Thermal rearrangement of oxygen adsorbed on oxygen-rich Ru(0001)

Atomic oxygen adsorbed on oxide domains terminating an oxidized Ru(0 0 0 1) surface is marked by its unusually high chemical reactivity as compared to other known oxygen species. We applied thermal desorption spectroscopy emp loying isotopic labeling to characterize the thermally driven incorporation of these oxygen atoms into the subsurface region. This O-ad --> O-sub conv ersion takes place in temperature region below 600 K where the pre-adsorbed oxygen becomes removed via the associative oxygen desorption. The efficien cy of the process depends linearly upon the occupation of the available ads orption sites. The conversion probability reaches a value of 0.25 per adato m. The rather low activation energy of 0.22 eV for this oxide mediated oxyg en incorporation promises a high efficiency of this reaction pathway in the high temperature regime. We propose a model based on a thermal transformat ion of RuxOy domains as the decisive step for the oxygen conversion. (C) 20 01 Elsevier Science B.V. All rights reserved.