In these calculations, we considered CO adsorption on the flat top layer (site Ru-1c in Figure ), denoted as 'top layer terrace site', on the edge site at the top layer (sites formed by Ru atoms 7a and 8a in Figure ), denoted as 'top layer edge site', on a site in the middle layer at the side of the Ru nanorod (mostly site Ru-5a in Figure ), denoted as 'middle layer site', and on two sites at the bottom layer, in the interface region. These two interface sites, which differ by their distances to the ZrO2 support, are formed either by Ru atoms 1a and 5a or by Ru atoms 2a and 6a in Figure . For adsorption on the 'interface (i)' site, CO may move also to a hollow site formed by Ru atoms 1a, 4a, and 5a, or a bridge site formed by Ru atoms 4a and 5a during optimization. For adsorption on the 'interface (ii)' site, CO may also move to a hollow site formed by Ru atoms 2a, 3a, and 6a, or to a bridge site formed by Ru atoms 2a and 3a.