Preparation,Modification And Photocatalytic Properties Of BiOBr Nanomaterials

The development of high-efficiency photocatalysts is a core part in the photocatalysis.However,there are two bottlenecks hindering the application of photocatalytic technology.One is the high recombination rate of the photo-induced electron-hole pairs;the other is the low utilization of solar energy.As alternative photocatalysts,BiOX?X=Cl,Br,I?have attracted considerable attention owing to their special crystal structure and electronic structure,strong visible-light absorption,low toxicity as well as high stability.In this study,the photocatalytic activity of BiOBr was optimized by tailoring morphology,facet-controlled fabrication and semiconductor coupling.The main research results can be summarized as follows.?1?Hierarchical BiOBr microspheres were synthesized via a facile solvothermal route in the presence of anionic surfactant sodium dodecyl sulfate?SDS?.To the best of our knowledge,it is for the first time to prepare BiOX with the assistance of anionic surfactant.SEM and TEM results showed that the 2D nanosheets,which were self-assembled to form the 3D structures,were achieved with the thickness decreasing from average 160 nm to 25 nm,and that the size of crystal particles was smaller in the presence of SDS.XPS results showed that the BiOBr products with the assistance of SDS had more O-vacancy.Photocatalytic activity of the as-prepared BiOBr samples was evaluated by the photocatalytic degradation of RhodamineB?RhB?under visible light irradiation.The BiOBr in the presence of SDS exhibited higher photocatalytic activity than that in the absence of SDS.?2?Based on the above studies,we obtained 3D flower-like BiOBr nanostructures by changing the concentration of Bi?NO₃?₃·5H₂O and KBr.The as-prepared BiOBr was self-assembled by 2D nanosheets which were partially enclosed by {111} facets due to the effect of SDS.To the best of our knowledge,it is the first report about {111} facets of BiOX.Compared with {001} facets of BiOBr,{111} facets exhibited open channel feature and had lower density of oxygen atoms,which was further confirmed by the adsorption of cationic dye RhB and anionic dye MO.UV-vis diffuse reflectance spectroscopy and Mott-Schottky curves showed that the band gap of BiOBr-111 was narrower than that of BiOBr-001,and both the CB and VB of BiOBr-111 up-shifted,which was beneficial to the separation of photo-induced electron-hole pairs.The as-prepared BiOBr with {111} facets exhibited excellent electrochemical behavior and photocatalytic activity under both visible light???420 nm?and monochromatic light??=420 nm?irradiation.?3?In order to improve the quantum efficiency of BiOBr and widen its application,BiOBr nanosheet@TiO₂ nanobelt p-n junction photocatalysts were prepared by assembling BiOBr nanosheets on the surface of TiO₂ nanobelts via a hydrothermal route followed by a co-precipitation process.Mott-Schottky plots confirmed the formation of p-n junctions in the interface of BiOBr and TiO₂.BiOBr@TiO₂ p-n junction photocatalysts exhibited enhanced photocatalytic activity in photocatalytic H2 production over water splitting and the photodegradation of RhB under visible light irradiation.This work showed a potential application of low cost BiOBr as a substitute for noble metals in photocatalytic H2 production under visible light irradiation.