed that the main active species in this system were superoxide radicals,hydroxyl radicals and holes.