were calculated for the pure support ZrO2 and for the Ru/ZrO2 model system. These oxygen atoms were found to be most favorable for O-vacancy formation in the respective layers. The resulting energies are displayed in Figure (see also Table and), together with the distance between O-vacancy and the nearest Ru atom (blue squares). Different from the Ovacancy in the topmost layer (site 1i, see Figure ), the influence of the Ru-nanorod on the vacancy formation energy is very small (-0.4 eV at site iii) or negligible (other sites) (Figure ). Hence, the Ru-induced lowering of the O-vacancy formation energy is essentially limited to O-vacancy generation in the topmost layer, with direct contact to the Ru nanorod. The slight stabilization of the O-vacancy in the third layer (site iii) seems to be related to a higher charge transfer (see below), indicating that in addition to the distance to the nearest Ru atom also other, local effects can play a role, though the latter is by far the most dominant factor. This will be discussed further in the next paragraph.