Vanadium Oxide Oligomers and Ordered Monolayers Supported on CeO2(111): Structure and Stability Studied by Density Functional Theory

Structures and stabilities of vanadium oxide oligomers as well as two candidate structures for a monolayer on the CeO2(111) surface have been studied by density functional theory, employing a genetic algorithm to determine the global energy minimum structures. These ceria-supported structures have predominantly 4-fold coordinated V5+ ions with V=O groups in common. The agglomeration of VO2 clusters deposited on the surface is a strongly exothermic process, particularly when ring structures with three or six VO2 units are formed that are commensurate with the close-packed surface-terminating oxygen layer. The VO2 and V2O5 monolayers feature larger coordination numbers (5, 6) of V and contain V atoms without V=O groups. Relative to oligomers, VO2 and V2O5 monolayer structures with and without together with the fact that flat monolayer clusters are preferred to bilayer clusters, indicates the preference for a complete two-dimensional wetting of the ceria support.