Details

Autor(en) / Beteiligte

• Degoulange, Damien
• Pandya, Raj
• Deschamps, Michael
• Skiba, Dhyllan A
• Gallant, Betar M
• Gigan, Sylvain
• de Aguiar, Hilton B
• Grimaud, Alexis

Titel

Direct imaging of micrometer-thick interfaces in salt-salt aqueous biphasic systems

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 2023-04, Vol.120 (17), p.e2220662120-e2220662120

Ort / Verlag

United States: National Academy of Sciences

Erscheinungsjahr

2023

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• 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.