钯基纳米晶体的可控合成及其性能研究

发布时间：2018-02-10 11:05

本文关键词： 钯基纳米催化剂晶体生长框架结构纳米片异质结构氧还原反应二氧化碳电还原反应　出处：《中国科学技术大学》2017年硕士论文　论文类型：学位论文

【摘要】：贵金属纳米材料作为一类重要的催化剂,在很多催化反应中都有着广泛的应用前景,例如,它们既可以被用于燃料电池中,也可以被用于CO2电还原反应以及光解水反应中。然而,贵金属在地球上的储量稀少,因此人们开始大力发展具有不同结构的催化剂,这样不仅可以在一定程度上减少贵金属的使用,并且往往还因为组分之间的协同效应而表现出更好的催化性能。对于贵金属纳米催化剂来说,它的催化性能与其尺寸、表面结构以及组分密切相关。因此,为了得到性能更优越的催化剂,我们常常通过调节这些参数来改善催化剂的性能。对于钯基纳米催化剂来说,大的比表面积、高指数晶面暴露以及组分之间的协同效应均能有效提高催化剂的催化性能。然而在晶体的生长过程中,金属纳米材料趋向形成最小表面积和低表面能晶面。因此,如何获得理想结构的催化剂也是相关研究的研究重点。本论文主要工作旨在合成一些钯基纳米材料,并运用动力学调控、晶种生长法等多种调控方法,精心设计合成了一些纳米结构,例如,结构开放度较高的框架结构、具有协同效应的异质结构。一方面,这些特殊结构的合成拓宽了催化剂的设计思路,另一方面,它们也在燃料电池、二氧化碳电还原等领域表现出了优越的性能。本论文共有四章,各章节内容简述如下:在第一章中,我们简单介绍了贵金属纳米材料的基本结构特征、性能影响因素、晶体生长理论以及合成现状。其中,我们通过实例说明了几个性能影响因素对贵金属纳米材料的催化性能的影响,以及如何根据这些影响因素设计一些对于催化反应有特殊贡献的金属纳米晶体,或者根据一些特殊结构在催化领域的显著性能来精心设计一些结构。在第二章中,我们首先介绍了框架结构在不同催化体系中的应用及其合成方法。然后我们通过动力学控制,在Pd八面体上选择性沉积Pt原子并通过硝酸刻蚀的方法去除Pd晶核成功制备了结构高度开放的Pt-Pd双金属框架结构,详细了分析了该框架结构的构造以及组成,并探索了该框架结构在燃料电池阴极氧还原反应中的电催化性能。在第三章中,我们首先介绍了 CO2电还原发展现状及其催化剂发展现状,然后我们通过模板诱导生长法成功合成了 Pd方形纳米片-rGO异质结构,详细分析了该异质结构中Pd方形纳米片的晶体结构,并探究了该异质结构在二氧化碳电还原方面的应用。在第四章中,我们展望了金属纳米材料应用前景,并从催化剂的合成、性能测试以及催化剂与性能之间的关系等多个方面阐述了贵金属纳米催化剂研究中存在的一些机遇和挑战。
[Abstract]:As a kind of important catalyst, noble metal nanomaterials have been widely used in many catalytic reactions. For example, they can be used in fuel cells. They can also be used in CO2 electroreduction and photolysis reactions. However, precious metals are scarce on Earth, so people are beginning to develop catalysts with different structures. This not only reduces the use of precious metals to a certain extent, but also tends to exhibit better catalytic performance because of the synergistic effect between components. The surface structure and composition are closely related. Therefore, in order to obtain better catalysts, we often improve the performance of the catalysts by adjusting these parameters. For palladium based nanocatalysts, the specific surface area is large. The high exponent crystal plane exposure and the synergistic effect among the components can effectively improve the catalytic performance of the catalyst. However, in the process of crystal growth, the metal nanomaterials tend to form the minimum surface area and the low surface energy crystal surface. The main purpose of this thesis is to synthesize some palladium based nanomaterials, and to use the kinetic control, seed growth method and other control methods. Some nanostructures have been carefully designed and synthesized, such as frame structures with high structural openness and heterogeneity with synergistic effects. On the one hand, the synthesis of these special structures broadens the design ideas of catalysts, on the other hand, They also show excellent performance in the fields of fuel cell, carbon dioxide electroreduction and so on. In this paper, there are four chapters, and the contents of each chapter are summarized as follows: in the first chapter, we briefly introduce the basic structural characteristics of noble metal nanomaterials. Among them, we illustrate the effect of several performance factors on the catalytic performance of noble metal nanomaterials through examples. And how to design some metal nanocrystals that have a special contribution to the catalytic reaction based on these factors, or elaborate some structures according to the remarkable performance of some special structures in the catalytic field. We first introduced the application of the frame structure in different catalytic systems and its synthesis methods. Selective deposition of Pt atoms on PD octahedron and removal of PD nucleus by nitric acid etching were used to fabricate the highly open Pt-Pd bimetallic frame structure. The structure and composition of the frame structure were analyzed in detail. The electrocatalytic properties of the frame structure in the cathodic oxygen reduction reaction of fuel cells were explored. In chapter 3, we first introduced the development of CO2 electroreduction and the current development of catalysts. Then we successfully synthesized the PD square nanochip -rGO heterostructure by template-induced growth method, and analyzed the crystal structure of the PD square nano-chip in detail. The application of the heterostructure in the electroreduction of carbon dioxide is also discussed. In Chapter 4th, we look forward to the application of metal nanomaterials and the synthesis of catalysts. Some opportunities and challenges in the research of noble metal nanocatalysts were discussed from the aspects of performance test and the relationship between catalyst and performance.
【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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