Modification Of The Nanostructure Of The Oxygen-rich Bismuth Oxyhalide Bi 5 O 7 I And Its Photocatalytic Properties

Recent years,bismuth based halogen oxide photocatalyst aroused great concern of scientists,owing to their unique layered structure with atoms arranged and beneficial for the transmission of photo-exited electronic.Among them,the oxygen-rich type bismuth halogen oxides have unique chemical composition and crystal structure which can greatly affect the band structure,optical absorption characteristics and the transfer of electric charge.So,different Bi:O:X ratio of bismuth halogen oxides lead to different photocatalytic performance.As a member of the oxygen-rich type bismuth halogen oxides,Bi5O7I get focus due to the similar crystal structure with BiOI and the appropriate position of valence band and conduction band.In this paper,pure Bi5O7I were prepared by Solvothermal-decomposition method,calcined pure spherical BiOI at 480? for 2h.The pure spherical BiOI were prepared using Bi?NO3?3·5H2O and KI as raw materials.In order to improve the photocatalytic activity of pure Bi5O7I,metal ion plasma resonance effect,rare earth ions doping induce phase transition and form heterojunction structure for modification were studied respectively.The main work as follows:?1?With plasmonic enhanced spherical photocatalysts Ag/AgI/Bi5O7I were synthesised by chemical precipitation method,whose average diameter is about 2-4?m.Based on the phase structure,microstructure and optical properties characterization analysis,it appeared obvious diffraction peak of AgI in XRD diffraction of Ag/AgI/Bi5O7I samples,obvious AgI particles on the surface of spherical Bi5O7I,and obvious reduce of the band gap of the composite samples.RhB was used as probe organic pollutant.Under LED light irradiation,it can be observed that the RhB solution was degraded more than 90%by S2-Ag/AgI/Bi5O7I sample within 60min for the initial concentration of 10mg/L.While,only about 60%of RhB be degraded by pure Bi5O7I.?2?Rare earth Er³⁺ doped Bi5O7I?Er-Bi5O7I?samples were synthesized using Er?NO3?3·6H2O as the erbium source.The structure,morphology,and optical property of the samples were characterized by XRD,XPS,SEM,TEM and UV-Vis spectroscopy,respectively.From the results,with the increase of Er³⁺ doping amount,Bi5O7I phase changing from orthorhombic ?-Bi5O7I to monoclinic ?-Bi5O7I.Under the irradiation of LED light,5%Er-Bi5O7I sample show the excellent photocatalytic performance for the degradation of different types of dyes?RhB,MB and MO?,the concentration of all the dyes are 10mg/L.Also,under monochromatic red light irradiation of 630nm,5%Er-Bi5O7I sample present excellent photocatalytic performance for the degradation of RhB,proved the importent role of the upconversion effect by Er³⁺.?3?In order to improve the photocatalytic activity of Er-Bi5O7I,C3N4/5%Er-Bi5O7I samples were synthesized,which combined the synergistic effect of Er³⁺ doping and heterojunction forming between g-C3N4 and 5%Er-BisO7I,improved the photocatalytic activity of 5%Er-Bi5O7I effectively.The SEM indicated that C3N4/5%Er-Bi5O7I samples were more cluster than 5%Er-Bi5O7I,which may due to the aggregation of g-C3N4 powder.S3-C3N4/5%Er-Bi5O7I sample with appropriate amount of g-C3N4 present the best photocatalytic proformance.Under the irradiation of LED light,it can be observed that the 20mg/L BPA solution degraded 98%by S3-C3N4/5%Er-Bi5O7I sample within 21min.Moreover,S3-C3N4/5%Er-Bi5O7I sample can reach 90%degradation rate of BPA after eight times recycle,which proved the strong stability of C3N4/5%Er-Bi5O7I sample.