SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 76: Poster Session VI: Supported nanoclusters: structure, reactions, catalysis
O 76.2: Poster
Mittwoch, 3. März 2021, 13:30–15:30, P
Metastability of Palladium Carbide Nanoparticles during Hydrogen Release from Liquid Organic Hydrogen Carriers — •Ralf Schuster1, Manon Bertram1, Henning Runge2, Simon Chung2, Vedran Vonk2, Heshmat Noei2, Yaroslava Lykhach1, Andreas Stierle2, and Jörg Libuda1 — 1Interface Research and Catalysis, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen — 2Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, D-22607 Hamburg
Surface carbon species can be formed by unselective decomposition during heterogeneously catalyzed dehydrogenation of liquid organic hydrogen carriers (LOHCs). These species may diffuse into the bulk of the catalyst, forming metal carbide phases and, thus, influence the activity and selectivity of the catalyst. For palladium, however, the carbide phase is metastable with respect to palladium and graphite. Therefore, we studied the formation and stability of palladium carbide phases on well-defined Pd/Al2O3 model catalysts. The phase composition of the nanoparticles was investigated as a function of particle size and gas flow rate under reaction conditions (500 K, 1 bar) by high-energy grazing incidence X-ray diffraction. We showed that the stability of palladium carbide critically depends on both nanoparticle size and gas flow rate. For small nanoparticles under low gas flow rate the Pd6C phase is stable, while a high gas flow rate results in immediate decomposition of the carbide after formation. For bigger particles at a low gas flow rate, however, the carbide is stable for an incubation period, after which the growth of graphene triggers its decomposition.