| 题名 | 贵金属基纳米材料结构调控及电催化性能 |
| 作者 | 刘卉 |
| 学位类别 | 博士 |
| 答辩日期 | 2014-04 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 杨军 |
| 关键词 | 贵金属 半导体 纳米材料 复合材料 纳米结构 电催化 |
| 其他题名 | Noble Metal Based Nanomaterials:Structure Tailoring and Electrocatalytic Property |
| 学位专业 | 化学工程 |
| 中文摘要 | 纳米颗粒的结构调控与催化应用是纳米科学技术研究的基本问题之一。具有超结构(核壳、空心、同质异聚、异质复合结构等)的贵金属基纳米颗粒在纳米体系中集成了性能差异明显的不同组分，并且在纳米尺度上各组分之间产生强相互耦合作用，因此贵金属基纳米材料不仅具有明显增强的本征性能，而且还表现出许多新特性，突破了单一结构材料性能的局限。贵金属基纳米材料独特的光、电、催化等性能使其在不同领域均表现出优异的应用前景。 本论文主要围绕贵金属基纳米材料的结构调控及电催化应用展开研究。介绍了核壳金属、空心和铃铛型金属、二元金属异聚体纳米材料和半导体-空心金属复合结构纳米材料等贵金属基纳米材料的制备、表征和电催化应用前景，并对贵金属基纳米材料中的电子耦合和晶格应变等可调控纳米材料物理和化学性质的特殊效应进行了阐述和解析，揭示了纳米材料中的一些新规律、新现象和新性能。所取得的主要的研究成果如下： 1. 核壳结构金属纳米材料：应用种子生长法，在油胺中制备得到了多种具有单一壳层的球形核壳结构或多个壳层的球形核-壳-壳结构纳米材料。通过改变内核金属及壳层金属前体的比例，可以制备得到具有特殊形状的核壳纳米材料。具有星星状的Ag-Pt核壳结构纳米材料，Pt的刺角状结构暴露出高化学活性的台阶原子和边角原子和更多高活性晶面，以及Ag内核给Pt带来的晶格应变及电子耦合等物理效应，共同影响着其化学催化反应中的活性。 2. 空心和铃铛型结构金属纳米材料：根据Ag在核壳结构纳米粒子中由内向外的扩散现象，发展了一个易于实现且具备普遍意义的制备空心结构和铃铛型结构贵金属纳米材料的方法。该方法进一步发展用以宏量制备活性炭负载的空心贵金属纳米材料，为炭载空心纳米催化剂的规模化生产提供了可能。与实心纳米材料相比，中空贵金属纳米材料的内表面可参与催化，具有较高的比表面积，在化学催化反应中具有更好的活性；而活性组分位于内核位置的铃铛型纳米材料，在多个化学反应共存的体系中，具有选择性催化性能。 3. 二元金属同质异聚结构纳米材料：根据Ag在核壳结构纳米粒子中由内向外的扩散现象，由Ag-Pt二元金属核壳结构纳米材料为前驱体，进一步制备了由Ag和中空贵金属Pt构成的异质二聚体纳米材料(Ag-hPt)。研究发现，具有相同金属成分而结构不同(Ag-Pt核壳结构和Ag-hPt异质二聚体结构)的纳米材料物化性质差异明显。该结果的重要意义就在于：（1）发展了一种通过纳米材料的结构转变，制备金属异质二聚体的方法；（2）为通过调控纳米材料的结构来修饰其物化性能提供了可行的思路。 4. 半导体Ag2S纳米材料：归纳整理得到了有机相中制备半导体Ag2S纳米晶体的融合-破碎-熟化机理。该机理适用于以有机相中的Ag离子或Ag纳米颗粒为前驱体与S粉反应制备Ag2S纳米晶体的反应。 5. Ag2S-hM复合结构纳米材料：将有机相中Ag与S反应制备半导体Ag2S纳米晶体，与Ag在核壳结构纳米粒子中由内向外的扩散制备空心贵金属纳米材料相结合，发展了一个普适性的方法制备Ag2S与空心或铃铛型贵金属构成的复合结构纳米材料。因Ag2S与Pt界面处存在着较强的电子耦合效应，与Ag2S复合的Pt基纳米材料在甲醇氧化电极反应中，表现出优良的催化活性。 |
| 英文摘要 | Mastery of the structure of nanomaterials enables control of their properties to enhance their performance for a given application. There has been increasing interest devoted towards the development of hybrid nanomaterials, for example, core-shell structure, hollow structure, bimetallic heterodimers and semiconductor-metal nanocomposites, that consist of different classes of materials with coherent interfaces. This type of nanostructure combines materials with distinctly different physical and chemical properties to yield a unique hybrid nanosystem with multifunctional capabilities and tunable or enhanced properties that may not be attainable otherwise. Noble metal based nanomaterials with unique optical, electronic, catalytic properties will have great potential for new or enhanced application prospects in different field. In this thesis, we report our experimental observations on the noble metal based nanomaterials with core-shell, hollow, cage-bell, or composite nanostructures. We aim at the controllable synthesis, structure tailoring, and electrocatalytic applications of these noble metal based nanomaterials. A number of characterization techniques, including transmission electron microscopy (TEM), high-resolution TEM (HRTEM), high-angle annular dark-field scanning TEM (HAADF-STEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX) will be used to characterize the morphology, structure, and chemical composition of the formed nanomaterials, and to address the following critical issues: i) the generic property of the strategy developed for the fabrication of the noble metal based nanomaterials; ii) the mechanism accounting for the structure tailoring of the nanomaterials; iii) the electronic coupling and lateral strain effect in the noble metal based nanomaterials, and iv) the electrocatalytic properties toward methanol oxidation and oxygen reduction reactions. The main achievements are outlined as following: 1. Core-shell structured nanomaterials. A number of noble metal based core-shell nanoparticles with single or multi-shells were synthesized using the seed-mediated growth method in oleylamine. In particular, bimetallic Ag-Pt with stellated morphology could be fabricated via the competing growth of Pt on the multiply twinned Ag nano seeds. In comparison with the commercial Pt/C catalysts, the stellated Pt surface, with an abundance of steps, edges, corner atoms, and {111} facets, is highly effective for the oxygen reduction reaction. The mechanistic understanding may provide new opportunities to design and fabricate heterogeneous nanostructures with interesting physicochemical properties. 2. Hollow and cage-bell structured nanomaterials. A facile generic approach, which based on the inside-out diffusion of Ag in core-shell structures, for the fabrication of hollow or cage-bell noble metal nanomaterials was developed. In this stragegy, core-shell Ag-M nanoparticles or core-shell-shell MA-Ag-MB nanoparticles are first prepared in an organic solvent, followed by the removal of Ag from the core or the inner shell with BSPP. Hollow Pt nanoparticles with intact stellation morphology were also synthesized by removal the Ag core from stellated Ag-Pt nanoparticles. A variation of this protocol was used to removal the Ag core from carbon-supported Pt containing metal core-shell nanoparticles by sodium sulfide (Na2S) and sodium chloride (NaCl), resulting in carbon-supported hollow Pt-containing metal nanoparticles. The hollow and CBS nanoparticles prepared as such have relatively lower densities, which usually translate to a higher surface area than their solid counterparts; hence, a higher degree of metal utilization can be expected. In particular, CBS Pt-Ru nanoparticles were found to exhibit outstanding methanol tolerance for the cathode reaction of the direct methanol fuel cell. 3. Bimetallic Ag-hollow Pt heterodimers. The synthesis of bimetallic heterodimers consisting of Ag and hollow |
| 语种 | 中文 |
| 公开日期 | 2015-07-08 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/15521]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 刘卉. 贵金属基纳米材料结构调控及电催化性能[D]. 中国科学院研究生院. 2014. |
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