Preparation and characterization of a model system for the study of monolayers and multilayers of vanadia supported on titania

A model system for the study of structural and chemical properties of monolayers and multilayers of vanadium oxide immobilized on titania is presented. Investigation of the planar oxide-oxide interface by XP, UV and IS spectroscopy indicated that vanadium immobilized by a single impregnation step exists as an incomplete heterogeneous layer containing well dispersed V⁴⁺ species. Increase of the vanadia loading by multiple impregnations led to vanadia agglomerates with higher apparent oxidation state of the vanadium. TD spectroscopy with O₂ and CO₂ as probe molecules revealed that the chemical reactivity of the vanadia surface species depends on their structure. The surface containing well-dispersed vanadia species exchanged oxygen more easily and showed pronounced interactions with CO₂.