Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 6: Catalysis
O 6.3: Hauptvortrag
Montag, 16. März 2015, 11:00–11:30, MA 043
CO oxidation over a Pt/Fe3O4 model catalyst: Watching Mars van Krevelen at work — •Gareth Parkinson — Institute of Applied Physics, TU Vienna, Vienna Austria
The nature of the active oxygen species during CO oxidation over supported metal catalysts is a long-standing and controversial issue. When metal oxides are utilized as the support, lattice O ions provide an additional pathway to CO2 formation via the so-called Mars-van Krevelen (MvK) mechanism. Here, we provide direct evidence of an active MvK process during CO oxidation over a Pt/Fe3O4 model catalyst. Atomically resolved scanning tunneling microscopy images reveal etching of the Fe3O4 support in the vicinity of Pt clusters following exposure to CO at 280 ∘C, with subsequent re-growth upon exposure to O2. The experimental data suggest CO oxidation is autocatalytic; extraction of the first O atom is most difficult energetically. The addition of H2 to the gas mixture accelerates the reaction because a similar, more efficient, MvK process roughens the surface through the formation of water.