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Publication type: Article in scientific journal
Type of review: Peer review (publication)
Title: Exploring the thermodynamics of the bromine electrode in concentrated solutions for improved parametrisation of hydrogen-bromine flow battery models
Authors: Wlodarczyk, Jakub K.
Küttinger, Michael
Friedrich, Andreas K.
Schumacher, Jürgen O.
et. al: No
DOI: 10.1016/j.jpowsour.2021.230202
Published in: Journal of Power Sources
Volume(Issue): 508
Issue Date: 6-Aug-2021
Publisher / Ed. Institution: Elsevier
ISSN: 0378-7753
Language: English
Subjects: Redox flow battery; Renewable energy; Bromine complexation; Energy storage; Thermodynamics; Concentrated electrolytes
Subject (DDC): 621.04: Energy engineering
Abstract: Thermodynamic properties of the bromine electrode in an exemplary hydrogen–bromine flow battery (HBFB) are investigated in detail. Open-circuit potential (OCP) measurements of HBRB electrolytes in a liquid junction-free setup and electrolyte Raman spectra are employed to estimate polybromides speciation. An improved mathematical description of the bromine electrode OCP versus state of charge is provided. This paper addresses the phenomenon of polybromides formation at concentrations up to 7.7 mol L-1 HBr and 3.85 mol L-1 Br2 and their significant impact on the OCP. The model takes into account tri-, penta- and heptabromides formation, precisely modelled electrolyte activity coefficients (up to 11-molal HBr), electrolyte density, and temperature. It is elucidated that the polybromide formation constants found in literature treating dilute electrolytes are substantially too low. Newly determined equilibrium constants, applicable over a wider concentration range are provided for 25 and 43 °C together with their standard enthalpy changes. The model is successfully validated in an independent experiment using a real, pilot-scale HBFB. It is concluded that the usage of a simple Nernst-like equation to calculate the OCP of flow battery electrodes containing concentrated electrolytes leads to erroneous results.
Fulltext version: Published version
License (according to publishing contract): CC BY 4.0: Attribution 4.0 International
Departement: School of Engineering
Organisational Unit: Institute of Computational Physics (ICP)
Appears in collections:Publikationen School of Engineering

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