Unraveling the Role of Solvation and Ion Valency on Redox-Mediated Electrosorption through In Situ Neutron Reflectometry and Ab Initio Molecular Dynamics

Riccardo Candeago; Hanyu Wang; Manh Thuong Nguyen; Mathieu Doucet; Vassiliki Alexandra Glezakou; James F. Browning; Xiao Su

doi:10.1021/jacsau.3c00705

Unraveling the Role of Solvation and Ion Valency on Redox-Mediated Electrosorption through In Situ Neutron Reflectometry and Ab Initio Molecular Dynamics

Riccardo Candeago, Hanyu Wang, Manh Thuong Nguyen, Mathieu Doucet, Vassiliki Alexandra Glezakou, James F. Browning, Xiao Su

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

5 Scopus citations

Abstract

Solvation and ion valency effects on selectivity of metal oxyanions at redox-polymer interfaces are explored through in situ spatial-temporally resolved neutron reflectometry combined with large scale ab initio molecular dynamics. The selectivity of ReO₄^- vs MoO₄^2- for two redox-metallopolymers, poly(vinyl ferrocene) (PVFc) and poly(3-ferrocenylpropyl methacrylamide) (PFPMAm) is evaluated. PVFc has a higher Re/Mo separation factor compared to PFPMAm at 0.6 V vs Ag/AgCl. In situ techniques show that both PVFc and PFPMAm swell in the presence of ReO₄^- (having higher solvation with PFPMAm), but do not swell in contact with MoO₄^2-. Ab initio molecular simulations suggest that MoO₄^2- maintains a well-defined double solvation shell compared to ReO₄^-. The more loosely solvated anion (ReO₄^-) is preferably adsorbed by the more hydrophobic redox polymer (PVFc), and electrostatic cross-linking driven by divalent anionic interactions could impair film swelling. Thus, the in-depth understanding of selectivity mechanisms can accelerate the design of ion-selective redox-mediated separation systems for transition metal recovery and recycling.

Original language	English
Pages (from-to)	919-929
Number of pages	11
Journal	JACS Au
Volume	4
Issue number	3
DOIs	https://doi.org/10.1021/jacsau.3c00705
State	Published - Mar 25 2024

Funding

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences Separations Science program, under Award Number DE-SC0021409 for X.S. M.-T.N was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, project 81462 (Harnessing Confinement Effects, Stimuli, and Reactive Intermediates in Separations). V.-A.G. acknowledges support from the LDRD program at ORNL. We thank Johannes Elbert for the synthesis of PFPMAm and PVFc, Haley Vapnik for the DSC analysis, Jisoo Choi, Beichen Xiong, and Celine Sutio for running bulk separation experiments. We also thank Jose Luis Vazquez for the graphics design of our cover art, and Dr. Cara Touretzky for providing the artistic concept. Spectroscopic ellipsometry, contact angle measurements, magnetron sputtering, spin coating in clean room were carried out in the Illinois Materials Research Laboratory Central Research Facilities, University of Illinois. A portion of this research used resources at the Spallation Neutron Source (SNS), a Department of Energy (DOE) Office of Science User Facility operated by Oak Ridge National Laboratory. Neutron reflectometry measurements were carried out on the Liquids Reflectometer at the SNS, which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, DOE.

Funders	Funder number
Basic Energy Sciences
Oak Ridge National Laboratory
U.S. Department of Energy
University of Illinois System
Scientific User Facilities Division
Laboratory Directed Research and Development
Office of Science	DE-SC0021409
Chemical Sciences, Geosciences, and Biosciences Division	81462

Keywords

ab initio molecular dynamics
electrochemical separations
electrosorption
ion selectivity
metallopolymers
neutron reflectometry
redox-polymers

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10.1021/jacsau.3c00705

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title = "Unraveling the Role of Solvation and Ion Valency on Redox-Mediated Electrosorption through In Situ Neutron Reflectometry and Ab Initio Molecular Dynamics",

abstract = "Solvation and ion valency effects on selectivity of metal oxyanions at redox-polymer interfaces are explored through in situ spatial-temporally resolved neutron reflectometry combined with large scale ab initio molecular dynamics. The selectivity of ReO4- vs MoO42- for two redox-metallopolymers, poly(vinyl ferrocene) (PVFc) and poly(3-ferrocenylpropyl methacrylamide) (PFPMAm) is evaluated. PVFc has a higher Re/Mo separation factor compared to PFPMAm at 0.6 V vs Ag/AgCl. In situ techniques show that both PVFc and PFPMAm swell in the presence of ReO4- (having higher solvation with PFPMAm), but do not swell in contact with MoO42-. Ab initio molecular simulations suggest that MoO42- maintains a well-defined double solvation shell compared to ReO4-. The more loosely solvated anion (ReO4-) is preferably adsorbed by the more hydrophobic redox polymer (PVFc), and electrostatic cross-linking driven by divalent anionic interactions could impair film swelling. Thus, the in-depth understanding of selectivity mechanisms can accelerate the design of ion-selective redox-mediated separation systems for transition metal recovery and recycling.",

keywords = "ab initio molecular dynamics, electrochemical separations, electrosorption, ion selectivity, metallopolymers, neutron reflectometry, redox-polymers",

author = "Riccardo Candeago and Hanyu Wang and Nguyen, {Manh Thuong} and Mathieu Doucet and Glezakou, {Vassiliki Alexandra} and Browning, {James F.} and Xiao Su",

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T1 - Unraveling the Role of Solvation and Ion Valency on Redox-Mediated Electrosorption through In Situ Neutron Reflectometry and Ab Initio Molecular Dynamics

AU - Candeago, Riccardo

AU - Wang, Hanyu

AU - Nguyen, Manh Thuong

AU - Doucet, Mathieu

AU - Glezakou, Vassiliki Alexandra

AU - Browning, James F.

AU - Su, Xiao

PY - 2024/3/25

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N2 - Solvation and ion valency effects on selectivity of metal oxyanions at redox-polymer interfaces are explored through in situ spatial-temporally resolved neutron reflectometry combined with large scale ab initio molecular dynamics. The selectivity of ReO4- vs MoO42- for two redox-metallopolymers, poly(vinyl ferrocene) (PVFc) and poly(3-ferrocenylpropyl methacrylamide) (PFPMAm) is evaluated. PVFc has a higher Re/Mo separation factor compared to PFPMAm at 0.6 V vs Ag/AgCl. In situ techniques show that both PVFc and PFPMAm swell in the presence of ReO4- (having higher solvation with PFPMAm), but do not swell in contact with MoO42-. Ab initio molecular simulations suggest that MoO42- maintains a well-defined double solvation shell compared to ReO4-. The more loosely solvated anion (ReO4-) is preferably adsorbed by the more hydrophobic redox polymer (PVFc), and electrostatic cross-linking driven by divalent anionic interactions could impair film swelling. Thus, the in-depth understanding of selectivity mechanisms can accelerate the design of ion-selective redox-mediated separation systems for transition metal recovery and recycling.

AB - Solvation and ion valency effects on selectivity of metal oxyanions at redox-polymer interfaces are explored through in situ spatial-temporally resolved neutron reflectometry combined with large scale ab initio molecular dynamics. The selectivity of ReO4- vs MoO42- for two redox-metallopolymers, poly(vinyl ferrocene) (PVFc) and poly(3-ferrocenylpropyl methacrylamide) (PFPMAm) is evaluated. PVFc has a higher Re/Mo separation factor compared to PFPMAm at 0.6 V vs Ag/AgCl. In situ techniques show that both PVFc and PFPMAm swell in the presence of ReO4- (having higher solvation with PFPMAm), but do not swell in contact with MoO42-. Ab initio molecular simulations suggest that MoO42- maintains a well-defined double solvation shell compared to ReO4-. The more loosely solvated anion (ReO4-) is preferably adsorbed by the more hydrophobic redox polymer (PVFc), and electrostatic cross-linking driven by divalent anionic interactions could impair film swelling. Thus, the in-depth understanding of selectivity mechanisms can accelerate the design of ion-selective redox-mediated separation systems for transition metal recovery and recycling.

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KW - electrochemical separations

KW - electrosorption

KW - ion selectivity

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Unraveling the Role of Solvation and Ion Valency on Redox-Mediated Electrosorption through In Situ Neutron Reflectometry and Ab Initio Molecular Dynamics

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