The energies of the d-band centers on the individual Ru surface atoms are tabulated in Table . The resulting energies obtained for the interface sites are illustrated in Figure . In perfect agreement with the trend in the CO adsorption energy, there is essentially no change in the d-band center on the Ru-5a atom (middle layer site) (Table ). For the interface (i) site, the bridge site with the Ru-1a and Ru-5a atoms is rather unfavorable due to the low d-band center of the Ru-1a atom (-2.95 eV), which is in good agreement with the spontaneous shift of CO adsorbed on the interface (i) site to the middle layer site. Formation of an O-vacancy on the 1i site, directly underneath the edge of the Ru nanorod (Figure ), results in a significant upshift of the d-band center (Figure ), which goes along with stable adsorption on this site.