Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 73: Nanostructures at Surfaces: Metals, Oxides and Semiconductors III

O 73.3: Vortrag

Mittwoch, 22. März 2017, 11:00–11:15, REC/PHY C213

Direct visualization of oxidation and reduction of FeO/Au(111) studied by time-resolved STM — •Yijia Li and Jeppe Lauritsen — Gustav Wieds Vej 14, 8000 Aarhus C

Iron oxide (FeO) is of significant interest due to its catalytical reactivity in several reactions such as CO oxidation and water-gas shift reaction, and as precursors for the formation of Fe-based Fischer Tropsch catalysts. The nature and the reaction mechanism of the active sites are fundamental questions to heterogeneous catalysis. Therefore, scanning tunneling microscopy (STM) which is capable to identify the active sites at atomic scale level is employed. Here we studied the oxidation and reduction of FeO islands on Au(111) by oxygen and hydrogen using in-situ STM measurements. It is found that the edges of FeO islands play an essential role for incorporating additional oxygen atoms and O adatoms form triangular bright features assigned to adatom defect loops. The excess O atoms are in different coordination with lattice O atoms and can be removed by molecular hydrogen dosing. On the other hand, upon hydrogen exposures FeO islands are reduced with hydroxyls formed initially on the surface and vacancy defect loops created later on. These vacancy defects can be refilled by oxygen dosing. The reversible appearance of FeO islands depending on whether it is in oxidizing or reducing atmosphere are observed dynamically by time-resolved STM movies and help to distinguish the active sites in redox reactions.