ICP Instituto de Catalisis y Petroquímica

We model monomeric vanadia adspecies on the CeO(2)(111) surface of composition VO(n)center dot Ce(12)O(24) (n = -1, 0, ... , 4) using the DFT+U approach and statistical thermodynamics. At low oxygen pressure (10(-9) atm), VO(4) is the most stable species below 400 K; in the 400-900 K range; VO(2) is stable; and above 900 K, VO becomes stable. In all of these systems, vanadium is stabilized in the +5 oxidation state. Using the energies of hydrogenation and oxygen vacancy formation as reactivity descriptors, we predict an enhanced reactivity of the vanadia/ceria system in Mars-van Krevelen-type oxidation reactions. At the orgin of this support effect is the ability of ceria to stabilize reduced states by accommodating electrons in localized f states. We also calculate the frequencies of the normal vibrat onal modes of the supported VO(n) species and their infrared intensity.