Monolayer vanadia-titania catalysts: Growth, structure, and NO catalytic reduction from DFT calculations

The structure and reactivity of several microscopic models of oxidized VO _x (sub)monolayers on TiO ₂ anatase (001) were studied by first principles DFT calculations. Tetrahedrally coordinated monovanadate units were stable for low V-coverages, but were readily converted to divanadate units for higher coverages. High V-coverages (> 0.5 ML) could be obtained if the substrate acquired the structure of a bulk-terminated TiO ₂(001) surface. In this case, a stable polymeric structure could be formed, which was structurally related to a (100)-oriented vanadia layer. Investigation of the adsorption of NH ₃ and the catalytic reduction of NO on these catalysts showed that neither the support, nor tetrahedral submonolayer vanadate species grafted on it were able to protonate NH ₃. Both Lewis-acidic V and V-OH sites gave NO reduction barriers, which were compatible with the experiment. This is an abstract of a paper presented at the 229th ACS National Meeting (San Diego, CA 3/13-17/2005).