Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 86: Heterogeneous catalysis I
O 86.6: Vortrag
Donnerstag, 17. März 2011, 17:45–18:00, WIL B122
Molecular-level understanding of the water-gas-shift reaction on Rh(111) — •Matteo Maestri1,3 and Karsten Reuter2,3 — 1Politecnico di Milano, Italy — 2Technische Universität München, Germany — 3Fritz-Haber-Institut der MPG, Berlin, Germany
The identification of the reaction mechanism is the center piece for the atomic-scale understanding of a catalytic process and requires the kinetic assessment of all potential steps at the surface. At this level, processes of technological interest involve a large number of potential reactions and, due to the huge computational costs, are still largely outside the capabilities of a full density-functional theory (DFT) analysis. To this end we propose a hierarchical approach for the identification of prevalent reaction mechanisms by efficiently combining DFT and semi-empirical methods [1]. The obtained computationally undemanding barrier estimates serve as initial approximate input for the identification of the prevalent paths that subsequently require refined kinetic parameters from explicit DFT calculations. As showcase we consider the water-gas-shift (WGS) and reverse reactions on Rh(111). Our results reveal that CO follows different chemical paths depending on the operating conditions. A carboxyl pathway is preferred for the consumption of CO, while its formation proceeds through the direct decomposition of carbon dioxide. These insights into the atomic-scale mechanism allow for a new understanding of the WGS system in full agreement with existing experimental evidence. [1] M.Maestri and K. Reuter, Angew. Chemie Int. Ed., 2010, in press.