Voltammetry study of quinoxaline in aqueous electrolytes

Milshtein, Jarrod D.; Su, Liang; Liou, Catherine; Badel, Andres F.; Brushett, Fikile R.

doi:10.1016/j.electacta.2015.07.063

Cited by 55 publications

(73 citation statements)

References 40 publications

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“…The peakheight ratio is calculated by first subtracting the background current, according to a prior literature procedure, to acquire corrected peak heights and then dividing the corrected peak current of the backward scan by the corrected peak current of the forward scan. 45 Finally, the reduced and oxidized species exhibit different iron oxidation states and associate with a different number of TFSI − anions. Thus, each species is likely to exhibit a different solvated radius and subsequently different diffusion coefficient, which will impact the observed peak currents and explains the asymmetry between Figure 3a and Figure 3b.…”

Section: Resultsmentioning

confidence: 99%

Towards Low Resistance Nonaqueous Redox Flow Batteries

Milshtein

Barton

Carney

et al. 2017

J. Electrochem. Soc.

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Nonaqueous redox flow batteries (NAqRFBs) are a promising, but nascent, concept for cost-effective grid-scale energy storage. While most studies report new active molecules and proof-of-concept prototypes, few discuss cell design. The direct translation of aqueous RFB design principles to nonaqueous systems is hampered by a lack of materials-specific knowledge, especially concerning the increased viscosities and decreased conductivities associated with nonaqueous electrolytes. To guide NAqRFB reactor design, recent techno-economic analyses have established an area specific resistance (ASR) target of <5 cm 2 . Here, we employ a state-of-the-art vanadium flow cell architecture, modified for compatibility with nonaqueous electrolytes, and a model ferrocene-based redox couple to investigate the feasibility of achieving this target ASR. We identify and minimize sources of resistive loss for various active species concentrations, electrolyte compositions, flow rates, separators, and electrode thicknesses via polarization and impedance spectroscopy, culminating in the demonstration of a cell ASR of ca. 1.7 cm 2 . Further, we validate performance scalability using dynamically similar cells with a ten-fold difference in active areas. This work demonstrates that, with appropriate cell engineering, low resistance nonaqueous reactors can be realized, providing promise for the cost-competitiveness of future NAqRFBs. Grid-scale energy storage has emerged as a critical technology for alleviating the intermittency of renewables, 1 improving the efficiency of the existing grid infrastructure, and offering frequency or voltage regulation.2 Redox flow batteries (RFBs) are particularly attractive storage devices for energy-intensive grid applications.2,3 In a typical RFB, charge-storing active species are dissolved in liquid electrolytes, which are housed in large and inexpensive tanks. The electrolytes are pumped through a power-generating electrochemical reactor, where the active species undergo reduction or oxidation on the surfaces of porous electrodes to charge or discharge the battery. [3][4][5][6] This unique architecture offers several advantages over conventional battery systems, including decoupled power and energy scaling, long operational lifetimes, easy maintenance, simplified manufacturing, and high active-to-inactive materials ratio (particularly at long storage durations). Despite many attractive features, state-of-the-art RFBs are currently too expensive for widespread adoption.7 While the majority of RFB electrolytes are aqueous, 6 transitioning to nonaqueous chemistries could enable higher cell potentials via wider electrolyte stability windows, subsequently increasing the electrolyte energy density and reducing chemical costs. 6,[8][9][10][11] Furthermore, the use of nonaqueous solvents enables a broader palette of potentially inexpensive active materials, which could significantly lower RFB costs. 7,12 In contrast to their aqueous counterparts, nonaqueous redox flow batteries (NAqRFBs) are a nascent technology,...

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Section: Resultsmentioning

confidence: 99%

Towards Low Resistance Nonaqueous Redox Flow Batteries

Milshtein

Barton

Carney

et al. 2017

J. Electrochem. Soc.

Self Cite

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“…Before the introduction of all-organic redox flow batteries, organic molecules contained in aqueous electrolytes (with reasonable solubilities (> 1 mol dm -3 )) were used in early studies of regenerative fuel cells [51] and organic fuel cells [52,53]. In the case of quinoxaline, the solubility is up to 4.0 mol dm -3 in potassium hydroxide solution (0.9 mol dm -3 potassium chloride + 0.1 mol dm -3 potassium hydroxide, pH 12.9) and the redox potential in such an electrolyte is more negative than -0.70 V vs. SHE [54], although the addition of salts and solvents could reduce the solubility significantly (e.g., solubilities of quinoxaline: 4.5 mol dm -3 at at c.a.…”

Section: Introductionmentioning

confidence: 99%

Recent developments in organic redox flow batteries: A critical review

Leung

Shah

Sanz

et al. 2017

Journal of Power Sources

444

318

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Redox flow batteries (RFBs) have emerged as prime candidates for energy storage on the medium and large scales, particularly at the grid scale. The demand for versatile energy storage continues to increase as more electrical energy is generated from intermittent renewable sources. A major barrier in the way of broad deployment and deep market penetration is the use of expensive metals as the active species in the electrolytes. The use of organic redox couples in aqueous or nonaqueous electrolytes is a promising approach to reducing the overall cost in long-term, since these materials are low-cost and abundant. The performance of such redox couples can be tuned by modifying their chemical structure. In recent years, significant developments in organic redox flow batteries has taken place, with the introduction of new groups of highly soluble organic molecules, capable of providing a cell voltage and charge capacity comparable to conventional metal-based systems. This review summarises the fundamental developments and characterization of organic redox flow batteries from both the chemistry and materials perspectives. The latest advances, future challenges and opportunities for further development are discussed. Metal deposition or anode in one half-celli.e. Lithium/ organic hybrid FB Metal 'This review'

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“…More recently, significant efforts have been devoted to the exploration of lower cost actives species such as metal-free redox couples. Fast and reversible redox couples including quinones [6,7], oxazolines [8,9] or redox active polymers [10] have shown some promise in RFB applications and are not resource constrained. However, most current metal-free RFBs utilize toxic (e.g.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen/manganese hybrid redox flow battery

et al. 2018

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Electrochemical energy storage is a key enabling technology for further integration of renewables sources. Redox flow batteries (RFBs) are promising candidates for such applications as a result of their durability, efficiency and fast response. However, deployment of existing RFBs is hindered by the relatively high cost of the (typically vanadium-based) electrolyte. Manganese is an earth-abundant and inexpensive element that is widely used in disposable alkaline batteries. However it has hitherto been little explored for RFBs due to the instability of Mn(III) leading to precipitation of MnO 2 via a disproportionation reaction. Here we show that by combining the facile hydrogen negative electrode reaction with electrolytes that suppress Mn(III) disproportionation, it is possible to construct a hydrogen/manganese hybrid RFB with high round trip energy efficiency (82%), and high power and energy density (1410 mW cm −2 , 33 Wh l −1 ), at an estimated 70% cost reduction compared to vanadium redox flow batteries.

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Voltammetry study of quinoxaline in aqueous electrolytes

Cited by 55 publications

References 40 publications

Towards Low Resistance Nonaqueous Redox Flow Batteries

Towards Low Resistance Nonaqueous Redox Flow Batteries

Recent developments in organic redox flow batteries: A critical review

Hydrogen/manganese hybrid redox flow battery

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