Controlling Hydrogen Activation, Spillover, and Desorption with Pd–Au Single-Atom Alloys

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• 作者：Felicia R. Lucci ; Matthew T. Darby ; Michael F. G. Mattera ; Christopher J. Ivimey ; Andrew J. Therrien ; Angelos Michaelides ; Michail Stamatakis ; E. Charles H. Sykes
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2016
• 出版时间：February 4, 2016
• 年：2016
• 卷：7
• 期：3
• 页码：480-485
• 全文大小：387K
• ISSN：1948-7185

文摘

Key descriptors in hydrogenation catalysis are the nature of the active sites for H₂ activation and the adsorption strength of H atoms to the surface. Using atomically resolved model systems of dilute Pd–Au surface alloys and density functional theory calculations, we determine key aspects of H₂ activation, diffusion, and desorption. Pd monomers in a Au(111) surface catalyze the dissociative adsorption of H₂ at temperatures as low as 85 K, a process previously expected to require contiguous Pd sites. H atoms preside at the Pd sites and desorb at temperatures significantly lower than those from pure Pd (175 versus 310 K). This facile H₂ activation and weak adsorption of H atom intermediates are key requirements for active and selective hydrogenations. We also demonstrate weak adsorption of CO, a common catalyst poison, which is sufficient to force H atoms to spill over from Pd to Au sites, as evidenced by low-temperature H₂ desorption.