Study on Catalytic and Electronic Properties of Deposited Alloy Clusters onto a Substrate

基底上沉积合金团簇的催化和电子性能研究

基本信息

批准号：
13640582
负责人：
NAKAJIMA Atsushi
金额：
$ 2.43万
依托单位：
Keio University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

This study has been focused on adsorption reactivity and electronic property of alloy clusters as a microscopic model of catalytic activity, because finite system of metal/alloy clusters having 2-100 atoms can be regarded as a minimum catalytic site. A couple of binary clusters were chosen in the viewpoint of useful catalytic activity ; (a) alloy clusters of niobium (Nb)-aluminum (Al), gold (Au)-palladium (Pd), and gold (Au)-zinc (Zn), (b) semiconductor clusters of lanthanide/transition-metal-silicon (Si), and (c) metal oxides of vanadium oxide and cobalt oxide. Furthermore, the soft-landing technique was successfully established to design catalytic surface with the deposition of alloy clusters synthesized in gas phase.The binary clusters were generated by the two-rod laser vaporization, and their electronic properties were studied with photoelectron spectroscopy. The results summarized as follows ; (a) Adsorption reactivity of the alloy clusters was correlated well with geometries rather than electronic structures. In Au-Pd clusters, interestingly, an electron promotion occurs from 4d to 5s orbital in the Pd atom. (b) In semiconductor binary clusters, adsorption reactivity provides the information on reaction sites, and metal-encapsulated silicon clusters were discovered. (c) In metal oxide clusters, geometric phase transition was drastically induced by the mixing of oxygen atoms into metal clusters, although oxygen atoms having less than 10% concentration could be treated as impurity atoms. Photoelectron spectroscopy and mass spectrometry for reactivity have revealed fundamental insight on composite effects in alloy/binary clusters, of which the principles can lead to design new catalyst with the soft-landing technique.

本研究重点关注合金团簇的吸附反应性和电子性质作为催化活性的微观模型，因为具有2-100个原子的金属/合金团簇的有限系统可以被视为最小的催化位点。考虑到有用的催化活性，选择了几个二元簇； (a) 铌 (Nb)-铝 (Al)、金 (Au)- 钯 (Pd) 和金 (Au)-锌 (Zn) 合金簇，(b) 镧系元素/过渡金属-硅半导体簇(Si)、(c)氧化钒、氧化钴的金属氧化物。此外，成功建立了软着陆技术，通过沉积气相合成的合金团簇来设计催化表面。通过双棒激光汽化产生二元团簇，并用光电子能谱研究了它们的电子性能。结果总结如下； (a) 合金簇的吸附反应性与几何形状而非电子结构密切相关。有趣的是，在 Au-Pd 团簇中，Pd 原子中的 4d 至 5s 轨道发生电子提升。（b）在半导体二元团簇中，吸附反应性提供了反应位点的信息，并且发现了金属封装的硅团簇。 (c)在金属氧化物团簇中，尽管氧原子浓度低于10%可以被视为杂质原子，但由于氧原子混合到金属团簇中，几何相变被剧烈诱导。反应性的光电子能谱和质谱分析揭示了合金/二元团簇中复合效应的基本见解，其原理可以引导使用软着陆技术设计新的催化剂。