Resolving charge-transfer and mass-transfer processes of VO2+/VO2+ redox species across the electrode/electrolyte interface using electrochemical impedance spectroscopy for vanadium redox flow battery

Pradipkumar Leuaa; Divya Priyadarshani; Debittree Choudhury; Rajan Maurya; Manoj Neergat

doi:10.1039/D0RA05224H

Resolving charge-transfer and mass-transfer processes of VO²⁺/VO₂⁺ redox species across the electrode/electrolyte interface using electrochemical impedance spectroscopy for vanadium redox flow battery†

Pradipkumar Leuaa,^a Divya Priyadarshani,^b Debittree Choudhury,^a Rajan Maurya^a and Manoj Neergat

*^a

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* Corresponding authors

^a Department of Energy Science and Engineering, Indian Institute of Technology Bombay (IITB), Powai, Mumbai 400076, India
E-mail: nmanoj@iitb.ac.in
Fax: +91 22 2576 4890
Tel: +91 22 2576 7893

^b Centre for Research in Nanotechnology & Science, Indian Institute of Technology Bombay (IITB), Powai, Mumbai 400076, India

Abstract

Electrochemical impedance spectroscopy is used to investigate the charge-transfer and mass-transfer processes of VO²⁺/VO₂⁺ (V⁴⁺/V⁵⁺) redox species across the carbon-modified glassy carbon disk electrode/electrolyte interface. The features of the EIS patterns depend on the potential, concentrations of the redox species and mass-transport conditions at the electrode/electrolyte interface. With the starting electrolyte containing either only V⁴⁺ or V⁵⁺ redox species, EIS shows a straight line capacitor feature, as no oxidation or reduction reaction take place at the measured open circuit potential (OCP). With the electrolyte containing equimolar concentration of V⁴⁺ and V⁵⁺, EIS pattern has both charge-transfer and mass-transfer features at the equilibrium potential. The features of the charge-transfer process are observed to be influenced by the mass-transfer process. Optimum concentrations of the V⁴⁺/V⁵⁺ redox species and supporting H₂SO₄ electrolyte are required to resolve the EIS features corresponding to the underlying physical processes. The semi-infinite linear diffusion characteristics of the V⁴⁺/V⁵⁺ redox species observed with a static condition of the electrode converges to that of a finite diffusion under hydrodynamic condition.

This article is part of the themed collection: Recent advances in redox-flow batteries

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DOI: https://doi.org/10.1039/D0RA05224H
Article type: Paper
Submitted: 14 Jun 2020
Accepted: 04 Aug 2020
First published: 20 Aug 2020
This article is Open Access

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RSC Adv., 2020,10, 30887-30895

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Resolving charge-transfer and mass-transfer processes of VO²⁺/VO₂⁺ redox species across the electrode/electrolyte interface using electrochemical impedance spectroscopy for vanadium redox flow battery

P. Leuaa, D. Priyadarshani, D. Choudhury, R. Maurya and M. Neergat, RSC Adv., 2020, 10, 30887 DOI: 10.1039/D0RA05224H

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