The Interplay between Charge Transport and CO2 Capturing Mechanism in [EMIM][SCN] Ionic Liquid: A Broadband Dielectric Study

The hoisted increment in the CO2 emission in the atmosphere is a noteworthy environmental problem. Gas–liquid absorption is a well-known strategy that can be used to control CO2 emissions from an increased rate of fossil fuel industrializations. In this work, a combination of broadband dielectric sp...

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Published in:The journal of physical chemistry. B 2019-08, Vol.123 (30), p.6618-6626
Main Authors: K. P, Safna Hussan, Thayyil, Mohamed Shahin, Rajan, Vijisha K, Antony, Anu
Format: Article
Language:English
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Summary:The hoisted increment in the CO2 emission in the atmosphere is a noteworthy environmental problem. Gas–liquid absorption is a well-known strategy that can be used to control CO2 emissions from an increased rate of fossil fuel industrializations. In this work, a combination of broadband dielectric spectroscopy, Fourier infrared (FTIR) spectroscopy, and quantum chemical calculations were used to study the absorption, desorption and kinetic mechanism of a room temperature imidazolium ionic liquid (IL) with cyanide anion, 1-ethyl-3-methylimidazolium thiocyanate ([EMIM]­[SCN]) on CO2 exposure. Initially, the charge transport and glassy dynamics of [EMIM]­[SCN] is investigated in a wide frequency and temperature range using broadband dielectric spectroscopy and differential scanning calorimetry. The conductivity relaxation was well fitted with Havriliak–Negami function in the modulus formalism, while the dc conductivity correlated well with the Barton–Nakajima–Namikawa relation. Then, the conductometric approach was taken to monitor the interplay between the ionic conductivity of [EMIM]­[SCN] and diffusion of captured CO2 in it. The resistance of the IL increases upon CO2 exposure, indicating a chemical change at the molecular level of [EMIM]­[SCN]. The possible CO2 capturing mechanisms for [EMIM]­[SCN] were investigated with density functional theory calculations and FTIR spectroscopy. Thus, this work proposes a new strategy to explain the mechanism underlined in chemisorption of CO2 in the [EMIM]­[SCN]. This can be extended to more promising CO2 capturing materials including ionic liquids especially imidazolium-based ionic liquids with cyanide anions like dicyanimide, tricyanometanide, tetracyanoborate, etc.
ISSN:1520-6106
1520-5207
DOI:10.1021/acs.jpcb.9b03929