Au/ZnO catalysts were prepared by the deposition-precipitation (DP) method. Effects of calcination temperature and pretreatment conditions on the structure and the catalytic performance of Au/ZnO catalysts were investigated for CO oxidation. For the samples calcined in 533～773 K, no diffraction peak of gold species could be detected by XRD measurement. Transmission electron microscopy (TEM) observation revealed that the particle sizes of gold were 2.7, 3.5 and 3.7 nm respectively, for the catalysts calcined at 533, 673 and 773 K. Temperature-programmed reduction (H₂-TPR) measurements further indicated that the pre-reduced gold species could be reoxidized at room temperature and the redox property of the catalyst could be enhanced through pretreatment with flowing air. However, its high redox properties still remained after several redox cycles. The result of CO oxidation on the catalytic behavior of the Au/ZnO catalysts was strongly influenced by the particle size and the surface area of the catalyst. The highly dispersed Au/ZnO catalyst with larger surface area and the least particle size can be prepared by the deposition-precipitation calcined at 533 K, resulting in the most promising activity and stability for CO oxidation. 95% CO conversion could be achieved after 300 h time-on-stream even though the feed gas contained 3.1 vol.% of water vapor.

Key words: Au/ZnO, CO oxidation, calcination temperature, pretreatment