Title: Theoretical and Experimental Investigation of Functionalized Cyanopyridines Yield an Anolyte with an Extremely Low Reduction Potential for Nonaqueous Redox Flow Batteries

Abstract

Abstract Cyanopyridines and cyanophenylpyridines were investigated as anolytes for nonaqueous redox flow batteries (RFBs). The three isomers of cyanopyridine are reduced at potentials of −2.2 V or lower vs. ferrocene ^+/0 (Fc ^+/0 ), but the 3‐CNPy⋅ ⁻ radical anion forms a sigma‐dimer that is re‐oxidized at E ≈−1.1 V, which would lead to poor voltaic efficiency in a RFB. Bulk electrochemical charge‐discharge cycling of the cyanopyridines in acetonitrile and 0.50 M [NBu ₄ ][PF ₆ ] shows that 2‐CNPy and 4‐CNPy lose capacity quickly under these conditions, due to irreversible chemical reaction/decomposition of the radical anions. Density‐functional theory (DFT) calculations indicated that adding a phenyl group to the cyanopyridines would, for some isomers, limit dimerization and improve the stability of the radical anions, while shifting their E _1/2 only about +0.10 V relative to the parent cyanopyridines. Among the cyanophenylpyridines, 3‐CN‐6‐PhPy and 3‐CN‐4‐PhPy are the most promising as anolytes. They exhibit reversible reductions at E _1/2 =−2.19 and −2.22 V vs. ferrocene ^+/0 , respectively, and retain about half of their capacity after 30 bulk charge‐discharge cycles. An improved version of 3‐CN‐6‐PhPy with three methyl groups (3‐cyano‐4‐methyl‐6‐(3,5‐dimethylphenyl)pyridine) has an extremely low reduction potential of −2.50 V vs. Fc ^+/0 (the lowest reported for a nonaqueous RFBmore » anolyte) and loses only 0.21 % of capacity per cycle during charge‐discharge cycling in acetonitrile.« less

Authors:

Vaid, Thomas P.  ^[1];

• Search DOE PAGES for author "Vaid, Thomas P."
• Search DOE PAGES for ORCID "0000-0003-4597-0847"

Cook, Monique E. ^[1]; Scott, Jessica D. ^[1]; Borjesson Carazo, Marino ^[2]; Ruchti, Jonathan ^[3]; Minteer, Shelley D. ^[3]; Sigman, Matthew S. ^[3]; McNeil, Anne J. ^[4]; Sanford, Melanie S.  ^[1]

• Search DOE PAGES for author "Sanford, Melanie S."
• Search DOE PAGES for ORCID "0000-0001-9342-9436"

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+ Show Author Affiliations

1. Joint Center for Energy Storage Research 9700 S. Cass Avenue Argonne, Illinois 60439 USA, Department of Chemistry University of Michigan 930 North University Avenue Ann Arbor, Michigan 48109 USA
2. Joint Center for Energy Storage Research 9700 S. Cass Avenue Argonne, Illinois 60439 USA, Institute of Chemical Research of Catalonia (ICIQ) The Barcelona Institute of Science and Technology Av. Països Catalans 16 43007 Tarragona Spain
3. Joint Center for Energy Storage Research 9700 S. Cass Avenue Argonne, Illinois 60439 USA, Department of Chemistry University of Utah 315 South 1400 East Salt Lake City, Utah 84112 USA
4. Joint Center for Energy Storage Research 9700 S. Cass Avenue Argonne, Illinois 60439 USA, Department of Chemistry University of Michigan 930 North University Avenue Ann Arbor, Michigan 48109 USA, Macromolecular Science and Engineering Program University of Michigan Ann Arbor, Michigan 48109 USA

Publication Date:

Thu Oct 27 00:00:00 EDT 2022

Sponsoring Org.:

USDOE

OSTI Identifier:

1894972

Alternate Identifier(s):

OSTI ID: 1905661

Resource Type:

Published Article

Journal Name:

Chemistry - A European Journal

Additional Journal Information:

Journal Name: Chemistry - A European Journal Journal Volume: 28 Journal Issue: 70; Journal ID: ISSN 0947-6539

Publisher:

Wiley Blackwell (John Wiley & Sons)

Country of Publication:

Germany

Language:

English