Physicochemical properties determined by ΔpKa for protic ionic liquids based on an organic super-strong base with various Brønsted acids

Miran, Muhammed Shah; Kinoshita, Hiroshi; Yasuda, Tomohiro; Susan, Md. Abu Bin Hasan; Watanabe, Masayoshi

doi:10.1039/c2cp00007e

Cited by 207 publications

(286 citation statements)

References 47 publications

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“…27 Possible causes of the significantly lower conductivities for the fully-converted RevIL include strong interactions between the anion and cation, bulky charge carriers and high viscosities. Furthermore, in the case of TEtoxySA-RevIL, which is a protic system, one must also consider the strong hydrogen bonding between the N-H groups 36 and the ionic bonding between the ammonium-carbamate ion pairs.…”

Section: Resultsmentioning

confidence: 99%

Ionicity Analysis of Silylamine-Type Reversible Ionic Liquids as a Model Switchable Electrolyte

Jiménez

Jung

Biddinger

2015

J. Electrochem. Soc.

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Separation of the electrochemical product from an electrolyte can add challenges to the overall process. Use of a switchable electrolyte offers the possibility to reduce or eliminate these separation challenges while maintaining high conductivity. Reversible ionic liquids (RevILs) are a type of switchable solvent that could be used as a switchable electrolyte. Switchable solvents are solvents that can have dramatic step-changes in their properties with the introduction of an external stimulus, in this case CO 2 . In order to determine the feasibility of using TEtoxySA-RevIL, which behaves similarly to protic ionic liquids, as an electrolyte an ionicity analysis utilizing binary mixtures of the RevIL and organic solvents were studied to determine the ionic behavior of the system. Both protic and aprotic solvents with a broad range of dielectric constants were used in order to elucidate the ionicity of the RevIL mixtures. When in the pure RevIL state, the conductivity is prohibitively low due to a heightened viscosity and poor ion mobility due to hydrogen bonding and coulometric attraction. We found that in the presence of protic solvents with high dielectric constants the conductivity of the RevIL increased by up to four orders of magnitude and achieved ideal ionicity.

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Section: Resultsmentioning

confidence: 99%

Ionicity Analysis of Silylamine-Type Reversible Ionic Liquids as a Model Switchable Electrolyte

Jiménez

Jung

Biddinger

2015

J. Electrochem. Soc.

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“…In this figure, ΔpK a is the difference between the pK a of the acid HA and that of the base B and represents the driving force for proton transfer. Correlations between ΔpK a and the physicochemical properties of PILs exist and, if ΔpK a is greater than 15, the resulting PILs are thermally stable and exhibit high ionicity, resulting in high conductivity and low vapour pressures [34]. It has also been suggested that the extent of proton transfer should be such that less than 1 % neutral species are present in order to form a pure or 'good' PIL [35,36].…”

Section: Protic Ionic Liquidsmentioning

confidence: 98%

Electrocatalysis in Room Temperature Ionic Liquids

Ejigu

Walsh

2015

Electrochemistry in Ionic Liquids

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Due to their high thermal and electrochemical stabilities, low vapour pressures, and the ability to readily alter their properties by changing the identity of the constituent ions, RTILs are being used as electrolytes in an increasing number of electrochemical investigations [1][2][3][4]. For example, many fundamental studies have explored the effects of changing the compositions of RTILs on parameters such as their viscosities and electrochemical windows, which are often up to 5 V wide [5,6]. The effects of the RTIL environment on molecular diffusion and electron transfer dynamics have also been studied in detail using simple redox species such as ferrocene [7][8][9]. Such studies have revealed that molecular diffusion coefficients are often up to three orders of magnitude lower in RTILs than in conventional aqueous and nonaqueous electrolytes due to the relatively high viscosities of most RTILs.In parallel with fundamental investigations into the electrochemical behaviour of RTILs, many groups have begun to use RTILs as electrolytes in electrochemical energy-conversion and storage devices. The high thermal stabilities of many RTILs have prompted the development of safer Li batteries by substituting RTILs for volatile and flammable organic electrolytes [10,11]. A number of groups have also begun to use RTILs as electrolytes in intermediate temperature (>100 C) fuel cells because, unlike the Nafion electrolytes usually used in proton exchange membrane fuel cells (PEMFCs), many RTILs can conduct protons in the absence of bulk water [12][13][14][15]. Due to the wide electrochemical windows of some RTILs, large amounts of energy can be stored in RTIL-based supercapacitors [16]. As these examples show, RTILs undoubtedly exhibit many properties that make them attractive for use in electrochemical energy conversion and storage. However, sluggish mass

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“…54 Interestingly, the ionicity of protic ILs is also a function of "pK a , increasing with increasing "pK a and leveling off at "pK a > 15. 54 The attained ionicities for protic ILs are ca. 0.5, being lower than that of typical aprotic ILs (for examples, see Fig.…”

confidence: 99%

“…By using a super-strong organic base and a variety of acids, different protic ILs are formed, where the thermal stability is greatly affected by "pK a . 53,54 Protic ILs with "pK a > 15 are thermally stable, suggesting that proton transfer is complete. 54 Interestingly, the ionicity of protic ILs is also a function of "pK a , increasing with increasing "pK a and leveling off at "pK a > 15.…”

confidence: 99%

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Design and Materialization of Ionic Liquids Based on an Understanding of Their Fundamental Properties

Watanabe

2016

Electrochemistry

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Ionic liquids (ILs) are defined as salts that have melting points lower than 100°C. Most are organic salts, and these may be designed and tailored to have suitable properties. ILs are recognized as a third group of solvents (and electrolytes), after water and organic solvents. They are characterized by their unique properties such as nonvolatilities, high thermal stabilities, and high ionic conductivities. In this article, our work on the design and preparation of ILs is briefly reviewed. The concept of ionicity is proposed as a metric to characterize the basic nature (dissociativity) of ILs, which is affected by the Lewis acidity/basicity of cations/anions (i.e., coulombic interactions), the directionality of interactions between cations and anions, and van der Waals interactions between ions. The ionicity of ILs is dominated by a subtle balance between coulombic and van der Waals interactions, which clearly discriminates ILs from conventional high-temperature inorganic molten salts. Here, the design of protic ILs for fuel cell electrolytes, electron-transporting ILs for dye-sensitized solar cell electrolytes, and Li + -conducting solvate ILs for lithium battery electrolytes are discussed based on an understanding of the fundamental properties of ILs. Furthermore, the combination of ILs with polymers and colloidal particles affords intriguing quasi-solid materials (ion gels), and the ion transport in these gels is decoupled from the mechanical relaxation time of these materials, yielding new solid electrolytes. The possibility of temperature and photo-sensitive solubility dependence of polymers in ILs allows the creation of stimuli-responsive materials. Finally, protic ILs/protic salts are demonstrated to be good precursors for N-doped carbon materials.

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Physicochemical properties determined by ΔpKa for protic ionic liquids based on an organic super-strong base with various Brønsted acids

Cited by 207 publications

References 47 publications

Ionicity Analysis of Silylamine-Type Reversible Ionic Liquids as a Model Switchable Electrolyte

Ionicity Analysis of Silylamine-Type Reversible Ionic Liquids as a Model Switchable Electrolyte

Electrocatalysis in Room Temperature Ionic Liquids

Design and Materialization of Ionic Liquids Based on an Understanding of Their Fundamental Properties

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