For CO adsorption on the partly or fully Ag film covered Pt [116] and Pd(111) surfaces, the rather inert Ag mainly acts as blocking species, at least during CO adsorption at room temperature and higher. Upon CO adsorption at liquid N2 temperatures, CO desorption from Ag/Pt is observed in a small peak at 130 K [116] (see Figure ). Note that this is much higher than CO desorption from Ag For Ag/Pd , neither desorption at 130 K nor a distinct higher-temperature CO desorption peak (at 550 K) were observed, indicating that similar PdAg configurations either do not exist or do not lead to a stabilization of the CO-Pd bond. The absence of CO adsorption on Ag monolayer films on Pd at temperatures above 90 K, as observed in this study, suggests a weak Ag-Pd interaction, and also agrees with recent calculations indicating that the Ag valence band in 1-2 ML Ag films is only weakly perturbed by the underlying Pd substrate . It also agrees with calculations, which show a significantly lower CO adsorption energy on monolayer Ag/Pd(111) systems than on Ag/Pt [114,117].