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Beh, Eugene

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Beh

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Beh, Eugene

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2016 - 20173

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Author's Publications: search.filters.isAuthorOfPublication.6d7fabb0-7cf1-43ed-beea-68268422edc0

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Now showing 1 - 3 of 3
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    A Neutral pH Aqueous Organic–Organometallic Redox Flow Battery with Extremely High Capacity Retention
    (American Chemical Society (ACS), 2017) Beh, Eugene; De Porcellinis, Diana; Gracia, Rebecca; Xia, Kay; Gordon, Roy; Aziz, Michael
    We demonstrate an aqueous organic and organometallic redox flow battery utilizing reactants composed of only earth-abundant elements and operating at neutral pH. The positive electrolyte contains bis((3-trimethylammonio)propyl)ferrocene dichloride, and the negative electrolyte contains bis(3trimethylammonio)propyl viologen tetrachloride; these are separated by an anion-conducting membrane passing chloride ions. Bis(trimethylammoniopropyl) functionalization leads to ∼2 M solubility for both reactants, suppresses higher-order chemical decomposition pathways, and reduces reactant crossover rates through the membrane. Unprecedented cycling stability was achieved with capacity retention of 99.9943%/cycle and 99.90%/ day at a 1.3 M reactant concentration, increasing to 99.9989%/ cycle and 99.967%/day at 0.75−1.00 M; these represent the highest capacity retention rates reported to date versus time and versus cycle number. We discuss opportunities for future performance improvement, including chemical modification of a ferrocene center and reducing the membrane resistance without unacceptable increases in reactant crossover. This approach may provide the decadal lifetimes that enable organic−organometallic redox flow batteries to be cost-effective for grid-scale electricity storage, thereby enabling massive penetration of intermittent renewable electricity.
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    A redox-flow battery with an alloxazine-based organic electrolyte
    (Springer Nature, 2016) Lin, Kaixiang; Gómez-Bombarelli, Rafael; Beh, Eugene; Tong, Liuchuan; Chen, Qing; Valle, Alvaro; Aspuru-Guzik, Alan; Aziz, Michael; Gordon, Roy
    Redox-flow batteries (RFBs) can store large amounts of electrical energy from variable sources, such as solar and wind. Recently, redox-active organic molecules in aqueous RFBs have drawn substantial attention due to their rapid kinetics and low membrane crossover rates. Drawing inspiration from nature, here we report a high-performance aqueous RFB utilizing an organic redox compound, alloxazine, which is a tautomer of the isoalloxazine backbone of vitamin B2. It can be synthesized in high yield at room temperature by single-step coupling of inexpensive o-phenylenediamine derivatives and alloxan. The highly alkaline-soluble alloxazine 7/8-carboxylic acid produces a RFB exhibiting open-circuit voltage approaching 1.2 V and current efficiency and capacity retention exceeding 99.7% and 99.98% per cycle, respectively. Theoretical studies indicate that structural modification of alloxazine with electron-donating groups should allow further increases in battery voltage. As an aza-aromatic molecule that undergoes reversible redox cycling in aqueous electrolyte, alloxazine represents a class of radical-free redox-active organics for use in large-scale energy storage.
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    Comparison of Capacity Retention Rates During Cycling of Quinone-Bromide Flow Batteries
    (Cambridge University Press (CUP), 2016) Gerhardt, Michael; Beh, Eugene; Tong, Liuchuan; Gordon, Roy; Aziz, Michael
    We use cyclic charge-discharge experiments to evaluate the capacity retention rates of two quinone-bromide flow batteries (QBFBs). These aqueous QBFBs use a negative electrolyte containing either anthraquinone-2,7-disulfonic acid (AQDS) or anthraquinone-2-sulfonic acid (AQS) dissolved in sulfuric acid, and a positive electrolyte containing bromine and hydrobromic acid. We find that the AQS cell exhibits a significantly lower capacity retention rate than the AQDS cell. The observed AQS capacity fade is corroborated by NMR evidence that suggests the formation of hydroxylated products in the electrolyte in place of AQS. We further cycle the AQDS cell and observe a capacity fade rate extrapolating to 30% loss of active species after 5000 cycles. After about 180 cycles, bromine crossover leads to sufficient electrolyte imbalance to accelerate the capacity fade rate, indicating that the actual realization of long cycle life will require bromine rebalancing or a membrane less permeable than Nafion® to molecular bromine.