Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 3: Oberfl
ächenreaktionen I

O 3.3: Vortrag

Montag, 24. März 2003, 11:45–12:00, HSZ/02

CO Adsorption and Oxidation at the V ₂ O ₅ (010) Surface with and without Oxygen Vacancies: ab-initio DFT Cluster Models — •Christoph Friedrich and Klaus Hermann — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin

While the catalytic behavior of vanadium oxide has been known and utilized for a long time many microscopic details of oxidation reactions at vanadium oxide surfaces are still not fully understood. Experiments indicate that CO binds weakly at the clean V₂O₅ surface but can adsorb strongly at oxygen vacancies of the reduced surface. In addition, there is experimental evidence that local electronic excitations at the clean V₂O₅ surface can facilitate CO oxidation involving surface oxygen. In this work we use embedded cluster models as large as V₁₀O₃₁H₁₂ together with DFT methods to examine the effect of local electronic excitations and the influence of O vacancies on the interaction of CO with the V₂O₅ (010) surface. The electronic structure of the surface in its ground state is modelled by the singlet cluster while local excitations are introduced by singlet to triplet excitations. Our calculations show, in qualitative agreement with experiment, that local excitations of the V₂O₅ surface can promote oxidation of CO while oxygen vacancies do not facilitate this reaction. Molecular CO adsorption can, however, take place at oxygen vacancy sites.

This work is supported by SFB 546 No-dqTransitionmetalaggregatesNo-dq.