SO2 Adsorption on Pt(111) and Oxygen Precovered Pt(111): A Combined Infrared Reflection Absorption Spectroscopy and Density Functional Study

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• 作者：Markus Happel ; Nicola Luckas ; Francesc Vin虄es ; Marek Sobota ; Mathias Laurin ; Andreas Go虉rling ; Jo虉rg Libuda
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：January 20, 2011
• 年：2011
• 卷：115
• 期：2
• 页码：479-491
• 全文大小：532K
• 年卷期：v.115,no.2(January 20, 2011)
• ISSN：1932-7455

文摘

We have performed a combined molecular beam (MB)/infrared reflection absorption spectroscopy (IRAS) and density functional (DF) study on the adsorption of sulfur dioxide (SO₂) on clean and oxygen precovered Pt(111). The adsorbate species formed as a function of coverage and their structural and chemical transformations upon subsequent annealing were followed systematically by IRAS. It is shown that, upon adsorption on clean Pt(111) at 100 K, SO₂ adsorbs molecularly in two geometries. Calculations reveal that these geometries correspond to molecules oriented parallel or perpendicular to the surface. Upon heating up to 250 K, conversion between the two species occurs with the fraction of upright standing SO₂ increasing with increasing temperature. Between 300 and 350 K, all surface species desorb without decomposition. This is in sharp contrast to oxygen precovered Pt(111), on which, in addition to the formation of molecular SO₂ in flat and perpendicular geometry, partial formation of SO₃ is observed even at low temperature. Upon annealing, part of the surface SO_x species are converted to SO₃ and, subsequently, to SO₄, which remains stable up to 450 K. DF calculations on the stable adsorption structures of SO_x species provide characteristic IR frequencies, which can be correlated with the present IRAS data and photoelectron spectroscopy (PES) data previously published.¹