铜基、铂基纳米材料的可控合成及其催化性能研究

发布时间：2018-03-05 09:57

本文选题：超细氧化铜　切入点：合金纳米晶　出处：《清华大学》2015年博士论文　论文类型：学位论文

【摘要】：纳米材料在催化领域的应用已成为当前纳米科学研究的热点之一。纳米材料的催化性质与其形貌、尺寸、组成等因素密切相关。因此,纳米合成技术的发展及对催化剂构效关系本质的深入理解有助于新型高效催化剂的开发。本论文以铜基、铂基纳米材料(氧化铜、铜单质、金属铂、铂基双金属)为研究对象,围绕当前纳米催化剂合成存在的挑战,以液相合成法为手段,探索了具有特殊形貌催化剂的制备方法、形成机制,并对其结构与性能之间的相关性进行了深入研究。纳米材料催化性能研究发现,高指数晶面比低指数晶面具有更好的催化活性。但目前具有高指数晶面纳米晶的研究主要集中于贵金属,对多组分且对称性较低的金属氧化物,报道较少。本论文第一部分工作选择了具有单斜结构的氧化铜为研究对象,利用油胺分子的特异性吸附,制备暴露高指数晶面的超细氧化铜纳米棒。该材料在催化苯乙烯环氧化生成环氧苯乙烷具有很高的活性和选择性。该方法可为合成其他高指数晶面的氧化物提供新思路。目前,无机类富勒烯结构纳米材料的制备仅限于自身具有层状结构的无机材料。由于缺少在三维空间折叠的驱动力,利用非层状材料合成类富勒烯结构一直是研究的难点。本论文第二部分工作利用十六胺在水中形成胶束,在组装成类富勒烯结构的同时,原位还原金属离子,成功制备了类富勒烯状的Pt-Cu合金纳米晶。通过球差电镜分析发现,该结构的形成是通过两种机制实现的:一种是大角度弯曲形成折线,通过产生孪晶界释放弯曲过程中产生的应力。另一种是在折线处,通过晶格膨胀或收缩引发小角度弯曲,从而形成曲线。这些结构缺陷的存在使该材料在电催化氧化甲醇乙醇,环加成反应均表现出比商业催化剂更优异的性质。高度支化的纳米材料,由于具有较大的比表面积,丰富的边、角和台阶原子,使得该材料在催化领域展现出良好的应用前景。然而大多数贵金属具有高度对称的面心立方结构,所以制备具有各向异性结构的纳米晶成为了一大挑战。本论文最后一部分工作利用界面合成的方法,以十六胺和水界面处形成的多枝状胶束为模板,制备出了具有规则结构的超细多枝状Pt纳米晶。通过对不同反应时间的观察,发现取向连接是形成该结构的主要原因。这种表面支化的材料在对氯硝基苯选择性还原反应中体现出较好的催化活性。
[Abstract]:The application of nanomaterials in the field of catalysis has become one of the hotspots in nanoscience research. The catalytic properties of nanomaterials are closely related to their morphology, size, composition and other factors. The development of nanosynthesis technology and the understanding of the nature of catalyst structure-activity relationship are helpful to the development of novel and high-efficient catalysts. In this thesis, copper based and platinum based nanomaterials (copper oxide, copper oxide, platinum, platin-based bimetallic) are studied. According to the existing challenges in the synthesis of nanocrystalline catalysts, the preparation and formation mechanism of catalysts with special morphology were explored by the method of liquid phase synthesis. The correlation between structure and performance was studied. The catalytic properties of nanomaterials were found. The high index crystal face has better catalytic activity than the low index crystal mask, but the research of nanocrystalline with high index crystal surface is mainly focused on precious metal, and it is more suitable for metal oxides with low symmetry and multicomponent. In the first part of this thesis, copper oxide with monoclinic structure was selected as the research object, and the specific adsorption of oleamine molecule was used. Ultrafine copper oxide nanorods exposed to high index crystal planes were prepared. The materials have high activity and selectivity in the catalytic epoxidation of styrene to epoxy-phenylethane. This method can provide a new idea for the synthesis of other oxides with high index crystal faces. The preparation of inorganic fullerene-like nanomaterials is limited to inorganic materials with layered structure. The synthesis of fullerene-like structure from non-layered materials has been a difficult point. In the second part of this thesis, 16 amines were used to form micelles in water, and the structure of fullerenes was assembled and metal ions were reduced in situ. Fullerene-like nanocrystals of Pt-Cu alloys were successfully prepared. By spherical differential electron microscopy analysis, it was found that the formation of the structure was realized by two mechanisms: one was the large angle bending to form a broken line, The curve is formed by creating twinning boundaries to release the stresses generated during bending. The other is to form curves at the broken line by lattice expansion or contraction, resulting in small angle bending. The existence of these structural defects causes the material to electrocatalyze the oxidation of methanol and ethanol. The cycloaddition reactions exhibit better properties than commercial catalysts. Highly branched nanomaterials, due to their large specific surface area, rich edge, angle and step atoms, However, most of the precious metals have a highly symmetrical face-centered cubic structure. Therefore, the preparation of anisotropic nanocrystals has become a challenge. In the last part of this thesis, the multi-dendritic micelles formed at the interface of 16 amine and water were used as templates in the last part of this thesis. Ultrafine multi-branched Pt nanocrystals with regular structure were prepared. It was found that the orientation connection was the main reason for the formation of the structure, and the surface branched material showed good catalytic activity in the selective reduction of p-chloronitrobenzene (p-chloronitrobenzene).
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1;O643.36

【相似文献】