Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 62: Surface Reactions and Heterogeneous Catalysis 1
O 62.3: Vortrag
Donnerstag, 8. September 2022, 11:00–11:15, H4
Atomic steps as active sites in the Co-catalyzed Fischer-Tropsch synthesis: Evidence from an operando STM study on a stepped model catalyst — •Katharina Golder and Joost Wintterlin — Ludwig-Maximilians-Universität München, Germany
Atomic steps are often assumed to represent the active sites on the surface of a heterogeneous catalyst. This assumption is based on turnover data that display a certain scaling of the activity with the particle sizes of the catalysts. However, this evidence is indirect and often controversial. We have recently shown that the activity of a Co(0001) single crystal surface in the Fischer-Tropsch synthesis of hydrocarbons is proportional to the density of atomic steps. This is a quite direct evidence for the activity of atomic steps, but it was obtained for a flat model system. Here we present results of investigations on a Co(10115) surface that has a similar step density as the Co particles of the industrial Fischer-Tropsch catalyst. The experiments were performed with a scanning tunneling microscope (STM) at a syngas (2H2+CO) pressure of ∼1 bar and a temperature of 503 K. Hydrocarbon products were detected by a special gas chromatograph (GC). The STM data show that the morphology of the stepped surface is stable under operando conditions. The activity measured by GC is considerably higher than that of the Co(0001) sample. It is close to the activities reported for supported Co catalysts, a result that bridges the materials gap between model systems and the industrial Fischer-Tropsch catalysts.