Preparation、characterization And Photocatalystic Activity Of Fe-TiO2/BiOI Composite Photocatalysts

In order to enhance the photocatalytic activity of Fe-TiO2 catalysts,highly active Fe-TiO2/BiOI composite photocatalysts with various weight percents of BiOI have been prepared by hydrothermal method.The photocatalysts were characterized by BET,XPS,TEM,XRD,and UV–vis.The photocatalytic activity and stability of Fe-TiO2/BiOI composites were evaluated by photocatalytic degradation of methyl orange under visible light irradiation.The role of p–p Fe-TiO2/ BiOI heterojunction was discussed in view of theory of semiconductor physics.(1)The photocatalytic activity analysis of Fe-TiO2/BiOI composite:The photocatalytic activity analysis of x%Fe-TiO2/y BiOI composite have been successfully prepared by hydrothermal method(x=0.1、0.2、0.5、1、2;y=0.11、0.25 、0.43、0.67、1、1.5、2.33、4 、 9).The photodegradation of methyl orange in aqueous solution under visible-light irradiation showed that the photocatalytic activity of the Fe-TiO2/BiOI composites was much higher than that of pure TiO2.The photocatalytic activity of Fe-Ti O2/BiOI improved remarkably with increasing Fe concentration,but when the Fe concentration more and more higer,the photocatalytic activity decreased slightly,0.5%Fe-TiO2 composite had the best photocatalytic activity.For the Fe-TiO2/BiOI,The photocatalytic activity improved with increasing concentration of Fe,but the photocatalytic activity began to decrease when the concentration of Fe is higher than x= 0.5.The photocatalytic activity showed the same trend when the concentration of BiOI improves.0.5%Fe-TiO2 /4BiOI composite had the best photocatalytic activity,which rate constant was about 3152 times as large as that of pure TiO2,111.3times as large as that of 0.5% Fe-TiO2,1.67 times as large as that of pure BiOI.(2)The effect of p–p heterojunction on the photocatalytic activity of 5%Fe-TiO2/4BiOI: When Fe-TiO2 particles were mixed with Bi OI particles,a p–p heterojunction formed at the interfaces between Fe-TiO2 and BiOI particles.Because energy band gap of BiOI is smaller,its absorbility of visible light is stronger than Fe-TiO2.Under visible light irradiation,BiOI induces the generation of photoelectrons and holes.Futhermore,the conduction band edge and the Femri level of BiOI are lower than that of 5% Fe-TiO2.When p-BiOI is in contact with p-5% Fe-TiO2,the energy level difference between 5% Fe-TiO2 and BiOI causes the electron flow from p-5% Fe-TiO2 to p-BiOI until the Fermi level of them reach an equilibrium.Under visible-light irradiation,BiOI could act as a sensitizer to absorb the visible-light,the excited electrons on the conduction band of p-BiOI transfer to that of p-5% Fe-TiO2,and holes remain in the valence band of p-BiOI.The recombination of electic-hole pairs could be reduced.Therefore,the 5%Fe-TiO2/4BiOI samples exhibit remarkable photocatalytic activity under visible-light irradiation.