Title: Colocalized Raman spectroscopy – scanning electrochemical microscopy investigation of redox flow battery dialkoxybenzene redoxmer degradation pathways

Abstract

Non-aqueous redox flow batteries offer high voltages for grid-level energy storage technologies. However, decomposition of the redoxmers - redox-active molecules that make up the anolyte and catholyte in the negative and positive cell compartments - is an important challenge to overcome for long-term storage. Here, we present a spectroelectrochemical study of the catholyte candidate 2,3-dimethyl-1,4-dialkoxybenzene (C7) and its decomposition mechanisms in the presence of a model nucleophilic base, pyridine. We utilize colocalized Raman microscopy and scanning electrochemical microscopy (Raman-SECM) to quantify the chemical rates of decom-position and qualitatively identify the reaction intermediates and products. A detailed study on how the Raman-SECM parameters (electrode distance, substrate electrode, and laser focal height) influence the Raman signal of the charged catholyte C7^∙+ is presented. Using optimized conditions, we monitored the deprotonation of C7^∙+ via Raman spectroscopy and the subsequent hydrogen abstraction from solvent molecules to regenerate C7 via electrochemistry. Finite element modeling was used to fit electrochemical and spectroscopic data, quantifying the deprotonation rates as k_dep = 2000 and 700 L mol^-1 s^-1 and abstraction rates as k_abs = 0.5 and 0.2 s^{- 1} in propylene carbonate and acetonitrile solvents, respectively. Our results show the value of spatiotemporal reso-lution in evaluating themore » chemical and electrochemical behavior of materials for redox flow batteries.« less

Authors:

Danis, Andrew S. ^[1]; Counihan, Michael J. ^[1]; Hatfield, Kendrich O. ^[2]; Zhang, Jingjing ^[3]; Agarwal, Garvit ^[4]; Zhang, Lu ^[3]; Assary, Rajeev S. ^[4]; Rodríguez-López, Joaquín  ^[1]

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+ Show Author Affiliations

1. Argonne National Laboratory (ANL), Argonne, IL (United States). Joint Center for Energy Storage Research (JCESR); University of Illinois at Urbana-Champaign, IL (United States)
2. University of Illinois at Urbana-Champaign, IL (United States)
3. Argonne National Laboratory (ANL), Argonne, IL (United States). Joint Center for Energy Storage Research (JCESR); Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division
4. Argonne National Laboratory (ANL), Argonne, IL (United States). Joint Center for Energy Storage Research (JCESR); Argonne National Laboratory (ANL), Argonne, IL (United States). Materials Science Division

Publication Date:

Mon Feb 27 00:00:00 EST 2023

Research Org.:

Argonne National Laboratory (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1970501

Grant/Contract Number:  

AC02-06CH11357

Resource Type:

Accepted Manuscript

Journal Name:

Electrochimica Acta

Additional Journal Information:

Journal Volume: 447; Journal ID: ISSN 0013-4686

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

25 ENERGY STORAGE; SECM; Raman; Redox flow battery; posolyte; catholyte; degradation; EC mechanism