Fabrication And Loading Of Dpped Bi Obr_xI_1-x Photocatalyst With Enhanced Separation Efficiency Mechanism Of Electron-hole

Recently, environmental pollution and energy shortage are two major problems for mankind. The semiconductor photocatalysis has attracted tremendous attention due to its great potential in solving the two major problems. Compared with the traditional water pollution treatment technology, photocatalytic material has attracted wordwide attention due to its economical, high photocatalytic efficiency, no secondary pollution and so on. As a novel photocatalytic materials, bismuth oxyhalide（BiOX, X=Br, Cl, I） semiconductor with a unique electronic structure,optical absorption and good optical properties has become the research focus of semiconductor photocatalytic materials. Thus, the aim of this thesis is to build a novel type of BiOBr_xI_1-x/semiconductor(BiOBr_xI_1-x/SC) heterojunction photocatalysts with high photocatalytic activity through doping and surface loading. Meanwhile, the types of the main active species were discussed, the detection process of reactive species, and the efficiency separation of photogenerated electron-hole pairs were improved and the mechanism of the enhanced photocatalytic activity was also discussed.The main research contents and important results of this thesis are presented as follows:（1） A novel flower-like BiOBr_xI_1-x/Bi OI（x=0.9） heterojunction was synthesized by a facile One-pot method. The structures of the obtained samples were systematically characterized using XRD, SEM, TEM, HRTEM, SAED, BET, XPS and DRS. The photocatalytic activities of BiOBr_xI_1-x/Bi OI were evaluated by the degradation of methyl orange and phenol under visible light（λ>400 nm）. The results showed that BiOBr_xI_1-x/Bi OI composites exhibited improved photocatalytic activities. Among the composites, 10% BiOBr_xI_1-x/Bi OI possessed the best photocatalytic activity. The ion doping and the construction of effective heterojunction BiOBr_xI_1-x-Bi OI plays a key role in improving the photocatalytic activity of 10% BiOBr_xI_1-x/Bi OI. Moreover, ?O2-and h+ were the main reactive species in BiOBr_xI_1-x/Bi OI photodegradation of phenol and methyl orange.（2） A novel I- doped Bi OBr/BiPO₄(BiOBr_xI_1-x/BiPO₄)（x=0.9） heterostructure was constructed by a facile deposition-precipitation method. Seeing that BiOBr_xI_1-x was a narrow band-gap semiconductor and possess good visible light absorption, wide band-gap semiconductor BiPO₄ which did not respond visible light could be modified by BiOBr_xI_1-x to expand the light absorption. The as-prepared BiOBr_xI_1-x/BiPO₄ composite exhibited a notably enhanced photocatalytic performance in decomposing phenol and methyl orange under visible light in comparison with the Bi OBr, BiOBr_xI_1-x, BiPO₄ and Bi OBr/BiPO₄ reference samples.The enhanced photocatalytic activity of BiOBr_xI_1-x/BiPO₄ mainly resulted from the synergetic effects of I- ions doping in Bi OBr and the heterojunction interface between BiOBr_xI_1-x and BiPO₄. I- ions doping narrowed the band gap energy of Bi OBr, broadened the visible light absorption and generated more photocharges.Meanwhile, BiOBr_xI_1-x/BiPO₄ interface accelerated the separation rate of photocharges. Moreover, ?O2- and h+ were the main reactive species in the BiOBr_xI_1-x/BiPO₄ photodegradation process.（3） BiOBr_xI_1-x/g-C₃N₄（x=0.95） organic-inorganic hybrid photocatalyst was prepared by deposition-precipitation method. The photocatalytic activity of BiOBr_xI_1-x/g-C₃N₄ was investigated by using methyl orange as a pollutant model under visible light（λ>420 nm）. The results showed that the photocatalytic activity of BiOBr_xI_1-x/g-C₃N₄ composite was about 5 times of Bi OBr and g-C₃N₄.BiOBr_xI_1-x/g-C₃N₄ is a typical double visible light excitation heterojunction and matching band structure, which is conducive to the rapid separation of electron hole and improve the photocatalytic efficiency.As stated previously, the synergetic effects of energy band regulation and semiconductor heterojunction of BiOX, which is an effective way of constructing composite photocatalytic materials. This paper provides an experimental basis for the development of novel visible-light photocatalyst, rich types of photocatalyst and an in-depth understanding of photocatalytic mechanism.