Physicochemical characterization of Au/CeO_2 solid. Part 1: The deposition-precipitation preparation method

摘要

Au/CeO_2 (4 wt.% gold) solid was prepared using the deposition-precipitation method. The deposition of gold on ceria did not affect its specific surface area (122 m~2 g~(-1)/400 ℃). The average diameter of gold particles obtained was estimated to be equal to 3.9 nm. Moreover, 60% of the gold was in the form of nanoparticles with a size ranging between 3 and 4 nm. 80% of the gold in the nanoparticles was in the metallic form Au~0 and 20% was present as Au~+. These latter cations interact directly with the O~(2-) anions of CeO_2. When evacuated at 400 ℃ for 1 h, the cations were reduced into Au~0. All the adsorptions were performed on solids treated under vacuum at 400 ℃ for 1 h. The adsorption of O_2 at room temperature led to the formation of O_2~- species. The adsorption of ~(17)O-enriched molecular oxygen demonstrated that the two oxygen atoms in O_2~- are equivalent. When CO was introduced, it reacted with the O_2~- of the support to give CO_2~-. When NO_2, NO or N_2O were added at room temperature, they decomposed to form adsorbed O_2~- species at the surface of the solid.