Abstract: A nanosized 2.5%Au/ZnO catalyst was prepared using the coprecipitation method at low temperature. The deactivation mechanism of the catalyst stored in ambient air was investigated using scanning transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The deactivation of the catalyst was partially reversible, and two factors interrelated the deactivation. One was the agglomeration of nanosized gold particles, which caused the irreversible deactivation. The other was the accumulation of carbonates on the catalyst surface, leading to the reversible deactivation. The carbonates could be decomposed when the deactivated catalyst was calcined at high temperature.

Key words: nanoparticle, gold, zinc oxide, supported catalyst, carbon monoxide oxidation, deactivation mechanism, carbonate