基于CdSe量子点构筑的半导体光催化材料及其光降解有机污染物的行为和机理研究

发布时间：2018-06-17 20:58

本文选题：CdSe量子点 + 双金属离子掺杂　；参考：《江苏大学》2017年博士论文

【摘要】：随着工业化程度的日益提高,越来越多的有机物被投入到现代生产和生活中,造成水环境中出现大量有机物残留,这些有机物残留对环境造成的污染日益加剧。近年来,利用太阳能光降解有机污染物的绿色光催化技术引起了科研工作者的广泛关注,如何获得高性能低成本的半导体光催化材料已然是光催化技术发展的关键问题。量子点材料由于具有尺寸小、比表面积大、光响应能力强、独特的电子态和光学吸收性能等优势,已成为光催化领域新兴的研究热点。同时,硒化镉(CdSe)半导体光催化材料具有合适的禁带宽度,独特的晶体结构特征以及在可见光下显示出优异的光降解有机污染物性能的优势,具有较高的研究价值。因此,结合量子点材料和CdSe半导体的多重优势,选择CdSe量子点作为光催化材料来降解环境废水中有机污染物具有很好的应用前景。但是由于单一 CdSe量子点材料存在着一些缺陷严重制约了其应用范围,例如:易于团聚,抗光腐蚀性差,稳定性较低等。为了克服CdSe量子点材料的这些缺点,本论文采取多种修饰技术对其进行改性,如离子掺杂技术对其进行修饰,克服CdSe量子点光生电子和空穴易复合的问题;结合贵金属纳米粒子等离子体共振效应,在提高光生电子与空穴的分离效率的同时还提高了光能利用率;选择合适载体制备负载-复合型多组分光催化材料,解决CdSe量子点材料吸附能力差、稳定性不高等问题。同时,通过多种分析测试方法,系统地研究了改性CdSe量子点光催化材料的物化特性以及光降解环境中有机污染物的反应机理。具体研究工作如下:(1)采用软模板法合成方案,以十六烷基三甲基氯化铵为表面活性剂,经过简单水浴回流过程,合成了 CdSe量子点囊泡状分级结构光催化材料。根据TEM等测试手段分析了囊泡状结构的成型机制。经过XRD、TEM、TGA等分析测试手段对量子点光催化材料的物化性质进行表征。相对于粒子结构CdSe量子点材料,该结构具有较大的比表面积和丰富的孔道结构。降解实验结果表明,CdSe量子点囊泡状分级结构光催化材料对盐酸四环素(Tetracycline hydrochloride,TC·HCl)展现出优异的光催化降解活性。通过活性物种捕获实验,分析其光催化降解反应机理。通过循环降解实验,考察催化剂的循环利用率。(2)采用简单的一步水热法,以3-巯基丙酸为修饰剂,合成了双离子共掺杂CdSe量子点光催化材料。通过调节离子掺杂种类以及掺杂比例,制备不同的金属离子掺杂CdSe量子点光催化材料。TEM研究发现,制备的金属离子掺杂CdSe量子点材料,纳米粒子尺寸均一,呈球状分布,纳米粒子平均尺寸约为8 nm。UV-vis DRS表明制备的所有离子掺杂CdSe量子点样品在可见光范围内均具有很强的光响应能力,相比于单一 CdSe量子点材料,金属离子掺杂CdSe量子点材料带隙值降低。同时,以TC·HCl溶液为目标物废水、详细探讨了光催化降解机理并研究不同条件对光催化降解性能的影响。通过考察掺杂金属离子的种类及比例,得出3%Co-4%K/CdSe量子点材料具有最佳的光催化性能。在30min内,其对TC·HCl的降解率达到78.4%。通过对降解不同时间的溶液质谱进行测定,分析了 TC·HCl降解的中间过程。(3)采用简单的水热法,将Al2Ti05陶瓷材料与CdSe量子点复合,构建异质结复合材料。在此基础上,制备了纳米Ag粒子修饰CdSe量子点负载Al2Ti05复合光催化剂。利用XRD、TEM、电化学等多种分析测试手段对光催化剂进行物化性质表征。以典型的亚甲基蓝染料(Methylene blue,MB)溶液为降解目标物验证制备的复合光催化剂的光催化活性。考察了 Al2Ti05的引入比例对复合材料光催化性能的影响。通过活性物种捕获实验,分析了光催化降解过程中起主要作用的活性因子并详细探讨了光催化降解有机染料的机理。(4)以箭竹叶为生物原材料,采用无氧炭化法制备蜂窝管状竹叶生物炭。通过XRD、SEM、N2吸脱附等多种不同分析测试手段对竹叶生物炭的物化性能进行表征。以竹叶生物炭为载体,可溶性金属盐溶液为金属源,硼氢化钠为还原剂,原位生长法与水热法相结合,成功制备了金属离子掺杂CdSe量子点负载竹叶生物炭复合光催化剂。通过光催化降解TC·HCl溶液验证其光催化活性。考察生物炭加入量对所制备的复合材料性能的影响规律;探究了金属离子掺杂比例对所制备的材料性能的影响规律。最终得出结论,生物炭加入量为35 wt%、Co离子掺杂比例为3%-7%时最佳。另外,通过多种实验手段相结合探讨了光催化降解抗生素废水的反应机理,揭示了其提高光催化性能的本质原因。
[Abstract]:With the increasing degree of industrialization, more and more organic compounds have been put into modern production and life, resulting in a large number of organic residues in the water environment, and the pollution of these organic residues to the environment is aggravated. In recent years, the green photocatalytic technology for the use of solar energy to degrade organic contaminants has caused scientific research workers. Widely concerned, how to obtain high performance and low cost semiconductor photocatalytic materials has been the key problem in the development of photocatalytic technology. Quantum dots have become a new research hotspot in the field of photocatalysis because of their advantages of small size, large specific surface area, strong light response ability, unique electronic state and optical absorption properties. Cadmium (CdSe) semiconductor photocatalyst has a suitable band gap, unique crystal structure characteristics and excellent advantages of showing excellent photocatalytic degradation of organic pollutants in visible light. Therefore, combining quantum dots and CdSe semiconductors, CdSe quantum dots are selected as photocatalytic materials. The degradation of organic pollutants in environmental wastewater has a good application prospect. However, there are some defects in the single CdSe quantum dot material which seriously restrict its application, such as easy reunion, poor anti light corrosion and low stability. In order to overcome these shortcomings of CdSe quantum dots, this paper adopts a variety of modification techniques to it Modification, such as the modification of ion doping technology, overcomes the problem that the photoelectrons and holes of the CdSe quantum dots are easily compound, and the efficiency of optical electron and hole separation is enhanced with the plasma resonance effect of noble metal nanoparticles. Catalytic materials can solve the problem of poor adsorption capacity and low stability of CdSe quantum dots. At the same time, the physicochemical properties of the modified CdSe quantum dots photocatalytic materials and the reaction mechanism of organic pollutants in the photodegradation environment are systematically studied by a variety of analytical testing methods. The specific research work is as follows: (1) a soft template synthesis scheme is used. With sixteen alkyl three methyl ammonium chloride as surface active agent, a CdSe quantum dot vesicular structured photocatalytic material was synthesized through a simple water bath reflux process. The forming mechanism of the vesicular structure was analyzed by TEM and other testing methods. The physicochemical properties of the quantum dots photocatalyst were characterized by XRD, TEM, TGA and other analytical methods. Compared with the particle structure CdSe quantum dots, the structure has a large specific surface area and rich pore structure. The results of degradation experiments show that the photocatalytic activity of CdSe quantum dots vesicular graded structure photocatalytic materials to Tetracycline hydrochloride (TC. HCl) is superior to the photocatalytic degradation activity. The reaction mechanism of photocatalytic degradation was analyzed. The cyclic utilization rate of the catalyst was investigated by cyclic degradation. (2) a simple one step hydrothermal method was used to synthesize a double ion Co doped CdSe quantum dot photocatalyst with 3- mercapto propionic acid as the modifier. The study of CdSe quantum dots photocatalytic material.TEM found that the prepared metal ions doped CdSe quantum dots were uniform in size and spherical distribution. The average size of the nanoparticles was about 8 nm.UV-vis DRS, indicating that all the ions doped CdSe quantum dots have strong light response ability in the range of visible light, compared with those in the visible light range. The band gap value of metal ions doped CdSe quantum dots is reduced by single CdSe quantum dots. At the same time, the photocatalytic degradation mechanism and the effect of different conditions on photocatalytic degradation are investigated in detail with TC / HCl solution as target wastewater. By investigating the species and proportion of doped metal ions, the 3%Co-4%K/CdSe quantum dots materials are obtained. With the best photocatalytic performance. In 30min, the degradation rate of TC HCl was reached to 78.4%. by the determination of the solution mass spectra at different time. The intermediate process of TC HCl degradation was analyzed. (3) a simple hydrothermal method was used to combine the Al2Ti05 ceramics with the CdSe quantum dots to construct the heterojunction composite. On this basis, the preparation was made. Nano Ag particles modified CdSe quantum dots loaded with Al2Ti05 composite photocatalyst. The physicochemical properties of photocatalyst were characterized by XRD, TEM, electrochemistry and other analytical testing methods. The photocatalytic activity of the composite photocatalyst prepared with the typical methylene blue (Methylene blue, MB) solution as the degradation target was investigated. The effect of the introduction ratio on the photocatalytic properties of composite materials. Through the experiment of active species capture, the active factors which play the main role in the process of photocatalytic degradation were analyzed and the mechanism of photocatalytic degradation of organic dyes was discussed in detail. (4) honeycomb shaped bamboo leaf biological charcoal was prepared by oxygen free carbonization by using arrows bamboo leaves as biological raw materials. The physicochemical properties of bamboo leaf biological carbon were characterized by XRD, SEM and N2 desorption. The bamboo leaf biological charcoal was used as the carrier, the soluble metal salt solution was used as the metal source, the sodium borohydride was the reductant, and the in situ growth method was combined with the hydrothermal method to prepare the gold ion doped CdSe quantum dots loaded bamboo leaf bio carbon composite successfully. Photocatalyst. The photocatalytic activity was verified by photocatalytic degradation of TC / HCl solution. The effects of carbon content on the properties of the composites were investigated, and the influence of the proportion of metal ions on the properties of the prepared materials was explored. Finally, it was concluded that the amount of bio carbon added to 35 wt% and the proportion of Co ion doping at 3%-7% was 3%-7%. In addition, the reaction mechanism of photocatalytic degradation of antibiotic wastewater was discussed through a variety of experimental methods, and the essential reasons for improving the photocatalytic performance were revealed.
【学位授予单位】：江苏大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X703;O643.36;O644.1

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