Influence of temperature on the structure and dynamics of the [BMIM][PF6] ionic liquid/graphite interface

Abstract

The influence of temperature on the structure and dynamics of the [BMIM][PF(6)] ionic liquid/graphite interface has been investigated by molecular dynamics simulations. The performed simulations cover a 100 K wide temperature interval, ranging from 300 K to 400 K. It was shown that the magnitudes of density peaks of anions in the vicinity of the surface decrease with increasing temperature while in the case of cations anomalous temperature behaviour of the density profile is observed: the magnitude of the second peak of cations increases with the increase of temperature. To characterize interface dynamics the local self-diffusion coefficients D(x) of ions in the normal direction to the surface and the residence time of ions in the first and second interfacial layer have been estimated. It was shown that the local self-diffusion coefficients in the vicinity of the surface correlate with the local ion density; the maxima of the function D(x)(x) for the cations (anions) coincide with the regions of reduced cation (anion) density and vice versa. Finally, the influence of temperature on the screening potential in the vicinity of a charged graphite surface has been studied. It was shown that the increase of temperature from 300 K to 400 K induces the decrease of the potential drop across the interface that implies the increase of the capacitance of the electrical double layer.

Ionic Liquids at Electrified Interfaces

“…Due to various interesting molecular-scale phenomena in RTILs at EIs and their importance for di erent applications there has been published a considerable number of molecular simulations works in the area during the last several years. 208,352,353,387,388,[440][441][442][443][444][445][446][447][448][449][450][451][452][453][454][455][456] Molecular modelling techniques were used to study not only neat RTILs at di erent EIs but also behaviour of RTIL mixtures with polar solvents. 205,[457][458][459][460] We have opted to discuss here in details only some of the molecular simulation papers, most closely related to the main line of this article.…”

Local Analyses of Ionic Liquid/Solid Interfaces by Frequency Modulation Atomic Force Microscopy and Photoemission Spectroscopy

“…As a distinctive example, alternating layers of cations and anions have been proposed as the interface structure between some ILs and negatively charged Al 2 O 3 substrate based on X‐ray reflectivity measurements, as shown schematically in Figure . Layer structures of ILs at the interfaces were also reported using force curve measurements from atomic force microscopy (AFM), resonance shear measurements, and are frequently found in molecular dynamics simulations . Formation of an EDL when the potential is applied to the electrode must modulate such unusual layered structures, thus it is apparent that a simple extension of the knowledge for usual EDL systems using other electrolytes is not enough.…”

Influence of cation chemical composition and structure on the double layer capacitance for Bi(111)|room temperature ionic liquid interface

“…The edl structure consisting of alternatingly charged layers was assumed in numerous simulations [55][56][57][58][59][60][61][62], which indirectly confirm an importance of an interesting feature of EMImBF 4 [25] and BMPyBF 4 ionic-pairs [24]. Namely the BF À 4 anion does not form H-bonds with hydrogen atoms of the pyridinium ring, but it does in EMImBF 4 ionic complex.…”