Structure and Stability of the Ionic Liquid Clusters [EMIM]n[BF4]n+1-(n = 1-9): Implications for Electrochemical Separations

Jun Zhang; Eric T. Baxter; Manh Thuong Nguyen; Venkateshkumar Prabhakaran; Roger Rousseau; Grant E. Johnson; Vassiliki Alexandra Glezakou

doi:10.1021/acs.jpclett.0c01671

Structure and Stability of the Ionic Liquid Clusters [EMIM]_n[BF₄]_n+1^-(n = 1-9): Implications for Electrochemical Separations

Jun Zhang, Eric T. Baxter, Manh Thuong Nguyen, Venkateshkumar Prabhakaran, Roger Rousseau, Grant E. Johnson, Vassiliki Alexandra Glezakou

Research output: Contribution to journal › Article › peer-review

15 Scopus citations

Abstract

Precise functionalization of electrodes with size-selected ionic liquid (IL) clusters may improve the application of ILs in electrochemical separations. Herein we report our combined experimental and theoretical investigation of the IL clusters 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM]n[BF4]n+1- (n = 1-9) and demonstrate their selectivity and efficiency toward targeted adsorption of ions from solution. The structures and energies of the IL clusters, predicted with global optimization, agree with and help interpret the ion abundances and stabilities measured by high-mass-resolution electrospray ionization mass spectrometry and collision-induced dissociation experiments. The [EMIM][BF4]2- cluster, which was identified as the most stable IL cluster, was selectively soft-landed onto a working electrode. Electrochemical impedance spectroscopy revealed a lower charge transfer resistance on the soft-landed electrode containing [EMIM][BF4]2- compared with an electrode prepared by drop-casting of an IL solution containing the full range of IL clusters. Our findings indicate that specific IL clusters may be used to increase the efficiency of electrochemical separations by lowering the overpotentials involved.

Original language	English
Pages (from-to)	6844-6851
Number of pages	8
Journal	Journal of Physical Chemistry Letters
Volume	11
Issue number	16
DOIs	https://doi.org/10.1021/acs.jpclett.0c01671
State	Published - Aug 20 2020
Externally published	Yes

Funding

This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. Part of this work was performed using EMSL, a National Scientific User Facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated for DOE by Battelle for the U.S. Department of Energy under Contract DE-AC05-76RL01830. Computer resources were provided by Research Computing at PNNL and the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility operated under Contract DE-AC02-05CH11231.

Funders	Funder number
U.S. Department of Energy
Office of Science	DE-AC02-05CH11231
Basic Energy Sciences
Biological and Environmental Research
Pacific Northwest National Laboratory	DE-AC05-76RL01830
Chemical Sciences, Geosciences, and Biosciences Division

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title = "Structure and Stability of the Ionic Liquid Clusters [EMIM]n[BF4]n+1-(n = 1-9): Implications for Electrochemical Separations",

abstract = "Precise functionalization of electrodes with size-selected ionic liquid (IL) clusters may improve the application of ILs in electrochemical separations. Herein we report our combined experimental and theoretical investigation of the IL clusters 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM]n[BF4]n+1- (n = 1-9) and demonstrate their selectivity and efficiency toward targeted adsorption of ions from solution. The structures and energies of the IL clusters, predicted with global optimization, agree with and help interpret the ion abundances and stabilities measured by high-mass-resolution electrospray ionization mass spectrometry and collision-induced dissociation experiments. The [EMIM][BF4]2- cluster, which was identified as the most stable IL cluster, was selectively soft-landed onto a working electrode. Electrochemical impedance spectroscopy revealed a lower charge transfer resistance on the soft-landed electrode containing [EMIM][BF4]2- compared with an electrode prepared by drop-casting of an IL solution containing the full range of IL clusters. Our findings indicate that specific IL clusters may be used to increase the efficiency of electrochemical separations by lowering the overpotentials involved.",

author = "Jun Zhang and Baxter, {Eric T.} and Nguyen, {Manh Thuong} and Venkateshkumar Prabhakaran and Roger Rousseau and Johnson, {Grant E.} and Glezakou, {Vassiliki Alexandra}",

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AU - Nguyen, Manh Thuong

AU - Prabhakaran, Venkateshkumar

AU - Rousseau, Roger

AU - Johnson, Grant E.

AU - Glezakou, Vassiliki Alexandra

PY - 2020/8/20

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N2 - Precise functionalization of electrodes with size-selected ionic liquid (IL) clusters may improve the application of ILs in electrochemical separations. Herein we report our combined experimental and theoretical investigation of the IL clusters 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM]n[BF4]n+1- (n = 1-9) and demonstrate their selectivity and efficiency toward targeted adsorption of ions from solution. The structures and energies of the IL clusters, predicted with global optimization, agree with and help interpret the ion abundances and stabilities measured by high-mass-resolution electrospray ionization mass spectrometry and collision-induced dissociation experiments. The [EMIM][BF4]2- cluster, which was identified as the most stable IL cluster, was selectively soft-landed onto a working electrode. Electrochemical impedance spectroscopy revealed a lower charge transfer resistance on the soft-landed electrode containing [EMIM][BF4]2- compared with an electrode prepared by drop-casting of an IL solution containing the full range of IL clusters. Our findings indicate that specific IL clusters may be used to increase the efficiency of electrochemical separations by lowering the overpotentials involved.

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Structure and Stability of the Ionic Liquid Clusters [EMIM]_n[BF₄]_n+1^-(n = 1-9): Implications for Electrochemical Separations

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