Person: Aziz, Michael
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Aziz
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Michael
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Aziz, Michael
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Publication A High Voltage Aqueous Zinc–Organic Hybrid Flow Battery(Wiley, 2019-05-17) Aziz, Michael; Park, Minjoon; Kerr, Emily; De Porcellinis, Diana; Beh, Eugene S.; Fell, Eric M.; Jing, Yan; Wong, Andrew; Goulet, Marc-Antoni; Ryu, Jaechan; Gordon, Roy G.; Cho, JaephilWater‐soluble redox‐active organic molecules have attracted extensive attention as electrical energy storage alternatives to redox‐active metals that are low in abundance and high in cost. Here an aqueous zinc–organic hybrid redox flow battery (RFB) is reported with a positive electrolyte comprising a functionalized 1,4‐hydroquinone bearing four (dimethylamino)methyl groups dissolved in sulfuric acid. By utilizing a three‐electrolyte, two‐membrane configuration this acidic positive electrolyte is effectively paired with an alkaline negative electrolyte comprising a Zn/[Zn(OH)4]2− redox couple and a hybrid RFB is operated at a high operating voltage of 2.0 V. It is shown that the electrochemical reversibility and kinetics of the organic redox species can be enhanced by an electrocatalyst, leading to a cyclic voltammetry peak separation as low as 35 mV and enabling an enhanced rate capability.Publication Effect of Molecular Structure of Quinones and Carbon Electrode Surfaces on the Interfacial Electron Transfer Process(American Chemical Society (ACS), 2020-01-28) De Porcellinis, Diana; Jing, Yan; Kerr, Emily; Mejia-Mendoza, Luis Martin; Vazquez-Mayagoitia, Álvaro; Aspuru-Guzik, Alán; Sedenho, Graziela Cristina; Gordon, Roy; Crespilho, Frank; Aziz, MichaelQuinones can undergo thermodynamically reversible proton-coupled electron transfer reactions and are being applied as electroactive compounds in aqueous organic batteries. However, the electrochemical reversibility of these compounds is affected not only by their molecular structure but also by the properties of a carbon-based electrode surface. This study combines experimental and theoretical approaches to understand this dependence. We study the electron transfer kinetics of two synthesized quinone derivatives and two commercially available ones with a glassy carbon, a highly ordered pyrolytic graphite, and a high-edge-density graphite electrode (HEDGE). The electrochemical reversibility is notably improved on the HEDGE, which shows a higher density of defects and presents oxygenated functional groups at its surface. The electron transfer kinetics are controlled by adsorbed species onto the HEDGE. Molecular dynamics simulation and quantum mechanics calculations suggest defects with oxygen-containing functional groups, such as C–O and C═O, on HEDGE surfaces drive the interaction with the functional groups of the molecules, during physisorption from van der Waals forces. The presence of sulfonic acid side groups and a greater number of aromatic rings in the molecular structure may contribute to a higher stabilization of quinone derivatives on HEDGEs. We propose that high-performance carbon-based electrodes can be obtained without catalysts for organic batteries, by the engineering of carbon-based surfaces with edge-like defects and oxygenated functional groups.Publication Non-corrosive, Low-Toxicity Gel-based Microbattery from Organic and Organometallic Molecules(Royal Society of Chemistry (RSC), 2019) Crespilho, Frank; Sedenho, Graziela Cristina; De Porcellinis, Diana; Kerr, Emily; Granados-Focil, Sergio; Gordon, Roy; Aziz, MichaelMicrobatteries with safe, non-corrosive electrolyte chemistries can have an immediate positive impact on modern life applications, such as ingestible electronic pills and system-on-chip bioelectronics. Here a safe, non-corrosive and non-flammable microbattery is reported. A natural agarose hydrogel is the electrolyte-supporting matrix, and organic and organometallic molecules are the redox-active species. This device can safely meet the needs of ingestible medical microdevices as a primary battery. Additionally, this redox gel system can be used as a secondary battery for on-chip electronics applications, potentially enabling safe and cost-effective small-scale energy storage.Publication An Extremely Stable, Highly Soluble Monosubstituted Anthraquinone for Aqueous Redox Flow Batteries(Wiley, 2023-01-24) Amini, Kiana; Kerr, Emily F.; George, Thomas Y.; Alfaraidi, Abdulrahman M.; Jing, Yan; Tsukamoto, Tatsuhiro; Gordon, Roy G.; Aziz, MichaelAn extremely stable, energy‐dense (53.6 Ah L−1, 2 m transferrable electrons), low crossover (permeability of <1 × 10−13 cm2 s−1 using Nafion 212 (Nafion is a trademark polymer from DuPont)), and potentially inexpensive anthraquinone with 2‐2‐propionate ether anthraquinone structure (abbreviated 2‐2PEAQ) is synthesized and extensively evaluated under practically relevant conditions for use in the negolyte of an aqueous redox flow battery. 2‐2PEAQ shows a high stability with a fade rate of 0.03–0.05% per day at different applied current densities, cut‐off voltage windows, and concentrations (0.1 and 1.0 m) in both a full cell paired with a ferro/ferricyanide posolyte as well as a symmetric cell. 2‐2PEAQ is further shown to have extreme long‐term stability, losing only ≈0.01% per day when an electrochemical rejuvenation strategy is employed. From post‐mortem analysis (nuclear magnetic resonance (NMR), liquid chromatography–mass spectrometry (LC‐MS), and cyclic voltammetry (CV)) two degradation mechanisms are deduced: side chain loss and anthrone formation. 2‐2PEAQ with the ether linkages attached on carbons non‐adjacent to the central ring is found to have three times lower fade rate compared to its isomer with ether linkages on the carbon adjacent to the central quinone ring. The present study introduces a viable negolyte candidate for grid‐scale aqueous organic redox flow batteries.Publication Near Neutral pH Redox Flow Battery with Low Permeability and Long‐Lifetime Phosphonated Viologen Active Species(Wiley, 2020-04-06) Jin, Shijian; Fell, Eric; Vina-Lopez, Lucia; Jing, Yan; Michalak, Winston; Gordon, Roy; Aziz, MichaelA highly stable phosphonate‐functionalized viologen is introduced as the redox‐active material in a negative potential electrolyte for aqueous redox flow batteries (ARFBs) operating at nearly neutral pH. The solubility is 1.23 m and the reduction potential is the lowest of any substituted viologen utilized in a flow battery, reaching −0.462 V versus SHE at pH = 9. The negative charges in both the oxidized and the reduced states of 1,1′‐bis(3‐phosphonopropyl)‐[4,4′‐bipyridine]‐1,1′‐diium dibromide (BPP−Vi) effect low permeability in cation exchange membranes and suppress a bimolecular mechanism of viologen decomposition. A flow battery pairing BPP−Vi with a ferrocyanide‐based positive potential electrolyte across an inexpensive, non‐fluorinated cation exchange membrane at pH = 9 exhibits an open‐circuit voltage of 0.9 V and a capacity fade rate of 0.016% per day or 0.00069% per cycle. Overcharging leads to viologen decomposition, causing irreversible capacity fade. This work introduces extremely stable, extremely low‐permeating and low reduction potential redox active materials into near neutral ARFBs.Publication A Phosphonate‐Functionalized Quinone Redox Flow Battery at Near‐Neutral pH with Record Capacity Retention Rate(Wiley, 2019-02-06) Ji, Yunlong; Goulet, Marc-Antoni; Pollack, Daniel; Kwabi, David; Jin, Shijian; De Porcellinis, Diana; Kerr, Emily; Gordon, Roy; Aziz, MichaelA highly stable phosphonate‐functionalized anthraquinone is introduced as the redox‐active material in a negative potential electrolyte (negolyte) for aqueous redox flow batteries operating at nearly neutral pH. The design and synthesis of 2,6‐DPPEAQ, (((9,10‐dioxo‐9,10‐dihydroanthracene‐2,6‐diyl)bis(oxy))bis(propane‐3,1‐diyl))bis(phosphonic acid), which has a high solubility at pH 9 and above, is described. Chemical stability studies demonstrate high stability at both pH 9 and 12. By pairing 2,6‐DPPEAQ with a potassium ferri/ferrocyanide positive electrolyte across an inexpensive, nonfluorinated permselective polymer membrane, this near‐neutral quinone flow battery exhibits an open‐circuit voltage of 1.0 V and a capacity fade rate of 0.00036% per cycle and 0.014% per day, which is the lowest ever reported for any flow battery in the absence of rebalancing processes. It is further demonstrated that the negolyte pH drifts upward upon atmospheric oxygen penetration but, when oxygen is excluded, oscillates reversibly between 9 and 12 during cycling. These results enhance the suitability of aqueous‐soluble redox‐active organics for use in large‐scale energy storage, potentially enabling massive penetration of intermittent renewable electricity.Publication High-Capacity and High-Stability Electrochemical CO2 Capture Cell with Coupled Electricity Storage(American Chemical Society (ACS), 2023-01-19) Wang, Pan; Pang, Shuai; Jin, Shijian; Yang, Fengcun; Alberts, Maia; Li, Lu; Xi, Dawei; Gordon, Roy; Aziz, Michael; Ji, YunlongWe report an electrochemical cell for CO2 capture based on pH swing cycles driven through proton-coupled electron transfer of a newly developed phenazine, 2,2'-(phenazine-1,8-diyl)bis(ethane-1-sulfonate) (1,8-ESP), which exhibits high aqueous solubility, > 1.35 M, over pH range 0.00–14.90. The system operates with a high capture capacity of 0.86–1.41 mol/L, a low energetic cost of 36.4–55.2 kJ/mol, and an extremely low capacity fade rate of < 0.01%/day, depending on organic concentration. The system charge-discharge cycle provides an electrical energy storage function that can be run efficiently only for storage when called for by electricity market conditions. These results demonstrate the great potential of electrochemically-driven pH swing cycles based on proton-coupled electron transfer of redox-active organics for CO2 capture.Publication Long-Term Stability of Ferri-/Ferrocyanide as an Electroactive Component for Redox Flow Battery Applications: On the Origin of Apparent Capacity Fade(The Electrochemical Society, 2023-07-01) Fell, Eric M.; De Porcellinis, Diana; Jing, Yan; Gutierrez-Venegas, Valeria; George, Thomas Y.; Gordon, Roy G.; Granados-Focil, Sergio; Aziz, MichaelWe assess the suitability of potassium ferri-/ferrocyanide as an electroactive species for long-term utilization in aqueous organic redox flow batteries. A series of electrochemical and chemical characterization experiments was performed to distinguish between structural decomposition and apparent capacity fade of ferri-/ferrocyanide solutions used in the capacity-limiting side of a flow battery. Our results indicate that, in contrast with previous reports, no structural decomposition of ferri-/ferrocyanide occurs at tested pH values as high as 14 in the dark or in diffuse indoor light. Instead, an apparent capacity fade takes place due to a chemical reduction of ferricyanide to ferrocyanide, via chemical oxygen evolution reaction. We find that this parasitic process can be further exacerbated by carbon electrodes, with apparent capacity fade rates at pH 14 increasing with an increased ratio of carbon electrode surface area to ferricyanide in solution. Based on these results, we report a set of operating conditions that enables the long-duration cycling of alkaline ferri-/ferrocyanide electrolytes and demonstrate how apparent capacity fade rates can be engineered by the initial system setup. If protected from direct exposure to light, the structural stability of ferri-/ferrocyanide anions allows for their practical deployment as electroactive species in long duration energy storage applications.Publication A High Voltage Aqueous Zinc–Organic Hybrid Flow Battery(Wiley, 2019-05-17) Park, Minjoon; Beh, Eugene S.; Fell, Eric; Jing, Yan; Kerr, Emily; De Porcellinis, Diana; Goulet, Marc‐Antoni; Ryu, Jaechan; Wong, Andrew A.; Gordon, Roy; Cho, Jaephil; Aziz, MichaelWater‐soluble redox‐active organic molecules have attracted extensive attention as electrical energy storage alternatives to redox‐active metals that are low in abundance and high in cost. Here an aqueous zinc–organic hybrid redox flow battery (RFB) is reported with a positive electrolyte comprising a functionalized 1,4‐hydroquinone bearing four (dimethylamino)methyl groups dissolved in sulfuric acid. By utilizing a three‐electrolyte, two‐membrane configuration this acidic positive electrolyte is effectively paired with an alkaline negative electrolyte comprising a Zn/[Zn(OH)4]2− redox couple and a hybrid RFB is operated at a high operating voltage of 2.0 V. It is shown that the electrochemical reversibility and kinetics of the organic redox species can be enhanced by an electrocatalyst, leading to a cyclic voltammetry peak separation as low as 35 mV and enabling an enhanced rate capability.Publication Long Lifetime Mild pH-decoupling Aqueous Flow Battery with Practical in Situ pH Recovery(American Chemical Society (ACS), 2023-08-03) Xi, Dawei; Alfaraidi, Abdulrahman; Gao, Jinxu; Cochard, Thomas; Italiano Faria, Luana Cristina; George, Thomas; Wang, Taobo; Gordon, Roy; Liu, Richard; Aziz, MichaelAqueous redox flow batteries (ARFBs) constitute a promising technology for grid-scale electricity storage, but it is challenging to implement cell voltages exceeding the 1.23 V thermodynamic water splitting window with high Coulombic efficiency and long lifetime. pH decoupling – the creation of a pH difference between the negolyte and posolyte – can broaden the operating voltage window and improve long-term operational stability. This penalizes the efficiency, however, due to acid-base crossover induced by the pH gradient. As the voltage of the water splitting window varies linearly with pH whereas crossover fluxes vary exponentially, we employed mildly acidic and mildly basic electrolytes to develop a cell with high round-trip energy efficiency at an open-circuit voltage > 1.7 V. Moreover, we implemented an in situ acid-base regeneration system to periodically restore the negolyte and posolyte pH to their initial values. The combined system exhibits a capacity fade rate of less than 0.07% per day, a roundtrip energy efficiency of over 85%, and a Coulombic efficiency of approximately 99%. This work demonstrates principles for addressing critical issues such as lifespan, rate capability, long-term practicability, and energy efficiency in pH-decoupling ARFBs, providing guidance for the design of the next generation of high-voltage ARFBs.