AVS 62nd International Symposium & Exhibition
    Surface Science Monday Sessions
       Session SS-MoA

Paper SS-MoA2
Characterizing the Influence of Water on Charging and Layering at Electrified Ionic-Liquid/Solid Interfaces

Monday, October 19, 2015, 2:40 pm, Room 113

Session: Organics and Ionic Liquids: Surfaces, Layers, Interfaces and Chirality
Presenter: Hsiu-Wei Cheng, Max-Planck-Institut für Eisenforschung GmbH, Germany
Authors: H.W. Cheng, Max-Planck-Institut für Eisenforschung GmbH, Germany
P. Stock, Max-Planck Institut für Eisenforschung GmbH, Germany
B. Moeremans, Universiteit Hasselt, Belgium
T. Bamipos, Max Planck Institut fur Eisenforschung GmbH, Germany
X. Banquy, University of Montreal, Canada
F.U. Renner, Universiteit Hasselt, Belgium
M. Valtiner, Max-Planck Institut für Eisenforschung GmbH, Germany
Correspondent: Click to Email
The importance of water on molecular ion structuring and charging mechanism of solid interfaces in room temperature ionic liquid (RTIL) is unclear and has been largely ignored. Water may alter structures, charging characteristics and hence performance at electrified solid/RTIL interfaces utilized in various fields including energy storage and conversion or catalysis. Here, we utilize Atomic Force Microscopy to directly measure how water alters the interfacial structuring and charging characteristics of [C2mim][ Tf2N] on mica and electrified gold surfaces. On hydrophilic and ionophobic mica surfaces, water-saturated RTILs induce strong ion layering by dissolution of surface-bound cations and a resulting high surface charging. In contrast, layering of dry RTIL at uncharged mica surfaces is weakly structured. At electrified, hydrophobic and ionophilic gold electrodes, significant water effects were found only at positive applied electrochemical potentials. Here, the influence of water is limited to interactions within the RTIL layers, and is not related to a direct electrosorption of water on the polarized electrode. More generally, our results suggest that effects of water on interfacial structuring of RTIL strongly depend on both (1) surface charging mechanism, and (2) interfacial wetting properties. This may greatly impact utilization and design of RTILs and surfaces for interface dominated processes.