Synthesis,Characterization And Properties Of Bismuth Oxyhalide BiOX (X=Cl,Br,I) Photocatalysts

Semiconductor photocatalysis,as an ideal "green" technology,is a kind of effective methods of solving global energy crisis and dealing with pollutants in the environment,especially for Ti02 semiconductor photocatalysts,with many advantages such as high efficiency,inexpensive,reaction thoroughly and good stability.However,Ti02 photocatalyst needs to inspire by the ultraviolet light at wavelengths less than 387 nm,which accounts for about 5%of the solar spectrum,and the recombination degree of photogenerated electron and hole is higher,which limits the extensive application of TiO2.As a result,it is indispensable to have some thoughts on new photocatalyst research&development.Recently,it has been reported that,halogen bismuth oxide BiOX(X= Cl,Br,I)are new type of semiconductor photocatalyst,which has unique layer structure,electronic structure and good optical properties with the excellent photocatalytic performance on the photocatalytic degradation of organic pollutant.In present paper,BiOX(X= Cl,Br,I)as a novel photocatalyst was synthesized with a simple method,and the preparation process is conveniently operated,low-cost,and saving time.These resulting materials were characterized by XRD,SEM,DRS and XPS,etc.The detailed works were shown as the following:(1)A novel photocatalyst,BiOCl micro-nano particles of ferrite plates,were prepared by a low-cost,simple hydrolytic method,and were used to degrade methylene orange(MO)in aqueous solution in order to evaluate their photocatalytic activity.The effect of preparation conditions such as sodium dodecyl benzene sulfonate(SDBS)dispersant,HCl concentration,the pH of BiCl3-HCl system and heat treatment temperature on BiOCl performances were investigated by SEM,DTA-TG,XRD and UV-vis DRS.In addition,the comparison of photocatalytic activity between BiOCl and Ti02-P25 were also studied in the degradation processes.The experimental results confirmed that BiOCl micro-nano particles prepared with SDBS,1.5mol/L HCl concentration,the pH=8 of BiCl3-HCl system and 80? heat treatment temperature exhibited the best performance for photodegradation MO in solution,and BiOCl with band gap of 3.3 eV showed a good stability and better photocatalytic activity than TiO2-P25 photocatalyst.(2)Two kinds of Sn/BiOCl photocatalyst were synthesized by hydrolysis method and impregnation method with BiCl3,SnCl4-5H20 and HCl as raw materials.The as-prepared photocatalyst were charaterized by X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and diffuse reflectance spectra(DRS).Under the irradiation of simulant sunlight(500 W Xenon lamp),the photocatalytic properties of photocatalysts were investigated by using degradation of MO solution as target decomposition material.The results demonstrated that Sn doped BiOCl photocatalyst by impregnation method has better photocatalytic activity,undoped BiOCl and Sn doped BiOCl were square crystalloid,but Sn doped BiOCl diffraction peak slightly towards to the high angle.The morphology of Sn doped BiOCl photocatalyst is piece of block structure,The result demonstrated that Sn doped BiOCl remarkably improved the photocatalytic activity of BiOCl for methyl orange degradation.The photocatalytic activity was the highest,when the suitable photocatalyst concentration was 1 g/L,doping amount of Sn was 9%,and the degradation rate of methyl orange solution(10 mg/L)reached 100%in 120 min.In addition,the photocatalyst of Sn doped BiOCl also has a good photocatalytic stability.(3)The BiOBr photocatalyst prepared via a facile hydrolysis method was characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),N2 sorption and diffuse reflectance spectra(DRS).As-prepared BiOBr photocatalyst with tetragonal crystal structure exhibited homogeneous particles of fine ferrite plates and possessed surface area of 32.19 m2/g and band gap of 2.92 eV.Besides,the photocatalytic property and mechanism of BiOBr were investigated by the degradation of methylene orange(MO)in aqueous solution under xenon lamp irradiation.The results indicated that the favorite amount of BiOBr powder was 0.8 g/L for MO degradation under xenon lamp irradiation,and its catalytic performance was as good as that of Ti02-P25.The mechanism research showed that photo-generated hole and ·OH played important roles in the photocatalytic degradation progress.The photocatalytic degradation results of humic acids,Rhodamine B and MO in aqueous solution further verified high catalytic activity and non-selectivity of BiOBr photocatalyst with wider range of adaptation.(4)BiOI photocatalyst were prepared with Bi(NO3)3·5H2O and KI as bismuth source and Iodine source respectively,in different solvent system(alcohol?alcohol and water?isopropanol),molar ratio,different surfactant(Cetyl trimethyl ammonium bromide(CTAB),sodium dodecyl benzene sulfonate(SDBS),polyvinylpyrrolidone(PVP)),stirring speed and heat treatment temperature,etc.for the effection of BiOI photocatalytic activity.The optimum preparation conditions of the BiOI were determined by photocatalytic degradation rate of methyl orange in water.The results demonstrated that BiOI photocatalyst prepared with SDBS,alcohol system,Bi(NO3)3·5H2O and KI molar ratio of 0.5:1,80 ? heat treatment temperature and 0.3 g SDBS surfactant reached the maximum activity for photodegradation MO in solution.(5)BiOI photocatalyst was prepared using alcoholysis method,and the DRS analysis result show that the band gap energy is 1.82 eV.When BiOI was used for the first time,the photocatalyst exhibited excellent photocatalytic activity under visible light or simulant sunlight,while its activity significantly decreased for the second time.Therefore,BiOI photocatalyst before used and have been used was characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),ultraviolet-visible spectrophotometry(UV-Vis)and X-ray photoelectron spectroscopy(XPS),in addition,photocatalytic activity of BiOI were evaluated according to degradation of methyl orange(MO)in water.The results demonstrated the reusability of the catalyst had obvious influence on the crystal phase and morphology of the BiOI photocatalyst with the tetragonal primitive crystal structure,plate structure,the UV-Vis analysis indicates that I-peak appear constantly during use,the XPS analysisi also confirmed the result.