铂族贵金属纳米材料的制备及其催化性能研究

发布时间：2018-01-13 23:01

本文关键词：铂族贵金属纳米材料的制备及其催化性能研究　出处：《山东大学》2015年博士论文　论文类型：学位论文

【摘要】：铂族贵金属纳米材料由于在异相催化、电化学等方面的独特性能而日益受到人们的重视。纳米材料的催化活性通常与纳米结构所暴露的晶面、组成和结构有着密切的关系。金属杂化纳米材料不仅能有效改变单一成分的电子结构,不同组分之间存在的协同效应,更能显著改变材料的宏观性质,提高催化剂的催化活性。同时,贵金属与过渡金属之间形成的杂化材料还能降低铂族金属的使用量,这对于地球上储量并不丰富的铂族元素来说,无疑能够显著降低催化剂用量和成本。铂族杂化纳米材料由于成分较多,催化剂的制备过程复杂,结构控制相当的困难,这对于催化剂的制备提出了很大的挑战。因此,设计和发展简单、有效的制备方法来制备铂族贵金属的杂化材料,对于促进铂族贵金属在催化等方面的广泛应用是非常必要的。本论文中,设法合成了一系列的Pt、Pd、Rh杂化纳米材料,研究了其形成机制,并探索了它们在液相催化,电催化等方面的应用。主要研究结果如下：1.通过动力学调控方法制备了Au纳米棒-RhAg杂化纳米材料,分别得到了哑铃状结构、毛刷状结构和棒状Au@Ag-Rh纳米摇铃结构。通过对反应机制的研究发现,随着Rh3+和Ag还原速率的增加,RhAg在Au纳米棒上的沉积方式是逐渐由两端沉积向全身沉积转变,进一步的增加还原速率,Ag首先在Au纳米棒表面形成壳层,随后Rh+与Ag壳层发生置换反应得到了纳米摇铃结构。以OPDA偶联反应为模型研究了这三种结构的催化效率,毛刷状结构哑铃型结构纳米摇铃结构,催化效率的差异主要和Rh暴露的活性面积有关。2.通过简单的水热方法成功制备了Pd-Rh双金属核-框架结构和核-壳结构,通过选择性的化学腐蚀,成功的得到了Pd-Rh双金属纳米框架结构和纳米盒子。通过一系列的对照实验以及详细的结构表征,研究了Pd-Rh核-框架结构和核-壳结构的形成过程和反应机制,揭示了Rh3+的存在抑制了Pd孪晶晶种的形成,使得Pd生成了更稳定的单晶立方块。利用OPDA偶联反应为模型评价了所得到的Pd-Rh四种不同结构的催化性能,催化效率如下：Pd-Rh纳米盒子Pd-Rh纳米框架Pd-Rh核-框架Pd-Rh核-壳结构。催化性能的差异主要和空心结构以及Rh含量有密切的关系。3.发展了简单的一锅法制备了三金属Au-Ag@Rh-Ag纳米摇铃结构和双金属Rh-Ag空心球结构。通过时间演化分析对其形成过程进行了详细研究,揭示了其形成纳米摇铃结构和空心结构的实质分别是首先形成了Au-Ag核-壳结构和Ag纳米球,随后Ag壳层与Rh3+发生置换反应形成上述空心结构。OPDA的催化偶联反应结果表明,Au-Ag@Rh-Ag纳米摇铃结构的催化活性要优于双金属Rh-Ag空心球结构,催化性能的差异可能源于Rh活性面积的差异。4.第一次实现了五重孪晶Pd纳米线到三组分PtPdCu内凹立方块的转变。通过对反应机制的详细研究发现,五重孪晶Pd纳米线到PtPdCu内凹立方块的转变经过了两步：孪晶Pd纳米线的腐蚀和Pt4+、Pd2+、Cu2+共还原,之所以孪晶Pd纳米线被腐蚀主要是因为孪晶的晶格应力所导致的晶体稳定性降低。电催化氧化甲酸表明,内凹的PtPdCu立方块相对于商业Pt/C催化剂具有更高的催化活性和更好的稳定性,催化活性的提高主要是因为内凹结构的存在提供了大量的台阶原子,同时杂原子的存在使得甲酸催化氧化更多的经过直接氧化路径,催化剂的稳定性得到提高。
[Abstract]:Platinum noble metal nano materials because of differences in the catalytic performance, unique electrochemistry increasingly attention. The catalytic activity of nano materials and nano structure usually exposed surface, composition and structure are closely related. The electronic structure of metal nano hybrid material not only can effectively change the single component, synergy the effect between different components can significantly change the macroscopic properties of materials, improve the catalytic activity of the catalyst. At the same time, the hybrid materials can also be formed between the noble metal and transition metal, reduce the amount of platinum metals, the earth is not rich in reserves of platinum group elements, it can significantly reduce the amount of catalyst and the cost of platinum. Hybrid nano materials because of the many components, preparation process of the catalyst complex structure, difficult to control, the preparation of the catalyst is a great The challenge. Therefore, the design and development of a simple and effective method for the preparation of hybrid materials for preparing platinum group metals, it is necessary to promote wide application of platinum group metals in catalytic fields. In this thesis, to a series of Pt, the synthesis of Pd, Rh hybrid nano materials. The formation mechanism of the research, and to explore their application in liquid phase catalysis, electrocatalysis and so on. The main results are as follows: 1. by dynamic regulation method to prepare Au nanorod -RhAg hybrid materials were obtained dumbbell shaped brush like structure and rod like Au@Ag-Rh nano structure. Through the research on the reaction bell the mechanism of Rh3+ and Ag, with the reduction rate of the increase of deposition in Au nanorods on RhAg is changing gradually from both ends to the body of sedimentary deposition, further increase the reduction rate of Ag, first formed shell on Au nanorods, then Rh+ and Ag shell replacement reaction of nano structures have been studied. A catalytic efficiency of the three kinds of OPDA coupling reaction was used as a model, a brush like structure of dumbbell shaped structure of nano structure between the catalytic efficiency of the bell, and the main active area exposed to Rh about.2. was successfully through a simple hydrothermal method Pd-Rh double metal core frame structure and core-shell structure were prepared by chemical etching selectivity, successfully obtained Pd-Rh double metal nano structure and nano box. Through a series of control experiments and detailed structural characterization, formation process and reaction mechanism of Pd-Rh nuclear structure and core-shell structure has been studied and revealed the presence of Rh3+ Pd inhibited the formation of twin crystal, making the Pd more stable single crystal cubic block is generated. The evaluation of Pd-Rh obtained by four different structures of catalytic coupling reaction using OPDA model Can, the catalytic efficiency is as follows: Pd-Rh nano Pd-Rh nano Pd-Rh frame box core framework Pd-Rh core-shell structure. The main difference of catalytic performance and hollow structure and the content of Rh.3. is closely related to the development of a simple one pot method three metal Au-Ag@Rh-Ag nano structure and preparation of double gold ring is Rh-Ag hollow spherical structure. By the time evolution analysis of the forming process were studied in detail, reveals the essence of the formation of nano structure and bell hollow structure are first formed core-shell structure Au-Ag and Ag nanoparticles, the catalytic coupling reaction of Ag and Rh3+ and shell replacement reaction to form the hollow structure of.OPDA showed that the photocatalytic activity of Au-Ag@Rh-Ag nano ring structure superior to the bimetallic Rh-Ag hollow spheres, differences in the catalytic performance could be attributed to the differences in the active area of Rh.4. for the first time to achieve a five fold twinned Pd nanowires to three Component change PtPdCu concave cube. Through detailed study of the reaction mechanism, change five fold twinned Pd nanowires to PtPdCu concave cubes through two steps: corrosion and Pt4+, twinned Pd nanowires Pd2+, Cu2+ coreduction, the twin Pd nanowires were mainly because of reduced corrosion the stability of crystal lattice stress caused by twinning. Showed that the electrocatalytic oxidation of formic acid, a concave PtPdCu cube with respect to the stability of commercial Pt/C catalyst has higher catalytic activity and better catalytic activity, the increase is mainly because the concave structure provides a step in a lot of atoms, and atoms in the presence of through direct oxidation of formic acid catalytic oxidation route more, the stability of the catalyst is improved.

【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1

【参考文献】