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NO2 Hydrogenation over Pt and Rh Catalysts: a Study at The Atomic Level by Field Emission Microscopy

par Barroo, Cédric ;De Decker, Yannick ;Visart de Bocarmé, Thierry ;Kruse, Norbert
Référence Microscopy and microanalysis, 21, page (1587)
Publication Publié, 2015-08

Article révisé par les pairs

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Résumé :

This study aims at investigating the catalytic hydrogenation of nitrogen dioxide (NO2) on Pt, Rh and Pt-Rh alloy catalysts. Nitrogen oxides (NOx) are produced during the combustion of gasoline in the lean-burn regime, and their emission remains an issue especially for Diesel-type engines. Platinum-Group-Metals are used as active components of the catalytic converter. They turn toxic gases into harm less compounds, for example, NOx into nitrogen. The catalyst is dispersed in the form of metallic nanoparticles of approximately 5 to 10 nm over a support of high specific surface area. In most studies of heterogeneous catalysis, the structure of the supported catalyst is determined before and after reaction. Unfortunately, very little information is available about the possible local morphological/structural changes that might occur during the reaction. Moreover, from a dynamical point of view, the kinetic parameters only reflect the global kinetics of the reaction taking place on the surface a large ensemble of nanoparticles with specific size and shape distribution. Thus, ensemble-averaging takes place eventually hiding more complex dynamics, such as periodic oscillations. A better understanding of the ongoing catalytic reaction would lead to a better reproducibility, predictability and control of this reaction. In this view, a study of the hydrogenation of NO2 gas over Pt, Rh and Pt-Rh nanocrystals is undertaken at the molecular level by means of field emission methods.