Reaction of NO on CeO2 and Rh/CeO2 thin films supported on α-Al2O3(0 0 0 1) and YSZ(1 0 0)

The adsorption and reaction of NO on ceria-based model catalysts was studied using a combination of temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Specific systems investigated included: CeO2(1 1 1), CeO2/α-Al2O3(0 0 0 1), CeO2/YSZ(1 0 0), Rh/α-Al2O3(0 0 0 1), Rh/CeO2/α-Al2O3(0 0 0 1), and Rh/CeO2/YSZ(1 0 0). The results of this study show that NO does not adsorb on fully oxidized CeO2 surfaces, while on partially reduced CeO2 surfaces NO adsorbs and dissociates. The reaction of NO on Rh supported on a ceria thin film was found to be similar to that for reaction on Rh/α-Al2O3(0 0 0 1) and Rh single crystals as long as the surface of the ceria film was fully oxidized. For Rh supported on partially reduced CeO2, adsorbed oxygen atoms, formed via dissociation of NO, migrated from the Rh to the ceria resulting in oxidation of the surface of the oxide film. The results of this study also demonstrate that interactions at the CeO2–YSZ(1 0 0) interface influence the extent of reduction of the ceria film, its thermal stability, and oxygen ion transport properties.