Water adsorption on metal surfaces: A general picture from density functional theory studies

We present a density functional theory study of water adsorption on metal surfaces. Prototype water structures including monomers, clusters, one-dimensional chains, and overlayers have been investigated in detail on a model system-a Pt(111) surface. The structure, energetics, and vibrational spectra are all obtained and compared with available experimental data. This study is further extended to other metal surfaces including Ru(0001), Rh(111), Pd(111), and Au(111), where adsorption of monomers and bilayers has been investigated. From these studies, a general picture has emerged regarding the water-surface interaction, the interwater hydrogen bonding, and the wetting order of the metal surfaces. The water-surface interaction is dominated by the lone pair-d band coupling through the surface states. It is rather localized in the contacting layer. A simultaneous enhancement of hydrogen bonding is generally observed in many adsorbed structures. Some special issues such as the partial dissociation of water on Ru(0001) and in the RT39 bilayer phase, the H-up and H-down conversion, and the quantum-mechanical motions of H atoms are also discussed.