The oxidation of CO by gaseous 1802 was investigated on electropromoted Pt films deposited on Y2O3-stabilized ZrO2 (YSZ) and on nanodispersed Pt/YSZ catalysts under high vacuum and under atmospheric pressure conditions. For both catalyst systems and in both cases it was found that the temperature dependence of the catalytic oxidation rate can be correlated directly with the corresponding TPD spectra of O-18(2), (OO)-O-16-O-18, and O-16(2) and that lattice oxygen plays a key role in the oxidation reaction, acting both as a reactant and as a sacrificial promoter. For both systems the results confirm the sacrificial promoter model of electrochemical promotion and metal-support interactions with O2--conducting supports. This mechanism contains as limiting cases the promoted Langmuir-Hinshelwood and the Mars-van Krevelen mechanisms, which predominate at low and high temperatures, respectively. (C) 2004 Elsevier Inc. All rights reserved.