A comparative theoretical study of Au, Ag and Cu adsorption on TiO2(110) rutile surfaces

The adsorption properties of Au, Ag and Cu on TiO2 (110) rutile surfaces are examined using density functional theory slab calculations within the generalized gradient approximation. We consider five and four different adsorption sites for the metal adsorption on the stoichiometric and reduced surfaces, respectively. The metal-oxide bonding mechanism and the reactivity of metal atoms are also discussed based on the analyses of local density of states and charge density differences. This Study predicts that An atoms prefer to adsorb at the fourfold hollow site over the fivefold-coordinated Ti(5c) and in-plane and bridging O(2c) atoms with the adsorption energy of approximate to0.6 eV. At this site, it appears that the covalent and ionic interactions with the Ti(5c) and the O(2c), respectively, contribute synergistically to the An adsorption. At a neutral F-0(s) center on the reduced Surface, An binds to the surface via a rather strong ionic interaction with Surrounding sixfold-coordinated Ti(6c) atoms, and its binding energy is much larger than to the stoichiometric surface. On the other hand, Ag and Cu strongly interact with the surface bridging O(2c) atoms, and the site between two bridging O(2c) atoms is predicted to be energetically the most favorable adsorption site. The adsorption energies of Ag and Cu at the B site are estimated to be approximate to1.2 eV and approximate to1.8 eV, respectively. Unlike Au, the interaction of Ag and Cu with a vacancy defect is much weaker than with the stoichiometric surface.