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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 69: Focus: Fundamentals of molecular liquids, ionic liquids and mixtures II
CPP 69.6: Vortrag
Mittwoch, 18. März 2020, 16:30–16:45, ZEU 222
Solvent effect on electrical double layers (EDL) in ionic liquid (IL) solutions — •Takeshi Kobayashi1, Maria Fyta1, and Jens Smiatek2 — 1Institute for Computational Physics, University of Stuttgart, Allmandring 3, 70569 Stuttgart, Germany — 2Boehringer Ingelheim Pharma GmbH & Co. KG, Development Biologicals, Biberach, Germany
The solvent effect on EDL in IL is studied through atomistic molecular dynamics (MD) simulations. Water and dimethyl sulfoxide (DMSO) in 1-Ethyl-3-methylimidazolium dicyanamide ([EMIM]+[DCA]-) in different concentrations show distinct features regarding the molecule accumulation near surfaces. A comparison between neutral [1] and charged surfaces clarifies the influence of the molecular size, molecule-molecule interactions, and surface-molecule interactions. Due to the large molecular size of DMSO, the accumulation of DMSO near the cathode is limited even at a high DMSO concentration. This indicates that DMSO hardly changes the EDL properties, while improving the conductivity of the solution. On the other hand, water accumulates near the surfaces regardless of the surface charge. This is not beneficial for practical applications due to the narrowing of the electrochemical window, though the total capacitance may increase. In order to further interpret the simulation results, we apply the lattice gas theory [2]. This allows us to understand the solvent effect for the prediction of better combinations of IL mixtures for EDL capacitors. [1] T. Kobayashi at al., J. Phys. Chem. C 2019, 123, 22, 13795-13803 [2] Alexei A. Kornyshev, J. Phys. Chem. B 2007, 111, 20, 5545-5557