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Title: Aqua Ions-Graphene Interfacial and Confinement Behavior: Insights from isobaric-isothermal molecular dynamics

Abstract

We carry out a systematic micro-structural characterization of the solidfluid interface (SFI) of water and simple metal chloride aqueous solutions in contact with a free standing plate or with two such plates separated by an inter-plate distance 0 ! h( ) ! 30 at ambient conditions via isothermalisobaric molecular dynamics. With this characterization we target the interrogation of the system in search for answers to fundamental questions regarding the structure of the external and internal (confined) SFI s, the effect of the differential hydration behavior among species and its link to species expulsion from confinement. For water at ambient conditions we found that the structure of the external SFI s is independent of the interplate distance h in the range 0 ! h( ) ! 30 , i.e., the absence of wallmediated correlation effects between external and internal SFI s, and that for h < 9 the slit-pores de-wet. Moreover, we observed a selective expulsion of ions caused by the differential hydration between the anion and the cations with a consequent charging of the slit-pore. All these observations were interpreted in terms of the axial profiles for precisely defined order parameters including tetrahedral configuration, hydrogen bonding, and species coordination numbers.

Authors:
 [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1021987
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry A; Journal Volume: 115; Journal Issue: 23
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ANIONS; AQUEOUS SOLUTIONS; BEHAVIOR; BONDING; CATIONS; CHLORIDES; CONFIGURATION; CONFINEMENT; COORDINATION NUMBER; CORRELATIONS; DISTANCE; DYNAMICS; HYDRATION; HYDROGEN; INTERFACES; IONS; METALS; MICROSTRUCTURE; MOLECULAR DYNAMICS METHOD; ORDER PARAMETERS; PLATES; RANGE; TARGETS; WATER

Citation Formats

Chialvo, Ariel A, and Cummings, Peter T. Aqua Ions-Graphene Interfacial and Confinement Behavior: Insights from isobaric-isothermal molecular dynamics. United States: N. p., 2011. Web. doi:10.1021/jp110318n.
Chialvo, Ariel A, & Cummings, Peter T. Aqua Ions-Graphene Interfacial and Confinement Behavior: Insights from isobaric-isothermal molecular dynamics. United States. doi:10.1021/jp110318n.
Chialvo, Ariel A, and Cummings, Peter T. Sat . "Aqua Ions-Graphene Interfacial and Confinement Behavior: Insights from isobaric-isothermal molecular dynamics". United States. doi:10.1021/jp110318n.
@article{osti_1021987,
title = {Aqua Ions-Graphene Interfacial and Confinement Behavior: Insights from isobaric-isothermal molecular dynamics},
author = {Chialvo, Ariel A and Cummings, Peter T},
abstractNote = {We carry out a systematic micro-structural characterization of the solidfluid interface (SFI) of water and simple metal chloride aqueous solutions in contact with a free standing plate or with two such plates separated by an inter-plate distance 0 ! h( ) ! 30 at ambient conditions via isothermalisobaric molecular dynamics. With this characterization we target the interrogation of the system in search for answers to fundamental questions regarding the structure of the external and internal (confined) SFI s, the effect of the differential hydration behavior among species and its link to species expulsion from confinement. For water at ambient conditions we found that the structure of the external SFI s is independent of the interplate distance h in the range 0 ! h( ) ! 30 , i.e., the absence of wallmediated correlation effects between external and internal SFI s, and that for h < 9 the slit-pores de-wet. Moreover, we observed a selective expulsion of ions caused by the differential hydration between the anion and the cations with a consequent charging of the slit-pore. All these observations were interpreted in terms of the axial profiles for precisely defined order parameters including tetrahedral configuration, hydrogen bonding, and species coordination numbers.},
doi = {10.1021/jp110318n},
journal = {Journal of Physical Chemistry A},
number = 23,
volume = 115,
place = {United States},
year = {Sat Jan 01 00:00:00 EST 2011},
month = {Sat Jan 01 00:00:00 EST 2011}
}
  • We carry out a systematic microstructural characterization of the solid–fluid interface (SFI) of water and simple metal chloride aqueous solutions in contact with a free-standing plate or with two such plates separated by an interplate distance 0 ≤ h (Å) ≤ 30 at ambient conditions via isothermal–isobaric molecular dynamics. With this characterization, we target the interrogation of the system in search for answers to fundamental questions regarding the structure of the “external” and “internal” (confined) SFIs, the effect of the differential hydration behavior among species, and its link to species expulsion from confinement. For water at ambient conditions, we foundmore » that the structure of the “external” SFIs is independent of the interplate distance h in the range 0 ≤ h (Å) ≤ 30, that is, the absence of wall-mediated correlation effects between “external” and “internal” SFIs, and that for h < 9 Å the slit-pores dewet. Moreover, we observed a selective expulsion of ions caused by the differential hydration between the anion and the cations with a consequent charging of the slit-pore. All these observations were interpreted in terms of the axial profiles for precisely defined order parameters, including tetrahedral configuration, hydrogen bonding, and species coordination numbers.« less
  • We present a detailed molecular-based characterization via isobaricisothermal molecular dynamics simulation of the microstructure and dynamics of water-rich aqueous CO2 solutions at silica surfaces and under extreme confinement between finite silica plates at state conditions relevant to geologic capture and sequestration of carbon dioxide. The study comprises three types of slit-pore plates to represent two extreme cases of surface polarity, and a mismatched pair of plates, to interrogate the fluid behavior at and confined between heterogeneous surfaces. We found layer formation of H2O and CO2 whose strength depends on the nature of the plate surface, i.e., stronger H2O layering atmore » hydrophilic than at hydrophobic plates with a simultaneous weaker water mediated CO2 /hydrophilic-surface interactions. We observed the opposite behavior with the hydrophobic plates where the weaker water layering results from the CO2 mediated H2O/hydrophobicsurface interactions. Moreover, we illustrated how the interplay between these types of interactions and extreme fluid confinement, i.e., strong overlapping of interfacial structures, can induce a drying out of the pore environment whose immediate consequence is a significant CO2 concentration enhancement relative to that of the bulk environment. Finally, we assessed the effect of the nature of the plate surfaces on the translational diffusion coefficient of water, where we found that this property changes 2 monotonically at purely interfacial regions, but non-monotonically under confinement.« less