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O: Fachverband Oberflächenphysik
O 20: Surface Chemical Reactions and Heterogeneous Catalysis II
O 20.3: Talk
Monday, March 11, 2013, 16:30–16:45, H33
Bistability during CO oxidation at Pd(100): Atomistic origin from first-principles kinetic Monte Carlo simulations — •Max Hoffmann1, Matthias Scheffler2, and Karsten Reuter1 — 1TU München, Germany — 2Fritz-Haber-Institut, Berlin, Germany
Despite numerous studies on Palladium as a catalyst for CO oxidation the nature of the active surface remains debated. Focusing on the (100) surface the pristine metallic surface, an ultra-thin surface oxide, and thicker oxide layers were each suggested as the active surface. However, already the fact that the surface state depends sensibly on the reaction conditions challenges the quest to understand the catalytic function in terms of one surface state. Hendriksen et al. [1] even observed an overlap in stability conditions between a smooth metal surface and a rough oxidic surface state. The two surfaces states were not only found to coexist in different places of the surface, but the entire surface was stabilized in either of the two states at identical reaction conditions.
Using first-principles kinetic Monte Carlo models for the pristine Pd(100) surface and the PdO(101) surface oxide we can reproduce this bistability behavior and furthermore elucidate its atomistic origin. The predicted bistable regime spans stoichiometric and technological reaction conditions. In fact, within this range we find that both surface states exhibit very similar intrinsic reactivity, which puts further doubts on attempts to assign the catalytic function to one active state. [1] B.L.M. Hendriksen, S.C. Bobaru, and J.W.M. Frenken, Catalysis Today 105, 234 (2005).