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Solvation and Ion‐Pairing Effects of Choline Acetate Electrolyte in Protic and Aprotic Solvents Studied by NMR Titrations
Choline‐based electrolytes have been proposed as environmentally friendly and low‐cost alternatives for secondary zinc air batteries. Choline acetate [Ch](+)[OAc](−) in protic (D(2)O) and aprotic (DMSO‐d(6)) solvents has been studied by means of concentration‐dependent (1)H NMR, viscosity, and densi...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2021
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9297985/ https://www.ncbi.nlm.nih.gov/pubmed/34708481 http://dx.doi.org/10.1002/cphc.202100602 |
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author | Veroutis, Emmanouil Merz, Steffen Eichel, Rüdiger‐A. Granwehr, Josef |
author_facet | Veroutis, Emmanouil Merz, Steffen Eichel, Rüdiger‐A. Granwehr, Josef |
author_sort | Veroutis, Emmanouil |
collection | PubMed |
description | Choline‐based electrolytes have been proposed as environmentally friendly and low‐cost alternatives for secondary zinc air batteries. Choline acetate [Ch](+)[OAc](−) in protic (D(2)O) and aprotic (DMSO‐d(6)) solvents has been studied by means of concentration‐dependent (1)H NMR, viscosity, and density measurements. The viscosities have been calculated on the basis of the Jones‐Dole equation and showed that the dominant contribution originates from short‐range ion‐solvent interactions. Site‐specific association affinities were assigned from NMR chemical shift titrations. In DMSO‐d(6), the hydroxyl group of choline was found to have the smallest dissociation constant followed by the methyl group of acetate. The corresponding Gibbs energies at low concentration were found to be in agreement with a solvent‐separated ion pair (2SIP) configuration, whereas at concentrations above 300 mM, a solvent‐shared ion pair (SIP) configuration was assigned. For [Ch](+)[OAc](−) in D(2)O, association effects were found to be weaker, attributed to the high dielectric constant of the solvent. On time scales on the order of 100 ms, NMR linewidth perturbations indicated a change in the local rotational dynamics of the ions, attributed to short‐range cation‐solvent interactions and not to solvent viscosity. At 184 mM, [Formula: see text] 40 % of the cations in DMSO‐d(6) and [Formula: see text] 10 % in D(2)O were found to exhibit short‐range interactions, as indicated by the linewidth perturbations. It was found that at about 300 mM, the ions in DMSO‐d(6) exhibit a transition from free to collective translational dynamics on time scales on the order of 400 ms. In DMSO‐d(6), both ions were found to be almost equally solvated, whereas in D(2)O solvation of acetate was stronger, as indicated by the obtained effective hydrodynamic radii. For [Ch](+)[OAc](−) in DMSO‐d(6), the results suggest a solvent‐shared ion association with weak H‐bonding interactions for concentrations between 0.3–1 M. Overall, the extent of ion association in solvents such as DMSO is not expected to significantly limit charge transport and hinder the performance of choline‐based electrolytes. |
format | Online Article Text |
id | pubmed-9297985 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2021 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-92979852022-07-21 Solvation and Ion‐Pairing Effects of Choline Acetate Electrolyte in Protic and Aprotic Solvents Studied by NMR Titrations Veroutis, Emmanouil Merz, Steffen Eichel, Rüdiger‐A. Granwehr, Josef Chemphyschem Articles Choline‐based electrolytes have been proposed as environmentally friendly and low‐cost alternatives for secondary zinc air batteries. Choline acetate [Ch](+)[OAc](−) in protic (D(2)O) and aprotic (DMSO‐d(6)) solvents has been studied by means of concentration‐dependent (1)H NMR, viscosity, and density measurements. The viscosities have been calculated on the basis of the Jones‐Dole equation and showed that the dominant contribution originates from short‐range ion‐solvent interactions. Site‐specific association affinities were assigned from NMR chemical shift titrations. In DMSO‐d(6), the hydroxyl group of choline was found to have the smallest dissociation constant followed by the methyl group of acetate. The corresponding Gibbs energies at low concentration were found to be in agreement with a solvent‐separated ion pair (2SIP) configuration, whereas at concentrations above 300 mM, a solvent‐shared ion pair (SIP) configuration was assigned. For [Ch](+)[OAc](−) in D(2)O, association effects were found to be weaker, attributed to the high dielectric constant of the solvent. On time scales on the order of 100 ms, NMR linewidth perturbations indicated a change in the local rotational dynamics of the ions, attributed to short‐range cation‐solvent interactions and not to solvent viscosity. At 184 mM, [Formula: see text] 40 % of the cations in DMSO‐d(6) and [Formula: see text] 10 % in D(2)O were found to exhibit short‐range interactions, as indicated by the linewidth perturbations. It was found that at about 300 mM, the ions in DMSO‐d(6) exhibit a transition from free to collective translational dynamics on time scales on the order of 400 ms. In DMSO‐d(6), both ions were found to be almost equally solvated, whereas in D(2)O solvation of acetate was stronger, as indicated by the obtained effective hydrodynamic radii. For [Ch](+)[OAc](−) in DMSO‐d(6), the results suggest a solvent‐shared ion association with weak H‐bonding interactions for concentrations between 0.3–1 M. Overall, the extent of ion association in solvents such as DMSO is not expected to significantly limit charge transport and hinder the performance of choline‐based electrolytes. John Wiley and Sons Inc. 2021-11-03 2022-01-05 /pmc/articles/PMC9297985/ /pubmed/34708481 http://dx.doi.org/10.1002/cphc.202100602 Text en © 2021 The Authors. ChemPhysChem published by Wiley-VCH GmbH https://creativecommons.org/licenses/by-nc-nd/4.0/This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ (https://creativecommons.org/licenses/by-nc-nd/4.0/) License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made. |
spellingShingle | Articles Veroutis, Emmanouil Merz, Steffen Eichel, Rüdiger‐A. Granwehr, Josef Solvation and Ion‐Pairing Effects of Choline Acetate Electrolyte in Protic and Aprotic Solvents Studied by NMR Titrations |
title | Solvation and Ion‐Pairing Effects of Choline Acetate Electrolyte in Protic and Aprotic Solvents Studied by NMR Titrations |
title_full | Solvation and Ion‐Pairing Effects of Choline Acetate Electrolyte in Protic and Aprotic Solvents Studied by NMR Titrations |
title_fullStr | Solvation and Ion‐Pairing Effects of Choline Acetate Electrolyte in Protic and Aprotic Solvents Studied by NMR Titrations |
title_full_unstemmed | Solvation and Ion‐Pairing Effects of Choline Acetate Electrolyte in Protic and Aprotic Solvents Studied by NMR Titrations |
title_short | Solvation and Ion‐Pairing Effects of Choline Acetate Electrolyte in Protic and Aprotic Solvents Studied by NMR Titrations |
title_sort | solvation and ion‐pairing effects of choline acetate electrolyte in protic and aprotic solvents studied by nmr titrations |
topic | Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9297985/ https://www.ncbi.nlm.nih.gov/pubmed/34708481 http://dx.doi.org/10.1002/cphc.202100602 |
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