Enhancement of dissociation by metal-support interaction: reaction of NO on Rh supported by ceria films of controlled oxidation state

Highly oriented thin films of cerium oxide with variable ratio of Ce3+/Ce4 were grown on Ru(0 0 0 1) single crystal surface and loaded with a fixed, low coverage of Rh. The chemisorption of NO on the resulting model catalyst was studied by soft X-ray photoemission which yielded the relative quantit ies of N containing species on the surface as a function of temperature, an d by thermal desorption which yielded the relative yields of NO and Nz deso rbed. It is found that the ability of the reduced Ph clusters to dissociate NO depends upon the oxidation state of the ceria upon which it is deposite d, and for highly reduced ceria surfaces effectively 100% of Rh-adsorbed NO dissociates by 350 K. Possible causes of this surprising behavior are disc ussed. (C) 2001 Elsevier Science B.V. All rights reserved.