title: Interfaces of ionic liquids and transition metal surfaces-adsorption, growth, and thermal reactions of ultrathin [C1C1Im][Tf2N] films on metallic and oxidised Ni(111) surfaces.
abstract: Ultrathin films of the ionic liquid 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide ([C(1)C(1)Im][Tf(2)N]) were deposited on differently terminated Ni(111) single crystal surfaces. The initial wetting behaviour, the growth characteristics, the molecular arrangement at the interface, and thermal reactivity were investigated using angle-resolved X-ray photoelectron spectroscopy (ARXPS). On clean Ni(111), the initial growth occurs in a layer-by-layer mode. At submonolayer coverages up to at least 0.40 ML, a preferential arrangement of the IL ions in a bilayer structure, with the imidazolium cations in contact with the Ni surface atoms and the anions on top of the cation, is deduced. For higher coverages, a transition to a checkerboard-type arrangement occurs, which is most likely due to repulsive dipole-dipole interactions in the first layer. An overall preference for a checkerboard-type adsorption behaviour, i.e., anions and cations adsorbing next to each other, is found on the oxygen-precovered O(√3×√3)R30° Ni(111) surface. The thermal stability of adsorbed IL layers on Ni(111) and on a fully oxidised Ni(111) surface was studied by heating the layers to elevated temperatures. For clean Ni(111) reversible adsorption takes place. For the oxidised surface, however, only cation-related moieties desorb, starting at ~450 K, while anion-related signals remain on the surface up to much higher temperatures.
authors.affiliation: Lehrstuhl für Physikalische Chemie 2 and Erlangen Catalysis Resource Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Cremer
authors.forename: L
authors.initials: L
authors.lastname: Wibmer
authors.forename: S Krick
authors.initials: SK
authors.lastname: Calderón
authors.forename: A
authors.initials: A
authors.lastname: Deyko
authors.forename: F
authors.initials: F
authors.lastname: Maier
authors.forename: H-P
authors.initials: HP
authors.lastname: Steinrück