Person: Amini, Kiana
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Amini
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Kiana
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Amini, Kiana
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Publication The Poor Academic’s DC-Offset for Reversing Polarity in Electrochemical Cells: Application to Redox Flow Cells(The Electrochemical Society, 2022-09-01) Amini, Kiana; Fell, Eric; Aziz, MichaelWe provide a simple and inexpensive manual DC-offset method for extending the accepted voltage range of a battery cycler to negative voltages, without interfering with the actual operation of the electrochemical cell under the test or exceeding the voltage specs of the battery cycler instrument. We describe the working principles of the method and validate the proposed setup by operating short-term and long-term redox flow battery cycling using compositionally symmetric cell, with open-circuit voltage of zero, and full cell configurations. The method can be used to extend the capability of battery cycler instrumentation to operate any electrochemical cell that requires the polarity to be reversed during operation. Applications include cycling of other symmetric cells (e.g., Li-ion cells), implementation of polarity reversal steps for rejuvenation of electroactive species or rebalancing electrochemical cells, and alternating polarity for electrochemical synthesis.Publication In Situ Techniques for Quinone-Mediated Electrochemical Carbon Capture and Release in Aqueous Environments(American Chemical Society (ACS), 2024-01-31) Amini, Kiana; Cochard, Thomas; Jing, Yan; Sosa, Jordan D.; Xi, Dawei; Alberts, Maia; Emanuel, Michael S.; Kerr, Emily F.; Gordon, Roy G.; Aziz, MichaelWe present two novel experimental techniques designed to quantify the contributions of nucleophilicity-swing and pH-swing mechanisms to carbon capture in the electrochemical aqueous quinone-based CO2 capture process. Through thermodynamic analysis, we elucidate the intricate interplay between these two mechanisms, and emphasize the critical role of understanding this interplay in the material discovery cycle for carbon capture applications. This insight prompts the development of two innovative in situ techniques. The first technique capitalizes on discernible voltage signature differences between quinone, and quinone-CO2 adducts. By incorporating a reference electrode into the carbon capture cell setup, we apply this method to investigate bis[3-(trimethylammonio)propyl]-anthraquinones (BTMAPAQs). Our findings reveal the isolated contributions of nucleophilicity-swing and pH-swing mechanisms to overall carbon capture capacity under varying wait times and CO2 partial pressures. The second method is developed based on our finding that the adduct form of the quinone exhibits a fluorescence emission from an incident light at wavelengths distinct from the fluorescence of the reduced form, enabling differentiation through optical band-pass filtering at each unique fluorescent signature. Thus, we introduce a non-invasive, in situ approach using fluorescence microscopy, providing the unique capability to distinguish between oxidized, reduced, and adduct species with sub-second time resolution at single digit micrometer resolution. This powerful technique holds significant promise for studying such systems, representing an advancement in our ability to understand carbon capture processes.Publication Electrochemical Performance of Mixed Redox-Active Organic Molecules in Redox Flow Batteries(The Electrochemical Society, 2023-12-01) Amini, Kiana; Jing, Yan; Gao, Jinxu; Sosa, Jordan; Gordon, Roy; Aziz, MichaelDesigning electrolytes based on mixture of different organic redox active molecules brings the opportunity of enhancing the volumetric energy density of flow batteries and removes the requirement of high solubility for individual organic species in the mixture. In the present work, we conduct computational and experimental analysis to investigate the electrochemical performance of mixed redox-active organic molecules. A zero-dimensional transient model is employed to investigate the changes in the half-cell potential and the concentrations and partial currents of individual redox reactions in a mixture of organic molecules over time. The model demonstrates the effects of individual properties of species such as kinetic rate constants, mass transfer coefficients, concentration ratios and standard redox potentials and reports the effect of energy-losing homogenous chemical redox reaction on the voltage efficiency and concentration ratios of the mixed species. Pairs of anthraquinone negolyte species were selected for an experimental case study. A mixture of 2,6-N-TSAQ and 2,6-DHAQ showed 40% increase in the volumetric energy density compared to the performance of 2,6-DHAQ alone. Based on the results of the experimental and computational analysis, we propose guidelines for the design of suitable mixed redox-active organic species.Publication Highly Stable, Low Redox Potential Quinone for Aqueous Flow Batteries(Wiley, 2022-02-24) Wu, Min; Bahari, Meisam; Jing, Yan; Amini, Kiana; Fell, Eric; George, Thomas; Gordon, Roy; Aziz, MichaelAqueous organic redox flow batteries are promising candidates for large-scale energy storage. However, the design of stable and inexpensive electrolytes is challenging. Here, we report a highly stable, low redox potential, and potentially inexpensive negolyte species, sodium 3,3′,3′′,3′′′-((9,10-anthraquinone-2,6-diyl)bis(azanetriyl))tetrakis(propane-1-sulfonate) (2,6-N-TSAQ), which is synthesized in a single step from inexpensive precursors. Pairing 2,6-N-TSAQ with potassium ferrocyanide at pH=14 yielded a battery with the highest open-circuit voltage, 1.14 V, of any anthraquinone-based cell with a capacity fade rate <10 %/yr. When 2,6-N-TSAQ was cycled at neutral pH, it exhibited two orders of magnitude higher capacity fade rate. The great difference in anthraquinone cycling stability at different pH is interpreted in terms of the thermodynamics of the anthrone formation reaction. This work shows the great potential of organic synthetic chemistry for the development of viable flow battery electrolytes and demonstrates the remarkable performance improvements achievable with an understanding of decomposition mechanisms.