Molecular dynamics simulation of the electrical double layer in ionic liquids

Kislenko, Sergey A.; Амиров, Р. Х.; Samoylov, I. S.

doi:10.1088/1742-6596/418/1/012021

Cited by 22 publications

(39 citation statements)

References 33 publications

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“…29 Appling a surface potential induces a re-ordering of the normal Stern layer structure to compensate the interfacial charge; the surface is enriched in anions at positive potentials and vice-versa. [29][30][31][32][33][34] This behaviour has been theoretically validated with several important computational studies modelling the ILelectrode interface. [30][31][32][33][34][35][36][37] In a landmark 2011 paper Bazant et al 38 predicted the potential dependant normal distribution of ions with focus on overscreening and crowding of ions at electrode interfaces.…”

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confidence: 54%

“…The shorter alkyl chain allows adsorbed cations to rotate about an axis near the centre of the aromatic ring, which π -π stacks on HOPG aromatic rings. 31,64 The distance from the centre of the cation ring to the terminal hydrogen of the alkyl chain is 0.5 nm, which defines the rotating radius and accounts of the 1 nm spacing (see Figure 1). …”

Section: Discussionmentioning

confidence: 99%

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Nanostructure of the Ionic Liquid–Graphite Stern Layer

et al. 2015

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Ionic liquids (ILs) are attractive solvents for devices such as lithium ion batteries and capacitors, but their uptake is limited, partially because their Stern layer nanostructure is poorly understood compared to molecular solvents. Here, in situ amplitude-modulated atomic force microscopy has been used to reveal the Stern layer nanostructure of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIm TFSI)-HOPG (highly ordered pyrolytic graphite) interface with molecular resolution. The effect of applied surface potential and added 0.1 wt/wt % Li TFSI or EMIm Cl on ion arrangements is probed between ±1 V. For pure EMIm TFSI at open-circuit potential, well-defined rows are present on the surface formed by an anion-cation-cation-anion (A-C-C-A) unit cell adsorbed with like ions adjacent. As the surface potential is changed, the relative concentrations of cations and anions in the Stern layer respond, and markedly different lateral ion arrangements ensue. The changes in Stern layer structure at positive and negative potentials are not symmetrical due to the different surface affinities and packing constraints of cations and anions. For potentials outside ±0.4 V, images are featureless because the compositional variation within the layer is too small for the AFM tip to detect. This suggests that the Stern layer is highly enriched in either cations or anions (depending on the potential) oriented upright to the surface plane. When Li(+) or Cl(-) is present, some Stern layer ionic liquid cations or anions (respectively) are displaced, producing starkly different structures. The Stern layer structures elucidated here significantly enhance our understanding of the ionic liquid electrical double layer.

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confidence: 54%

Section: Discussionmentioning

confidence: 99%

Nanostructure of the Ionic Liquid–Graphite Stern Layer

et al. 2015

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“…With minor differences in the values of the peaks minima and relative distance to the interface, the global value of the peaks are quite similar, showing that at zero charge the packing of the ions is more dependent on the IL than on the impact of these two interfaces. 55 It is important to note that the changes in excess of local charges occur in narrow distances. In each layer of the double layer, the charge excess occurs only in a region with less than 1 Å thickness, and 3 Å is the distance that goes from the starting of the charge excess to the end of the first double layer.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Molecular Dynamics Study of the Gold/Ionic Liquids Interface

et al. 2015

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The results of a systematic molecular dynamics study of the interfacial structure between the gold (100) surface and two room-temperature ionic liquids, namely, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]) and 1-butyl-3-methylimadazolium bis(trifluoromethylsulfonyl)imide ([BMIm][NTf2]), are herein reported. It is found that near an uncharged surface the IL structure differs from its bulk, having an enhanced density extended until the two first layers. Interfacial layering is clearly observed at the gold surface, with a higher effect for the [BMIm][NTf2] IL but a higher packing for [BMIm][PF6]. In both ILs the alkyl side chains are oriented parallel to the interface while the imidazolium rings tend to be parallel to the interface in about 60% of the cases. The presence of the interface has a higher impact on the orientation of the cations than on the chemical properties of the counterion. The surface potential drop across the interface is more pronounced toward a negative value for ([BMIm][PF6]) than for ([BMIm][NTf2]), due to relatively larger local density of the anions for ([BMIm][PF6]) near the gold surface.

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“…Charge/voltage driven structural transitions in the electrical double layer (EDL) in ionic liquids (ILs) have recently attracted large interest in experimental [1,2,3,4,5,6], theoretical [7] and computational [8,9,10,11,12,13,14] communities due to the importance of this subject for a variety of IL applications [15,16].…”

Section: Introductionmentioning

confidence: 99%