Highly active supported gold catalysts frequently undergo substantial decrease in activity due to deactivation. The aim of this paper is to investigate a reversible inhibition phenomenon of the CO oxidation in an Au/Ce0.62Zr0.38O2 (Au/CZ) catalyst. The results of a systematic study of CO oxidation conditions (CO, O-2, and CO2) are discussed. By identifying CO2 as an Au/CZ poison using isotopic transient analysis ((CO)-C-13/(CO2)-C-12), we also investigate the origin of inhibition activity by transient and modulated infrared spectroscopy in DRIFT mode. Results demonstrate that carbonate species are formed by reaction of CO2 with reactive lattice oxygen at the metal-support interphase, which in turn inhibits the replenishment of the vacancies by molecular oxygen. A microkinetic model that accounts for the reaction mechanism and inhibition by CO2 is proposed. (C) 2014 Elsevier Inc. All rights reserved.