Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 14: Surface Chemical Dynamics
O 14.6: Hauptvortrag
Montag, 7. März 2016, 16:15–16:45, S053
In-situ Studies of the Reactivity of Pt Model Catalysts: from Flat Surfaces to Nanoparticles — •Christian Papp — Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg
Nanocluster arrays on supported graphene are intriguing model systems for catalysis, modeling the highly dispersed particles on real catalysts. We studied the adsorption and oxidation of CO and the chemistry of the catalyst poison SO2 on Pt/Gr/Rh(111) with synchrotron-based high-resolution X-ray photoelectron spectroscopy.
On the Pt nanoclusters, we resolved CO adsorbed at three different sites, that is, on-top, bridge and step. The C 1s spectra exhibit remarkable similarities to those on single crystal surfaces: Similar to the case for stepped Pt(111) surfaces, a clear preference for the adsorption on the step sites is found, while the preference for the adsorption on the on-top site over the bridge site on the terraces is less pronounced than on Pt(111). Temperature-programmed X-ray photoelectron spectroscopy revealed an enhanced binding energy for the cluster step sites, similar to the situation on stepped Pt surfaces. The oxidation of CO follows roughly pseudo first order kinetics. The activation energy determined from an Arrhenius analysis was found to be smaller than for stepped and flat platinum crystals.
SO2 adsorbs in two geometries, perpendicular and parallel to the surface, on both cluster facets and steps. While we again find a remarkable similarity to the adsorption situation on single crystals at low temperature, the reactivity of the nanoclusters is strongly increased.
Support by the DFG through SFB 953 is gratefully acknowledged.