Direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems
Name
degoulange-et-al-2023-direct-imaging-of-micrometer-thick-interfaces-in-salt-salt-aqueous-biphasic-systems.pdf
Description
Published version
Size
1.16 MB
Format
Adobe PDF
Checksum (MD5)
636ebf84b643554220fd9f3d69f72101
Author(s)
Degoulange, Damien
Pandya, Raj
Deschamps, Michael
Skiba, Dhyllan A
Gallant, Betar M
Gigan, Sylvain
de Aguiar, Hilton B
Grimaud, Alexis
Date Issued
April 25, 2023
Journal
Proceedings of the National Academy of Sciences
Publisher
Proceedings of the National Academy of Sciences
Citation
Degoulange, Damien, Pandya, Raj, Deschamps, Michael, Skiba, Dhyllan A, Gallant, Betar M et al. 2023. "Direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems." Proceedings of the National Academy of Sciences, 120 (17).
Version
Final published version
Abstract
Unlike the interface between two immiscible electrolyte solutions (ITIES) formed between water and polar solvents, molecular understanding of the liquid–liquid interface formed for aqueous biphasic systems (ABSs) is relatively limited and mostly relies on surface tension measurements and thermodynamic models. Here, high-resolution Raman imaging is used to provide spatial and chemical resolution of the interface of lithium chloride - lithium bis(trifluoromethanesulfonyl)imide - water (LiCl–LiTFSI–water) and HCl–LiTFSI–water, prototypical salt–salt ABSs found in a range of electrochemical applications. The concentration profiles of both TFSI anions and water are found to be sigmoidal thus not showing any signs of a positive adsorption for both salts and solvent. More striking, however, is the length at which the concentration profiles extend, ranging from 11 to 2 µm with increasing concentrations, compared to a few nanometers for ITIES. We thus reveal that unlike ITIES, salt–salt ABSs do not have a molecularly sharp interface but rather form an interphase with a gradual change of environment from one phase to the other. This knowledge represents a major stepping-stone in the understanding of aqueous interfaces, key for mastering ion or electron transfer dynamics in a wide range of biological and technological settings including novel battery technologies such as membraneless redox flow and dual-ion batteries.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1073/pnas.2220662120
