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O: Fachverband Oberflächenphysik
O 78: Poster: Surface Dynamics - Reactions, Elementary Processes and Phase Transitions
O 78.1: Poster
Mittwoch, 14. März 2018, 18:15–20:30, Poster A
X-ray photoemission studies of the liquid metal catalyst Pd/Rh-Ga — •Haiko Wittkämper1, Mathias Grabau1, Jannis Erhard3, Nicola Taccardi2, Peter Wasserscheid2, Christian Neiss3, Andreas Görling3, Hans-Peter Steinrück1, and Christian Papp1 — 1Physikalische Chemie 2 — 2Chemische Reaktionstechnik — 3Theoretische Chemie, FAU Erlangen
Mixtures of Pd and Ga on porous silica were shown to be stable and selective alkane dehydrogenation catalysts. The beneficial effects of Ga addition to the active transition metal are due to the fact that the catalyst is in the liquid phase during reaction, which is indicated by SEM and XRD measurements, and termed supported catalytically active liquid metal solution (SCALMS).[1] We herein present XPS studies of Pd-Ga and Rh-Ga alloys as model systems for catalytically-active, supported liquid catalysts. In an effort to understand the underlying principles of the catalyst, the temperature-dependent Pd/Rh concentrations at the surface of the liquid phase were evaluated by quantitative XPS. The observed temperature-dependence is explained by the formation of transition metal-rich intermetallic phases, leading to the depletion of the liquid phase and the surface from the transition metal. For the Pd-Ga alloy, additionally, an inhomogeneous Pd distribution with depletion at the interface is suggested by ARXPS and DFT-based MD simulation. [2] Data on the Rh-Ga system will be presented and compared to the results obtained for the Pd-Ga alloy. [1] Taccardi, N., Grabau. M., et al. NatChem 9, 862-867 (2017). [2] Grabau. M., Erhard J., et al. ChemEurJ 23, 1-8 (2017).