Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 58: Poster Session III (Solid/liquid interfaces; Metals; Semiconductors; Oxides and insulators)
O 58.9: Poster
Wednesday, March 28, 2012, 18:15–21:45, Poster B
Molecular Scale Structure of Ionic Liquids near Electrodes — •Peter Reichert1, Jannis Ochsmann1, Kasper Skov Kjaer2, Tim Brandt van Driel2, Martin Meedom Nielsen2, Harald Reichert3, Diego Pontoni3, and Markus Mezger1 — 1Max-Planck-Institut für Polymerforschung, Mainz, Germany — 2Technical University of Denmark and Risø National Lab, Roskilde, Denmark — 3European Synchrotron Radiation Facility, Grenoble, France
To understand and optimize electrochemical processes in ionic liquids (ILs), information on their molecular-scale structure near electrodes is essential. Recent high-energy x-ray reflectivity experiments on dielectric substrates revealed interfacial layering comprised of alternating anion and cation enriched regions with this modulation decaying into the bulk liquid. To investigate the molecular-scale arrangement of ions near electrodes under electrochemical control, a novel sample chamber was developed. For the in-situ experiments at the High-Energy Micro Diffraction instrument at ID15, ESRF we selected two hydrophobic ILs based on butyl-1-methylpyrolidonium and tetrabutylammonium cations with the tris(pentafluoroethyl)trifluorophosphate anion that exhibit an exceptional wide electrochemical window. The solid-liquid interface between the ILs and a boron doped diamond substrate was studied at electrochemical potentials between -2.5 V and +1.6 V vs. platinum quasi reference electrode. Quantitative analysis of the experimental x-ray reflectivity data revealed distinct changes in the ion distribution near the interface, induced by the applied potentials.