Interaction of CO with Rh Supported on Stoichiometric and Reduced CeO2(111) andCeO2(100) Surfaces

The structure and reactivity of Rh films supported on thesurface of a CeO2single crystal were studied using Augerelectron spectroscopy (AES) and temperature-programmeddesorption (TPD). Rhodium films deposited from the vapor phasewere found to grow via the nucleation of three-dimensionalparticles at a sample temperature of 300 K. Annealing of the Rhfilms resulted in further agglomeration of the metal layer.Carbon monoxide TPD spectra obtained from Rh supported onoxygen-annealed CeO2(111) and CeO2(100) substrates weresimilar to those obtained from the low-index planes of Rh singlecrystals, with the exception that a small fraction of the CO(ca. 2%) was oxidized to CO2. In contrast, a newhigh-temperature CO desorption state was observed in the TPDspectra obtained from Rh supportedon partially reduced CeO2surfaces.