Thermal rearrangement of oxygen adsorbed on oxygen-rich Ru(0 0 0 1)

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 employing isotopic labeling to characterize the thermally driven incorporation of these oxygen atoms into the subsurface region. This Oad→Osub conversion takes place in temperature region below 600 K where the pre-adsorbed oxygen becomes removed via the associative oxygen desorption. The efficiency of the process depends linearly upon the occupation of the available adsorption sites. The conversion probability reaches a value of 0.25 per adatom. The rather low activation energy of 0.22 eV for this oxide mediated oxygen incorporation promises a high efficiency of this reaction pathway in the high temperature regime. We propose a model based on a thermal transformation of RuxOy domains as the decisive step for the oxygen conversion.