| Abstract
| - Low-coverage vanadia species (monomers, dimers, trimers, and one-dimensional vanadia rows) as well asvanadium oxide films of varying thickness supported on the metastable κ-Al2O3(001) surface are investigatedby density functional theory in combination with statistical thermodynamics. At low-vanadium chemicalpotentials and typical reducing conditions, species with V−O(3)−Al interface bonds are stable. These aggregatesare partially reduced with vanadium in the VIII oxidation state. This correlates with defect formation energyvalues for the initial removal of lattice oxygen in the range of 1.3−2.7 eV. As the length of the polymericspecies increases, the reduction energy decreases. We demonstrate that the support structure does affect thestructure of the model catalyst and the lattice oxygen bond strength. On the α-Al2O3(0001) surface, the onlystable low-coverage VOx species are dimers with V−O(2)−Al interface bonds and a defect formation energyof 2.8 eV. Reduction remains more facile for vanadia films on κ-Al2O3 than on α-Al2O3. The systematiclower values relate to the presence of tetrahedral sites that allow for significant lattice relaxation upon reduction.Using the oxygen defect formation energy as a reactivity descriptor, we discuss possible effects of the supportstructure and vanadia loading in Mars-van Krevelen-type oxidation reactions. We also analyze the influenceof the support structure on the interface vibrational modes.
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