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O: Fachverband Oberflächenphysik
O 95: Metal Substrates: Adsorption of Atoms and Inorganic Molecules
O 95.12: Vortrag
Donnerstag, 23. März 2017, 18:00–18:15, WIL A317
Field emission microscopy study of nonlinear dynamics during NO2 hydrogenation — •Cédric Barroo1, Yannick De Decker1, Pierre Gaspard1, Norbert Kruse1, and Thierry Visart de Bocarmé2 — 1Universiteé libre de Bruxelles, Brussels, Belgium — 2Washington State University, Pullman WA, USA
Field emission microscopy (FEM) is a technique that enables to probe reactions and their dynamics at the scale of a single nanoparticle. This study reports on the observation and analysis of various nonlinear behaviors during the catalytic hydrogenation of NO2 on Pt. A tip-sample is used to study reactions during the ongoing reactive processes and down to 10nm2. By changing a control parameter, it is possible to observe different behaviors, among which self-sustained periodic oscillations, and to determine the type of bifurcation leading to the emergence of the oscillations. In the case of periodic oscillations, the robustness is quantified via Fourier transform and temporal autocorrelation functions analyses. We also show how the dynamical attractor and the phase space dynamics can be reconstructed from experimental time series, and we prove that the periodic oscillations can be linked to a limit cycle. Experiments at high temporal resolutions show the presence of propagating processes at the surface of the catalyst, and the propagation of chemical waves on a single facet of the nanocrystal is also observed. These waves take the form of target patterns with a velocity in the order of a few μm/s, in good agreement with previous studies of catalytic reactions at the mesoscale. The experiments prove the robustness of nonlinear behaviors down to the nanoscale.