Eu掺杂的ZnO/MIL-53(Fe)光催化剂的合成及其对醇类选择性氧化的催化性能研究

Preparation of Eu-Doped ZnO/MIL-53(Fe) Photocatalyst and Its Catalytic Performance for Selective Oxidation of Alcohols

采用原位合成法将稀土元素Eu掺杂到半导体ZnO中,并与MIL-53(Fe)复合,成功制备了三维(3D)纳米复合光催化剂Eu-ZnO/MIL-53(Fe),通过X射线衍射(XRD)、红外(FT-IR)、扫描电子显微镜(SEM)、紫外可见漫反射光谱(UV-Vis DRS)、光致发光光谱(PL)、X射线光电子能谱分析(XPS)及电化学阻抗谱(EIS)等手段对复合材料的结构、形貌以及光学电学性能进行了详细的表征.实验结果表明:引入稀土元素可以极大地提高MIL-53(Fe)的光催化效率,同时促进光生电子-空穴的有效分离,使得催化活性进一步提高.通过活性捕捉实验和电化学手段对该反应可能的反应机理进行探究,结果表明:该光催化过程是通过空穴(h^+)和羟基自由基(·OH)共同作用实现苯甲醇的选择性氧化.通过循环实验和表征参加光反应前后的催化剂的结构来探究该催化剂的光稳定性和热稳定性,结果表明该复合型光催化剂具有良好的光稳定性和热稳定性.

The novel 3 dimension(3 D) nanocomposite photocatalyst Eu-ZnO/MIL-53(Fe) was successfully prepared with in situ synthesis. Firstly the rare earth element Eu was doped into semiconductor ZnO and then Eu-ZnO was combined with MIL-53(Fe). The structure, morphology, optical and electrical properties of the nanocomposites were thoroughly characterized by X-ray diffraction(XRD), fourier infrared spectroscopy(FT-IR), scanning electron microscopy(SEM), ultraviolet-visible diffuse reflectance spectroscopy(UV-vis DRS), X-ray photoelectron spectroscopy(XPS), N2 adsorption-desorption isotherms(SBET), photoluminescence spectra(PL) and electrochemical impedance(EIS) spectra and the like. The FT-IR and XRD results showed that the photocatalysts were successfully prepared and SEM results showed that morphology of the MIL-53(Fe) were all well remained after the preparing process. The photocatalytic experiment data, UV-Vis DRS spectra and PL spectra and the like results showed that the introduction of rare earth elements Eu could greatly improve the photocatalytic efficiency of MIL-53(Fe), and promote the effective separation of photogenerated electron-hole, which further improved the catalytic activity. The results of electrochemical impedance spectra further supported the conclusion. By exploring the photocatalytic activity of Eu-ZnO/MIL-53(Fe) under visible light conditions, the photocatalyst showed excellent photocatalytic activity. Some derivatives of benzalcohol were more affected by electronic effects, the conversion of the derivative having an electron-withdrawing group was relatively high, and the conversion of the derivative having an electron-donating group was low. The possible mechanism of the photocatalytic reaction was explored via the active species capture experiment and Mott-schottky(M-S) curve test. The results showed that the photocatalytic selective oxidation of alcohols achieved with photogenerated holes(h^+) and hydroxyl radicals(·OH). The photo stability and thermal stability of the photocatalyst was investigated by cyclic experiments and the structure characterization of the photocatalyst before and after the photoreaction. The results showed that the photocatalyst had outstanding light stability and thermal stability.