Hannover 2020 – scientific programme
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MO: Fachverband Molekülphysik
MO 1: Clusters I (joint session MO/A)
MO 1.5: Talk
Monday, March 9, 2020, 12:15–12:30, f102
N2 activation on size selected Tantalum clusters investigated by cryo kinetics and IR spectroscopy — •Matthias P. Klein1, Daniela V. Fries1, Annika Steiner1, Helmut Schwarz2, and Gereon Niedner-Schatteburg1 — 1Fachbereich Chemie and Forschungszentrum OPTIMAS, TU Kaiserslautern, Erwin-Schrödinger-Straße 52, 67663 Kaiserslautern — 2Institut für Chemie, Technische Universität Berlin, 10623 Berlin
Catalytic N2 activation by active transition metal surfaces is one of the most important industrial processes. For a thorough understanding of the activation steps, we need suitable model systems. By means of cryo IR-PD spectroscopy and cryo adsorption kinetics supported by DFT modelling, we are able to investigate the vibrational and kinetic behavior of various transition-metal-cluster-N2/H2 complexes (Fe, Co, Ni, Rh, Ru) and gain information about reaction precursors and intermediates. Small tantalum clusters have shown to activate N2 dissociatively and even support the formation of ammonia. We chose to examine the Ta4+ and Ta5+ clusters in more detail. We observe a rearrangement of the adsorbate shell and activated N2 upon stepweise N2 adsorption. In the Ta4+ case, the adsorption kinetics suggest a complex dynamics for large adsorption shells. A pseudo-first-order kinetic fit fails in this case. In contrast, the adsorption kinetics of the Ta5 cluster are reproducible by such a fit. IR bands represent a range from weakly bound N2 to actual N2 activation precursors.