Interactions of Hydrogen and Carbon Monoxide on Pd–Au Bimetallic Surfaces

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• 作者：Wen-Yueh Yu ; Gregory M. Mullen ; C. Buddie Mullins
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：January 30, 2014
• 年：2014
• 卷：118
• 期：4
• 页码：2129-2137
• 全文大小：443K
• ISSN：1932-7455

文摘

Pd鈥揂u bimetallic catalysts have shown potential applications in numerous heterogeneous reactions in which hydrogen and CO act as reactants, intermediates, or products. A fundamental understanding of the interplay between coadsorbed H and CO on the Pd鈥揂u surface is necessary for improving the understanding of catalytic performance. In this study, the interactions of hydrogen and CO with Pd/Au(111) model surfaces were investigated by temperature-programmed desorption (TPD) and molecular beam scattering (MBS) experiments, carried out under ultra-high-vacuum conditions. Our results reveal that CO adsorbs competitively on the hydrogen-precovered Pd鈥揂u surface, causing surface H adatoms to diffuse away from stronger-binding sites (e.g., Pd(111)-like islands) to weaker-binding sites (e.g., Pd鈥揂u alloy sites and subsurface), as evidenced by a shift of the H₂ desorption feature to lower temperatures in TPD measurements. Additionally, evolution of H₂ was observed when a CO molecular beam was impinged onto the H-precovered Pd鈥揂u surface, providing direct evidence that CO induces recombinative desorption of H adatoms. The presence of H adatoms on the Pd鈥揂u surface was found to decrease the initial sticking probability of CO during MBS experiments but had little influence on CO desorption during subsequent TPD measurements.