Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5424140 | Surface Science | 2010 | 10 Pages |
Abstract
In this work, the adsorption of several unsaturated hydrocarbon molecules on a stepped Pd(4Â 2Â 2) surface was studied. Using a periodic method based on the Density Functional Theory (DFT) formalism, different adsorption geometries for ethylene, three butene isomers (cis/trans-2-butene and 1-butene), acetylene and 2-butyne were investigated. The results were compared with those obtained for a free defect surface as Pd(1Â 1Â 1). The 1-butene is more stable on the free defect surface than on Pd(4Â 2Â 2). On the stepped surface, the olefins adsorb tilted towards the step and increases, in almost all the cases, the magnitude of the adsorption energy. Conversely, the 3-fold site is the most stable for the alkynes adsorption on the stepped surface, as it was found on Pd(1Â 1Â 1). The analysis of the dipole moment change indicate a charge transfer from the double bond of the olefin to the metallic surface, being higher for the Pd(1Â 1Â 1) surface. In case of the alkynes, an important back-donation is produced. Except the alkynes and the 1-butene molecule, the results show the preference of ethylene and cis/trans-2-butene to be adsorbed on the stepped surface. These observations are related with experimental catalytic results.
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Authors
Patricia G. Belelli, Ricardo M. Ferullo, Norberto J. Castellani,