J. Knudsen, J. N. Andersen (Division of Synchrotron Radiation Research and the MAX IV Laboratory, Lund University), E. Grånäs, M. A. Arman, J. Schnadt (Division of Synchrotron Radiation Research, Lund University), K. Schulte (The MAX IV Laboratory, Lund University), U. Schröder, T. Gerber, P Stratmann, T. Michely (Physikalisches Institut, Universität zu Köln), M. Andersen, B. Hammer (Interdisciplinary Nanoscience Center and Department of Physics and Astronomy, Aarhus University) 

Graphene (Gr) covered transition metal surfaces are attractive model systems for studying confinement effects. Here, we show and discuss how it is possible to run a catalytic reaction underneath Gr flakes.

First, we will present an atomic scale picture of H2-, O2- and CO-structures formed under Ir(111) supported Gr based on X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory [1, 2, 3]. We will demonstrate how the dosing conditions can be used to control the intercalation: Oxygen intercalates Gr above 400 K, CO intercalates Gr in the mbar regime, and H2 only intercalates Gr at temperatures close to 100 K.

Finally, we will compare H2 and CO titration of chemisorbed oxygen on clean Ir(111) and intercalated underneath Gr. Without Gr, both H2 and CO react with oxygen and form H2O and CO2, respectively, which desorb directly. With Gr, the CO2 formation is unaffected, while the water formation is significantly changed, leading to a trapped superdense phase of mixed H2O and OH intercalating Gr [4].

[1] Grånäs et al., ACS nano, 11, 9951 (2012)
[2] Grånäs et al., Journal of Physcial Chemistry C, 117, 16438 (2013)
[3] Grånäs et al., In manuscript
[4] Grånäs et al., In manuscript 

Jan Knudsen is a researcher at the MAX IV Laboratory, Sweden, where he is project manager for the new high pressure X-ray photoelectron spectroscopy beamline, named HIPPIE. His research is focused on understanding 2D materials and their catalytic properties and he mainly study ultra-thin oxides and graphene with scanning tunneling microscopy and high resolution (HRXPS) and high pressure (HPXPS) X-ray photoelectron spectroscopy.

He received a Ph.D. in Physics (2008) from University of Aarhus, for his scanning tunneling microscopy studies of surface alloys and ultrathin metal oxide films and their catalytic properties under guidance of F. Besenbacher. From 2008 – 2012 he had a postdoctoral position at the division of ynchrotron radiation research, Lund University, where he started to study ultra-thin oxides and graphene with high resolution and high pressure X-ray photoelectron spectroscopy. He has been main responsible for commissioning the first synchrotron based HPXPS instrument in Sweden and in 2012 he was employed as a permanent researcher at the MAX IV Laboratory.