From atoms to crystallites: adsorption on oxide-supported metal particles
From atoms to crystallites: adsorption on oxide-supported metal particles
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DOI：
10.1039/b004091f
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发表时间：
2000
影响因子：
3.3
通讯作者：
M. Frank;M. Bäumer
中科院分区：
文献类型：
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作者：
M. Frank;M. Bäumer
金属团簇和纳米粒子的性质在基础研究和应用研究中受到越来越多的关注。这类结构在多相催化中的应用是一个尤为重要的领域。然而，关于吸附行为和催化活性对粒子尺寸的依赖性，只有有限的基础知识。在本文中，我们描述了一种基于模型体系来解决此类问题的方法，这些模型体系是在超高真空条件下通过金属气相沉积制备的。在金属基底上生长的一层薄氧化铝膜被用作载体。这具有一个优点，即可以应用扫描隧道显微镜和光电子能谱，而不会有任何充电问题。首先，涵盖钯、铑和铱沉积物的结构数据表明，通过利用动力学控制的成核和生长过程，可以获得广泛的粒子尺寸和形态。随后，我们讨论了简单分子在粒子上的吸附，例如一氧化碳和乙烯。这些利用红外光谱和光电子发射光谱进行的研究，说明了吸附和反应行为随粒子尺寸可能发生的变化。将要考虑的方面包括：在晶面和缺陷处的吸附、吸附位点随尺寸的变化、表面络合物的形成、分子的分解以及共吸附现象。
The properties of metal clusters and nanoparticles are attracting more and more attention in fundamental and applied research. The application of such structures in heterogeneous catalysis is a particularly important area. Nevertheless, there is only limited fundamental knowledge about the dependence of adsorption behaviour and catalytic activity on particle size. In this article, we describe an approach to tackle such questions on the basis of model systems which are prepared by metal vapour deposition under ultrahigh vacuum conditions. A thin alumina film grown on a metal substrate is used as support. This has the advantage that scanning tunneling microscopy and photoelectron spectroscopy can be applied without any charging problems. Firstly, structural data covering palladium, rhodium and iridium deposits demonstrate that a wide spectrum of particle sizes and morphologies may be obtained by taking advantage of kinetically controlled nucleation and growth processes. Subsequently, we discuss the adsorption of simple molecules on the particles, such as CO and ethene. These studies, which have been carried out using infrared and photoemission spectroscopy, illustrate possible variations in the adsorption and reaction behaviour as a function of particle size. Aspects which will be considered include: adsorption at facets and defects, size-dependent variation of adsorption sites, formation of surface complexes, decomposition of molecules as well as co-adsorption phenomena.