A Density Functional Theory Study of the Water−Gas Shift Reaction Promoted by Neutral, Anionic, and Cationic Gold Dimers

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• 作者：Yingying Wang ; Dongju Zhang ; Rongxiu Zhu ; Changqiao Zhang ; Chengbu Liu
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：April 16, 2009
• 年：2009
• 卷：113
• 期：15
• 页码：6215-6220
• 全文大小：237K
• 年卷期：v.113,no.15(April 16, 2009)
• ISSN：1932-7455

文摘

While nanoscale gold particles show exceptional catalytic activity toward the water−gas shift (WGS) reaction, not much is known about the detailed reaction mechanism and the influence of charge state of Au nanoparticles on the reactivity. We here report a systematic theoretical study by carrying out density functional theory calculations for the WGS reaction promoted by cationic, neutral, and anionic Au dimers, which represent three simplest prototypes of Au nanoparticles with different charge states. The reaction mechanism is explored along two possible entrances: one involves the complexes of the dimers with CO and the other is related to the complexes of the dimers with H₂O. In all cases, it is found that the catalytic cycle proceeds via the formate mechanism and involves two sequential elementary steps: the rupture of the O−H bond in H₂O and the formation of H₂ molecule. The calculated results show that the reaction mediated by Au₂⁺ is energetically most favorable compared to those promoted by Au₂ and Au₂⁻, indicating that the charge state of Au dimers plays an essential role for the catalyzed WGS. The present theoretical study rationalizes the early experimental findings well and enriches our understanding of the catalytic WGS by Au-based catalysts.