Ethene to graphene : surface catalyzed chemical pathways, intermediates, and assembly

Financial support by the Friedrich Ebert-Stiftung to M.K. is gratefully acknowledged. The work of B.Y. at the Georgia Institute of Technology was supported by Grant FA9550-14-1-0005 from the U.S. Air Force Office of Scientific Research, and the work of U.L. was supported in part by a Grant FG05-86ER45234 from the Office of Basic Energy Sciences of the U.S. Department of Energy.R.S. and N.V.R. acknowledge financial support from the Scottish Funding Council through EaStCHEM and SRDG Grant HR07003. R.S. and H.F. acknowledge EPSRC for the use of the ARCHER U.K. National Supercomputing service, and for the funding of PhD studentships (JAGT − EP/M506631/1, and MJT − EP/K503162/1).Diverse technologies, from catalyst coking to graphene synthesis, entail hydrocarbon dehydrogenation and condensation reactions on metals, and assembly into carbon overlayers. Imperative to gaining control over these processes, through thermal steering of the formation ofpolyaryl intermediates and the controlled prevention of coking, is the exploration and elucidation of the detailed reaction scheme that starts with adsorbed hydrocarbons and culminates with the formation of extended graphene. Here we use scanning tunneling microscopy, high-resolution electron energy loss and thermal desorption spectroscopies, in combination with theoretical simulations to uncover the hierarchy of pathways and intermediates underlying the catalyzed evolution of ethene adsorbed on Rh(111) to form graphene. These investigations allow formulation of a reaction scheme whereby, upon heating, adsorbed ethene evolves via coupling reactions to form segmented one-dimensional polyaromatic hydrocarbons (1D-PAH). Further heating leads to dimensionality crossover (1D→2D) and dynamical restructuring processes at the PAH chain ends, with subsequent activated detachment of size-selective carbon clusters. Rate-limiting diffusional coalescence of these dynamically self-evolved precursors culminates (≤1000 K) in condensation into graphene of high structural perfection.Publisher PDFPeer reviewe