Berlin 2015 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

O: Fachverband Oberflächenphysik

O 24: Catalysis: Structural Effects

O 24.11: Vortrag

Dienstag, 17. März 2015, 13:00–13:15, MA 144

In Situ Scanning Tunneling Microscopy of a Co(0001) Fischer-Tropsch model catalyst — •Martin Ehrensperger, Bernhard Böller, and Joost Wintterlin — Ludwig-Maximilians-Universität, Munich, Germany

The low temperature Fischer-Tropsch process produces long chain hydrocarbons over cobalt catalysts, starting from syngas, a mixture of hydrogen and carbon monoxide. Whereas the reaction mechanism has been intensively discussed, key questions about molecular processes and the structure of the catalyst surface remain unanswered. We have investigated a Co(0001) single crystal in 10 mbar of syngas at 493 K with in situ high temperature and high pressure scanning tunneling microscopy (STM). Methane was catalytically produced on the cobalt surface, as proven by quadrupole mass spectrometry. The STM data show a metallic surface. The surface was neither transformed into a surface oxide or carbide nor was it reconstructed. A reorganization of the surface morphology during reaction, as has often been postulated, was not observed under the applied experimental conditions. The STM images are in agreement with reversibly bound molecules that form a mobile mixed adsorbate layer on a flat metallic surface. Using ex situ x-ray photoelectron spectroscopy only low amounts of carbon and oxygen were detected.