Person: Chen, Qing
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Chen
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Qing
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Chen, Qing
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Publication UV-Vis Spectrophotometry of Quinone Flow Battery Electrolyte for in Situ Monitoring and Improved Electrochemical Modeling of Potential and Quinhydrone Formation(Royal Society of Chemistry (RSC), 2017) Tong, Liuchuan; Chen, Qing; Wong, Andrew; Gómez-Bombarelli, Rafael; Aspuru-Guzik, Alan; Gordon, Roy; Aziz, MichaelQuinone-based aqueous flow batteries provide a potential opportunity for large-scale, low-cost energy storage due to their composition from earth abundant elements, high aqueous solubility, reversible redox kinetics and their chemical tunability such as reduction potential. In an operating flow battery utilizing 9,10-anthraquinone-2,7-disulfonic acid, the aggregation of an oxidized quinone and a reduced hydroquinone to form a quinhydrone dimer causes significant variations from ideal solution behavior and of optical absorption from the Beer-Lambert law. We utilize in-situ UV-Vis spectrophotometry to establish (a), quinone, hydroquinone and quinhydrone molar attenuation profiles and (b), an equilibrium constant for formation of the quinhydrone dimer (KQHQ) ~ 80 M-1. We use the molar optical attenuation profiles to identify the total molecular concentration and state of charge at arbitrary mixtures of quinone and hydroquinone. We report density functional theory calculations to support the quinhydrone UV-Vis measurements and to provide insight into the dimerization conformations. We instrument a quinone-bromine flow battery with a Pd-H reference electrode in order to demonstrate how complexation in both the negative (quinone) and positive (bromine) electrolytes directly impacts measured half-cell and full-cell voltages. This work shows how accounting for electrolyte complexation improves the accuracy of electrochemical modeling of flow battery electrolytes.Publication Quinone electrochemistry in acidic and alkaline solutions and its application in large scale energy storage(2015) Gerhardt, Michael; Lin, Kaixiang; Chen, Qing; Marshak, Michael; Tong, Liuchuan; Gordon, Roy; Aziz, MichaelPublication High-performance Aqueous Redox Flow Battery (ARFB)(2015) Lin, Kaixiang; Chen, Qing; Eisenach, Louise; Valle, Alvaro; Gordon, Roy; Aziz, Michael; Marshak, MichaelPublication Dissection of the Voltage Losses of an Acidic Quinone Redox Flow BatteryChen, Qing; Gerhardt, Michael; Aziz, MichaelWe measure the polarization characteristics of a quinone-bromide redox flow battery with interdigitated flow fields, using electro- chemical impedance spectroscopy and voltammetry of a full cell and of a half cell against a reference electrode. We find linear polarization behavior at 50% state of charge all the way to the short-circuit current density of 2.5 A/cm2. We uniquely identify the polarization area-specific resistance (ASR) of each electrode, the membrane ASR to ionic current, and the electronic contact ASR. We use voltage probes to deduce the electronic current density through each sheet of carbon paper in the quinone-bearing electrode. By interpreting the results using the Newman 1-D porous electrode model, we deduce the volumetric exchange current density of the porous electrode. We uniquely evaluate the power dissipation and identify a correspondence to the contributions to the electrode ASR from the faradaic, electronic, and ionic transport processes. We find that, within the electrode, more power is dissipated in the faradaic process than in the electronic and ionic conduction processes combined, despite the observed linear polarization behavior. We examine the sensitivity of the ASR to the values of the model parameters. The greatest performance improvement is anticipated from increasing the volumetric exchange current density.