Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 33: Graphene
O 33.20: Poster
Dienstag, 17. März 2015, 18:15–21:00, Poster A
Water chemistry beneath graphene: Formation and breathing of a super-dense OH-H2O phase under graphene — Elin Grånäs1, •Ulrike A. Schröder2, Mohammad A. Arman1, Mie Andersen3, Timm Gerber2, Karina Schulte4, Jesper N. Andersen1,4, Thomas Michely2, Bjørk Hammer3, and Jan Knudsen1,4 — 1Division of Synchrotron Radiation Research, Lund University, Sweden — 2II. Physikalisches Institut, Universität zu Köln, Germany — 3Interdisciplinary Nanoscience Center and Department of Physics and Astronomy, Aarhus University, Denmark — 4MAX IV Laboratory, Lund University, Sweden
Placing catalysts in confined environments, e.g. carbon nanotubes, is a powerful method to modify their activity or selectivity. Unfortunately, atomic level understanding of the confinement effects is hindered by the complexity of these materials.
We use Ir(111)-supported graphene (Gr) flakes to study room temperature reduction of atomic oxygen in a confined 2D nano-reactor with X-ray photoelectron spectroscopy and scanning tunneling microscopy. The Gr cover can be used to trap OH-H2O phases that otherwise would desorb directly. Our study of these Gr-stabilized phases and their response to oxygen and hydrogen exposure reveals 2D breathing of a O-OH-H2O phase as O-atoms are dissolved into the structure (expansion) and subsequently converted to OH and H2O (contraction). Using density functional theory calculations combined with a genetic search algorithm, the structure and stability of the trapped OH-H2O structures were determined.