Physicochemical properties of ammonium-based deep eutectic solvents and their electrochemical evaluation using organometallic reference redox systems

Bahadori, Laleh; Chakrabarti, Mohammed Harun; Mjalli, Farouq S.; AlNashef, Inas M.; Manan, Ninie Suhana Abdul; Hashim, Mohd Ali

doi:10.1016/j.electacta.2013.09.102

Cited by 96 publications

(69 citation statements)

References 44 publications

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“…Similar results are reported in our earlier publications and reproduced with permission from RSC, Elsevier and ECS respectively. 27,30 stability of V(acac) 3 show that redox couples can be observed within the stability window. 3 in DESs.-The solubility results for DES3, DES8 and DES10 are shown in Table II Table II.…”

Section: Resultsmentioning

confidence: 99%

“…Results for other DESs are not shown here as our earlier experiments with ferrocene and cobaltocenium (Nernstian redox systems) couples displayed irreversible behavior. 11,12,27,30,33 These current peaks are attributed to the redox couples observed in Figure 3 to the following eactions (as represented in Figure A1 of the Appendix for acetonitrile): Figure 3 shows the cyclic voltammograms for the electrolyte containing 0.01 M V(acac) 3 and 0.5 M TEABF 4 in DES3, DES8, DES10 and DES14. Figure 4 compares different DESs at various scan rates in which, for the V(II)/V(III) redox couple in DES3, E p increased from 60 to 90 mV and the ratio of anodic to cathodic peak currents increased from 0.97 to 1.20 as the scan rate was raised from 0.05 to 0.50 V s −1 .…”

Section: Resultsmentioning

confidence: 99%

“…Electrochemical potential windows of DESs.-The limiting reduction and oxidation potentials of the DESs are analyzed by performing cyclic voltammetry using a GC working electrode at ambient temperature and a scan rate of 0.1 V s −1 as shown in Figure 2 (full details are available in our earlier publications 27,30,33 where the limiting current density reached 0.2 mA cm −2 ). It is discovered that some of the tested DESs have similar potential ranges to typical ILs.…”

Section: Resultsmentioning

confidence: 99%

“…Preparation of DESs.-The original procedure of synthesizing DESs as reported by Abbott et al 29 and Mjalli et al 30 was used in this work. Briefly, a jacketed cup with a magnetic stirrer was used to mix both the salt and HBD at 383.15 K (at a maximum) and atmospheric pressure for a period of 3 h (at a minimum) until a homogenous colorless liquid was formed.…”

mentioning

confidence: 99%

“…The counter electrode was a Pt wire, and an Ag wire (immersed in 65% HNO 3 prior to experiments, then rinsed thoroughly with water and ethanol) was used as a quasi-reference electrode (QRE). 27,30 Glassy Carbon (GC, 3 mm diameter) was used as the working electrode. The working electode was carefully polished before each voltammetry experiment with 0.3 μm alumina paste (Wirth Buehler) and ultrasonically rinsed in acetone.…”

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confidence: 99%

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Investigation of Ammonium- and Phosphonium-Based Deep Eutectic Solvents as Electrolytes for a Non-Aqueous All-Vanadium Redox Cell

Bahadori

Hashim

Manan

et al. 2016

J. Electrochem. Soc.

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The charge/discharge characteristics for vanadium acetylacetonate in deep eutectic solvents were evaluated using an H-cell with an anion-exchange membrane separator for the first time. Coulombic (CE) and energy efficiencies (EE) of the electrolyte containing V(acac) 3 /0.5 M TEABF 4 in DES3 (a hydrogen bonded eutectic between choline chloride and ethylene glycol) were obtained as 49-52% and 25-31%, respectively, when charging from 0 to 50% of theoretical maximum state-of-charge for 12 cycles. The low CE may be due to the crossover of the active species through the separator, or to the loss of active vanadium due to a parasitic reaction. However, the CE was similar to that for acetonitrile (CH 3 CN) indicating the promise of DESs as suitable electrolytes for future evaluation. Charge and discharge voltages are respectively higher and lower than the formal cell potential obtained by voltammetry. Ohmic drop in the DES results from the low conductivity of the electrolyte and the relatively large distance between the two electrodes in the H-cell. Further studies require investigation in a flow cell with analyses of polarization curves and impedance to determine the loss mechanisms in sufficient detail. Low energy density is often reported as a barrier in the commercialization of redox flow batteries using current aqueous electrolytes. Non-aqueous electrolytic solvents offer a wide potential window of operation and increase the energy capacity of the system.2-4 In contrast to organic systems which are either scarce or environmentally unfriendly, ionic liquids (ILs) have emerged as a relatively new class of non-aqueous electrolytes for energy storage applications. [5][6][7][8][9] ILs are salts that are liquid below 100• C. ILs have many favorable characteristics, e.g., low volatility, high intrinsic conductivity, large electrochemical window, etc. In addition, ILs can be tuned by combining different cations and anions. However, many reports point out the hazardous toxicity and the poor biodegradability of most ILs.7 ILs with high purity are also required since impurities, even in trace amounts, affect their physical properties. Additionally, their synthesis is not entirely environmentally friendly since it generally requires a large amount of salts and solvents in order to completely exchange the anions.10 These drawbacks together with the high price of common ILs unfortunately hamper their industrial applications. Such issues may be overcome by using deep eutectic solvents (DESs). 11,12A DES is a eutectic mixture of an organic salt (ammonium or phosphonium) and a hydrogen bond donor (HBD), that is made up of different components such as amides, metallic salts, alcohols, carboxylic acids and amines that may be used as complexing agents (typically an H-bond donor).13,14 DESs have a melting point that is far below that of either individual constituent. The mechanism is that the complexing agent interacts with the anion and increases its effective size. This, in turn, decreases the anionic interaction with the cation ther...

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