Specific distributions of anions and cations of an ionic liquid through confinement between graphene sheets

Abstract

This work was aimed to investigate the behavior, morphology, structure, and dynamical properties of pure ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]) confined between two parallel and flat graphene sheets at different interwall distances, H. Thus, molecular dynamic (MD) simulations were performed for different interwall distances including (10, 14, 16, 20, 23, and 28) Å at seven temperatures from 278 to 308 K. These results showed that the distribution and orientation of cations and anions on the graphene sheets depended on H. At the shortest H, a dense monolayer of the anions and cations was formed between two graphene sheets. The number of these layers increased as H increased. The potential energy diagram as a function of H demonstrated a minimum potential energy at H = 16 Å. Also, there was a minimum overlap between the density profiles of the cations and anions at H = 16 Å. Diffusion coefficients of the cations and anions increased as temperature and H increased. Moreover, slope of the plot of the diffusion coefficients of the cations and anions versus H significantly changed at H = 16 Å. Orientation functions revealed that most of the cations oriented parallel to the graphene sheets.

Elucidating the Properties of Graphene–Deep Eutectic Solvents Interface

“…The confinement of fluids between graphene sheets has been scarcely studied in the literature, some studies for systems closely related to DESs such as ionic liquids have been reported, , with some studies analyzing the effect of graphene–graphene distance on the properties of the confined IL . These previous results for ILs showed that adsorbed densified layers are formed on both graphenes confining the IL with a region with bulk properties separating them, which extension is dependent on the graphene–graphene distance and the type of involved ions.…”

Capillary evaporation of the ionic liquid [EMIM][BF4] in nanoscale solvophobic confinement

“…Recently, atomic force microscopy, 22,23 surface force measurements, [24][25][26] and X-ray reflectivity 27 have been used to study the layering of ILs at extended surfaces, and molecular simulations have provided a) Authors to whom correspondence should be addressed: rremsing@ temple.edu and hkashyap@chemistry.iitd.ac.in molecular-scale insights into the structural ordering of ILs at these interfaces. [28][29][30][31] In addition, the dynamics of ILs are typically slowed near surfaces, and dynamics are further slowed as the degree of confinement is increased. 26,[32][33][34][35][36][37] In many applications, self-assembly and EDLCs in particular, solvophobic effects, whereby solvent-induced forces drive the assembly of solutes, may play an essential role.…”

“…Previous work has even suggested that solvophobic effects in ILs can be more significant than those in some molecular organic solvents. 42 Although the structure of ILs in confinement and at interfaces is now becoming increasingly understood, [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] our understanding of the thermodynamics of solvophobicity in ILs is limited, and further investigation is needed to inform the development of applications that involve ILs at extended interfaces.…”

Probing the nanofriction of non-halogenated phosphonium-based ionic liquid additives in glycol ether oil on titanium surface

“…The number density profile [65][66][67] of the [P6, 6,6,14][BScB]-oil mixture (1:10) along the direction perpendicular to the substrate was calculated by molecular dynamics (MD) simulation to reveal the spatial distribution of the cation, anion, and molecules of the DEGDBE oil in a slit pore (pore width of 10.7 nm) composed of graphene and rutile. Since the Ti surface is usually covered by a native dense titanium dioxide (TiO2) layer [42], we employed rutile-TiO2 as the model substrate, and the AFM tip is modeled by a bilayer graphene.…”