New Composite BiOX (X = Cl, Br, I) Preparation And Photocatalytic Properties Of The Photocatalyst

BiOX(X=Cl，Br，I) is a novel kind of photocatalyst with special layered structure and highchemical stability. The strong intrinsic electric field between the bismuth oxide layer and thehalogen atom layer can effectively promote the separation of photo-generated e-/h+pairs. Thenovel photocatalytic performance of BiOX has aroused widespread concern in rencent years.However, due to wide bandgap of BiOCl, it only absorb ultraviolet sunlight which is less than4%energy in the sunlight and60%energy as visible light in sunlight can not be used. Thus itgreatly limits the efficiency application of solar energy. Despite BiOBr and BiOI are able toabsorb the visible sunlight, but their photocatalytic activity is not enough to deal with thepractical environment pollution. Therefore, it is important to improve their performance inphotocatalytic reaction. The main focus of this research is to improve their photocatalytic activityby design the composition and structure.In view of the photocatalytic shortcomings of BiOX as a photocatalyt, a series of novel noblemetal (Ag, Pd, Pt) deposited BiOX photocatalysts were prepared by photodeposited method andheterostructured BiOCl/BiOBr photocatalysts were also prepared by calcination. The obtainedsamples were well characterized by XRD, N2physical adsorption, SEM, TEM, DRS, PL, andXPS. A model pollutant of acid orange II was used to photocatalytic activity test. The detailsworks were shown as the following:1. The effects of typical noble metals (Ag, Pd, Pt) deposition on the structure, optical absorptionand photocatalytic property of BiOX were investigated. The influences of the depositing contentof Ag, Pd and Pt on the structure property such as the crystal, morphology, optical absorption andphotocatalytic degradation acid orange II performance of BiOX were discussed. Results showedthat the deposition of noble metals leads to no difference on total morphology between pure andnoble metal deposited samples. Depositing appropriate amout of Ag can reduce band gap energiesof BiOCl and BiOBr, but it increases band gap energies of BiOI; Depositing appropriate amout ofPd can reduce band gap energies of BiOX; Depositing appropriate amout of Pt can reduce bandgap energies of BiOCl. The deposited noble metal nanoparticles as metallic state could act aselectron traps to accelerate the separation of photo-generated e-/h+pairs, thus the photocatalyticefficiency has been increased.2．The effects of the formation of heterojunction structure over BiOCl by coupling with BiOBron the structure, optical absorption and photocatalytic performance of BiOCl were investigated.Results showed that the presence of BiOBr slightly extends the absorption edge of BiOCl to thedirection of visible light region, and reduce band gap energies of BiOCl. The formation ofBiOBr/BiOCl heterojunction could effectively decrease the recombination rate of thephoto-generated e-/h+pairs and improve the photocatalytic properties. When the preparation conditions of the calcinations temperature are at200℃and the composite content of4wt%ofBiOBr, the photocatalytic activity is the best.The research results indicated that the depositing of suitable noble metal and the formation ofsemiconductou heterojunction could effectively improve the photocatalytic properties of BiOX.This provides a new insight in desing of high efficient BiOX photocatalyts.