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  1. Article ; Online: Electric double layer formation and storing energy processes on graphene-based supercapacitors from electrical and thermodynamic perspectives.

    Fileti, Eudes Eterno

    Journal of molecular modeling

    2020  Volume 26, Issue 6, Page(s) 159

    Abstract: Atomistic molecular dynamics simulations were used to investigate the processes of electrical double layer formation and electrolyte confinement in graphene-based supercapacitors. For both processes, free energy calculations were used to analyze the ... ...

    Abstract Atomistic molecular dynamics simulations were used to investigate the processes of electrical double layer formation and electrolyte confinement in graphene-based supercapacitors. For both processes, free energy calculations were used to analyze the thermodynamics involved in the electrolyte confinement and its re-arrangement in a double layer on the electrode surface. The value of the free energy of the formation of the double electric layer was related to the energy required to charge the supercapacitor, i.e., the energy density stored, and compared with values obtained using Poisson's electrostatic formalism, which is the conventionally employed approach. Both analyzes were consistent with each other, presenting compatible values for the stored energy.
    Language English
    Publishing date 2020-05-28
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 1284729-X
    ISSN 0948-5023 ; 1610-2940
    ISSN (online) 0948-5023
    ISSN 1610-2940
    DOI 10.1007/s00894-020-04428-y
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Assessing the impact of valence asymmetry in ionic solutions and its consequences on the performance of supercapacitors.

    Messias, Andresa / Fileti, Eudes E

    Physical chemistry chemical physics : PCCP

    2022  Volume 24, Issue 34, Page(s) 20445–20453

    Abstract: Molecular dynamics simulations were performed to describe the properties of hypothetical salt electrolytic solutions. The main focus of this work is the valence asymmetry, which in recent years has been considered an important aspect in the physical ... ...

    Abstract Molecular dynamics simulations were performed to describe the properties of hypothetical salt electrolytic solutions. The main focus of this work is the valence asymmetry, which in recent years has been considered an important aspect in the physical chemistry of aqueous electrolytes. In general, our results show that the structural, energetic, and dynamic properties respond differently to the asymmetry of ionic solutions, but in all cases, appreciable changes were observed. Graphene supercapacitors based on the investigated electrolytes were studied in light of their electrostatic properties. We observed that the electrode capacitances, positive and negative, were greatly influenced by the presence of cations in the electrical double layer of the negative electrode and by the absence of these cations, in the double layer of the positive electrode. In general, we assess that quantitative variations due to valence asymmetry may indeed be an important factor for the development of new and more efficient electrolytes.
    MeSH term(s) Cations/chemistry ; Electric Capacitance ; Electrodes ; Electrolytes/chemistry ; Ionic Liquids/chemistry
    Chemical Substances Cations ; Electrolytes ; Ionic Liquids
    Language English
    Publishing date 2022-08-31
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/d2cp00348a
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Investigating the asymmetry in the EDL response of C

    Fileti, Eudes Eterno / Colherinhas, Guilherme

    Physical chemistry chemical physics : PCCP

    2019  Volume 21, Issue 28, Page(s) 15362–15371

    Abstract: Development of efficient electrodes is one of the main ways to increase the performance of an electrochemical energy storage device. It is known that such performance is associated with the electrode specific area, which allows a much larger interfacial ... ...

    Abstract Development of efficient electrodes is one of the main ways to increase the performance of an electrochemical energy storage device. It is known that such performance is associated with the electrode specific area, which allows a much larger interfacial interaction with the electrolyte. In this work, molecular dynamics is employed to model C60/graphene composite electrodes that can expand the effective area by approximately 70% relative to a pure graphene electrode. Our simulations indicate that the performance of supercapacitors of C60/graphene electrodes is superior to those made of planar graphene, in some cases up to 150%. The inherent electrolyte asymmetry in the investigated supercapacitors has a negative effect on the total capacitance, indicating that even better results could be obtained after rational design of the fullerene density on the surface of the graphene as well as the choice of the ions in the liquid ionic composition.
    Language English
    Publishing date 2019-07-25
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/c9cp02664a
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Atomistic description of fullerene-based membranes.

    Fileti, Eudes Eterno

    The journal of physical chemistry. B

    2014  Volume 118, Issue 43, Page(s) 12471–12477

    Abstract: We present extensive atomistic molecular dynamics simulations of the structure and stability of fullerene-based membranes. The simulations provide a molecular description of the PhK (pentaaryl[60]fullerene anions, C60Ar5(-)·K(+)) and C8K (C60Ar5(-)·K(+) ... ...

    Abstract We present extensive atomistic molecular dynamics simulations of the structure and stability of fullerene-based membranes. The simulations provide a molecular description of the PhK (pentaaryl[60]fullerene anions, C60Ar5(-)·K(+)) and C8K (C60Ar5(-)·K(+) with octyl substituents) membranes. Physical chemical properties and molecular organization of PhK and C8K membranes elucidate various aspects related to their formation and potential applications. Our simulations evidence that such membranes are robust and stable. PhK membranes proved very stable and compact. Considering experimental evidence, PhK bilayer is an adequate model for the surface of the PhK vesicle.
    Language English
    Publishing date 2014-10-30
    Publishing country United States
    Document type Journal Article
    ISSN 1520-5207
    ISSN (online) 1520-5207
    DOI 10.1021/jp507296r
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article: Computational Study of the Properties of Acetonitrile/Water-in-Salt Hybrid Electrolytes as Electrolytes for Supercapacitors

    Inoue, Pedro / Fileti, Eudes / Malaspina, Thaciana

    Journal of physical chemistry. 2020 June 18, v. 124, no. 27

    2020  

    Abstract: Normal and water-in-salt Li–bis(trifluoromethane) sulfonimide anion-based electrolytes were modeled using atomistic molecular dynamics simulations. Their acetonitrile (ACN) mixtures, in various concentrations, were also studied to evaluate the impact of ... ...

    Abstract Normal and water-in-salt Li–bis(trifluoromethane) sulfonimide anion-based electrolytes were modeled using atomistic molecular dynamics simulations. Their acetonitrile (ACN) mixtures, in various concentrations, were also studied to evaluate the impact of a cosolvent on the structural, dynamical, and electrical properties of the electrolytes using liquid electrolyte and supercapacitor models. Our simulations for pure and ACN-based electrolytes revealed a drastic difference that exists between normal electrolytes and water-in-salt electrolytes and a systematic reduction of the diffusion of species by approximately a factor of 2 because of the ACN impact. Electrolytic cells for each electrolyte were built with graphene as the electrode. Our results for capacitance reveal an asymmetry between the electrode capacitances, with negative electrode capacitance systematically higher than those of the positive electrode. The total capacitance of the electrode exhibited negligible variations regardless of the concentration and composition of the electrolyte.
    Keywords acetonitrile ; asymmetry ; capacitance ; electrochemical capacitors ; electrodes ; electrolytes ; graphene ; liquids ; molecular dynamics
    Language English
    Dates of publication 2020-0618
    Size p. 5685-5695.
    Publishing place American Chemical Society
    Document type Article
    Note NAL-AP-2-clean
    ISSN 1520-5207
    DOI 10.1021/acs.jpcb.0c03516
    Database NAL-Catalogue (AGRICOLA)

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  6. Article ; Online: Computational Study of the Properties of Acetonitrile/Water-in-Salt Hybrid Electrolytes as Electrolytes for Supercapacitors.

    Inoue, Pedro / Fileti, Eudes / Malaspina, Thaciana

    The journal of physical chemistry. B

    2020  Volume 124, Issue 27, Page(s) 5685–5695

    Abstract: Normal and water-in-salt Li-bis(trifluoromethane) sulfonimide anion-based electrolytes were modeled using atomistic molecular dynamics simulations. Their acetonitrile (ACN) mixtures, in various concentrations, were also studied to evaluate the impact of ... ...

    Abstract Normal and water-in-salt Li-bis(trifluoromethane) sulfonimide anion-based electrolytes were modeled using atomistic molecular dynamics simulations. Their acetonitrile (ACN) mixtures, in various concentrations, were also studied to evaluate the impact of a cosolvent on the structural, dynamical, and electrical properties of the electrolytes using liquid electrolyte and supercapacitor models. Our simulations for pure and ACN-based electrolytes revealed a drastic difference that exists between normal electrolytes and water-in-salt electrolytes and a systematic reduction of the diffusion of species by approximately a factor of 2 because of the ACN impact. Electrolytic cells for each electrolyte were built with graphene as the electrode. Our results for capacitance reveal an asymmetry between the electrode capacitances, with negative electrode capacitance systematically higher than those of the positive electrode. The total capacitance of the electrode exhibited negligible variations regardless of the concentration and composition of the electrolyte.
    Language English
    Publishing date 2020-06-30
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 1520-5207
    ISSN (online) 1520-5207
    DOI 10.1021/acs.jpcb.0c03516
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Salt-in-water and water-in-salt electrolytes: the effects of the asymmetry in cation and anion valence on their properties.

    Messias, Andresa / C da Silva, Débora A / Fileti, Eudes E

    Physical chemistry chemical physics : PCCP

    2021  Volume 24, Issue 1, Page(s) 336–346

    Abstract: We investigated the structural, dynamic, energetic, and electrostatic properties of electrolytes based on the ion pairs LiCl and ... ...

    Abstract We investigated the structural, dynamic, energetic, and electrostatic properties of electrolytes based on the ion pairs LiCl and Li
    Language English
    Publishing date 2021-12-22
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/d1cp04259a
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Solubility origin at the nanoscale: enthalpic and entropic contributions in polar and nonpolar environments.

    Fileti, Eudes / Chaban, Vitaly V

    Physical chemistry chemical physics : PCCP

    2017  Volume 19, Issue 5, Page(s) 3903–3910

    Abstract: Nanostructures are known to be poorly soluble, irrespective of their elemental composition, shape, electronic structure, dipole moment, hydrophobicity/hydrophilicity and the employed solvent. The methods of colloid chemistry allow for preparing ... ...

    Abstract Nanostructures are known to be poorly soluble, irrespective of their elemental composition, shape, electronic structure, dipole moment, hydrophobicity/hydrophilicity and the employed solvent. The methods of colloid chemistry allow for preparing suspensions - metastable systems, the stabilities of which differ greatly from one another - but not real solutions. A systematic investigation of the solubility origin at the nanoscale is hereby reported in terms of its fundamental constituents: enthalpy and entropy. Slightly different one-dimensional solutes - narrow carbon nanotubes (CNTs) of different lengths - were considered in hydrophilic (water) and hydrophobic (benzene) environments. We decompose the process of solvation into the solid → gas transition (sublimation) and the gas → liquid transition (condensation). Sublimation is a thermodynamically unfavorable process under room conditions, while the condensation transition depends on the solvent-solute interactions (enthalpic contribution). Unlike solvation of small molecules, solvation of the nanostructures results in a significant alteration of entropy. This alteration is proportional to the linear dimensions of the nanostructure. If the solvent exhibits peculiar solvent-solvent interactions (such as hydrogen bonding in water), solvation is entropically forbidden, irrespective of the solute nature and its nanoscale dimensions. In the case of the hydrophobic solvent (benzene), the condensation transition can be both enthalpically and entropically favorable. The free energy of solvation is in direct proportion to the CNT length. While highlighting principal difficulties in solvating nanostructures, this paper discusses an optimal choice of solvents for solutes exhibiting hydrophobic and hydrophilic interactions with their environments. Our results allow us to predict the solvation of an arbitrary nanostructure using its small, about 2 nm, atomistic model.
    Language English
    Publishing date 2017-02-01
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/c6cp07667j
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article: Comparing Graphite and Graphene Oxide Supercapacitors with a Constant Potential Model

    Pereira, Guilherme Ferreira Lemos / Fileti, Eudes Eterno / Siqueira, Leonardo José Amaral

    Journal of physical chemistry. 2021 Jan. 26, v. 125, no. 4

    2021  

    Abstract: Electric double-layer capacitors store energy because of the adsorption of ions on the surface of electrodes. A realistic model to describe the electrolyte–electrode interface is based on the constant potential method that allows the electrode charges to ...

    Abstract Electric double-layer capacitors store energy because of the adsorption of ions on the surface of electrodes. A realistic model to describe the electrolyte–electrode interface is based on the constant potential method that allows the electrode charges to fluctuate in order to try to mimic the polarization of metallic electrodes [J. Phys. Chem. Lett. 2013, 4, 264–268]. We performed molecular dynamics simulations of graphene oxide (GO) electrodes using the constant potential model comparing carefully the interface structure, polarization, and charging processes of an ionic liquid with the respective properties calculated for graphite electrodes. The layered structure of the ions at the electrode–electrolyte interface is less organized in comparison with that observed for graphite electrodes, which reduces overscreening. With regard to performance in terms of energy storage, graphite performs better than GO in a wide range of applied voltages. The charging dynamics of GO is slower at low applied voltages. At high voltages, the stronger electrostatic interactions between the charged electrode and electrolyte prevail, allowing for similar charging times for both supercapacitors.
    Keywords adsorption ; electrochemical capacitors ; graphene ; graphene oxide ; ionic liquids ; molecular dynamics
    Language English
    Dates of publication 2021-0126
    Size p. 2318-2326.
    Publishing place American Chemical Society
    Document type Article
    Note NAL-AP-2-clean
    ISSN 1932-7455
    DOI 10.1021/acs.jpcc.0c10347
    Database NAL-Catalogue (AGRICOLA)

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  10. Article ; Online: Atomically precise understanding of nanofluids: nanodiamonds and carbon nanotubes in ionic liquids.

    Chaban, Vitaly V / Fileti, Eudes Eterno

    Physical chemistry chemical physics : PCCP

    2016  Volume 18, Issue 38, Page(s) 26865–26872

    Abstract: A nanofluid (NF) is composed of a base liquid and suspended nanoparticles (NPs). High-performance NFs exhibit significantly better heat conductivities, as compared to their base liquids. In the present work, we applied all-atom molecular dynamics (MD) ... ...

    Abstract A nanofluid (NF) is composed of a base liquid and suspended nanoparticles (NPs). High-performance NFs exhibit significantly better heat conductivities, as compared to their base liquids. In the present work, we applied all-atom molecular dynamics (MD) simulations to characterize diffusive and ballistic energy transfer mechanisms within nanodiamonds (NDs), carbon nanotubes (CNTs), and N-butylpyridinium tetrafluoroborate ionic liquid (IL). We showed that heat transfer within both NDs and CNTs is orders of magnitude faster than that in the surrounding IL, whereas diffusion of all particles in the considered NF is similar. Intramolecular heat transfer in NPs is a key factor determining the difference of NFs from base liquids. Solvation free energy of NDs and CNTs in ILs was estimated from MD simulations. The geometric dimensions of NPs were shown to be a major source of entropic penalty. Temperature adjusts the entropic factor substantially by modifying a genuine local structure of the bulk base liquid. Our work contributes to engineering more stable and productive suspensions of NPs in ILs, which are necessary for essential progress in the field of NFs.
    Language English
    Publishing date 2016-09-29
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/c6cp04786f
    Database MEDical Literature Analysis and Retrieval System OnLINE

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