Department of Physics, Nanoscience Center, P. O. Box 35, University of Jyväskylä, FIN-40014 Jyväskylä, Finland.
Phys Chem Chem Phys. 2010 Feb 21;12(7):1483-92. doi: 10.1039/b917723j. Epub 2010 Jan 6.
We have investigated the adsorption of O(2) on Au(n) clusters (n = 1-6) supported by an ultra thin (3ML)MgO(001) film on Mo metal via density functional theory calculations. On thin films, these small clusters have chain like structures and their electronic states resemble 1D quantum well states. The Au(1-3) are charged by one electron whereas the larger Au(4-6) get two electrons from the substrate. This is confirmed both by the symmetries of the HOMO and LUMO states of the clusters and the Bader charge analysis. In contrast to the O(2) adsorption on gas-phase clusters, the adsorption energy of O(2) molecule does not show pronounced oscillations as a function of cluster size. The O(2) is activated (i.e. the O-O bond is elongated and the molecule is charged) in contact with all the cluster sizes. O(2) activation and strong binding is also observed on bare MgO/Mo, whereas the molecule interacts only weakly with bulk MgO. The activation of O(2) is mainly due to charge transferred from the support. The relevance of these results for catalytic activity of small thin-film-supported clusters is discussed.
我们通过密度泛函理论计算研究了在 Mo 金属上的超薄（3ML）MgO(001) 薄膜上支撑的 Au(n) 团簇（n = 1-6）对 O(2)的吸附。在薄膜上，这些小团簇具有链状结构，其电子态类似于 1D 量子阱态。Au(1-3) 通过一个电子被带电，而较大的 Au(4-6)从衬底获得两个电子。这一点通过团簇的 HOMO 和 LUMO 态的对称性和 Bader 电荷分析得到证实。与气相团簇上的 O(2)吸附相反，O(2)分子的吸附能作为团簇尺寸的函数并不表现出明显的振荡。在与所有团簇尺寸接触时，O(2)分子被激活（即 O-O 键被拉长且分子带电）。在裸 MgO/Mo 上也观察到 O(2)的激活和强结合，而分子与块状 MgO 仅弱相互作用。O(2)的激活主要是由于来自载体的电荷转移。讨论了这些结果对小薄膜支撑团簇催化活性的相关性。
