Preparation And Photoreactivity Of Bismuth Oxyhalides Photocatalysts With Ultrasmall-exposed {001} Facets

Semiconductor catalysts,as a photocatalysis,can degrade the pollutants from water and air under sunlight irradiation.Therefore,it has a strong potential application in many field.However,wide band semicondutors cannot make efficient use of solar power because it can only use UV light.In these years,visible-light-induced semiconductors has attracted more and more attention.BiOX(X=Cl,Br,I)can be an outstanding visible-light-induced semiconductor due to its stable molecule structure,excellent optical properties and nontoxicity.But the high recombination efficiency of photogenerated electron-hole pairs,which could reduce the photoactivity,and the low adsorption capacity about bismuth oxyhalides materials are disadvantages for the photocatalytic applications of them.On the one hand,the decrease of exposed {001} facets is an effective way to increase its adsorption capacity,on the other hand,forming heterojunctions with other semiconductor can reduce the recombination of photo-generated electron-holes of bismuth oxyhalides materials.In this study,we had prepared BiOCl,BiOCl/Br and BiOCl/I heterojunctions photocatalysts with ultrasmall-exposed {001} facets by hydrolysis precipition process.The microstructure,morphology and optical properties of the prepared BiOCl and BiOCl hybrid photocatalysts were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscope(TEM),infrared spectroscopy(FT-IR),Raman spectroscopy and UV–Vis diffuse reflection spectroscopy(DRS).Moreover,the photocatalytic performance of the photocatalysts have been evaluated by degradation of model contaminants of Rhodamine B(RB)under visible light irradiation.We have discussed the influence of {001} exposing percentages on the photodegradation efficiency and determine the optimum parameter.The main results and conclusions in this study are summarized as following:(1)BiOCl photocatalysts with low {001} exposing percentages was prepard by hydrolysis precipition process.40% enhanced adsorption was observed over BiOCl-59 as compared to BiOCl-95.And the photocatalytic performance was enhanced by the reducing of {001} exposing percentages.(2)We studied the photodegradation of RB using the BiOCl catalysts with different {001} exposing percentages.The best degradation rate is 0.14842 min-1 when BiOCl catalyst with ultrasmall-exposed {001} facets(57%)was used as photocatalyst,which 17 folder than BiOCl-94 photocatalyst.(3)The BiOCl/Br hybrid photocatalysts with low {001} exposing percentages were prepared by hydrolysis precipition process.The doping ratio of Br can affect the band gap of BiOCl/Br heterojunctions photocatalysts.And the band gap of BiOCl0.5Br0.5 composite photocatalyst is 3.0 eV.The photodegradation rate of BiOCl0.5Br0.5 composite photocatalyst 0.07535min-1,which are 1.3 and 2 folder than BiOCl and BiOBr catalyst,respectively.(4)The BiOCl/I composite photocatalysts with low {001} exposing percentages were synthesized by hydrolysis precipition process.The BiOCl0.75I0.25 composite photocatalyst ahs a best photodegradation rate for RB molecules under visible light irradiation.And its photodegradation rate of 0.10112min-1 are 1.75 and 37 folder of BiOCl and P25,respectively.