Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 86: Nanostructure at Surfaces: Molecular Assembly
O 86.6: Talk
Thursday, March 19, 2015, 16:30–16:45, HE 101
Ethene to graphene: surface catalyzed chemical pathways, intermediates, precursors, and assembly — Bo Wang1, Michael König1, Catherine J. Bromley2, Bokwon Yoon3, •Friedrich Esch1, Ulrich Heiz1, Uzi Landman3, and Renald Schaub2 — 1Chemistry Dept., Technische Universität München, Catalysis Research Center, 85748 Garching, Germany — 2EaStCHEM and School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, United Kingdom — 3School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA
Diverse technologies, from catalyst coking to graphene synthesis, entail hydrocarbon dehydrogenation and condensation reactions on transition metal surfaces and assembly into carbon overlayers. Scanning-tunneling microscopy (STM), thermal-desorption spectroscopy (TDS), and density-functional theory (DFT) simulations were used to uncover the hierarchy of atomic-scale pathways and reaction intermediates underlying the catalyzed thermal evolution of ethene adsorbed on Rh(111) to form 2D graphene overlayers:
Upon heating, adsorbed ethene molecules evolve at first via coupling reactions to form segmented 1D polyaromatic hydrocarbon chains. Further heating leads to dimensionality-crossover (1D to 2D) and dynamical restructuring processes at the PAH chain-ends, with subsequent activated detachment of 24-carbon-atom dehydrogenated-coronene-like clusters. Rate-limiting diffusional coalescence of these dynamically self-evolved precursors culminates at even higher temperatures (1000 K) in condensation into a graphene adlayer of high structural perfection.