Bias-Dependent Molecular-Level Structure of Electrical Double Layer in Ionic Liquid on Graphite

Abstract

Here we report the bias-evolution of the electrical double layer structure of an ionic liquid on highly ordered pyrolytic graphite measured by atomic force microscopy. We observe reconfiguration under applied bias and the orientational transitions in the Stern layer. The synergy between molecular dynamics simulation and experiment provides a comprehensive picture of structural phenomena and long and short-range interactions, which improves our understanding of the mechanism of charge storage on a molecular level.

Topological defects in electric double layers of ionic liquids at carbon interfaces

“…Theories describing the electrical double layer for ionic liquid electrolytes have been proposed including over-screening and crowding; however, a full molecular level description of the double-layer is still required [3]. Ionic liquids form alternating layers of anions and cations extending several nm from the interface, akin to the smectic phase of liquid crystals (LC), as evidenced in numerous experimental and computational studies [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. It is crucial to have a full molecular scale picture of the electrical double layer for advances to be made in the numerous areas of application for ionic liquids including energy storage, catalysis, lubrication and many others [23].…”

High viscosity environments: an unexpected route to obtain true atomic resolution with atomic force microscopy

“…Previously, imaging with comparable amplitudes allowed for the visualization of dehydrated ions at the mica surface in aqueous solutions whereby the small oscillation amplitude excludes water from the tip-sample gap as described above [17]. Under similar conditions in viscous, ionic liquids, it may be possible to directly measure the charge distribution at the solid-liquid interface [10].…”

“…Nevertheless, AFM studies in non-aqueous liquid environments are also of great interest as they enable in situ investigations of various processes including chemical reactions [1], lubrication [2] and molecular ordering [3][4][5]. In particular, devices based on ionic liquid electrolytes have been proposed as promising systems for energy applications [6], often in combination with graphene as the electrode material [7][8][9][10]. Despite the scientific need for investigations into the interfacial and transport properties of such systems with high spatial resolution, AFM in highly viscous liquids remains underutilized.…”

Molecular Insights into Electrical Double Layers in Graphene-Based Supercapacitors

“…This talk would include: 1) MD modeling on ILs-based EDLs at open surfaces (e.g., planar, cylindrical, spherical, with defects, etc.) [1][2] and the integration with experiments (e.g., atomic force microscopy, AFM) [3][4], which would focus on the EDL structure and its influence from ion size, ion type, applied potential, electrode curvature, etc.…”

“…This talk would include: 1) MD modeling on ILs-based EDLs at open surfaces (e.g., planar, cylindrical, spherical, with defects, etc.) [1][2] and the integration with experiments (e.g., atomic force microscopy, AFM) [3][4], which would focus on the EDL structure and its influence from ion size, ion type, applied potential, electrode curvature, etc.2) MD modeling on ILs-based porous carbon supercapacitors [5][6][7], which would embody the pore size effects on capacitance, the ion dynamics under porous confinement, and pore expansion during charging.3) The anatomy of electrosorption for water in ionic liquids at electrified interfaces [8], which would show, for the first time, the work on the adsorption of water on electrode surfaces in contact with humid ILs. …”