Forschung im HLRN-Verbund 2011

9Figure 1: Ceria supported VO and CH 3 OH.tion), monomeric vanadia species remain in the +5oxidation state, whereas Ce ions are reduced fromCe(f0) 4+ to Ce(f1) 3+ . Reduction of the ceria supportis the key factor determining the superior activityof ceria supported vanadia catalysts. The resultsobtained from DFT+U and hybrid approaches(HSE) show that both these methods are suitable,with the former being computationally less costly.To this end, in this project the structure, electronicand vibrational properties and the reactivityof VO n /CeO 2 (111) model catalysts by meansof DFT+U and hybrid functionals calculations weresuccessfully investigated [3]. Under an oxygenambient pressure at a given temperature thermodynamicallystable monomeric and polymeric adspeciesare identified.The normal vibrational modes for the VO n adspeciesand their IR activity are described. The reactivityof these systems using reactivity descriptors,the oxygen defect formation and the hydrogenationreaction energies are evaluated. Furtheron the oxidation of methanol to formaldehyde, examiningthe role of the ceria support and the roleof the VO n structures, is investigated.The first-principles spin-polarized calculationsare performed using density functional theory withdifferent exchange-correlation energy functionals,such as PBE corrected by the Hubbard parameterU (PBE+U) and the hybrid functional HSE. Weemploy the Vienna Ab-Initio Simulation Package(VASP) [4], which is one of the most efficient implementationsof the plane-wave based methodsused for periodic solid state systems, especially forthose containing d and f electrons.More Information1. M. Baron, H. Abbott, O. Bondarchuk, D. Stacchiola,A. Uhl, S. Shaikhutdinov, H.-J. Freund,C. Popa, M. V. Ganduglia-Pirovano, J. Sauer,’Resolving the Atomic Structure of VanadiaMonolayer Catalysts: Monomers, Trimers andOligomers on Ceria’, Angew. Chem. Int. Ed.,48, 1, 20092. M. V. Ganduglia-Pirovano, C. Popa, J. Sauer, H.Abbott, A. Uhl, M. Baron, D. Stacchiola, O. Bondarchuk,S. Shaikhutdinov, H.-J. Freund, ’TheRole of Ceria in Oxidative Dehydrogenation onSupported Vanadia Catalysts’, J. Am. Chem.Soc., 132, 2345, 20103. C. Popa, M. V. Ganduglia-Pirovano, J. Sauer,’Periodic density functional theory study of VO nadsorbed on CeO 2 (111) surfaces’, J. Phys.Chem. C, 2011, accepted4. http://cms.mpi.univie.ac.at/vaspFundingDFG Collaborative Research Centre 546”Struktur, Dynamik und Reaktivität vonÜbergangsmetalloxid-Aggregaten”Chemie