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O: Fachverband Oberflächenphysik
O 16: Nanoscale Heterogeneous Catalysis
O 16.9: Vortrag
Montag, 16. März 2020, 17:15–17:30, TRE Ma
Nanoscale surface chemistry of Au-based catalysis studied by field emission techniques — Luc Jacobs1, Thierry Visart de Bocarmé1, Austin Akey2, David Bell2, and •Cédric Barroo1,2 — 1Université Libre de Bruxelles — 2Harvard University
To improve the efficiency of binary catalysts, it is crucial to understand the surface composition/reactivity relationships. Here, we studied the AuAg system exhibiting high activity and selectivity for deNOx and selective oxidation reactions. The catalytic performance of AuAg is attributed to the presence of traces of silver allowing to provide adsorbed atomic oxygen, the key factor for activity/selectivity on gold surfaces. To do so, we used field ion microscopy (FIM), field emission microscopy (FEM) and atom probe tomography (APT). APT is used to characterize the structure of nanoporous gold catalysts and to study the non-homogeneous distribution of Ag within the 3D-structure. The size of a single ligament corresponds to ~50nm and can be modelled by sharp tips. Such samples are analyzed with atomic-scale resolution by FIM to study the structure before and after reaction; but also by FEM to observe the structure-reactivity relationships during the ongoing process. N2O+H2 was selected for its ability to provide atomic oxygen at the surface, and the experiments provide insights into the local reactivity of the sample: within a very strict temperature range, we can study the relative reactivity of different crystallographic orientations. Further experiments were performed during O2+H2 and CH3OH+O2 reactions. These results prove the relevance of field emission techniques to study the catalytic activity of alloys.