Adsorption of the formate species on copper surfaces: a DFT study

• Published in: Surface science 1999-07, Vol.432 (3), p.279-290
• Main Authors: Gomes, J.R.B, Gomes, J.A.N.F
• Format: Article
• Language: English
• Subjects: Adsorption and desorption kinetics; evaporation and condensation; Chemisorption; Condensed matter: structure, mechanical and thermal properties; Copper; DFT; Dynamics; vibrations; Exact sciences and technology; HCO 2; Heterogeneous catalysis; Physics; Solid-fluid interfaces; Surface and interface dynamics and vibrations; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theoretical study; Vibrations of adsorbed molecules
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(99)00605-6

The density functional theory and the cluster model approach have been applied to study the interaction of the formate species with the copper (100), (110) and (111) surfaces. The short-bridge, long-bridge and cross-bridge sites of the copper surface have been modelled by Cu 7 and Cu 8 metal clusters after checking the validity of the results against those obtained with much larger clusters. The results show that the formate species is stabilized strongly on the short-bridge site of the surfaces considered and this is in agreement with available experimental data. For adsorption on the short-bridge site, and for the three surfaces considered, the Cu surfO is close to 2.02 Å, the CO bond length is 1.26 Å and the OCO angle is 128°. On this adsorption site, formate is bridge-bonded with the two oxygens almost in a top position on two copper atoms. For the long-bridge site, the oxygen atoms of the adsorbate are not located above the two copper atoms. The two OC bonds are equivalent when formate is adsorbed on these two sites. On the cross-bridge site, the formate species is bonded to the surface in a monodentate conformation. The two OC bonds are different with two clearly different bond lengths. The difference is larger for adsorption on the Cu (100) surface. In this case, the bond lengths are typical of a bond order of one and two. The bonding to the surface is essentially ionic, and the total charge in the adsorbate is 0.75 ±0.05 e, approximately.