【作者】 丁洁；

【导师】 杨志泉；

【作者基本信息】 华南理工大学 ， 环境工程， 2017， 硕士

【摘要】 能源短缺和环境污染是困扰人类社会可持续发展的两大挑战。基于半导体的光催化技术可以将光能转化为化学能,该技术具有高效节能、清洁无毒、无二次污染的优点,是一种极具发展前途的环境污染绿色治理技术。光催化技术的核心是光催化剂,即半导体材料。目前人们研究得最多的高效的催化剂是TiO₂,遗憾的是TiO₂的带隙较宽,导致它只能利用紫外和近紫外波长范围的光（仅占太阳光能量的5%）,为了更加高效地利用太阳光,开发高效的可见光响应的催化剂成为必然。20世纪末起,金属有机骨架材料（Metal-organic Frameworks,MOFs）成为材料领域的研究热点,由于MOFs材料具有比表面积大,孔径可调,使得其在催化领域有广泛研究,其中光催化性能备受关注。然而MOFs材料作为光催化剂的光量子产生率比较低,这严重制约了其实际应用。近几年,铋系半导体光催化剂已经被开发,铋系半导体材料对可见光有很好的吸收率。因此,本文利用MOFs材料比表面积和结构孔隙可调的特点,选取MOFs材料作为载体与铋系半导体材料结合,制备异质结,以提升整体的光催化性能。具体研究内容如下:（1）通过两部水热法,成功制备了Bi VO₄/MIL-125（Ti）复合材料,采用XRD,SEM,HRTEM,FTIR,XPS,UV-Vis DRS等多种分析手段对复合材料的样品组成、结构形貌、光学性能做了研究,并以染料罗丹明B为目标污染物,考察材料的可见光催化活性,研究了Bi VO4在复合材料中的比例和罗丹明B的初始浓度对复合物可见光催化性能的影响。通过5次重复性实验,考察了Bi VO4/MIL-125（Ti）的重复利用能力。通过离子抑制实验,研究光催化过程重起重要作用的离子,提出了合理的Bi VO4/MIL-125（Ti）异质结的催化机理。（2）通过静电作用引导的自助装反应,成功合成了Bi₂MoO₆/UiO-66（Zr）复合材料,采用XRD,SEM,FTIR,XPS,BET,UV-Vis DRS等多种分析手段对复合材料的样品结构、形貌特征、光学特性做了表征,并以罗丹明B为目标污染物,考察材料的可见光催化活性。研究了Bi₂MoO₆在复合材料中的比例对复合物可见光催化性能的影响。此外,研究了Bi2MoO6/UiO-66（Zr）的重复利用能力。通过离子抑制实验,研究参与光催化过程的重要离子,提出了合理的罗明明B光催化降解的催机理。实验结果表明,MOFs材料和铋系半导体复合所生成的复合物具有比本体更高的催化效果,催化效果的提高归因于两者形成的异质结有效抑制了光生电子和空穴的复合速率,从而使催化剂的可见光光催化活性得到明显提升。本论文所制备的光催化剂对罗丹明B有很好的降解效果,且本文中的静电作用引导的字组装方式的合成方法对合成复合材料提供了新的设计思路和借鉴。更多还原

【Abstract】 Solving energy shortages and environmental pollution are two major challenges for human beings to achieve the sustainable development of human society.With energy efficient,clean non-toxic,no secondary pollution advantages,photocatalytic technology is expected to become an effective way to solve environmental and energy problems and is a highly promising environmental pollution green governance technology.Besides,it can degrade pollutants into CO₂ and H₂O.The core of photocatalytic technology is photocatalyst.At present,the most widely studied catalyst is TiO₂.Unfortunately,the band gap of TiO₂ is too wide to utilize solar energy,it only absorb ultraviolet light and near ultraviolet light（which only account for 5% energy of the solar energy）.In order to make more efficient use Sunlight,the development of efficient visible light response catalyst becomes inevitable.Since last decade,a class of porous materials called Meatal-organic Frameworks（MOFs）materials have attracted much attention.With pecific surface area,tolarial pore,MOFs have been applied as a photocatalytic catalyst.However,MOFs have a low photon production rate,which seriously restricts its practical application.In recent years,bismuth-based semiconductor photocatalyst has been developed,bismuth-based materials have a good absorption of visible light.Therefore,this paper uses MOFs as carrier and supports bismuth-based semiconductor materials to prepare heterojunctions.The main contents are as follows:（1）A novel visible-light-responsive photocatalyst that comprised BiVO₄ together with MIL-125（Ti）,was synthesized by a two-step hydrothermal approach.The characterization of asobtained samples as performed by X-ray diffraction,scanning electron microscopy,high resolution transmission electron microscopy,Fourier transform infrared spectroscope,X-ray photoelectron spectroscopy and ultraviolet-visible diffuse reflection spectra.Rhodamine B was selected being a target for the evaluation of the photocatalytic function of as-developed photocatalyst.The photocatalytic reaction parameters,for example,the content of Bi VO₄ as well as initial concentration of Rhodamine B was researched.The composite photocatalyst possessing Bi:Ti molar ratio of 3:2 brought to light the fact that the greatest photocatalytic activity had the ability to degrade 92% of Rhodamine B in 180 min.In addition to that,The Bi VO₄/MIL-125（Ti）composite could keep its photocatalytic activity during the recycling test.The phenomenon of disintegration of the photo-generated charges in the Bi VO₄/MIL-125（Ti）composite was brought to discussion as well.（2）This study provides the first attempt to combine UiO-66（Zr）with Bi₂MoO₆ for the preparation of composite via electrostatic interaction induced self-assembly process.Synthesized products were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Fourier transform infrared spectroscope（FT-IR）,X-ray photoelectron spectroscopy（XPS）,Brunauer-Emmett-Teller（BET）surface area analyse and UV-vis diffuse reflectance spectroscopy（UV-vis DRS）.The photocatalytic activities of as-obtained Bi₂MoO₆/UiO-66（Zr）composites were assessed by degradation of Rhodamine B（Rh B）under the visible-light irradiation.Comparing to the pristine materials,the developed Bi₂MoO₆/UiO-66（Zr）composite with Bi:Zr molar ratio 2:1,labelled as BMUO-2,showed the best photocatalytic activity.It was supposed that the participation of Bi₂MoO₆ increased the use of solar energy and the existence of Ui O-66（Zr）restrained the recombination rate of photo-generated electron-hole pairs.Moreover,Bi₂MoO₆/UiO-66（Zr）composite showed excellent stability and recyclability during cycling experiment.The mechanism and plausible pathway of Rh B degradation were also discussed in this paper.The experimental results show that the composite produced by MOFs and bismuth-based semiconductors has a higher catalytic effect than pristine materials.The improvement of the catalytic effect is attributed to the fact that the heterojunction formed by the two forms,which can suppresses the recombination rate of photogenerated electrons and holes,and leading to the improvement of visible-light-driven photocatalytic activity.The photocatalyst prepared in this paper has a good degradation effect on rhodamine B,and the research work provides a new design idea and reference for the application of MOFs in water phase.更多还原