Steric effects on ion dynamics near charged electrodes

Alijó, Pedro Henrique Rodrigues; Tavares, Frederico W.; Biscaia, Evaristo C.; Secchi, Argimiro Resende

doi:10.1016/j.fluid.2013.09.065

Cited by 11 publications

(10 citation statements)

References 40 publications

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“…The non-mean-field effects are significant for RTILs due to strong electrostatic interactions and high ion densities. [41][42][43] While steric interactions and electrostatic correlations have received much attention in the recent literatures, the van der Waals attractions are often not included in the coarse-grained models for RTILs. Because dispersion forces play an important role on the bulk properties of the ionic liquids, their effects may not be negligible at interfaces and lead to a different mechanism for EDL charging process.…”

Section: Introductionmentioning

confidence: 99%

Time-dependent density functional theory for the charging kinetics of electric double layer containing room-temperature ionic liquids

Lian

Zhao

Liu

et al. 2016

The Journal of Chemical Physics

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Understanding the charging kinetics of electric double layers is of fundamental importance for the design and development of novel electrochemical devices such as supercapacitors and field-effect transistors. In this work, we study the dynamic behavior of room-temperature ionic liquids using a classical time-dependent density functional theory that accounts for the molecular excluded volume effects, the electrostatic correlations, and the dispersion forces. While the conventional models predict a monotonic increase of the surface charge with time upon application of an electrode voltage, our results show that dispersion between ions results in a non-monotonic increase of the surface charge with the duration of charging. Furthermore, we investigate the effects of van der Waals attraction between electrode/ionic-liquid interactions on the charging processes.

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Section: Introductionmentioning

confidence: 99%

Time-dependent density functional theory for the charging kinetics of electric double layer containing room-temperature ionic liquids

Lian

Zhao

Liu

et al. 2016

The Journal of Chemical Physics

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“…The Poisson-Nernst-Planck framework presented here, as well as other mean-field models with different methodologies to describe non-electrostatic effects, have a wide potential of application, with little additional effort in terms of computational cost for the numerical solution. Finally, we should emphasize that the methodology presented here improves the description of our previous model (Alijó et al, 2014a) by including electrostatic correlations under ac voltages; also allowing the exploration of new modifications, representing a possible way for future advances on the description of mobile charge dynamics via Poisson-Nernst-Planck approach.…”

Section: Alternating Current (Ac) Voltage Effectsmentioning

confidence: 94%

“…In the former we apply a dc step voltage of Here we skip the details of model derivation and show only the final formulation of mPNP model equations. For a complete description, we refer the reader to our previous work on steric effects in dc voltages (Alijó et al, 2014a), and to the manuscript that we recently submitted to Langmuir for publication (Alijó et al, 2014b). …”

Section: Methodsmentioning

confidence: 99%

“…In addition to those inherent to mean-field approaches (the solvent is a continuum without any local correlation), the ions are point-like charges, without fluctuations due to ion-ion size and electrostatic correlations, and also dispersion (van der Waals) interactions between each ion and the electrode are not considered (Alijó et al, 2014a). Although modified PNP (mPNP) derived by the inclusion of size correlation effects have experienced some success, such models fail to describe short-range Coulomb correlations, the so called electrostatic correlations.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electrostatic Correlations and Non-Electrostatic Effects on Ion Dynamics in Alternating Current Voltages*

Alijó¹,

Tavares²,

Biscaia³

et al. 2015

Anais Do XX Congresso Brasileiro De Engenharia Química

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RESUMO -We present a modified Poisson-Nernst-Planck (mPNP) model to include both non-electrostatic effects and electrostatic correlations on ion dynamics near charged parallel blocking electrodes. The first contribution appears directly on ion chemical potential, whereas the latter is addressed by a modified Poisson equation. The model consists in a partial-differential-algebraic equation system, solved by the DASSLC code, implemented in EMSO simulator. Monte Carlo simulation results were properly described without the aid of fitting parameters. The model predicts overscreening for 2:1 electrolytes, which was not accessed by classical PNP-like approaches. Alternate voltage simulations show a meaningful effect of electrostatic correlations on mobile charge dynamics for 2:1 electrolytes, where ion-ion correlations are stronger near the electrodes. This is the first report accounting for electrostatic correlations on ion dynamics via PNPlike models under alternating current (ac) voltages to the best of our knowledge.

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“…CDFT can be used to account for the ionic steric effects and electrostatic correlations neglected in the Poisson-Nernst-Planck (PNP) or Poisson-Boltzmann (PB) equations, a conventional microscopic theory for EDLs. The non-mean-field effects are significant for room-temperature ionic liquids (RTILs) due to strong electrostatic interactions and high ion densities [38][39][40].…”

Section: Introductionmentioning

confidence: 99%

Classical Density Functional Theory Insights for Supercapacitors

Lian¹,

Liu²

2018

Supercapacitors - Theoretical and Practical Solutions

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The most urgent issue for supercapacitor is to improve their energy density so that they can better compete with batteries. To design materials and interfaces for supercapacitor with higher energy density requires a deeper understanding of the factors and contributions affecting the total capacitance. In our recent works, the classical density functional theory (CDFT) was developed and applied to study the electrode/electrolyte interface behaviors, to understand capacitive energy storage. For porous electrode materials, we studied the pore size effect, curvature effect, and the surface modification of porous materials on the capacitance. Thought CDFT, we have found that the curvature effects on convex and concave EDLs are drastically different and that materials with extensive convex surfaces will lead to maximized capacitance; CDFT also predicts oscillatory variation of capacitance with pore size, but the oscillatory behavior is magnified as the curvature increases; an increase in the ionophobicity of the nanopores leads to a higher capacity for energy storage, and a pore-like impurity can enter the pore, makes the pore ionophobic and storage more energy. We also find the mixture effect, which makes more counterions pack on and more co-ions leave from the electrode surface, leads to an increase of the counterion density within the EDL and thus alargercapacitance.

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Steric effects on ion dynamics near charged electrodes

Cited by 11 publications

References 40 publications

Time-dependent density functional theory for the charging kinetics of electric double layer containing room-temperature ionic liquids

Time-dependent density functional theory for the charging kinetics of electric double layer containing room-temperature ionic liquids

Electrostatic Correlations and Non-Electrostatic Effects on Ion Dynamics in Alternating Current Voltages*

Classical Density Functional Theory Insights for Supercapacitors

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