| AVS 57th International Symposium & Exhibition | |
| In Situ Microscopy and Spectroscopy Topical Conference | Tuesday Sessions |
| Session IS+SS-TuM |
| Session: | In Situ Spectroscopy – Interfacial Chemistry/Catalysis |
| Presenter: | A. Shavorskiy, Lawrence Berkeley National Laboratory |
| Authors: | A. Shavorskiy, Lawrence Berkeley National Laboratory T. Eralp, The University of Reading, UK F. Aksoy, Lawrence Berkeley National Laboratory Z. Liu, Lawrence Berkeley National Laboratory H. Bluhm, Lawrence Berkeley National Laboratory A. Cornish, The University of Reading, UK D. Watson, The University of Reading, UK K. Schulte, Lund University, Sweden J.N. Andersen, Lund University, Sweden G. Held, The University of Reading, UK |
| Correspondent: | Click to Email |
Many important catalytic reactions take place at the interface between a solid catalyst and a solution, in particular aqueous solutions play a crucial role in all biological systems. The presence of the solvent at the solution-catalyst interface can dramatically change the chemical surface properties and, therefore, the entire catalytic process. Although surface science has been very successful in studying gas-surface reactions, most UHV-based surface science techniques cannot be applied to the co-adsorption of solvent and reactant molecules of important reaction systems because the solvent desorption temperature in UHV is too low to allow co-adsorption at realistic reaction temperatures. In order to keep significant amounts of water adsorbed near room temperature pressures of up to 1 mbar are needed for most metals. Recently, ambient pressure X-ray photoelectron spectroscopy (APPES), has become available for studying these systems at close-to-real conditions [Bluh09].
For the experiments reported here we chose to study the influence of water on the adsorption of glycine and alanine on Pt[111[ and Pt[110[ in UHV and on Cu[110[ at near-ambient pressure. The comparison between results obtained in UHV and at AP allows us to reveal importance of the reaction conditions (in particular reaction pressure and temperature) on the chemical composition and stability of the molecular adlayers on metals. It also bridges the pressure gap in studies of such kind of bio-related systems. Our results show an absence of any noticeable changes in the chemical composition of the aminoacids on Pt[111[ and Pt[110[ when co-adsorbed with water in UHV. On the other hand we observed clear decrease of the amino acid desorption temperature and a change of the desorption pathway (compared to UHV [Barl05]) on Cu[110[ when the H2O pressure is increased above 10-5 mbar. Two possible mechanisms of lowering the stability of the amino acids in the presence of water are discussed: (a) oxidation of the amino acid by OH or O or (b) hydrogenation of the anionic amino acid followed by desorption of the less stable intact form [Jone06].
[Bluh09] H. Bluhm. J. El. Spec. Rel. Phen., doi:10.1016/j.elspec.2009.08.006, 2009.
[Jone06] G. Jones et al Surf. Sci. 600 (2006) 1924.
[Barl05] S. M. Barlow et al Surf. Sci 590 (2005) 243.
[Ande07] K. Andersson et al. J. Phys. Chem. C 111 (2007) 14493.