The adsorption of ethylene on the (110) surfaces of copper, silver and platinum: a DFT study

Density functional theory calculations have been performed for the adsorption of the ethylene molecule on the (110) surfaces of platinum, silver and copper. The cluster model approach has been used to model the metal surfaces. For each metal surface, four adsorption sites have been considered: the atop site, the shortbridge site, the longbridge site and the trough site, For each case, optimized geometries and adsorption energies have been calculated. Vibrational wavenumber calculations have been performed for the energetically more favored adsorption modes on each metal surface, The results show that on the (110) surfaces of copper and silver, the ethylene molecule adsorbs preferentially above the close-packed rows of metal atoms of the first layer, the atop adsorption site being slightly preferred over the shortbridge site on both metal surfaces. On the (110) surface of platinum a comparison between our results and the available experimental results suggests that beyond the thermodynamic factors, kinetic factors may play an important role on the adsorption process. The results also show that upon adsorption, both the degree of distortion of the ethylene molecule (relative to its gas phase geometry) and the binding strength to the metal surface increase in the order Ag < Cu much less than Pt. (C) 2002 Elsevier Science B.V, All rights reserved.