Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 72: Oxide and Insulator Surfaces: Adsorption I

O 72.9: Vortrag

Mittwoch, 22. März 2017, 12:30–12:45, WIL C107

Structure determination of the (7x√3)rect phase on Ag(111) — •Regina Wyrwich¹, Travis Jones², Wolfgang Moritz¹, Sebastian Günther³, Martin Ehrensperger¹, Sebastian Böcklein¹, Tevfik Menteş⁴, Andrea Locatelli⁴, Miguel Niño⁴, Simone Piccinin⁵, Axel Knop-Gericke², Robert Schlögl², and Joost Wintterlin¹ — ¹Ludwig-Maximilians-Universität München, Germany — ²Fritz-Haber-Institut Berlin, Germany — ³Technische Universität München, Germany — ⁴Sincrotrone Trieste S.C.p.A., Italy — ⁵CNR-IOM Demicritos Trieste, Italy

The so-called electrophilic oxygen’, characterized in XPS by an O 1s energy of 530.7 eV, is considered to be responsible for the Ag-catalyzed epoxidation of ethylene, a large-scale industrial process. The chemical nature of this oxygen species has remained unclear, but is certainly different from the known oxygen-induced reconstructions on the silver surface. A (7x√3)rect phase on Ag(111) incorporates this oxygen species, but all attempts to find a structure model have failed for a long time. Recent DFT calculations revealed that only covalently bound oxygen species exhibit O 1s energies in this region, which led to the consideration of oxygen bound to sulfur, a common contamination in ethylene. Based on a model proposed by DFT we have now solved the structure by a LEED I(V) analysis. The structure involves a reconstruction consisting of alternating rows of Ag triangles and SO₄ units along the √3 direction of Ag(111). The Ag atoms are found in three different geometries, on hcp, fcc, and bridge position. The findings shed new light on the already complex Ag/O system.