Exciting H2 Molecules for Graphene Functionalization

Line Kyhl, Régis Bisson, Richard Balog, Michael N. Groves, Esber Leonhard Kolsbjerg, Andrew Martin Cassidy, Jacob Holm Jœrgensen, Susanne Halkjær, Jill A. Miwa, Antonija Grubišić Čabo, Thierry Angot, Philip Hofmann, Alif Arman, Samuli Urpelainen, Paolo Lacovig, Luca Bignardi, Hendrik Bluhm, Jan Knudsen, Bjœrk Hammer, Liv Hornekaer

Research output: Contribution to journalArticlepeer-review

Abstract

Hydrogen functionalization of graphene by exposure to vibrationally excited H2 molecules is investigated by combined scanning tunneling microscopy, high-resolution electron energy loss spectroscopy, X-ray photoelectron spectroscopy measurements, and density functional theory calculations. The measurements reveal that vibrationally excited H2 molecules dissociatively adsorb on graphene on Ir(111) resulting in nanopatterned hydrogen functionalization structures. Calculations demonstrate that the presence of the Ir surface below the graphene lowers the H2 dissociative adsorption barrier and allows for the adsorption reaction at energies well below the dissociation threshold of the H–H bond. The first reacting H2 molecule must contain considerable vibrational energy to overcome the dissociative adsorption barrier. However, this initial adsorption further activates the surface resulting in reduced barriers for dissociative adsorption of subsequent H2 molecules. This enables functionalization by H2 molecules with lower vibrational energy, yielding an avalanche effect for the hydrogenation reaction. These results provide an example of a catalytically active graphene-coated surface and additionally set the stage for a re-interpretation of previous experimental work involving elevated H2 background gas pressures in the presence of hot filaments.
Original languageEnglish
JournalACS Nano
DOIs
Publication statusPublished - 2017 Dec 18

Subject classification (UKÄ)

  • Atom and Molecular Physics and Optics
  • Condensed Matter Physics

Free keywords

  • graphene, vibrational excitation, nanostructured functionalization, band gap engineering, molecular hydrogen, catalysis

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