The Preparation Of Bismuth Oxyhalide Photocatalysts And Their Thermal Stability And Photocatalytic Performance

BiOX is a semiconductor with layer structure(X=I, Br, Cl), it has the characteristics of anarrow band gap and gap adjustment, it is easy to generate election hole pairs irradiation under thelight. The strong electric field exists between bismuth oxide layer and a halogen atom layer, whichcan make the electron hole pair separation to produce strong oxidizing OH、 O2-radices. Theproduced OH、 O2-caneffectly degradetheorganic pollutantsto H2O andCO2.In this thesis, acid orange II was selected as the degradation object, we studied BiOX indifferent calcination temperature, holding time, calcination atmosphere and forming ofphotocatalytic performance under the conditions of heterogeneity. X ray diffraction (XRD),scanning electron microscopy (SEM), Fu Liye transform infrared spectroscopy (FT-IR), UV Visdiffuse reflectance spectroscopy (UV-vis DRS) and differential thermal analysis (TG-DTA), areused to investigate the thermal stability of BiOX and its effect on the heterogeneous phasecrystallinity, particle morphology and the width of band gap properties. The main research contentsandresultsareshownas following twopoints:1. The thermal stability and photocatalytic performance of BiOX at different calcinationtemperature, calcination atmosphere and holding time were investigated. The results show that, interms of thermal stability, BiOI <BiOBr <BiOCl. BiOI and BiOBr can generate Bi5O7I andBi24O31Br10in the calcination process. BiOCl has good thermal stability, and it is not easy toproduce new oxyhalide new in the calcination process; Study on the catalytic performance of thesamples under visible light show that, without calcination conditions, BiOI>BiOBr> BiOCl,under the optimal calcination conditions, BiOBr>BiOI>BiOCl.The optimal conditions ofcalcination of BiOBr are as following: air atmosphere, the calcination temperature of450℃andholding timeof150min.2. We examined the Pd doped BiOBr and Ag2O doped BiOI, Ag2O doped BiOBr formed theheterogeneity effect on its performance. The results show that, deposition of Pd nanoparticles onthe surface has little influence on the area of BiOBr, however, the doping of Pd to a certain extent,improves the catalyst absorption and inhibition of photogenerated electron and hole compositeability. The optimal content doping Pd under visible light is4%, and the optimal doping Pd underUV light is0.5%. Ag2O can form hetero with BiOX, which can improvethe performance of BiOX. The optimal doping Ag2O composite BiOI is4%, the optimal doping Ag2O composite BiOBr is2%.The above results showed that, suitable calcination temperature, holding time, calcinationatmosphere and heterojunction can improve the crystal structure of BiOX, which can improve thelight absorption, the separation of the photogenerated electron hole, and improve its photocatalyticperformance.