Preparation,Characterization And Photocatalytic Properties Of Compound BiOCl As Visible Light Photocatalyst

Recently, the environmental problem has gradually become the focus of our attention, and the degradation of pollutants also attracts people’s eyes. Photocatalytic technology becomes the most promising environmental protection technology due to the characteristics of mild reaction conditions and degrading pollutants into CO₂ and H₂ O. Photocatalytic technology is based on the degradation of organic pollutants by photocatalyst under visible light irradiation. BiOX（X=Cl, Br, I） could be the photocatalysts because of its unique layered structure, optical properties, electronic propertities, good photocatalytic activity and stability. BiOCl exhibits better catalytic efficiency, which could be promising photocatalytic materials. However, with the large band gap（≈ 3.5 eV）, BiOCl could only absorb ultraviolet light at wavelengths less than 410 nm, so its solar energy utilization rate is low. Thus, BiOCl was modified by different methods to broaden the visible adsorption range. The detailed works were shown as follows:Firstly, the BiOCl_xI_y solid solution catalysts were synthesized by hydrolysis method, solvent thermal method and ultrasonic method using Bi（NO₃）3·5H₂O as a precursor. The prepared samples were characterized by XRD, SEM, EDS, BET-BJH, TEM/HRTEM UV-vis DRS, SPS and tests of absorption and photocatalytic activity. Results showed that the BiOCl_xI_y solid solution catalysts exhibit not only better adsorption properties but also better photocatalytic activities for organic dyes than pure BiOCl. Particularly, the BiOCl3I1 samples show the best performance in both adsorption and photocatalytic propertities. In addition, the relationship between adsorption and photocatalystic activity was dicussed.Secondly, a series of different molar ratio of heterostructure NiO/BiOCl photocatalysts were prepared by hydrolysis method. The photocatalytic degradation of organic dyes by NiO/BiOCl（molar ratio is 0.6:1） was the best. A series of characterization methods are applied to explore the relevant photocatalytic mechanism and the degradation products. Results showed that the formation of heterostructure made NiO/ BiOCl composite photocatalyst not only broadens visible light response range, but also can use absorbed light energy more effectively.Thirdly, a light deposition method was successfully applied to loading Ag nanoparticles on the surface of BiOCl photocatalyst. The as-prepared photocatalyst exhibited visible light response properties due to the Surface Plasmon Resonance（SPR） of Ag nanoparticles. The crystalline structure, morphology and photoabsorption performance were characterized by characterization methods. Results showed that the Ag existed in the form of metallic state and Ag nanoparticles with an average diameter of 5 nm were uniformly loaded on BiOCl. The SPR peak of Ag nanoparticles was clearly observed at about 500 nm in the visible light region. In addition, the photocatalyst Ag/BiOCl exhibited an efficient photocatalytic activity for degrading methyl orange（MO） under visible light irradiation.Finally, the mechanism of photocatalysts and photocatalytic degradation products were also studied. Otherwise, the preliminary exploration on the practical wastewater treatment and the photoelectric conversion performance of the above three kinds of photocatalysts were carried out.