Synthesis And Visible Light Photocatalytic Activity Enhancement Of Ionic Liquid Modified BiOI

In recent years, various advanced oxidation processes (AOPs) have been developed rapidly in treating of wastewater. Recently, bismuth oxyhalides, BiOX (X=Cl, Br, I), have received much attention for the potential photocatalytic application. Among them, BiOI has the smallest band gap (about1.8eV) and strong absorption in visible-light region, thus might have an excellent photocatalytic performance under sunlight irradiation. Herein, BiOI can also be used as a new research direction in environmental remediation.In this thesis, we investigate the photocatalysis mechanism of BiOI in detail and therefore demonstrate that the photocatalytic activity of BiOI could be enhanced greatly by in-situ modification of an ionic liquid [Bmim]I (1-Buty-3-methylimidazolium iodide). The ionic liquid modified BiOI (IL-BiOI) was prepared by reacting bismuth nitrate with [Bmim]I in water at70℃, where the ionic liquid could act as both iodine source and surface modified agent. On degradation of methyl orange under the visible light irradiation (κ>420nm), IL-BiOI photocatalyst exhibited superior photocatalytic activity to the unmodified counterpart synthesized in the absence of [BmimJI. The effects of ionic liquid modification on the photocatalytic activity enhancement were systematically investigated. We found that IL modification could not only enlarge band gap energy to improve direct hole oxidation ability of BiOI, but also trap the photoexcited electron at conduction band of BiOI to inhibit the recombination of photoinduced electron-hole pairs, and thus enhance its photocatalytic activity on the degradation of organic pollutants.On the basis of our previous work, we also chose the ionic liquid as both iodine source and surface modified agent to synthesize BiOI/Bi2O3heterostructures by milling method at room temperature. The visible-light photocatalytic activity of these BiOI/Bi2O3heterostructure could be evaluated on the degradation of methyl orange. The results revealed that BiOI/Bi2O3heterostructure hold much higher visible-light photocatalytic activity than pure BiOI and Bi2O3, respectively. In addition, we investigated the process of its formation and the photocatalysis mechanism of BiOI/Bi2O3in detail. The photocatalytic activity enhancement of BiOI/Bi2O3heterostructures under visible light irradiation could be primarily attributed to in-situ modification of an ionic liquid and the heterojunction formed between BiOI and BiO3...