calque
calque

Workshops

Interactions and Transport of Charged Species in Bulk and at Interfaces

July 4, 2016 to July 7, 2016
Location : CECAM-AT

Structural Transition at Ionic Liquid Interfaces

Benjamin Rotenberg
CNRS and University Pierre and Marie Curie, Paris, France

Coauthor(s) : C. Merlet [1], D. Limmer [2], M. Salanne [3], D. Chandler [4], P.A. Madden [5] R. van Roij [6]
[1] University of Cambridge, United Kingdom [2] Princeton University, USA [3] CNRS and UPMC, Paris, France [4] University of California, Berkeley, USA [5] University of Oxford, United Kingdom [6] University of Utrecht, The Netherlands

Abstract

Room Temperature Ionic Liquids (RTILs) consist of mixtures of cations and ions, without any solvent, with a low melting point so that, unlike common salts, they are liquid at ambient or moderate temperature. They are now widely used as electrolytes in electrochemical devices, in particular Electrochemical Double Layer Capacitors (EDLCs) also known as supercapacitors [1,2]. In this context, understanding the structure, thermodynamics and dynamics of RTIL-metal interfaces is of primary importance. However the Gouy-Chapman-Stern theory, which remains the cornerstone of theoretical electrochemistry since over a century, is of limited help due to the strong ionic correlations within the fluid [3]. I will discuss the properties of such interfaces, emphasizing the recent contributions of molecular simulations. I will illustrate in particular the insights provided by the simulation of electrodes maintained at a constant potential, as well as the analysis of the charge fluctuations of the electrode to analyze and predict the evolution of the interfacial properties with applied voltage [4,5,6].



References

[1] Chmiola J et al., Anomalous Increase in Carbon Capacitance at Pore Sizes Less Than 1 Nanometer, Science 313, 1760–1763 (2006)
[2] Merlet C et al., On the molecular origin of supercapacitance in nanoporous carbon electrodes, Nature Materials 11, 306 (2012)
[3] Fedorov MV and Kornyshev AK, Ionic Liquids at Electrified Interfaces, Chem. Rev. 114, 2978 (2014)
[4] Limmer DT et al., Charge fluctuations in nanoscale capacitors, Phys. Rev. Lett. 111, 106102 (2013)
[5] Merlet C et al., The electric double layer has a life of its own, J. Phys. Chem. C 118, 18291 (2014)
[6] Rotenberg B and Salanne M, Structural Transitions at Ionic Liquid Interfaces, J. Phys. Chem. Lett., 6, 4978 (2015)