Static dielectric permittivity of ionic liquids ultraconfined in carbon nanotubes

Nadia Ben Cheick Mansour,Anthony Szymczyk,Aziz Ghoufi,Armand Soldera,Mohammed-Lamine Ouiten

doi:10.1088/2632-959x/abed3f

Abstract

In this work the parallel component of the static dielectric permittivity, of ionic liquids ultraconfined into flexible carbon nanotubes of radius of 1.2 nm and 2.4 nm is evaluated from molecular dynamics simulations. We show an enhancement of with respect to bulk value and a counter-intuitive temperature dependence. Indeed an increase of as a function of the temperature opposed to a bulk behavior is evidenced. Increase in is the result of the strong orientation of ionic liquid close to the pore wall. The temperature dependence is the consequence of the thermal fluctuations increasing the dipolar fluctuations such that the strong orientation is conserved. Eventually, we show a molecular stacking between [C4mim+][Tf2N−] and CNT decreasing dipolar fluctuations close to the CNT surface reducing .

Highlights

Ionic Liquids (ILs) are molten salts composed of large organic cations and inorganic or organic anions
Over the last few years, the confinement of ILs at the nanoscale has gained much attention given their applications as electrochemical double-layer capacitors (EDLCs) [1,2,3,4,5]
We report in figure 2(a) the profile of ∣∣(r) for [BuMe3N+][Tf2N−] confined in the carbon nanotubes (CNTs)(20,20) for two different temperatures T

Summary

Introduction

Ionic Liquids (ILs) are molten salts composed of large organic cations and inorganic or organic anions. ILs are widely studied given their applications [1, 2] associated with their physical properties such as negligible vapor pressure, thermal stability, high ionic conductivity, etc. Over the last few years, the confinement of ILs at the nanoscale has gained much attention given their applications as electrochemical double-layer capacitors (EDLCs) [1,2,3,4,5]. ILs are considered as potential lubricants [6] when confined into nanoporous materials such as carbon nanotubes (CNTs) [7]. The macroscopic performance of nanoconfined ILs is controlled by their physical properties at the nanoscale [8,9,10], that are deviated from the bulk phase. Determination and understanding of the physical properties at the molecular scale of confined ILs is critical for the rational design of industrial processes with optimal properties

Methods

Results

Conclusion