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O: Fachverband Oberflächenphysik
O 16: Nanoscale Heterogeneous Catalysis
O 16.10: Vortrag
Montag, 16. März 2020, 17:30–17:45, TRE Ma
In situ SEM as surface-sensitive tool to study catalytic reactions — •Cédric Barroo1, Zhu-Jun Wang2, and Marc Willinger2 — 1Université Libre de Bruxelles — 2ETH Zurich
Non-equilibrium reactions are observed in a variety of reactive systems, including at the surface of catalytic materials. Probing such reactions and their dynamics during the ongoing processes remains challenging due to the scarcity of techniques allowing for in situ experiments. Here we report the observation and analysis of nonlinear behaviours during NO2+H2 on Pt catalysts using in situ environmental scanning electron microscopy (ESEM), a technique sensitive to the variations of work function due to the presence of adsorbates. The ESEM instrument allows to study samples with various morphologies, allowing to bridge the materials-gap, and can be used with gas pressures up to tens of Pa. Experiments during the NO2 hydrogenation were performed on Pt single crystals and on Pt foils, and several types of nonlinear behaviours were observed, mainly in the form of spiral patterns. Different brightness levels can be distinguished on a single propagating wave, sign of different surface adsorbate composition. These patterns were observed on regions as large as 100 *m and over a wide range of pressures: from 10-3 to 20 Pa. ESEM can be used to observe similar phenomena over different pressure conditions, allowing to, somewhat, bridge the pressure-gap; but also analysing the same reaction on single crystal and foils: it is then possible to study the various reaction behaviors, the structure sensitivity of the reaction, the spillover between different facets, and how the presence of boundaries affects the reactivity.