Ⅰ-Ⅲ-Ⅵ族多元硫化物量子点基光催化剂的结构调控及性能研究

发布时间：2018-07-08 10:37

本文选题：可见光响应 + 四元硫化物　；参考：《江苏大学》2017年硕士论文

【摘要】：光催化技术是利用半导体将光能转化为化学能的一种方法,它以其高效、低成本、环保等优点,被认为是解决全球能源危机有效的途径之一。目前研究的大多数宽带隙的光催化剂只能响应紫外光(仅占太阳光谱的5%),为了拓宽光响应范围,提高光能利用率,高活性的可见光响应多元金属硫化物光催化剂成为研究热门问题之一。量子点具有独特的光学性质,尺寸仅为几纳米,量子限域效应使得其尺寸与光学性质相关联可调,但是存在制备方法复杂、放大过程中优异性能无法保持的问题。本文针对四元Ag-In-Zn-S量子点基光催化剂,围绕减少量子点自身缺陷、增强光生载流子分离效率和有效抑制电子空穴复合的中心问题,开发了一系列低温水相基的制备和后处理方法,实现克级以上高质量Ⅰ-Ⅲ-Ⅵ族量子点及量子点异质结的可控制备,并从组分调控、表面包覆、构筑异质结和助催化剂负载等方面探究了该体系的光催化降解和制氢的机理,优化半导体量子点材料性能和反应条件,为实现工业放大应用提供了一定的技术基础。本文的主要研究内容如下:1.利用水热法合成一系列Ag:Zn-In-S量子点光催化剂,系统研究了Ag掺杂量对Ag:Zn-In-S量子点的微观结构、光学性质、化学组分和光催化制氢性能的影响。实验结果表明制氢效率与Ag含量存在火山型关系,主要是由于适量掺杂Ag可拓宽可见光响应范围,减少内部缺陷,提高了光生电子空穴对分离效率,增强了光催化活性;然而过量Ag可导致高浓度缺陷态,成为光生载流子的复合中心,影响光催化效率。在Pt作助催化剂条件下,优化的Ag:Zn-In-S量子点光催化分解水制氢速率比未掺杂Zn-In-S活性显著提高。证明三元硫化物纳米晶在可见光区域的光催化制氢方面具有很大的潜力。2.通过低温水热处理原位生长合成准II型ZAIS/ZnS核壳结构量子点光催化剂,利用紫外吸收和荧光光谱研究了包覆ZnS后样品的光学性质,瞬态荧光和电化学阻抗研究了光生电子空穴复合机理。发现ZnS在构建的准II型ZAIS/Zn S核壳异质结中光催化分解水系统中起着重要作用,可以减少表面缺陷,延长载流子寿命,有效提高光生电子-空穴对分离效率,增强光催化制氢速率,提高催化剂稳定性。这为今后构建准II型核壳异质结光催化材料包覆厚度调控提供了有效的借鉴。3.采用原位生长法制备Zn-AgIn5S8/g-C3N4量子点/纳米片复合光催化剂,对复合材料的微观结构、化学组成和光催化分解水制氢性能进行研究,确定复合材料最佳优化比例,通过分析异质结光电流及阻抗探究Zn-AgIn5S8/g-C3N4复合材料光催化制氢机理。当g-C3N4和Zn-AgIn5S8量子点质量比为10%时,可见光下光催化分解水制氢效率达到最大值,比纯Zn-AgIn5S8量子点制氢效率提高了1.39倍。这项工作提供了一种相对简单的高质量0D/2D量子点/纳米片异质结的构筑方法,并对提高硫化物光催化剂的稳定性有重要的指导意义。4.通过MoS2在Zn-AgIn5S8量子点表面的原位水热沉积,制备ZnAgIn5S8/MoS2量子点复合光催化剂,研究MoS2作为助催化剂对Zn-AgIn5S8/Mo S 2复合体系中结构、光学性质及光催化活性的影响。研究表明由光生电子与氧气反应生成的超氧自由基在RhB降解中起主要作用。荧光寿命测试表明异质界面构筑能够促进电子-空穴对的分离,有利于光生电子从Zn-AgIn5S8量子点导带转移到MoS2助催化剂。进一步分析Zn-AgIn5S8/MoS2复合光催化剂的加入对RhB溶液的荧光猝灭及寿命的影响,发现引入MoS2的主要作用是促进染料分子与催化剂之间的电荷转移,并提出了一个连续电荷转移机理。这些结果为廉价二维MoS2材料在催化剂设计中的作用提供了新的理解,具有重要的指导意义。
[Abstract]:Photocatalytic technology is a method using semiconductors to convert light energy into chemical energy. It is considered to be one of the effective ways to solve the global energy crisis with its advantages of high efficiency, low cost and environmental protection. Most of the broadband gap photocatalysts currently studied can only respond to ultraviolet light (only 5% of the solar spectrum), in order to broaden the range of light response. Increasing the utilization rate of light energy, high active visible light response to multi metal sulfide photocatalyst has become one of the hot issues. Quantum dots have unique optical properties, the size of which is only a few nanometers. The quantum confinement effect makes its size and optical properties adjustable, but the preparation method is complex and the excellent performance in the process of amplification is no more. In this paper, based on the four element Ag-In-Zn-S quantum dot based photocatalyst, a series of low temperature aqueous phase based preparation and post-processing methods have been developed to reduce the defects of the quantum dots, enhance the efficiency of optical carrier separation and effectively suppress the recombination of electron holes. The controllable preparation of the quantum dots heterojunction, and the mechanism of photocatalytic degradation and hydrogen production of the system are explored from the component regulation, the surface coating, the construction of the heterojunction and the support of the catalyst, and the optimization of the properties and the reaction conditions of the semiconductor quantum dots, which provides a certain technical basis for the realization of industrial amplification. The following contents are as follows: 1. a series of Ag:Zn-In-S quantum dots photocatalysts are synthesized by hydrothermal method. The effects of Ag doping amount on the microstructure, optical properties, chemical composition and photocatalytic hydrogen production of Ag:Zn-In-S quantum dots are systematically investigated. The experimental results show that the hydrogen production efficiency is related to the Ag content in the volcanic type, mainly due to a proper doping of Ag. Broadening the range of visible light response, reducing internal defects, improving the separation efficiency and enhancing the photocatalytic activity of the photogenerated electron hole, however, excessive Ag can lead to high concentration defect state, become a composite center of photogenerated carrier, and influence the photocatalytic efficiency. Under the condition of Pt as a catalyst, the optimized Ag:Zn-In-S quantum dots photocatalytic decomposition of water to hydrogen production It is proved that the rate of the rate is significantly higher than that of the undoped Zn-In-S. It is proved that the three element sulfides nanocrystals have great potential for the photocatalytic hydrogen production in the visible region. The quasi II ZAIS/ZnS nuclear shell structure quantum dot photocatalyst is synthesized by the low temperature hydrothermal treatment, and the UV absorption and fluorescence spectra have been used to study the light after the coating of ZnS. The study of properties, transient fluorescence and electrochemical impedance studies the mechanism of photoelectron hole recombination. It is found that ZnS plays an important role in the photocatalytic decomposition of water system in the quasi II ZAIS/Zn S nuclear shell heterojunction constructed, which can reduce surface defects, prolong the carrier lifetime, improve the efficiency of photoelectron hole pair separation and enhance the photocatalytic hydrogen production. At the same time, the stability of the catalyst is improved. This provides an effective reference for the construction of the coating thickness of the quasi II nuclear shell heterojunction photocatalyst in the future. The.3. in situ growth method is used to prepare the Zn-AgIn5S8/g-C3N4 quantum dots / nanoscale composite photocatalyst. The microstructure and chemical composition of the composite and the hydrogen production performance of the photocatalytic decomposition water are carried out. The optimum ratio of composite material is determined, and the mechanism of photocatalytic hydrogen production of Zn-AgIn5S8/g-C3N4 composites is investigated by analyzing the photocurrent and impedance of heterojunction. When the mass ratio of g-C3N4 and Zn-AgIn5S8 quantum dots is 10%, the maximum hydrogen production efficiency of photocatalytic decomposition water under visible light is reached, and the hydrogen production efficiency is 1.39 higher than that of pure Zn-AgIn5S8 quantum dots. This work provides a relatively simple construction method for high quality 0D/2D quantum dots / nanoscale heterojunction, and has important guiding significance for improving the stability of the sulfide photocatalyst..4. is prepared by MoS2 in situ hydrothermal deposition on the surface of Zn-AgIn5S8 quantum dots, and the preparation of ZnAgIn5S8 /MoS2 quantum dots composite photocatalyst, and the study of MoS2 as a catalyst. The effect of catalyst on the structure, optical properties and photocatalytic activity of the Zn-AgIn5S8/Mo S 2 composite system. The study shows that the superoxide radicals produced by the photoinduced electron and oxygen reaction play a major role in the degradation of RhB. The fluorescence lifetime test shows that the structure of the heterogeneous interface can promote the separation of the electron hole pair, and is beneficial to the photoelectron from the Z. The conduction band of n-AgIn5S8 quantum dots is transferred to the MoS2 cocatalyst. The effect of the addition of Zn-AgIn5S8/MoS2 composite photocatalyst on the fluorescence quenching and the life of RhB solution is further analyzed. It is found that the main function of the introduction of MoS2 is to promote the charge transfer between the dye molecules and the catalyst, and the mechanism of continuous charge transfer is proposed. These results are the results. The role of cheap two-dimensional MoS2 materials in catalyst design provides a new understanding and has important guiding significance.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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