Unraveling pH dependent cycling stability of ferricyanide/ferrocyanide in redox flow batteries

Luo, Jian; Sam, Alyssa; Hu, Bo; Debruler, Camden; Wei, Xiaoliang; Wang, Wei; Liu, Tianbiao

doi:10.1016/j.nanoen.2017.10.057

Cited by 241 publications

(240 citation statements)

References 40 publications

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“…It should be noted, however, that Fe(CN) 6 may also suffer from irreversible decomposition due to loss of CN − groups and eventual formation of iron hydroxide at high pH. [24][25][26][27] These reactions are expected to occur at much longer timescales than those studied here.…”

Section: Materials Interactions and Ph Effects: Stability Of Fe(cn)mentioning

confidence: 99%

Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods

Goulet

Aziz

2018

J. Electrochem. Soc.

207

334

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We present an unbalanced compositionally-symmetric flow cell method for revealing and quantifying different mechanisms for capacity fade in redox flow batteries that are based on molecular energy storage. We utilize it, accompanied in some cases by a corresponding static-cell cycling method, to study capacity fade in cells comprising anthraquinone di-sulfonate, di-hydroxy anthraquinone, iron hexacyanide, methyl viologen, and bis-trimethylammoniopropyl viologen. In all cases the cycling capacity decay is reasonably consistent with exponential in time and is independent of the number of charge-discharge cycles imposed. By introducing pauses at various states of charge of the capacity-limiting side during cycling, we show that in some cases the temporal fade time constant is dependent on the state of charge. These observations suggest that molecular lifetime is dominated by chemical rather than electrochemical mechanisms. Growing interest in redox flow batteries (RFBs) for grid-scale energy storage has prompted development of new redox-active organic and organometallic molecules synthesized from commonly available raw materials containing earth-abundant elements such as carbon, nitrogen and oxygen. Flow batteries based upon these synthetic compounds might achieve lower electrolyte capital costs than current vanadium-based technologies without the scarcity risks associated with finite resources.1 To become a cost-effective solution for matching of intermittent renewable energy supply to demand, these flow batteries should retain most of their capacity over decadal time scales. As opposed to the elements of the periodic table, e.g. transition metals, traditionally used for the redox-active components of flow batteries, these new organic and organometallic compounds may be susceptible to molecular decomposition, leading to an additional mechanism for flow battery charge storage capacity fade.2 Typically, capacity fade in conventional flow batteries can occur through various mechanisms such as precipitation of reactant species or crossover of these species through the membrane.3,4 Some of these sources of capacity loss are theoretically reversible while others are not. Some are related to device engineering, such as electrolyte leakage, whereas others are intrinsic to the electrolyte chemistry. RFBs that rely upon electrolytes with different dissolved redox-active species on either side, such as the chromium/iron cell, suffer from irreversible crossover of these species unless their electrolytes are balanced by putting both species on both sides, thereby doubling the cost of active materials.5 a The all-vanadium RFB was developed to avoid these problems by having a single common redox-active species on both sides of the cell such that any asymmetric crossover of active species could be reversed by rebalancing the electrolytes by simple remixing. 6 Other examples of capacity fade that can be recovered by electrolyte rebalancing methods include those due to heterogeneous side reactions, such as hydrogen evolution, or fro...

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Section: Materials Interactions and Ph Effects: Stability Of Fe(cn)mentioning

confidence: 99%

Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods

Goulet

Aziz

2018

J. Electrochem. Soc.

207

334

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“…Another advantage of having near neutral solution is the high stability and solubility of ferrocyanide, which is the most promising posolyte (positive electrolyte) in terms of stability. [ 11,17,22 ] First generation viologen‐based flow batteries utilized methyl viologen (MV) electrolytes as active material. The high solubility of MV in neutral pH solution and its fast kinetics, decent reduction potential (−0.45 V vs SHE, ≈0.9 V cell voltage when paired with ferrocene derivatives) and facile synthesis have been demonstrated by researchers.…”

Section: Introductionmentioning

confidence: 99%

Near Neutral pH Redox Flow Battery with Low Permeability and Long‐Lifetime Phosphonated Viologen Active Species

Jin

Fell

Vina-Lopez

et al. 2020

Advanced Energy Materials

137

119

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A 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.

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“…In spite of their robust chemistry and high power performance, however, their widely applications suffer from several major drawbacks, [2,3] expensive redox active materials, expensive separators, corrosive electrolytes, and electrolyte crossover. To overcome these technical challenges, we and other groups have developed aqueous organic RFBs (AORFBs) [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and nonaqueous organic RFBs (NAORFBs) [20][21][22][23][24][25][26][27][28][29][30][31][32][33] employing sustainable and abundant redox active organic molecules as a new generation of RFBs for green energy storage. Among explored redox active organic compounds, viologen compounds are especially attractive due to its outstanding stability, redox reversibility, and low costs [13] .…”

Section: Introductionmentioning

confidence: 99%

“…energy density, was hindered [9,13,15] . In order to utilize the second electron of viologen compounds, we have reported two molecular engineering approaches [16,17] . In the first molecular engineering approach, we introduced highly hydrophilic pendant ammonium groups into the viologen molecules to ensure the high solubility of the doubly reduced species in aqueous solutions, thereby achieved two electron utilization in AORFBs [16] .…”

Section: Introductionmentioning

confidence: 99%

Two electron utilization of methyl viologen anolyte in nonaqueous organic redox flow battery

Liu

2018

Journal of Energy Chemistry

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118

111

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Unraveling pH dependent cycling stability of ferricyanide/ferrocyanide in redox flow batteries

Cited by 241 publications

References 40 publications

Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods

Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods

Near Neutral pH Redox Flow Battery with Low Permeability and Long‐Lifetime Phosphonated Viologen Active Species

Two electron utilization of methyl viologen anolyte in nonaqueous organic redox flow battery

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