Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 9: Surface Chemical Reactions and Heterogeneous Catalysis I

O 9.3: Talk

Monday, March 31, 2014, 11:00–11:15, PHY C 213

From qualitative to atomistic: First-principles kinetic modeling of Pd surface oxide reduction by CO — •Max J Hoffmann and Karsten Reuter — TU München, Germany

Obtaining detailed atomistic insight into oxide formation and reduction at metal surfaces is a key step to understand and ultimately engineer the function of these surfaces in a multitude of applications, not least in oxidation catalysis. On the modeling side, the analysis of kinetic measurements in terms of reaction rate laws is traditionally employed to extract qualitative information. First-principles calculations, on the other hand, describe the microscopic processes underlying the actual phase transition. First-principles microkinetic models offer the prospect to join these two strands and subject atomistic models to scrutiny against measured kinetic data. We illustrate this approach with first-principles kinetic Monte Carlo (1p-kMC) simulations of the reduction of a (√5× √5)R27^∘ surface oxide on Pd(100) in a CO atmosphere, and reference against kinetic data derived from X-ray photoelectron spectroscopy [1]. In full agreement with the experimental rate law analysis our atomistic simulations demonstrate that the reduction process can not occur via a homogeneous decomposition of the oxide phase. We overcome prevalent limitations to lattice-based 1p-kMC through a novel multi-lattice approach and present a mechanistic model that includes the full transformation from oxide to metal. This model fully rationalizes the measured data and proves that under the investigated gas-phase conditions the reduction is a phase-boundary controlled process. [1] V.R. Fernandes et al., Surf. Sci. (in press).