Physicochemical characterization of Au/CeO ₂ solid. Part 1: The deposition-precipitation preparation method

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 °C). 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 °C for 1 h, the cations were reduced into Au ⁰. All the adsorptions were performed on solids treated under vacuum at 400 °C for 1 h. The adsorption of O ₂ at room temperature led to the formation of O ₂ ^- species. The adsorption of ¹⁷O-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.