Cooperative H2 Activation at Ag Cluster/胃-Al2O3(110) Dual Perimeter Sites: A Density Functional Theory Study

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• 作者：Pussana Hirunsit ; Ken-ichi Shimizu ; Ryoichi Fukuda ; Supawadee Namuangruk ; Yoshitada Morikawa ; Masahiro Ehara
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：April 17, 2014
• 年：2014
• 卷：118
• 期：15
• 页码：7996-8006
• 全文大小：790K
• 年卷期：v.118,no.15(April 17, 2014)
• ISSN：1932-7455

文摘

H₂ dissociation by Ag clusters supported on the 胃-Al₂O₃(110) surface has been investigated using density functional theory calculations. The crucial role of the dual perimeter site of Ag cluster and the surface oxygen (O) site of the alumina support is demonstrated with three theoretical models: anchored cluster, isolated cluster, and anchored cluster on hydroxylated alumina. The heterolytic cleavage of H₂ at the silver鈥揳lumina interface, yielding Ag鈥揌^{未鈭?/sup> and O鈥揌未+, is thermodynamically and kinetically preferred compared with H₂ cleavage at two Ag atomic sites on top of the Al₂O₃-supported Ag cluster and the homolytic cleavage of H₂ on the isolated Ag cluster. The hydroxylation at the O site of the alumina reduces the H₂ dissociation activity, which indicates that the interfacial bare O site is indispensible. It is concluded that the interfacial cooperative mechanism between the Ag cluster and Lewis acid鈥揵ase pair site (bare Al鈥揙 site) is essentially relevant for the H₂ activation over Ag-loaded Al₂O₃ catalysts.}