NH3鈥揘O Coadsorption System on Pt(111). I. Structure of the Mixed Layer

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• 作者：Angelo Peronio ; Andrea Cepellotti ; Stefano Marchini ; Nasiba Abdurakhmanova ; Carlo Dri ; Cristina Africh ; Friedrich Esch ; Maria Peressi ; Giovanni Comelli
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：October 17, 2013
• 年：2013
• 卷：117
• 期：41
• 页码：21186-21195
• 全文大小：452K
• 年卷期：v.117,no.41(October 17, 2013)
• ISSN：1932-7455

文摘

In the selective catalytic reduction (SCR) process, nitrogen oxides are selectively transformed to N₂ by reductants such as ammonia. The specificity of this reaction on platinum-based catalysts was tentatively attributed to the formation of NH₃鈥揘O coadsorption complexes, as indicated by several surface science techniques. Here we combine scanning tunneling microscopy (STM) and density functional theory (DFT) calculations to characterize the NH₃鈥揘O complex at the atomic scale on the (111) surface of platinum, investigating the intermolecular interactions that tune the selectivity. In this first article, we analyze the structures that arise upon coadsorption of NH₃ and NO in terms of adsorption sites, geometry, energetics, and charge rearrangement. An ordered 2 脳 2 adlayer forms, where the two molecules are arranged in a configuration that maximizes mutual interactions. In this structure, NH₃ adsorbs on-top and NO on fcc-hollow sites, leading to a cohesional stabilization of the extended layer, calculated to be 0.29 eV/unit cell. The calculated vibrational energies of the coadsorption structure agree with the experimental values found in the literature.