Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 90: Surface Dynamics: Experiments

O 90.3: Vortrag

Donnerstag, 23. März 2017, 11:00–11:15, WIL C107

On the reduction behavior of CeO2 (100) and (111) surfaces — •Johanna Hackl1, Tomas Duchoň2, David Nikolaus Müller1, Daniel Marius Gottlob3, Imtiaz Khan1, Stefan Cramm1, Slavomir Nemšák1, and Claus Michael Schneider11Peter Grünberg Institut PGI-6, Forschungszentrum Jülich, Germany — 2Department of Surface and Plasma Science, Charles University in Prague, Czech Republic — 3SPEC, CEA, CNRS, Université Paris Saclay, F-91191 Gif-sur-Yvette, France

Ceria has an ability to store and release oxygen by changing its oxidation state reversibly between CeO2 and Ce2O3. This gives ceria unique catalytic properties with many applications. DFT calculations predict a strong dependence of oxygen vacancy formation energies for different CeO2 surface orientations. Particularly the (100) surface is expected to have a lower oxygen vacancy formation energy than the (111) surface. In the present work CeO2 islands with (111) and (100) surfaces are simultaneously grown in-situ onto a Cu (111) substrate. The island formation is observed and characterized with low energy electron microscopy (LEEM) and micro-LEED. Using laterally resolved x-ray absorption spectroscopy (XAS) performed in a photoemission electron microscope (PEEM) the partial reduction of CeO2 to Ce2O3 in an H2 environment is observed in-situ and in real-time, directly comparing the reduction kinetics of the (111) and the (100) islands. Spectra of the Ce M5 edge show a more pronounced reduction state of cerium for the (100) islands. This behavior can be connected to a higher catalytic activity of CeO2 (100) for some types of the oxidizing reactions.

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