Metal-support interaction in Pd/CeO2 catalysts .2. Ceria textural effects

Two Pd catalysts supported on ceria of high (HS) and low (LS) surface area have been investigated. Palladium morphologies and palladium accessibility were studied by CO adsorption using FTIR spectroscopy. Methanol and carbon monoxide were used as probes to assess the surface reduction state and the surface oxygen vacancies of the ceria. Well dispersed palladium on the Pd/ceria (HS) catalyst was found to encapsulate irreversibly into ceria for reduction temperatures higher than 623 K. For less dispersed palladium on Pd/ceria (LS) catalysts, decoration of palladium crystallites by ceria was observed for temperatures as low as 673 K. Reversibility of the decoration upon reoxidation at 873 K was found to depend on the Pd faces, CO adsorption on (111)faces being more easily recovered than CO adsorption on (100) faces and edges.