Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 82: Fundamentals of Catalysis II
O 82.6: Vortrag
Donnerstag, 4. April 2019, 16:15–16:30, H5
Atomic oxidation of supported CoTPP films — •Jakob Hauns, Artur Böttcher, and Manfred M. Kappes — Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany
Thin Co-Tetraphenylporphyrin films, CoTPP, were grown on HOPG under UHV conditions by applying the low-energy cluster beam deposition technique (LECBD, [1]). The oxidation has been performed by exposing the films kept at room temperature to a beam of nearly-thermal oxygen atoms at a constant flux. UPS based analysis of the valence band revealed a gradual quenching of the HOMO state (EB∼ 1.8 eV). The oxygen conditioned evolution of all relevant CoTPP core states supported by DFT calculations of the most stable oxides enables to follow the oxidation pathways. The sublimation of the oxidized CoTPP films has been studied by monitoring the mass spectra of the volatile species during heating the sample (MSTDS, [1]). The emission of oxidized multilayers proceeds within a broad temperature interval (450-850K). It is dominated by a series of CoTPP-On oxides (0≤n≤5) which implies that an intact CoTPP is capable to adopt up to five oxygen atoms. In contrast, the sublimation of a CoTPP monolayer deposited on preoxidized HOPG gives rise to a completely different product spectrum indicating that the substrate uniquely participates in the reaction.
[1] J. Weippert, et al. J. Phys. Chem. C DOI:10.1021/acs.jpcc.8b01655