Abstract: Au/CoCeOx catalysts were prepared by a deposition-precipitation method. Au chemical states were controlled by varying the temperature of pretreatment in an oxygen-containing atmosphere. The catalysts were characterized by powderX-raydiffraction, high-resolution transmission electron microscopy, temperature-programmed reduction, andX-rayphotoelectron spectroscopy. The catalytic performance for CO oxidation was investigated at ambient temperature. It was found that the conversion of CO increased with increasing amount of Au+ in the catalyst, and thus the cationic gold (Au+) was considered the main active species. Addition of water vapor to the feed gas promoted CO conversion to some degree, but the catalytic performance decreased rapidly due to the disproportionation of Au+ to Au3+and Au0, particularly for the catalyst that contained relatively large amounts of Au+ species.

Key words: cobalt oxide, ceria, composite oxide, gold, chemical state, carbon monoxide, low temperature oxidation