For CO adsorption at the interface (ii) site (Ru-2a, Ru-6a), the CO adsorption energy is generally smaller than for adsorption at the middle layer and the interface (i) sites and more comparable to adsorption on the top layer sites. Similar as in the case of O-vacancies directly underneath the Ru nanorod (section 3.2.1), we attribute this mainly to larger positive contributions from COad induced deformation energies and differences in the interface energies, which result in a lower CO adsorption energy. This is reflected also by the larger difference between CO binding energy and CO adsorption energy for adsorption on the interface (ii) site