Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 15: Heterogeneous catalysis I
O 15.9: Vortrag
Montag, 26. März 2012, 18:00–18:15, MA 042
When atomic-scale resolution is not enough: Spatial effects in in-situ model catalyst studies — •Sebastian Matera1,2 and Karsten Reuter1 — 1TU München — 2Fritz-Haber-Institut der MPG
A central goal in in-situ studies of defined model catalysts has been to obtain (at best) equally resolved spectro- or microscopic information as has been established in UHV surface science. With this focus possible heat and mass transport limitations in the ambient environments have not received much attention. We investigate such effects with our newly developed first-principles based multi-scale modeling approach integrating kinetic Monte Carlo simulations into a fluid dynamical treatment [1]. We consider two limiting cases for flow geometries in modern in-situ reaction chambers: i) the gas approaches the single crystal from the side, ii) the flow direction is perpendicular to the surface. Using the CO oxidation at RuO2(110) as a showcase we obtain a strong coupling between surface chemistry and mass, heat and momentum transfer. This generates substantial variation in gas-phase pressures and temperature between the inlet and the catalyst surface. In particular for case i) we obtain large lateral changes in surface composition across the catalyst surface. This prevents the aspired direct relation between measured activity and defined catalyst structure, and therewith underscores the importance of carefully designed reactor geometries in in-situ studies. [1] S. Matera and K. Reuter, Catal. Lett. 133, 156 (2009); Phys. Rev. B 82, 085446 (2010).