A density functional study of the adsorption of methane-thiol on the (111) surfaces of the Ni-group metals: I. Molecular and dissociative adsorption
- Author(s)
- David Karhanek, Tomas Bucko, Juergen Hafner
- Abstract
The molecular and dissociative adsorption of methane-thiol (CH3SH) in the high-coverage limit on the (111) surfaces of the Ni-group metals has been investigated using ab initio density functional techniques. In molecular form, methane-thiol is bound to the surface only by weak polarization-induced forces in a slightly asymmetric configuration with the C-S axis tilted by 35-60 degrees relative to the surface normal. On Ni and Pd surfaces the S atom occupies a position close to a bridge site; on Pt it is located close to an on-top position. The length of the S-H bond is only slightly stretched relative to its value in the gas phase, indicating only a very modest degree of activation for dehydrogenation. A strong covalent adsorbate/substrate bond is formed upon adsorption of a methane-thiolate (CH3S) radical. On Ni(111) in the energetically most favorable configuration the S atom occupies a position in a threefold hollow, slightly displaced towards a bridge site. The C-S axis is tilted by about 35 degrees across the bridge. On Pd(111) and Pt(111) the S atom of thiolate occupies a position between a hollow and a bridge site, with the C-S axis tilted even more strongly across a neighboring threefold hollow. On all three surfaces our calculations demonstrate the existence of multiple metastable adsorption configurations, including upright CH3S bound in the center of a threefold hollow as reported in some earlier studies. Dehydrogenation of the adsorbed methane-thiol to form co-adsorbed methane-thiolate and atomic hydrogen is an exothermic process, which is not activated on Ni(111) but activated on Pd(111) and Pt(111).
- Organisation(s)
- Computational Materials Physics
- Journal
- Journal of Physics: Condensed Matter
- Volume
- 22
- No. of pages
- 14
- ISSN
- 0953-8984
- DOI
- https://doi.org/10.1088/0953-8984/22/26/265005
- Publication date
- 2010
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 1030 Physics, Astronomy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/9715d828-3482-4652-8467-dedf8d69a41a