Regensburg 2022 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 32: Nanomaterials: Surface Effects
MM 32.5: Vortrag
Donnerstag, 8. September 2022, 12:45–13:00, H45
Probing the oxide formation on Pt, Pd and Pt/Pd catalysts during NO oxidation by Atom Probe Tomography (APT) — •Yoonhee Lee1, Daniel Dobesch2, Ute Tuttlies2, Patrick Stender1, Ulrich Nieken2, and Guido Schmitz1 — 1Institute of Materials Science, University of Stuttgart, Heisenbergstr. 3, 70569 Stuttgart, Germany — 2Institute of Chemical Process Engineering, University of Stuttgart, Böblinger Str. 78, 70199 Stuttgart, Germany *Yoonhee.lee@mp.imw.uni-stuttgart.de
Inverse hysteresis behavior of Pt, Pd and PtPd alloy catalysts during NO conversion can be attributed to the formation of metal oxides. Even though there were many efforts to study the oxidation of these noble metals experimentally, still the surface change of the pure catalyst has not been observed yet. In this work, NO conversion measurements were carried out with nanoparticles of Pt, Pd and Pt/Pd alloy, produced by spark discharge method, in an isothermal flatbed reactor. The catalyst was subjected to alternating heating and cooling ramps in conditions prone to surface oxide formation. Besides, the oxygen content formed on the surface of catalyst was determined during Temperature-Programmed Reduction(TPR) in H2 atmosphere. The same conditions (gas concentration, heating and cooling rate) of the NO conversion experiments have been achieved in a reaction chamber directly connected to the Atom Probe Tomography (APT) under ultra-high vacuum conditions. The samples were exposed to the gas and measured in APT. The 3D chemical structure was reconstructed and the effective thickness of formed oxides was determined.