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Title: Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores

Authors:
; ; ; ; ; ORCiD logo; ; ;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Fluid Interface Reactions, Structures and Transport Center (FIRST)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1389046
DOE Contract Number:
ERKCC61
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nature Materials; Journal Volume: 16; Journal Issue: 12; Related Information: FIRST partners with Oak Ridge National Laboratory (lead); Argonne National Laboratory; Drexel University; Georgia State University; Northwestern University; Pennsylvania State University; Suffolk University; Vanderbilt University; University of Virginia
Country of Publication:
United States
Language:
English
Subject:
catalysis (heterogeneous), solar (fuels), energy storage (including batteries and capacitors), hydrogen and fuel cells, electrodes - solar, mechanical behavior, charge transport, materials and chemistry by design, synthesis (novel materials)

Citation Formats

Futamura, Ryusuke, Iiyama, Taku, Takasaki, Yuma, Gogotsi, Yury, Biggs, Mark J., Salanne, Mathieu, Ségalini, Julie, Simon, Patrice, and Kaneko, Katsumi. Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores. United States: N. p., 2017. Web. doi:10.1038/NMAT4974.
Futamura, Ryusuke, Iiyama, Taku, Takasaki, Yuma, Gogotsi, Yury, Biggs, Mark J., Salanne, Mathieu, Ségalini, Julie, Simon, Patrice, & Kaneko, Katsumi. Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores. United States. doi:10.1038/NMAT4974.
Futamura, Ryusuke, Iiyama, Taku, Takasaki, Yuma, Gogotsi, Yury, Biggs, Mark J., Salanne, Mathieu, Ségalini, Julie, Simon, Patrice, and Kaneko, Katsumi. 2017. "Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores". United States. doi:10.1038/NMAT4974.
@article{osti_1389046,
title = {Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores},
author = {Futamura, Ryusuke and Iiyama, Taku and Takasaki, Yuma and Gogotsi, Yury and Biggs, Mark J. and Salanne, Mathieu and Ségalini, Julie and Simon, Patrice and Kaneko, Katsumi},
abstractNote = {},
doi = {10.1038/NMAT4974},
journal = {Nature Materials},
number = 12,
volume = 16,
place = {United States},
year = 2017,
month = 9
}
  • Thermolysis of an ionic liquid (IL) gives no char residue, whereas heating the same IL trapped within an oxide framework affords high carbonization yields (see picture). This confinement method allows incorporation of heteroatoms from the parent IL in the final products, for the development of functionalized porous carbon and carbon-oxide composite materials.
  • A dynamic nuclear magnetic resonance (NMR) study of the polar fluids ethanol (EtOH) and 2,2,2-trifluoroethanol (TFE) confined to porous silica sol-gel glasses is reported. The {sup 13}C NMR spin-lattice relaxation times, T{sub 1}, were measured in glasses with pore radii ranging from 18.9 to 54.8 A, over a temperature range from -13.6 to 30.5{degree}C. The data were analyzed in terms of the two-state, fast exchange model, and surface layer relaxation times, T{sub 1s}, were calculated. On the basis of surface enhancement factors, T{sub 1b}/T{sub 1s}, where T{sub 1b} is the relaxation time of the bulk liquid, it was concluded thatmore » the more acidic TFE has a weaker hydrogen bond interaction with silica, due to the fact that the alcohols serve as hydrogen bond acceptors. The experiment shows that EtOH and TFE have nearly identical surface layer viscosities, originating from the differences in hydrogen bonding with the silica surface. Confinement was found to have little effect on the internal rotation of terminal CF{sub 3} or CH{sub 3} groups. 32 refs., 2 figs., 3 tabs.« less
  • Recent experiments have shown that the capacitance of subnanometer pores increases anomalously as the pore width decreases, thereby opening a new avenue for developing supercapacitors with enhanced energy density. However, this behavior is still subject to some controversy since its physical origins are not well understood. Using atomistic simulations, we show that the capacitance of slit-shaped nanopores in contact with room-temperature ionic liquids exhibits a U-shaped scaling behavior in pores with widths from 0.75 to 1.26 nm. The left branch of the capacitance scaling curve directly corresponds to the anomalous capacitance increase and thus reproduces the experimental observations. The rightmore » branch of the curve indirectly agrees with experimental findings that so far have received little attention. The overall U-shaped scaling behavior provides insights on the origins of the difficulty in experimentally observing the pore-width-dependent capacitance. We establish a theoretical framework for understanding the capacitance of electrical double layers in nanopores and provide mechanistic details into the origins of the observed scaling behavior. The framework highlights the critical role of 'ion solvation' in controlling pore capacitance and the importance of choosing anion/cation couples carefully for optimal energy storage in a given pore system.« less
  • Recent experiments have shown that the capacitance of sub-nanometer pores increases anomalously as the pore width decreases, thereby opening a new avenue for developing supercapacitors with enhanced energy density. However, this behavior is still subject to some controversy since its physical origins are not well understood. Using atomistic simulations, we show that the capacitance of slit-shaped nanopores in contact with room-temperature ionic liquids exhibits a U-shaped scaling behavior in pores with width from 0.75 to 1.26 nm. The left branch of the capacitance scaling curve directly corresponds to the anomalous capacitance increase and thus reproduces the experimental observations. The rightmore » branch of the curve indirectly agrees with experimental findings that so far have received little attention. The overall U-shaped scaling behavior provides insights on the origins of the difficulty in experimentally observing the pore-width dependent capacitance. We establish a theoretical framework for understanding the capacitance of electrical double layers in nanopores and provide mechanistic details into the origins of the observed scaling behavior. The framework highlights the critical role of ion solvation in controlling pore capacitance and the importance of choosing anion/cation couples carefully for optimal energy storage in a given pore system.« less
  • Here, we studied the transport of room-temperature ionic liquids (RTILs) through charged conical nanopores using a Landau-Ginzburg-type continuum model that takes steric effect and strong ion-ion correlations into account. When the surface charge is uniform on the pore wall, weak current rectification is observed. When the charge density near the pore base is removed, the ionic current is greatly suppressed under negative bias voltage while nearly unchanged under positive bias voltage, thereby leading to enhanced current rectification. These predictions agree qualitatively with prior experimental observations, and we elucidated them by analyzing the different components of the ionic current and themore » structural changes of electrical double layers (EDLs) at the pore tip under different bias voltages and surface charge patterns. These analyses reveal that the different modifications of the EDL structure near the pore tip by the positive and negative bias voltages cause the current rectification and the observed dependence on the distribution of surface charge on the pore wall. The fact that the current rectification phenomena are captured qualitatively by the simple model originally developed for describing EDLs at equilibrium conditions suggests that this model may be promising for understanding the ionic transport under nonequilibrium conditions when the EDL structure is strongly perturbed by external fields.« less