NO2 Hydrogenation on Rh Catalysts: Bifurcations and Oscillations at the Nanoscale

• Published in: Journal of physical chemistry. C 2017-08, Vol.121 (32), p.17235-17243
• Main Authors: Barroo, Cédric, De Decker, Yannick, Visart de Bocarmé, Thierry
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.7b04123

In this work, we report complex kinetic phenomena observed during the reduction of NO2 on rhodium model catalysts followed by field emission microscopy (FEM). This technique uses samples prepared as sharp tips, mimicking the size and shape of one catalytic nanoparticle. The method enables one to study catalytic reactions in real time down to the nanoscale. Running the NO2 + H2 reaction on Rh at 450 K and in the 10–5 Pa range, we observe nonlinear behaviors on the facets corresponding to {011} and {012} crystallographic orientations. The emergence of nonlinearities is studied as a function of the control parameters, and the particular case of self-sustained periodic oscillations is analyzed in detail. The corresponding bifurcation diagram shows that the oscillations appear via a supercritical Hopf bifurcation. It is moreover possible to reconstruct the underlying dynamical attractorhere, the limit cycleusing the time-delay embedding method. Different possible mechanisms of reaction leading to these oscillations are discussed.