While for the pure Pt(111) surface the center of the d-band is located at -2.07 eV, surface alloying with Ag leads to an upshift of the center of the d-band on the Pt atoms in the topmost layer, to -1.49 eV for Pt1Ag8, to -1.65 eV for Pt2Ag7 and to -1.72 eV for Pt3Ag6 (see Table ). According to the d-band model, this upshift should correspond to an increase in CO adsorption energy on the Pt ensembles, which fully agrees with experimental findings. Increasing the size of the Pt ensembles in the overlayer downshifts the center of the d-band and brings it closer to that in pure Pt(111). Though not very big, these shifts are significant when comparing with shifts reported for structural effects, e.g., for steps or for lattice strain effects. The catalytic activity, in turn, would depend on the optimum adsorption strength for a given reaction. As an example, for the oxygen reduction reaction (ORR) the optimum oxygen adsorption strength was reported to be at slightly weaker bonding than on Pt(111). Hence, in that case the Pt1Ag8/Pt(111) sites would be less active than Pt(111) sites.