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O: Fachverband Oberflächenphysik

O 60: Poster Session IV (Solid/liquid interfaces; Semiconductors; Oxides and insulators; Graphene; Plasmonics and nanooptics; Electronic Structure; Surface chemical reactions; Heterogeneous catalysis)

O 60.110: Poster

Mittwoch, 16. März 2011, 17:30–21:00, P4

Photoinduced CO oxidation by association with defect-bound atomic oxygen on thin MgO films — •Philipp Giese, Harald Kirsch, Christian Frischkorn, and Martin Wolf — Fritz-Haber-Institut, Abt. Physikalische Chemie, Faradayweg 4-6, 14195 Berlin

As a prototype system for chemistry of defect-bound atomic oxygen on MgO, the CO oxidation has been studied. Atomic oxygen species were generated by photoinduced N₂O dissociation on thin MgO films grown on Ag(100). CO oxidation was studied as a function of photon exposure and initial CO coverage. The reaction products were studied by temperature programmed desorption spectroscopy (TPD). Carbon monoxide was co-adsorbed on films with atomic oxygen (10¹³ atoms/cm²) at 20 K. If the coadsorbate is irradiated with UV light (5 eV), a CO₂ desorption peak at about 300 K appears, accompanied by a depletion of the atomic oxygen. The amount of CO oxidation increases with photon exposure and stops when the atomic oxygen is completely depleted. However, this process does not happen by irradiation of CO without previous atomic oxygen preparation, thus a direct reaction between the adsorbed CO molecules can be excluded. In addition, without UV excitation of the coadsorbate no reaction occurs either, revealing that the activation barrier for the CO oxidation on MgO surfaces is too high for a thermally activated reaction.