Synthesis and Electrochemical Characterization of [3]Radialene-based Catholytes for Aqueous Organic Redox Flow Batteries

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Turner, N. (2020). Synthesis and Electrochemical Characterization of [3]Radialene-based Catholytes for Aqueous Organic Redox Flow Batteries. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

The unsubstituted [n]radialenes are a unique class of alicyclic hydrocarbons with radiating alkenes. These compounds are typically difficult to handle and polymerize rapidly. A number of stable radialene derivatives that exhibit reversible electron transfer events are known and are candidates for use in energy storage applications. Specifically, substituted trimethylenecyclopropane dianions, a subclass of hexasubstituted [3]radialenes, are stable in water, exhibit reversible redox processes, and can be synthetically modified. These compounds are thus attractive for use in redox flow batteries (RFBs). Hexacyano-[3]radialene disodium is investigated as a pH 7 aqueous organic catholyte. The dianion and radical anion are stable in air and aqueous solutions at neutral pH. Systematic introduction of asymmetry via step-wise synthesis leads to enhanced solubility and higher capacity retention during galvanostatic cycling. An aqueous flow cell comprising a disester-tetracyano [3]radialene catholyte, sulfonated-methyl viologen as the anolyte, and a cation exchange membrane provides an operating Vcell = 0.9 V, 99.609 % coulombic efficiency, and minimum capacity fade over 50 cycles. Additionally, derivates modified with polyethylene glycol (PEG) units were synthesized in an effort to increase water solubility. A monosubstituted (monoglycol) [3]radialene dipotassium salt, 2K+[C6(CN)5(EG)]2- (EG = Ethylene glycol), was synthesized and structurally characterized. It retained its redox activity in aqueous solutions. Longer glycol chains are also being synthesized to increase solubility.

Details
Author

Turner, Nicholas

Title

Synthesis and Electrochemical Characterization of [3]Radialene-based Catholytes for Aqueous Organic Redox Flow Batteries

Physical Description

1 online resource (111 pages) : PDF

Date

2020

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

The unsubstituted [n]radialenes are a unique class of alicyclic hydrocarbons with radiating alkenes. These compounds are typically difficult to handle and polymerize rapidly. A number of stable radialene derivatives that exhibit reversible electron transfer events are known and are candidates for use in energy storage applications. Specifically, substituted trimethylenecyclopropane dianions, a subclass of hexasubstituted [3]radialenes, are stable in water, exhibit reversible redox processes, and can be synthetically modified. These compounds are thus attractive for use in redox flow batteries (RFBs). Hexacyano-[3]radialene disodium is investigated as a pH 7 aqueous organic catholyte. The dianion and radical anion are stable in air and aqueous solutions at neutral pH. Systematic introduction of asymmetry via step-wise synthesis leads to enhanced solubility and higher capacity retention during galvanostatic cycling. An aqueous flow cell comprising a disester-tetracyano [3]radialene catholyte, sulfonated-methyl viologen as the anolyte, and a cation exchange membrane provides an operating Vcell = 0.9 V, 99.609 % coulombic efficiency, and minimum capacity fade over 50 cycles. Additionally, derivates modified with polyethylene glycol (PEG) units were synthesized in an effort to increase water solubility. A monosubstituted (monoglycol) [3]radialene dipotassium salt, 2K+[C6(CN)5(EG)]2- (EG = Ethylene glycol), was synthesized and structurally characterized. It retained its redox activity in aqueous solutions. Longer glycol chains are also being synthesized to increase solubility.

Genre

masters theses

Subjects--Topics

Chemistry

Degree

M.S.

Subject Area

Chemistry

Advisor(s)

Bejger, Christopher

Committee Members

Zhang, HaiTao
Walter, Michael
Etzkorn, Markus

Degree Note

Thesis (M.S.)--University of North Carolina at Charlotte, 2020.

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Rights Holder Information

Copyright is held by the author unless otherwise indicated.

Identifier

Turner_uncc_0694N_12671

Permalink

http://hdl.handle.net/20.500.13093/etd:2577