基于液相晶种介导生长法构筑核—壳结构金属纳米催化剂

发布时间：2018-04-06 23:07

本文选题：核-壳结构　切入点：金属纳米晶　出处：《中国科学技术大学》2017年硕士论文

【摘要】：核-壳结构金属纳米晶是一类独特的功能化材料,在催化等领域表现出巨大的应用潜力。一方面,单组分金属纳米晶的性能调控范围有限,而以核-壳结构为代表的金属纳米晶由于不同组分间的复合作用往往表现出多样化的功能性,在催化领域往往表现出不俗的催化活性、产物选择性和稳定性。另一方面,具有核-壳结构的金属纳米晶能够减少贵金属材料的消耗,增加了外壳活性金属的原子利用率和分散性,能够为实用催化体系的构筑提供基础性的研究思路。因此,设计和构筑具有核-壳结构的金属纳米晶既属于基础研究的前沿领域,又兼具应用研究的深远前景。迄今,随着纳米材料可控制备方法学的不断完善,研究人员已经成功构筑了具有不同金属组分和不同形貌的核-壳结构金属纳米晶,在众多合成方法中,液相晶种介导生长法在构筑这种核-壳结构金属纳米晶方面具有独特的优势。所谓液相晶种介导生长法,是将具有特定结构的晶种在已知的化学环境中进行投料,然后在其表面进行异相成核和外延生长。异相成核的能垒比较低,使得金属纳米晶能够在一种比较温和的条件下进行定向生长,生长出来的结构纯度也比较高。在此背景下,本论文涉及的主要研究工作是以液相晶种介导生长法为基础,结合其它金属纳米晶的可控合成方法制备出一些具有独特结构的核-壳金属纳米催化剂,例如,基于共形外延生长制备Pd@CuPd核-壳纳米立方体结构、结合氧化刻蚀手段制备Pd@CuPd核-壳超立方体结构、基于动力学调控制备Pd@CuAu二维四角棒结构。本论文内容共有四章,各章内容如下:在第一章中,我们简单介绍了具有核-壳结构金属纳米晶的合成及其在催化领域的应用。然后,我们重点回顾了液相晶种介导生长法的相关知识。在第二章中,我们重点阐述了如何在液相晶种介导生长法中引入氧化刻蚀技术,从而达到控制核-壳结构Pd基纳米晶表界面结构的目的。首先,我们以Pd纳米立方体作为种子和支撑材料,然后通过液相晶种介导生长法在其表面沉积一层均匀的CuPd双金属合金形成Pd@CuPd核-壳结构纳米立方体结构。接着,借助氧气的刻蚀作用,产物变成了具有高度开放结构的Pd@CuPd核-壳超立方体纳米晶。我们对刻蚀前后两种Pd@CuPd核-壳结构纳米晶进行了详细的表征,并研究了其形成机理。而电化学催化实验的结果表明,这种Pd@CuPd核-壳超立方体催化剂在电化学催化还原CO2反应中表现不俗。在第三章中,我们重点介绍了如何在液相晶种介导生长法中结合动力学调控手段制备Pd@CuAu核-壳结构二维四角棒纳米材料,而且,通过改变Pd纳米立方体种子和支撑材料的添加量,我们能够控制最终产物的尺寸。然后,我们以邻苯二酚氧化作为模型催化体系详细研究了这种Pd@CuAu核-壳结构二维四角棒纳米材料的催化性能。在第四章中,我们主要总结了本文的相关工作,并对相关领域的发展提出了进一步的展望。
[Abstract]:The core-shell structure of metal nanocrystals is a kind of functional material with unique, showing great potential applications in catalytic fields. On the one hand, one component of metal nanocrystals performance control scope is limited, the metal nanocrystalline core-shell structure represented as the composite effect between different components often a functional diversification, in the field of catalysis often exhibit good catalytic activity, selectivity and stability. On the other hand, metal nanocrystals with core-shell structure can reduce precious metal material consumption, increase housing active metal atom utilization and dispersion, can provide the basic thoughts for research to build a practical catalytic system. Therefore, Frontiers of design and construction of metal nanocrystals with core-shell structure which belongs to the basic research, applied research and has far-reaching prospects. So far, with controllable nano materials The preparation method of continuous improvement, the researchers have successfully fabricated with different metal components and core-shell structure of metal nanocrystals with different morphologies, in various synthesis methods, which mediated growth method has a unique advantage in the construction of the core-shell structure of metal nanocrystals in liquid phase. The so-called liquid crystal the seed mediated growth method, is to have a specific crystal structure in the chemical environment known for feeding, and heterogeneous nucleation and epitaxial growth on its surface. The heterogeneous nucleation energy barrier is relatively low, making the metal nanocrystals for directional growth in a relatively mild condition, structure the purity of growth is relatively high. Under this background, the main research work of this thesis is involved in the liquid phase, the seed mediated growth method, prepared some of the unique structure of the nuclear with controllable synthesis of other metal nanocrystals Shell metal nano catalyst, for example, conformal epitaxial growth of preparation of Pd@CuPd core-shell nano cube structure based on the preparation of Pd@CuPd core-shell hypercube structure combined with oxidation etching method, dynamic controlled fabrication of Pd@CuAu four dimensional angle bar structure based on. This thesis consists of four chapters, each chapter is as follows: in the first in the chapter, we briefly introduce the synthesis of core-shell structure of metal nanocrystals and their application in catalysis. Then, we reviewed the related knowledge of liquid crystal seed mediated growth method. In the second chapter, we focus on how the liquid crystal seed mediated growth into oxidation etching technology in the method, so as to control the core-shell structure of Pd based nanocrystalline surface structure. Firstly, we use Pd nanocubes as seed and support material, and then through the liquid crystal seed mediated growth method uniformly deposited on the surface of a layer The formation of core-shell structure Pd@CuPd nano cube structure CuPd bimetallic alloy. Then, the etching effect of oxygen, the product into a hypercube Pd@CuPd core shell nano crystals have a highly open structure. We conducted a detailed characterization of etching before and after two Pd@CuPd core-shell nanocrystals, and studied its the formation mechanism and electrochemical catalysis. The experimental results show that the Pd@CuPd core-shell hypercube catalyst in electrochemical catalytic reduction of good performance in the CO2 reaction. In the third chapter, we mainly introduced how to liquid crystal seed mediated by two-dimensional Pd@CuAu core-shell structure four aluminumstick nano materials, dynamic regulation system combined with the growth law and, by changing the amount of Pd nanocubes seeds and supporting materials, we can control the size of the final product. Then, we using catechol oxidation as a model catalytic system The catalytic properties of the Pd@CuAu core shell two-dimensional four bar rod nanomaterials were studied in detail. In the fourth chapter, we summarized the related work in this paper, and made further prospects for the development of related fields.

【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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