Understanding the detailed structure and nature of the active site is a central paradigm in modern molecular-level catalysis. For transition metal (TM) based heterogeneous catalysts, this has motivated extensive studies of low-index single-crystal model catalysts, initially under controlled ultrahigh vacuum (UHV) conditions and increasingly at higher pressures. Notwithstanding, despite significant advances in in situ methods for surface characterization, even qualitative structural and compositional properties remain to date surprisingly unclear for the technological near-ambient regime. There is e.g. little doubt that late TMs like Pd oxidize under ambient oxygen pressures. What remains unclear, though, is whether or to what degree the presence of the other reactant, CO in the case of CO oxidation, inhibits oxide formation under steady-state operation.We contribute to this context with a predictive-quality multi-scale modeling approach that integrates first-principles based microkinetic models into a macroscale description of the heat and mass transport in a given reactor geometry. Specifically addressing recent in situ experiments on CO oxidation at Pd(100) I will illustrate how this approach can be employed to conclude on the active surface present in the measurements. Important issues to this end are the explicit consideration of mass-transfer limitations present in the experimental setups and the development of a multi-lattice kinetic Monte Carlo approach that allows to treat potential transitions between metallic and (surface) oxidic phase at near-ambient operation.

Near-ambient oxidation catalysis at late transition metals � metal, oxide, both? How first-principles multiscale modeling can help

248th National Meeting (2014)

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