Study On The Crystal Structure And Photocatalytic Properties Based On The Layered BiOCl

Semiconductor photocatalysis technology presents potential applications for environmental remediation and energy conversion,and has become a hot topic in the field of environment,energy,and materials.During the past ten years,bismuth oxyhalides(BiOCl),as a ternary compound,have aroused great interesting due to their layered structure and higher photocatalytic activity than tranditional TiO2.However,as a wide bandgap semiconductor,BiOCl can merely be excited by the UV light below 360 nm,which account for 4% of solar light,result in the low efficiency under solar light and the practical application be greatly limited.Moreover,the recombination of photo-induced electron hole pairs will be increased via only narrowing bandgap to broaden the light absorption.It is not benefit for improvement the visible light activity.Thereby,developing the visible light driven photocatalyst would consider the two facets simultately: expanding the visible light absorption of BiOCl and effectively suppressing the recombination of photo-induced electron hole pairs.As the properties of materials are determined by their crystal structure,electronic structure,surface and interface structure,it provides an effective way to expand the light absorption and improve the separation effiency of photo-induced electron hole pairs.In this thesis,firstly,we realized the tailoring of band structure and the surface crystal structure of BiOCl through carbon and silver doping,respectively.And then,through electron beam irradiation and chemical reduction,we also successfully realized the tailoring of band structure and interfacial structure by inducing defaults into BiOCl.The main results are following:(1)The band structure of BiOCl was tailored through doping carbon atoms into the shallow layers,resulting in the effective expanding of visible light absorption.At the same time,the separation of photo-induced electron hole pairs could be maintained with carbon atomic hybridization state changes from sp3 to sp2,with the increase of π bond in carbon atomic sp2 hybridization,the visible light degradation efficiency of phenol increases from 38.9×10-4 min-1 to 134.7×10-4 min-1.(2)Comparing to carbon doping,the Ag atoms existed as independent 100 nm particles instead of being induced into lattices.Local surface plasmon resonance(LSPR)of Ag could effectively expand the visible light absorption of BiOCl,resulting in the superior photocatalytic degradation of RhB,which is 3 times higher than BiOCl.With the transfer of Ag to Ag2 O,the red shift of LSPR was achieved.Besides,with the assistance of oxydoreduction properties of photo-induced electron hole pairs,Ag2 O could transfer to Ag again,so as to realize the practical realization of the reciprocal modification of LSPR.(3)Under the irradiation of electron beam,large amounts of Bi nanoparticles formed on the surface of BiOCl.With the broken of bonds,the ·Cl,·O22-,·O2-free radicals were trapped between BiOCl layers and showed a gas state,which could accelerate the evolution of BiOCl structure,further resulting in the band structure modification tailoring.Electron injection experiments simulated the process of Bi formation in BiOCl body,and we found that the visible light photocurrent could be improved by two orders of magnitude,compared with the pure BiOCl.(4)After annealing Bi/Bi_xOyCl_z under high temperature,we successfully obtained the Bi12O15Cl6,Bi24O31Cl10.Both of the visible light absorptions were expanded through tailoring the band structure of BiOCl.The Bi24O31Cl10 showed a selective adsorption of RhB and MO dye,because of the existence of vacancies.The vacancies could also work as the recombination center of photo-induced electron hole pairs,resulting in worse visible light photocatalytic effect.