Metal hybrid nanoparticles for catalytic organic and photochemical transformations.
Metal hybrid nanoparticles for catalytic organic and photochemical transformations.
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DOI：
10.1021/ar500411s
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发表时间：
2015-03
影响因子：
18.3
通讯作者：
Hyunjoon Song
中科院分区：
文献类型：
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作者：
Hyunjoon Song
为了理解多相催化反应，模型催化剂如单晶表面已经被广泛研究了几十年。然而，实际上促进反应的催化体系是三维的，通常具有多种组分，包括活性金属纳米颗粒和金属氧化物载体。另一方面，随着纳米化学的迅速发展和应用到各个领域，许多研究人员开始讨论纳米化学对多相催化的影响。多组分金属杂化纳米粒子的结构与实际催化剂非常接近，其均匀可控的形貌适合于详细研究结构与催化性能之间的关系。在这个帐户中，我们介绍了四种典型的结构的金属混合纳米粒子，可用于进行催化有机和光化学反应。金属@二氧化硅（或金属氧化物）蛋黄壳纳米颗粒（其中金属核存在于由薄二氧化硅（或金属氧化物）壳包围的内部空隙中）由于二氧化硅层对金属核的几何保护而表现出极高的热稳定性和化学稳定性。金属核的形态和中空壳的孔密度被精确地调节，以优化反应物的反应活性和扩散速率。金属@金属氧化物核-壳纳米颗粒和倒置结构（其中核支撑充当活性表面的壳）表现出高活性，对反应物和产物没有扩散障碍。这些纳米结构被用作各种有机和气相反应的有效催化剂，包括氢转移，铃木偶联和蒸汽甲烷重整。相反，蛋黄和核壳结构，一个不对称的安排不同的域产生偏心哑铃和倾斜杆。每种成分的大范围增加了多种功能，如磁性和光吸收，以催化性能。特别是，金属-半导体混合纳米结构可以表现为有效的可见光催化剂的析氢和CO氧化反应。由于反应物的大比表面积和高局部浓度，双壳空心结构比填充纳米粒子具有更高的反应活性。将等离子体激元Au探针引入到Pt-CdS双壳层中空颗粒中有助于通过单颗粒测量监测在单个颗粒表面上发生的光催化制氢。使用定义明确的金属混合纳米催化剂与各种原位光谱工具的催化研究的进一步发展提供了一种最大化催化性能的手段，直到它们与均相催化剂相当或优于均相催化剂，这可能对工业应用具有有用的影响。
In order to understand heterogeneous catalytic reactions, model catalysts such as a single crystalline surface have been widely studied for many decades. However, catalytic systems that actually advance the reactions are three-dimensional and commonly have multiple components including active metal nanoparticles and metal oxide supports. On the other hand, as nanochemistry has rapidly been developed and been applied to various fields, many researchers have begun to discuss the impact of nanochemistry on heterogeneous catalysis. Metal hybrid nanoparticles bearing multiple components are structurally very close to the actual catalysts, and their uniform and controllable morphology is suitable for investigating the relationship between the structure and the catalytic properties in detail. In this Account, we introduce four typical structures of metal hybrid nanoparticles that can be used to conduct catalytic organic and photochemical reactions. Metal@silica (or metal oxide) yolk-shell nanoparticles, in which metal cores exist in internal voids surrounded by thin silica (or metal oxide) shells, exhibited extremely high thermal and chemical stability due to the geometrical protection of the silica layers against the metal cores. The morphology of the metal cores and the pore density of the hollow shells were precisely adjusted to optimize the reaction activity and diffusion rates of the reactants. Metal@metal oxide core-shell nanoparticles and inverted structures, where the cores supported the shells serving an active surface, exhibited high activity with no diffusion barriers for the reactants and products. These nanostructures were used as effective catalysts for various organic and gas-phase reactions, including hydrogen transfer, Suzuki coupling, and steam methane reforming. In contrast to the yolk- and core-shell structures, an asymmetric arrangement of distinct domains generated acentric dumbbells and tipped rods. A large domain of each component added multiple functions, such as magnetism and light absorption, to the catalytic properties. In particular, metal-semiconductor hybrid nanostructures could behave as effective visible photocatalysts for hydrogen evolution and CO oxidation reactions. Resulting from the large surface area and high local concentration of the reactants, a double-shell hollow structure showed reaction activities higher than those of filled nanoparticles. The introduction of plasmonic Au probes into the Pt-CdS double-shell hollow particles facilitated the monitoring of photocatalytic hydrogen generation that occurred on an individual particle surface by single particle measurements. Further development of catalysis research using well-defined metal hybrid nanocatalysts with various in situ spectroscopic tools provides a means of maximizing catalytic performances until they are comparable to or better than those of homogeneous catalysts, and this would have possibly useful implications for industrial applications.