Dresden 2006 – scientific programme
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O: Oberflächenphysik
O 24: Adsorption III
O 24.3: Talk
Tuesday, March 28, 2006, 16:15–16:30, TRE Phys
A first-principles statistical mechanics investigation of the stability of a thin surface oxide in reactive environments — •Jutta Rogal, Karsten Reuter, and Matthias Scheffler — Fritz-Haber-Institut, Faradayweg 4-6, D-14195 Berlin, Germany
Sufficiently oxygen-rich environmental conditions lead to the formation of oxides at metal surfaces. This could for example happen under the oxygen-rich conditions of high-pressure oxidation catalysis, and oxide films forming in the reactive environment could then actuate the catalytic behavior that is traditionally ascribed to the pristine transition metal substrate. At more noble metals with their rather unstable bulk oxides, the focus is here primarily on the relevance of so-called “surface oxides”, i.e. nanometer thin oxide films.
Using the CO oxidation over Pd(100) as example, we investigate the composition and stability of this model catalyst in the reactive environment with a first-principles statistical mechanics approach. In a first step we consider the surface in constrained thermodynamic equilibrium with an O2 and CO gas phase. Under ambient gas phase conditions representative of technological CO oxidation catalysis the known (√5 × √5)R27∘ surface oxide structure on Pd(100) is then indeed the most stable structure. In a second refined step we explicitly consider the effect of the reaction kinetics on the stability of this surface oxide through first-principles kinetic Monte Carlo simulations. Our simulations indicate that the stability of this surface oxide depends intricately on the ratio of reactant partial pressures in the environment.