Hamburg 2001 – wissenschaftliches Programm
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O: Oberflächenphysik
O 28: Adsorption an Oberfl
ächen (III)
O 28.5: Vortrag
Donnerstag, 29. März 2001, 11:30–11:45, C
Atomic Oxygen below the Ag(111): A DFT-GGA STUDY — •Weixue Li1, Catherine Stampfl1,2, and Matthias Scheffler1 — 1Fritz-Haber-Institut der MPG, Berlin, Germany — 2Department of Physics and Astronomy, Northwestern University,USA
It is recognised that the high activity of Ag for industrially important processes such as the oxidation of ethylene to epoxide and partial oxidation of methanol to formaldehyde, is linked with the different oxygen species that form depending on the temperature and pressure, yet very little on a microscopic level and especially the interaction between various oxygen species is known. Using density-functional theory, atomic oxygen below the Ag(111) surface (subsurface, bulk-dissolved and bulk Ag2O) has been investigated. It has been found that atomic oxygen prefers to stay on-surface in fcc hollow sites at lower coverage, however it can distribute into subsurface sites at higher coverages. The energy diagram has been studied for oxygen moving from the bulk to the surface either by octahedral hole jumping or vacancy diffusion, and the associated energy barrier has been calculated. We discuss these results in detail which, together with experiments, provide valuable insights into the formation of catalytically active O species.