Surface enhancement of water at the ionic liquid–gas interface of [HMIM][Cl] under ambient water vapor

Khalifa, Yehia; Broderick, Alicia; Newberg, John T.

doi:10.1088/1361-648x/aad102

Cited by 7 publications

(8 citation statements)

References 57 publications

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“…Upon introduction of water vapor, two additional peaks appear at higher BEs in the O 1s spectra due to interfacial water (O w ) at the gas−IL interface and gas phase water (O g ) that is present between the sample surface and the 0.5 mm aperture above the sample. Consistent with our previous water/IL AP-XPS studies, 46,47 these spectra do not change as a function of time, indicating that the surface water concentration does not change for a given pressure and the interfacial region is in equilibrium with gas phase water. Representative spectra of [C 4 mim][Ace] in the presence of 2.5 Torr for each isotherm are shown in Figure 1b.…”

Section: Resultssupporting

confidence: 90%

“…The interfacial region shows a consistently higher water mole fraction relative to the bulk. We have observed previously in a room temperature isothermal study of [C 6 mim][Cl] via AP-XPS that water is enhanced at the interface when compared to bulk absorption . This behavior of water enhancement at the IL interface relative to the bulk has also been observed by MD simulations of [C 1 mim][Cl]. , The difference in the observed x w at the gas–IL interface compared to the bulk in Figure c suggests that the thermodynamics of water varies as it crosses the [C 4 mim][Ace] gas–liquid interface during absorption and evaporation under equilibrium conditions.…”

Section: Resultssupporting

confidence: 69%

“…Recently, we have shown the ability to quantitatively assess the amount of water at the gas−IL interface as a function of variable pressure (at room temperature) using AP-XPS. 46,47 Herein, we extend these studies by assessing water as a function of both pressure and temperature using AP-XPS to extract surface thermodynamics. The standard state surface enthalpy, entropy, and free energy are compared to bulk thermodynamics modeled from existing bulk absorption measurements 48,49 in order to assess the mass transfer thermodynamics across the gas−liquid interface.…”

Section: Introductionmentioning

confidence: 99%

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Mass Transfer Thermodynamics through a Gas–Liquid Interface

et al. 2019

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Molecular level information about thermodynamic variations (enthalpy, entropy, and free energy) of a gas molecule as it crosses a gas–liquid interface is strongly lacking from an experimental perspective under equilibrium conditions. Herein, we perform in situ measurements of water interacting with the ionic liquid (IL) 1-butyl-3-methylimidazolium acetate, [C4mim][Ace], using ambient pressure X-ray photoelectron spectroscopy in order to assess the interfacial uptake of water quantitatively as a function of temperature, pressure, and water mole fraction (x w). The surface spectroscopy results are compared to existing bulk water absorption experiments, showing that the amount of water in the interfacial region is consistently greater than that in the bulk. The enthalpy and entropy of water sorption vary significantly between the gas–liquid interface and the bulk as a function of x w, with a crossover that occurs near x w = 0.6 where the water–IL mixture converts from being homogeneous (x w < 0.6) to nanostructured (x w > 0.6). Free energy results reveal that water at the gas–IL interface is thermodynamically more favorable than that in the bulk, consistent with the enhanced water concentration in the interfacial region. The results herein show that the efficacy for an ionic liquid to absorb a gas phase molecule is not merely a function of bulk solvation parameters but also is significantly influenced by the thermodynamics occurring across the gas–IL interface during the mass transfer process.

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Section: Resultssupporting

confidence: 90%

Section: Resultssupporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

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Mass Transfer Thermodynamics through a Gas–Liquid Interface

et al. 2019

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“…Rivera-Rubero and Baldelli, for example, showed that water can be removed from the IL 1-butyl-3-methylimidazolium tetrafluoroborate ([C 4 C 1 Im][BF 4 ]) at pressures of <1 × 10 –5 mbar at room temperature . The recent availability of near-ambient pressure XPS (NAPXPS) has opened up the possibility of measurements of liquid surfaces in gas pressures of up to a few tens of mbar. ,,− In our own work and in works of groups such as the Newberg group, − NAPXPS has allowed for surface-sensitive studies of the interactions between gas molecules and ILs. Herein, we examine the reaction of the superbasic IL, [P 66614 ][benzim], with CO 2 , H 2 O, and two mixed CO 2 /H 2 O vapor regimes using NAPXPS.…”

Section: Introductionmentioning

confidence: 90%

Reversible Reaction of CO₂ with Superbasic Ionic Liquid [P₆₆₆₁₄][benzim] Studied with in Situ Photoelectron Spectroscopy

Henderson

Thomas²,

Wagstaffe³

et al. 2019

J. Phys. Chem. C

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Ionic liquids (ILs) are of significant interest as CO2 capture agents, and one subgroup of ILs that has shown particular promise is that of superbasic ILs. They can absorb large quantities of CO2 in the dry state, but some will have a diminished CO2 capacity when pre-wetted. In the work presented here, the superbasic IL trihexyl-tetradecylphosphonium benzimidazolide, or [P66614][benzim], was exposed to 3 mbar CO2, 2 mbar H2O vapor, and a CO2 + H2O gas mixture; and investigated using near-ambient pressure X-ray photoelectron spectroscopy. The results show that the IL reacts with CO2 to form carbamate, and that the reaction is reversible through reduction of the surrounding gas pressure. Regardless of whether the IL was exposed to CO2 or H2O vapor first, the presence of H2O under these experimental conditions does not significantly hinder the IL's ability to absorb and react with CO2. Furthermore, the IL appears to preferentially react with CO2 over H2O vapor.

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“…An Ag/AgCl is used as a QRE in order to appropriately control the WE. Recently, our group has utilized APXPS to examine IL/gas interfaces in the presence of water vapor [63–66] . Herein these studies are extended by examining the IL 1‐butyl‐3‐methyimidazolium acetate, [C 4 mim][OAc], as a function of water vapor pressure and external bias.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Water Vapor on the Electrochemical Shift of an Ionic Liquid Measured by Ambient Pressure X‐ray Photoelectron Spectroscopy

2021

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Ionic liquids (ILs) are considered to be one of the steppingstones to fabricate next generation electrochemical devices given their unique physical and chemical properties. The addition of water to ILs significantly impact electrochemical related properties including viscosity, density, conductivity, and electrochemical window. Herein we utilize ambient pressure X‐ray photoelectron spectroscopy (APXPS) to examine the impact of water on values of the electrochemical shift (S), which is determined by measuring changes in binding energy shifts as a function of an external bias. APXPS spectra of C 1s, O 1s and N 1s regions are examined for the IL 1‐butyl‐3‐methylimidazolium acetate, [C4mim][OAc], at the IL/gas interface as a function of both water vapor pressure and external bias. Results reveal that in the absence of water vapor there is an IL ohmic drop between the working electrode and quasi reference electrode, giving rise to chemical specific S values of less than one. Upon introducing water vapor, S values approach one as a function of increasing water vapor pressure, indicating a decrease in the IL ohmic drop as the IL/water mixture becomes more conductive and the potential drop is driven by the electric double layer at the electrode/IL interface.

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Surface enhancement of water at the ionic liquid–gas interface of [HMIM][Cl] under ambient water vapor

Cited by 7 publications

References 57 publications

Mass Transfer Thermodynamics through a Gas–Liquid Interface

Mass Transfer Thermodynamics through a Gas–Liquid Interface

Reversible Reaction of CO₂ with Superbasic Ionic Liquid [P₆₆₆₁₄][benzim] Studied with in Situ Photoelectron Spectroscopy

The Influence of Water Vapor on the Electrochemical Shift of an Ionic Liquid Measured by Ambient Pressure X‐ray Photoelectron Spectroscopy

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Surface enhancement of water at the ionic liquid–gas interface of [HMIM][Cl] under ambient water vapor

Cited by 7 publications

References 57 publications

Mass Transfer Thermodynamics through a Gas–Liquid Interface

Mass Transfer Thermodynamics through a Gas–Liquid Interface

Reversible Reaction of CO2 with Superbasic Ionic Liquid [P66614][benzim] Studied with in Situ Photoelectron Spectroscopy

The Influence of Water Vapor on the Electrochemical Shift of an Ionic Liquid Measured by Ambient Pressure X‐ray Photoelectron Spectroscopy

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Product

Resources

About

Reversible Reaction of CO₂ with Superbasic Ionic Liquid [P₆₆₆₁₄][benzim] Studied with in Situ Photoelectron Spectroscopy