金属硫化物半导体光催化剂对有机光化学合成和产氢性能研究

发布时间：2018-04-21 20:54

本文选题：可见光催化剂 + Zn_3In_2S_6　；参考：《淮北师范大学》2017年硕士论文

【摘要】：在温和的条件下选择性氧化芳香醇生成芳香醛,在工业上有很好的应用前景。在这里,我们将光催化剂和热催化剂结合起来成功的制备出一种新型的光热耦合催化剂——球状分级结构Zn_3In_2S_6@ZnO。催化剂分别用X射线衍射(XRD)、X射线光电子能谱分析(XPS)、扫描电镜(SEM)、透射电镜(TEM)、紫外可见漫反射光谱(DRS)和BET吸附脱附分析等进行物理化学性质表征。光热催化剂Zn_3In_2S_6@10%ZnO是通过有机溶剂沉淀法制备出来。在可见光照射下,相对于纯ZnO和Zn_3In_2S_6,Zn_3In_2S_6@10%ZnO具有最出色的催化活性。提高的催化活性主要是归功于光催化和低温热催化的耦合作用。催化剂Zn_3In_2S_6@ZnO自身的稳定性和能够吸收更宽的光谱的特性使其有非常广阔的应用前景。光催化和热催化的耦合作用是通过电化学实验和固体荧光特性检测以及一系列的控制实验证明。根据实验结果分析,我们提出了一个可能的反应机理,即作为热催化剂的ZnO可以弱化芳香醇上将被脱去H原子之间的键能,而通过光催化反应生成的超氧自由基(.O2-)更加易于脱去H原子而生成H_2O,达到生成相应的芳香醛的目的。这个研究证明了一个结合光催化剂和热催化剂的催化剂进行选择性氧化芳香醇生成芳香醛的可行方法,对于光催化有机合成有十分深远的意义。与此同时,光催化氧化芳香醇,选择性生成芳香醛的反应体系在隔绝空气的条件下进行时,我们发现在生成芳香醛的同时还会产生氢气。这个反应更有意义的地方是在于不仅可以制备清洁的能源氢气和重要精细化学品的中间体芳香醛,而且还可以充分利用光生电子空穴对,而不造成能量的流失。同样是以Zn_3In_2S_6作为主体催化剂,用光还原法负载Pt,生成Pt/Zn_3In_2S_6,在可见光照射下,光催化剂Pt/Zn_3In_2S_6的活性相对于Zn_3In_2S_6的活性有很大的提高,催化剂Zn_3In_2S_6和Pt/Zn_3In_2S_6分别用X射线衍射(XRD)、X射线光电子能谱分析(XPS)、扫描电镜(SEM)、透射电镜(TEM)、紫外可见漫反射光谱(DRS)和电化学工作站进行物理化学性质表征。最后我们采用荧光、控制实验和元素示踪法等,对光催化氧化芳香醇,在隔绝空气的条件下定向生成苯甲醛和氢气的反应机制进行了深入的研究,并提出了可能的反应机理。
[Abstract]:The selective oxidation of aromatic alcohols to aromatic aldehydes under mild conditions has a good application prospect in industry. In this paper, we have successfully prepared a new photothermal coupling catalyst, Zn3In2S6ZnO, by combining photocatalyst with thermal catalyst. The catalysts were characterized by X-ray diffraction (XRD) X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and BET adsorption and desorption analysis. Photothermal catalyst Zn_3In_2S_6@10%ZnO was prepared by organic solvent precipitation method. Under visible light irradiation, compared with pure ZnO and Zn3Ins, ZnO has the best catalytic activity. The enhanced catalytic activity is mainly attributed to the coupling of photocatalysis and low temperature thermal catalysis. The stability of the catalyst Zn_3In_2S_6@ZnO and its ability to absorb wider spectrum make it have a very broad application prospect. The coupling effect of photocatalysis and thermal catalysis is proved by electrochemical experiments, solid-state fluorescence measurements and a series of controlled experiments. Based on the analysis of the experimental results, a possible reaction mechanism is proposed, that is, ZnO, as a thermal catalyst, can weaken the bond energy between the H atoms that will be removed from aromatic alcohols. However, the superoxide radical produced by photocatalytic reaction is easier to remove H atoms and form H _ 2 O _ 2O, so that the corresponding aromatic aldehydes can be obtained. This study proves a feasible method for selective oxidation of aromatic alcohols to aromatic aldehydes by combining photocatalyst and thermal catalyst, which is of great significance for photocatalytic organic synthesis. At the same time, when the reaction system of photocatalytic oxidation of aromatic alcohols and selective formation of aromatic aldehydes is carried out under the condition of air isolation, it is found that both aromatic aldehydes and hydrogen can be produced. The more significant aspect of this reaction is that it can not only produce aromatic aldehydes, which are the intermediates of clean energy, hydrogen and important fine chemicals, but also make full use of photogenerated electron hole pairs without causing energy loss. In the same way, Zn_3In_2S_6 was used as the main catalyst, and the Pt- / Zn3In2S6 was formed by the photoreduction method. Under visible light irradiation, the activity of the photocatalyst Pt/Zn_3In_2S_6 was greatly improved compared with the activity of Zn_3In_2S_6. The physical and chemical properties of the catalysts Zn_3In_2S_6 and Pt/Zn_3In_2S_6 were characterized by X-ray diffraction X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and electrochemical workstation. Finally, the mechanism of photocatalytic oxidation of aromatic alcohols to benzaldehyde and hydrogen under the condition of air isolation was studied by fluorescence, control experiment and elemental tracer method, and the possible reaction mechanism was proposed.
【学位授予单位】：淮北师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ116.2

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