Atomistic simulations of ammonium-based protic ionic liquids: steric effects on structure, low frequency vibrational modes and electrical conductivity

Sunda, Anurag Prakash; Mondal, Anirban; Balasubramanian, Sundaram

doi:10.1039/c4cp05353b

Cited by 38 publications

(48 citation statements)

References 48 publications

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“…The FF MD approach gives no IR signal below 200 cm −1 . As a side remark we note that Sunda et al 57 reported FF MD simulations of power spectra (vibrational density of states) for triethylammonium triflate, which showed only one band in region of 100 to 200 cm −1 .…”

Section: Ir Spectramentioning

confidence: 65%

Hydrogen bonding in the protic ionic liquid triethylammonium nitrate explored by density functional tight binding simulations

Zentel

Kühn

2016

The Journal of Chemical Physics

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The applicability of the density functional based tight binding (DFTB) method to the description of hydrogen bond dynamics and infrared spectroscopy is addressed for the exemplary protic ionic liquid triethylammonium nitrate. Potential energy curves for proton transfer in gas and liquid phase are shown to be comparable to high level coupled cluster theory in the thermally accessible range of bond lengths. Geometric correlations in the hydrogen bond dynamics are analyzed for a cluster of six ion pairs. Comparing DFTB and regular DFT data lends further support for the reliability of the DFTB method. Therefore, DFTB bulk simulations are performed to quantify the extent of geometric correlations in terms of Pauling's bond order model. Further, infrared (IR) absorption spectra are obtained and analyzed putting emphasis on the signatures of hydrogen bonding in the NH-stretching and far IR hydrogen bond range.

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Section: Ir Spectramentioning

confidence: 65%

Hydrogen bonding in the protic ionic liquid triethylammonium nitrate explored by density functional tight binding simulations

Zentel

Kühn

2016

The Journal of Chemical Physics

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“…It should be mentioned, however, that the MD relaxation processes appear to be significantly slower as compared to the experiment. This a major drawback of non-polarizable force fields 28 , 38 , 39 . Moreover, while a sum of several exponents is a good approximation for the QENS intermediate scattering functions, the corresponding MD curves are decidedly “stretched”, requiring, for example, Kohlrausch-Williams-Watts (KWW) functions for modeling.…”

Section: Resultsmentioning

confidence: 99%

Linking Structure to Dynamics in Protic Ionic Liquids: A Neutron Scattering Study of Correlated and Single-Particle Motions

Burankova

Cardozo

Rauber

et al. 2018

Sci Rep

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Coupling between dynamical heterogeneity of ionic liquids and their structural periodicity on different length-scales can be directly probed by quasielastic neutron scattering with polarization analysis. The technique provides the tools to investigate single-particle and cooperative ion motions separately and, thus, dynamics of ion associations affecting the net charge transport can be experimentally explored. The focus of this study is the structure-dynamic relationship in the protic ionic liquid, triethylammonium triflate, characterized by strong hydrogen bonds between cations and anions. The site-selective deuterium/hydrogen-isotope substitution was applied to modulate the relative contributions of different atom groups to the total coherent and incoherent scattering signal. This approach in combination with molecular dynamics simulations allowed us to obtain a sophisticated description of cation self-diffusion and confined ion pair dynamics from the incoherent spectral component by using the acidic proton as a tagged particle. The coherent contribution of the neutron spectra demonstrated substantial ion association leading to collective ion migration that preserves charge alteration on picosecond time scale, as well as correlation of the localized dynamics occurring between adjacent ions.

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“…3b and c) at $4 Å corresponds to hydrogen bonding interactions between the acidic hydrogen attached to nitrogen (H N ) and oxygen atoms of the SO 3 À group (of [TfO À ] anions or Naon) within the rst solvation shell. The N-S RDF peak at $5.5 Å arises due to the weak hydrogen bonding interactions between methyl/methylene hydrogen atoms of [dema + ] and oxygen atoms of the SO 3 À group as shown in the atomistic simulation study by Sunda et al 27 on [dema][TfO] PIL. The peak intensity of N-S RDF decreases with an increase in PIL concentration.…”

Section: Radial Distribution Functionsmentioning

confidence: 98%

“…The Molecular Dynamics (MD) simulation study by Sunda et al 26 on benzyltrialkylammonium triuoromethanesulfonate ILs has shown that the presence of C-H/phenyl interactions has a pronounced effect on ionic conductivity. Subsequently, Sunda et al 27 examined the inuence of steric effects on dynamics of ammonium triate PILs by varying the alkyl groups (methyl, ethyl, and n-propyl) on the ammonium cation. The authors concluded that an increase in the alkyl tail length leads to a decrease in electrical conductivity.…”

Section: Introductionmentioning

confidence: 99%

Ammonium-based protic ionic liquid doped Nafion membranes as anhydrous fuel cell electrolytes

Sunda

2015

J. Mater. Chem. A

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Polymer Electrolyte Membrane doped with Protic Ionic Liquids (PILs) can serve as promising materials for anhydrous proton conduction. In the present study, Molecular Dynamics simulations are performed to characterize the structure and dynamics of diethylmethylammonium triflate ([dema][TfO]) PIL doped Nafion membrane at various PIL doping and temperature. The polymer membrane PIL interface structure shows that the hydrogen bonding interactions predominantly exist between the acidic site (N-H) of the ammonium cation and SO − 3 group of [TfO − ] anion or Nafion. The distribution of SO − 3 group (of [TfO − ] anion or Nafion) around the ammonium cation increases with PIL concentration. The existence of weak hydrogen bonding interactions between the alkyl hydrogen atoms of the [dema + ] and the SO − 3 group of Nafion remain unaffected by PIL concentration. An increase in PIL doping level and temperature results in faster diffusion (higher ionic conductivity) which is in qualitative agreement with experiments. An atomic-level understanding of interfacial characteristic of quasi-solid Nafion membrane comprising with [dema][TfO] PIL is presented using classical MD simulations. Interactions of the ammonium cation with the SO − 3 group of [TfO − ] anion and Nafion membrane are similar. The intensity of hydrogen bond interactions between the ammonium cation with SO − 3 group decreases with an increase in Nafion:PIL ratios. This impact of increase in PIL doping is reflected in spatial density maps of SO − 3 distribution at the acidic site of the ammonium cation. The SO − 3 distribution over N-H bond vector becomes broad with increase in PIL concentration. The existence of weak hydrogen bonding between the alkyl tail length of the ammonium cation and [TfO − ] anion is seen from SDFs and the distribution of SO − 3 group around the alkyl tails increases Interfacial structure correlation of cation interactions with sulfonate groups (of anion or Nafion) in [dema][TfO] doped Nafion composite are competitive and equivalent.

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Atomistic simulations of ammonium-based protic ionic liquids: steric effects on structure, low frequency vibrational modes and electrical conductivity

Cited by 38 publications

References 48 publications

Hydrogen bonding in the protic ionic liquid triethylammonium nitrate explored by density functional tight binding simulations

Hydrogen bonding in the protic ionic liquid triethylammonium nitrate explored by density functional tight binding simulations

Linking Structure to Dynamics in Protic Ionic Liquids: A Neutron Scattering Study of Correlated and Single-Particle Motions

Ammonium-based protic ionic liquid doped Nafion membranes as anhydrous fuel cell electrolytes

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