本文選題：可見光響應 + 四元硫化物��； 參考：《江蘇大學》2017年碩士論文

【摘要】：光催化技術是利用半導體將光能轉化為化學能的一種方法,它以其高效、低成本、環(huán)保等優(yōu)點,被認為是解決全球能源危機有效的途徑之一。目前研究的大多數寬帶隙的光催化劑只能響應紫外光(僅占太陽光譜的5%),為了拓寬光響應范圍,提高光能利用率,高活性的可見光響應多元金屬硫化物光催化劑成為研究熱門問題之一。量子點具有獨特的光學性質,尺寸僅為幾納米,量子限域效應使得其尺寸與光學性質相關聯可調,但是存在制備方法復雜、放大過程中優(yōu)異性能無法保持的問題。本文針對四元Ag-In-Zn-S量子點基光催化劑,圍繞減少量子點自身缺陷、增強光生載流子分離效率和有效抑制電子空穴復合的中心問題,開發(fā)了一系列低溫水相基的制備和后處理方法,實現克級以上高質量Ⅰ-Ⅲ-Ⅵ族量子點及量子點異質結的可控制備,并從組分調控、表面包覆、構筑異質結和助催化劑負載等方面探究了該體系的光催化降解和制氫的機理,優(yōu)化半導體量子點材料性能和反應條件,為實現工業(yè)放大應用提供了一定的技術基礎。本文的主要研究內容如下:1.利用水熱法合成一系列Ag:Zn-In-S量子點光催化劑,系統(tǒng)研究了Ag摻雜量對Ag:Zn-In-S量子點的微觀結構、光學性質、化學組分和光催化制氫性能的影響。實驗結果表明制氫效率與Ag含量存在火山型關系,主要是由于適量摻雜Ag可拓寬可見光響應范圍,減少內部缺陷,提高了光生電子空穴對分離效率,增強了光催化活性;然而過量Ag可導致高濃度缺陷態(tài),成為光生載流子的復合中心,影響光催化效率。在Pt作助催化劑條件下,優(yōu)化的Ag:Zn-In-S量子點光催化分解水制氫速率比未摻雜Zn-In-S活性顯著提高。證明三元硫化物納米晶在可見光區(qū)域的光催化制氫方面具有很大的潛力。2.通過低溫水熱處理原位生長合成準II型ZAIS/ZnS核殼結構量子點光催化劑,利用紫外吸收和熒光光譜研究了包覆ZnS后樣品的光學性質,瞬態(tài)熒光和電化學阻抗研究了光生電子空穴復合機理。發(fā)現ZnS在構建的準II型ZAIS/Zn S核殼異質結中光催化分解水系統(tǒng)中起著重要作用,可以減少表面缺陷,延長載流子壽命,有效提高光生電子-空穴對分離效率,增強光催化制氫速率,提高催化劑穩(wěn)定性。這為今后構建準II型核殼異質結光催化材料包覆厚度調控提供了有效的借鑒。3.采用原位生長法制備Zn-AgIn5S8/g-C3N4量子點/納米片復合光催化劑,對復合材料的微觀結構、化學組成和光催化分解水制氫性能進行研究,確定復合材料最佳優(yōu)化比例,通過分析異質結光電流及阻抗探究Zn-AgIn5S8/g-C3N4復合材料光催化制氫機理。當g-C3N4和Zn-AgIn5S8量子點質量比為10%時,可見光下光催化分解水制氫效率達到最大值,比純Zn-AgIn5S8量子點制氫效率提高了1.39倍。這項工作提供了一種相對簡單的高質量0D/2D量子點/納米片異質結的構筑方法,并對提高硫化物光催化劑的穩(wěn)定性有重要的指導意義。4.通過MoS2在Zn-AgIn5S8量子點表面的原位水熱沉積,制備ZnAgIn5S8/MoS2量子點復合光催化劑,研究MoS2作為助催化劑對Zn-AgIn5S8/Mo S 2復合體系中結構、光學性質及光催化活性的影響。研究表明由光生電子與氧氣反應生成的超氧自由基在RhB降解中起主要作用。熒光壽命測試表明異質界面構筑能夠促進電子-空穴對的分離,有利于光生電子從Zn-AgIn5S8量子點導帶轉移到MoS2助催化劑。進一步分析Zn-AgIn5S8/MoS2復合光催化劑的加入對RhB溶液的熒光猝滅及壽命的影響,發(fā)現引入MoS2的主要作用是促進染料分子與催化劑之間的電荷轉移,并提出了一個連續(xù)電荷轉移機理。這些結果為廉價二維MoS2材料在催化劑設計中的作用提供了新的理解,具有重要的指導意義。
[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.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O643.36

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本文編號：2107156