Organic Ionic Liquids Research Articles

Electrochemical conversion of CO2 in non‐conventional electrolytes: Recent achievements and future challenges

AbstractElectrochemical reduction of CO2 in traditional aqueous electrolytes suffers from low faradaic efficiency towards desired products which can be traced back to low CO2 solubility and strong competition from the hydrogen evolution reaction. The use of non‐conventional electrolytes aims to mitigate these issues. This review will give a focused overview summarizing some of the most recent contributions on the electrochemical conversion of CO2 in organic solvents, ionic liquids, solid electrolytes, and brines. We summarize the findings in terms of activity, selectivity, and durability for each of the systems. In addition, it provides an outlook about the role of water, cations, and anions in the reaction. We also highlight the challenges of the electrochemical reduction of CO2 in each of the electrolytes. All the studies referred to in this review contribute meaningfully to reaching the technical targets for CO2 electrolyzers in non‐conventional electrolytes.

Analysis of the behavior of Sn2+ and In3+ ions in DES and in water: A theoretical approach

An alternative for replacing conventional organic solvents and ionic liquids, the Deep Eutectic Solvents (DES) emerged, a class of compounds with essential properties in the industry. These solvents have numerous advantages regarding ionic liquids, such as low price, biodegradability, and low toxicity. Furthermore, the DES has many applications in science, for example, organic synthesis, electrodeposition of metals, catalytic process. In this work, the behavior of Sn2+ and In3+ ions were analyzed in the solvents 1ChCl:2EG (chloride choline and ethylene glycol, DES) and water through computational simulations by molecular dynamics (MD) and Quantum Theory of Atoms in Molecules (QTAIM) calculations.The results showed that the Sn2+ and In3+ ions strongly interact with the chloride anion in DES. Furthermore, only the Sn2+ ion showed interaction with the ethylene glycol molecules in DES, which was not observed for In3+, which led to no interaction with EG. In contrast, the most likely interaction is between cations and oxygen from water in a water solvent. The analysis of Bond Critical Points (BCPs) showed that the strength of these interactions follows the following sequence: In-Ow > In-Cl > Sn-Ow > Sn-Cl. The behavior of both ions in the metallic mixture was invariant in DES and in water when compared to the same isolated ions. Furthermore, it may be observed that the increase in the number of water molecules in the systems containing water did not cause relevant changes.

Prototropic behavior of naphthalene derived probes in deep eutectic solvents

Deep eutectic solvents (DESs) have garnered widespread acceptance as novel and biodegradable substitutes to the volatile organic solvents and ionic liquids in both biological and chemical sciences. The prototropic equilibria of fluorescent probes is known to be largely controlled by its surrounding milieu. The prototropic behavior of four naphthalene derivatives: 1-naphthol, 2-naphthol, 1-naphthylamine, and 1,8-bis(dimethylamino)naphthalene (the proton sponge) is investigated within five different DESs constituted of choline chloride (ChCl) as a common H-bond acceptor (HBA) with five different H-bond donors (HBDs). UV–vis molecular absorption and steady-state fluorescence spectroscopies along with time-resolved fluorescence measurements are used to investigate the ground-state and excited-state prototropic behavior of these four probes dissolved in the five DESs. For 2-naphthol, neutral form is the only absorbing and emitting form observed in all the investigated DESs. In the ground-state, 1-naphthol is predominantly present in its neutral form within all the investigated DESs. However, both neutral and anionic forms of 1-naphthol are supported in the excited-state of ChCl:Urea DES whereas neutral form remains the preferred form in other DESs. In all the investigated DESs, the neutral form of 1-naphthylamine is the only prominent form in both ground- and excited-state. The cationic form of 1,8-bis(dimethylamino)naphthalene remains the dominant prototropic form in ground- as well as excited-state in all the investigated DESs upholding the high photo-basicity of this probe in DESs as well.

Photovoltaic performance of eutectic ionic liquids as potential electrolytes in dye-sensitized solar cells

Ionic liquids (ILs) have been utilized as the electrolyte in dye-sensitized solar cells (DSSCs) to replace organic solvents due to their non-flammability, chemical and thermal stability, as well as less tendency to evaporate and causing leakage. Herein, we report the photovoltaic performance of dye-sensitized solar cells for novel organic solvent-free eutectic ionic liquids (ILs) mixture as potential electrolytes in dye-sensitized solar cells (DSSCs). Eutectic ionic liquid mixtures based on 1-ethyl-3-methylimidazolium iodide [C2C1im]I and 1-butylpyridinium iodide [C4py]I were studied and further incorporated with triiodide providers namely iodine, I2, and tetrabutylammonium triiodide [TBA][I-I-I], as well as 1-butyl-3-methylimidazolium thiocyanate [BMIM][SCN] to form nine electrolytes formulations and their photovoltaic performances were evaluated. The selection of suitable triiodide providers as well as the effect of concentrations were reported along with the effect of viscosity on the performances of the devices. The best performing device was exhibited by [C2C1im]I: [C4py]I: I2 (5 wt%) with a short circuit current of 2.68 mA cm−2, an open-circuit voltage of 0.43 V, and a fill factor of 0.44, corresponding to an overall power conversion efficiency (PCE) of 0.51% which shows their potentials for electrolyte application in dye-sensitized solar cells.

Historical development and novel concepts on electrolytes for aqueous rechargeable batteries

In battery systems, aqueous electrolytes are superior in ionic conductivity, interfacial wettability, safety and environmentally benign compared to organic liquids, polymers, inorganic solid-state and ionic liquid electrolytes.

Current understanding and insights towards protein stabilization and activation in deep eutectic solvents as sustainable solvent media.

Deep eutectic solvents (DESs) have emerged as a new class of green, designer and biocompatible solvents, an alternative to conventional organic solvents and ionic liquids (ILs) which are comparatively toxic and non-biodegradable. DESs are eutectic mixtures that are formed when a hydrogen bond acceptor (HBA) is mixed with a hydrogen bond donor (HBD) at particular molar ratios by mechanical grinding or under mild heating conditions. Very recently, these solvents have been the center of attention for researchers in biotechnology, biomedicine and various scientific applications. These environmentally benign solvents have a close analogy with ILs; however, they offer certain unique merits over traditional ILs. DESs display remarkable properties such as easy preparation, tunable composition, biodegradability, recyclability, inherently low toxicity, sustainability and biocompatibility; these special features validate DESs as new potential solvents/co-solvents for biomolecules. Mechanistically, the biocompatibility and protein friendly nature of DESs depend on various factors, which include the composition of the DES, viscosity and hydration level. Therefore, it becomes an essential task to bring together all the studies related to protein behaviour in DESs to unlock their biomolecular proficiency. This review specifically highlights recent insights into the biomacromolecular functionality in DESs, including outlines of the solubilization and stabilization of proteins, long term protein packaging, different extraction methods and enzyme activation in the presence of DESs. A literature survey reveals that DESs act as green media in which the protein structure and activity are retained. In some cases, proteins refolded and enzymatic activity was enhanced several fold in the presence of DESs. Furthermore, we have reviewed the possible mechanistic behaviour behind protein stabilization, refolding and activation in DESs. Overall, the main objective of this review is to explicate the advantages of the introduction of DESs for biomolecules and to demonstrate the versatility of these eco-friendly solvents for future bio-based applications.

Composite SPE Paper Membrane Based on the Functional Superstructure of Metal-Organic Frameworks and Ionic Liquids for Detection of Tetracycline-like Antibiotics.

Composite adsorbents based on metal-organic frameworks (MOFs) are excellent candidates for solid-phase extraction (SPE) due to their diverse chemical functionality and multilevel porosity. MOF superstructures based on self-assembly at room temperature (RT) could have less energy consumption and easier manipulation due to the larger complex geometry. The π-π stacking of the benzene ring could not only enhance the interaction toward hydrophobic or plane-structured targets but also be expected to promote the formation of the MOF superstructure. In this work, in the established RT self-assembly synthesis system, several factors were investigated to see how to obtain functional MOF superstructures with a regular geometry, among which the number of benzene rings in the ligand was mainly tested for its impact on self-assembly and adsorption capacity. By means of adsorption experiments and computational fluid dynamics (CFD) simulation, the relationship between structure and activity (SARs) was further explored. Interestingly, the MOF unit with the lowest specific surface area performed the best in adsorption. Then, the selected functional MOF superstructure and ionic liquid were used to produce the composite paper membrane facilely applied in the SPE device. After optimization of the preparation conditions and operation parameters, the established SPE-HPLC-UV method could selectively analyze tetracycline-like antibiotics in the range of 16.6-833.3 ng/g (ppb) in a meat sample. This work provided an RT synthesis method to produce a microsize MOF superstructure, with experimental and theoretical insights into the SARs, which could be expanded in the design of other MOF-based SPE composite membranes toward one group of analogues.

Anion‐Decoordination Cell Formation Process Stabilizes Dual Electrodes for Long‐Life Quasi‐Solid‐State Lithium Metal Battery

AbstractCompared with the complete replacement of liquid electrolytes by solid electrolytes, the hybrid quasi‐solid electrolyte (HQSE) has more practical application potential due to its high thermal stability and high ionic conductivity as well as good interface wettability. In this work, a HQSE film is prepared using the Li6.40La3Zr1.40Ta0.60O12 (LLZTO) nanoparticles localized composite liquid electrolyte (CLE) composed of TEGDME (0.5 m LiTFSI) organic electrolyte and Pyr14TFSI ionic liquid. The HQSE film exhibits high ionic conductivity of 1.77 × 10−3 S cm–1 and a high Li‐ion transference number of 0.56 at 25 °C. More importantly, a formation process is designed by utilizing the oxidative decomposition of the free TFSI– anions caused by the substitution of ion cluster Li(TFSI)n+1n− by Li(TEGDME)x+ in HQSE, achieving the in‐situ construction of the stable and complete cathode electrolyte interface and solid electrolyte interface in the cathode and anode simultaneously, and benefiting from the liquid electrolyte being confined to the surface of LLZTO particles, the HQSE film finally exhibits high stability to the dual electrodes, ensuring that the quasi‐solid‐state Li metal battery exhibits capacity retention of 80% after 1000 cycles at 0.2 C rate, and 90% after 500 cycles at 0.5 C rate.

Quinoline-cored Poly(Aryl Ether) Dendritic Organogels with Multiple Stimuli-Responsive and Adsorptive Properties.

Functional supramolecular gel materials have potential applications in sensors, optical switches, artificial antennae, drug delivery and so on. In this paper, quinoline-cored poly(aryl ether) dendritic organogelators were designed, synthesized and fully characterized. The gelation behaviour of the dendritic organogelator was tested in organic solvents, mixed solvents and ionic liquids. The dendron Q-G1 was found to be an efficient and versatile organogelator toward various apolar and polar organic solvents with the critical gelation concentrations (CGCs) approaching 1.2×10-2 mol/L, indicating one dendritic organogelator could immobilize 1.2×103 solvent molecules in the organogel network. Interestingly, these dendrons exhibited excellent gel formation in ionic liquids. Notably, these dendritic organogels were found to display multiple stimuli-responsive properties toward external stimuli including heat, ultrasound and shear stress, with a reversible sol-gel phase transition. In addition, the dendritic organogel could effectively adsorb heavy metals and organic dyes. The removal rate of Pb2+ was up to 20% and the adsorption rate for Rhodamine B was as high as 89%.

An insight of novel eutectic mixture between thiazolidine‐2,4‐dione and zinc chloride: Temperature‐dependent density functional theory approach

AbstractDeep eutectic solvents (DESs) are the mixture of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA) in a particular equivalent ratio. They gained popularity because of low melting point and green (non‐toxic) in nature. DESs showed promising ability as solvents and found to be better than traditional organic solvents and ionic liquids. They are being explored solvents in organic synthesis, substance dissolution, corrosion inhibition, biofuel generation, SO2/CO2 absorption, and extraction. In the present work, thioazolidine‐2,4‐dione (T) is taken as hydrogen bond donor, and zinc chloride (Z) is taken as hydrogen bond acceptor. Nine DESs are created using T and Z having different equivalent ratio. Further, they were studied using density functional theory (DFT) approach in gaseous state at different temperatures. T4Z1 found to most soluble in water as the dipole moment is maximum. Free energy of T1Z4 found to be least so may be most stable among all. Further, on changing the temperature from 298 to 323 K and then to 348 K, thermodynamic parameters are determined. Further, the change in free energy for the formation of the DESs are calculated in Hartree per particle as well in kcal/mol. At 298 K, the change in free energy for the formation of T2Z3 is minimum and indicates it feasibility or spontaneity at this temperature. But at temperature of 323 K, T1Z4 and T2Z3 are found to be same. Further, on increasing temperature to 348 K, the change in free energy for T1Z4 and T2Z3 is same and minimum. It means on changing the temperature, the spontaneity for the formation of DES changes. Based on the method of Jakob et al., it can be seen that the temperature changes with the change in composition, that is, the ratio of HBD and HBA. The composition of HBD and HBA is 1:2 and is called deep eutectic mixture as the melting temperature observed is least. There is not a complete agreement between the results obtained by DFT calculations and Jakob et al method.

Recent Advances in Electrolytes for "Beyond Aqueous" Zinc-Ion Batteries.

With the growing demands for large-scale energy storage, Zn-ion batteries (ZIBs) with distinct advantages, including resource abundance, low-cost, high-safety, and acceptable energy density, are consideredas potential substitutes for Li-ion batteries. Although numerous efforts are devoted to design and develop high performance cathodes and aqueous electrolytes for ZIBs, many challenges, such as hydrogen evolution reaction, water evaporation, and liquid leakage, have greatly hindered the development of aqueous ZIBs. Developing "beyond aqueous" electrolytes can be able to avoid these issues due to the absence of water, which are beneficial for the achieving of highly efficient ZIBs. In this review, the recent development of the "beyond aqueous" electrolytes, including conventional organic electrolytes, ionic liquid, all-solid-state, quasi-solid-state electrolytes, and deep eutectic electrolytes are presented. The critical issues and the corresponding strategies of the designing of "beyond aqueous" electrolytes for ZIBs are also summarized.

A Review of the electrochemical corrosion of metals in choline chloride based deep eutectic solvents

Deep eutectic solvents (DESs) are a class of mixtures with melting points notably lower than those of their raw constituent components. These liquids have found a tremendously wide spectrum of applications in the last two decades of their research, so their contact and interaction with technical metals and alloys are inevitable. Therefore, the corrosivity of DESs towards metals is an extremely important topic. This review summarizes research efforts collected in the last two decades related to the corrosion rate of various metals in different DESs. Since the DESs are mainly composed of organic raw compounds, and by their physicochemical properties they may be regarded as a separate class of ionic liquids, the literature data about DESs corrosivity has been compared to the data related to the corrosivity of various organic solvents and ionic liquids as well. All the results gained until now show significantly low corrosivity of DESs. This observation is discussed in relation to the chemical composition of DESs. The absence of the oxidizing agents, the inhibitory action of organic ions and molecules, high viscosity and low electrical conductivity have been recognized as the main factors contributing to the low metal corrosion rate in DESs.

In Situ Preparation of MXenes in Ambient-Temperature Organic Ionic Liquid Aluminum Batteries with Ultrastable Cycle Performance.

A fluorine-free and water-free electrochemical preparation of MXenes is achieved in Lewis acidic molten salts at ambient temperature. In addition, the anode reaction of the MAX phase V2AlC is studied in the organic ionic liquid aluminum battery and the extraction voltages of the metal atoms Al and V in the MAX phase V2AlC are determined. This points out the direction for the constant-voltage electrochemical preparation of MXenes. Furthermore, the electrochemical performance of the etched V2AlC (E-V2AlC) in an aluminum battery is studied. The one-stop preparation-application process prevents the MXenes from contacting water and air, and the MXenes etched in the aluminum battery are more conducive to the intercalation/deintercalation of Al3+. Therefore, E-V2AlC exhibits excellent electrochemical performance in an aluminum battery. Under the conditions of a voltage window of 0.01-2.3 V (V vs Al/Al3+) and a current density of 500 mA g-1, the specific discharge capacity is about 100 mAh g-1 after 6500 cycles. In addition, the energy storage mechanism and Faraday energy storage method of E-V2AlC in an aluminum battery are studied. The diffusion coefficient D of Al3+ is determined by a galvanostatic intermittent titration technique. The reasons for its excellent electrochemical performance are clarified from the perspective of kinetics.

Etidronate-based organic salts and ionic liquids: In vitro effects on bone metabolism

Bisphosphonates are a class of drugs widely used for the treatment of several pathologies associated with increased bone resorption. Although displaying low oral bioavailability, these drugs have the ability to accumulate in bone matrix, where the biological effects are exerted. In the present work, four mono- and dianionic Etidronate-based Organic Salts and Ionic Liquids (Eti-OSILs) were developed by combination of this drug with the superbases 1,1,3,3-tetramethylguanidine (TMG) and 1,5-diazabicyclo(4.3.0)non-5-ene (DBN) as cations, aiming to improve not only the physicochemical properties of this seminal bisphosphonate, but also its efficacy in the modulation of cellular behavior, particularly on human osteoclasts and osteoblasts. It was observed that some of the developed compounds, in particular the dianionic ones, presented very high water solubility and diminished or absent polymorphism. Also, several of them appeared to be more cytotoxic against human breast and osteosarcoma cancer cell lines while retaining low toxicity to normal cells. Regarding bone cells, a promotion of an anabolic state was observed for all Eti-OSILs, primarily for the dianionic ones, which leads to an inhibition of osteoclastogenesis and an increase in osteoblastogenesis. The observed effects resulted from differential modulation of intracellular signaling pathways by the Eti-OSILs in comparison with Etidronate. Hence, these results pave the way for the development of more efficient and bioavailable ionic formulations of bisphosphonates aiming to effectively modulate bone metabolism, particularly in the case of increased bone resorption.

Challenges and Perspective of Recent Biomass Pretreatment Solvents

The increased demands on renewable and sustainable products require enhancing the current conversion efficiency and expanding the utilization of biomass from a single component (i.e., cellulose) to entire biomass components in the biorefinery concept. Pretreatment solvent plays a critical role in various biorefinery processes. Recent pretreatment solvents such as organic co-solvents, acid hydrotropes, ionic liquids and deep eutectic solvents showed effective biomass fractionation as well as preservation of high-quality cellulose and lignin under mild conditions. Despite these significant enhancements in biomass pretreatment solvent, there are still many challenges, such as feedstock variety, valorization of non-cellulose components, and eco-friendliness of the applied catalyst and solvent. These technical, economic and environmental obstacles should be considered in future biomass pretreatment solvents. In particular, the development of feedstock-agnostic solvent with high fractionation performance for high quality and quantity of all three major components (i.e., cellulose, hemicellulose, and lignin) together would be an ideal direction.

Two-dimensional MOF Cu-BDC nanosheets/ILs@silica core-shell composites as mixed-mode stationary phase for high performance liquid chromatography

Here, silica microspheres were decorated with two-dimensional metal–organic frameworks (2D MOFs) nanosheets and ionic liquids, and evaluated as the mixed-mode stationary phase for chromatographic separation. The ionic liquids were used to assist the synthesis of 2D MOFs nanosheets, and also acted as adhesives among the nanosheets and silica. In contrast with the 2D MOFs-based column without ionic liquids and commercial columns, the prepared column exhibited enhanced chromatographic separation performance for partially hydrophilic compounds such as alkaloids, sulfonamides and antibiotics, etc. In addition to excellent chromatographic repeatability and stability, it has also been verified that the composites could be easily and repeatedly prepared. The relative standard deviation of the retention time of the same type of analyte between the three batches of materials was ranging from 0.21% to 1.7%. In short, these results indicated that the synthesized composites were promising separation material for liquid chromatography, which made it possible to broaden the application of 2D MOFs in the field of chromatography.

Some thermodynamic properties and computational study of DESs (choline chloride/ethylene glycol and choline chloride/malonic acid) in lithium nitrate + propylene carbonate solutions at T = 298.15 K

Deep eutectic solvents (DESs) with propylene carbonate represent an appealing alternative for organic solvents and ionic liquids to dissolve lithium salts. The present research reports the effect of deep eutectic solvents {DESs (choline chloride/ethylene glycol with the molar ratio of 1.00:2.00) and (choline chloride/malonic acid with the molar ratio of 1.00:1.00) on the thermodynamic and transport properties of solutions of lithium nitrate (LiNO3) in propylene carbonate (PC). To evaluate solute–solvent interactions in the above systems first the volumetric, ultrasonic, and viscometric properties were studied. For this purpose, the density (d), speed of sound (C) and viscosity (η) were measured for the binary solutions of (LiNO3 + PC) and quaternary solutions containing (LiNO3 + PC) and DES in different mass fraction of, w = (0.05, 0.010, 0.015 and 0.020), at 298.15 K under ambient pressure. The measured data were used for calculation of the apparent molar volume (Vφ), standard partial molar volume (Vφ0), apparent molar isentropic compressibility (κϕ), partial molar isentropic compressibility (κφ0), partial molar volumes of transfer (ΔtrVφ0) and viscosity B-coefficient of (LiNO3 + PC + DES) solutions. Then, to evaluate the interaction energies, the density functional theory (DFT) of LiNO3 with DESs in PC has also been studied. The thermodynamic and transport investigations indicated that the choline chloride/ethylene glycol interactions are more favorable than choline chloride/malonic acid with LiNO3 in the presence of PC. Generally, the additions of these DESs on the solution of LiNO3 + PC lead to enhancing of the solute–solvent interactions. Also, the DFT results revealed that the interaction between the ChCl/EG with LiNO3 in PC is stronger than ChCl/MA with LiNO3 in PC confirming the result deduced from our experimental studies.

Sodium-Based Dual-Ion Battery Based on the Organic Anode and Ionic Liquid Electrolyte.

Combining the advantages of dual-ion batteries (DIBs) and sodium-ion batteries (SIBs), we herein develop a superior sodium-based dual-ion battery (Na-DIB) based on the PTCDA organic anode and ionic liquid (IL) electrolyte. The system shows the highest specific discharge capacity of 177 mAh g-1 at 0.5C and excellent capacity retention over 100% at 2C after 200 cycles. Notably, even at an ultrahigh rate of 20C, the battery still maintains a considerable capacity of 60 mAh g-1 with a coulombic efficiency (CE) close to 100 and 94% capacity retention after 1000 cycles. Moreover, the self-discharge of the system has been investigated and shown to have an extremely low value of 0.18% h-1. Consequently, this work presents an excellent Na-DIB system, which could be a promising candidate for large-scale applications.

Acceleration under solvent-drop grinding: Synthesis of bis(indolyl)methanes using small amounts of organic solvents or ionic liquids

The reactions for the synthesis of bis(indolyl)methanes were accelerated by the addition of a few drops of solvents. Solvent effect for the addition of organic solvents and ionic liquids was examined. The yields of bis(indolyl)methanes increased by the addition of THF, 1-ethyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide ([emim]NTf2), and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6). Solvent-drop grinding methodology was quite useful for the reactions of “solid + liquid” as well as “solid + solid”.

Evaluation of canonical choline chloride based deep eutectic solvents as dye-sensitized solar cell electrolytes.

Deep eutectic solvents (DESs) are beginning to attract interest as electrolyte alternatives to conventional organic solvents and ionic liquids within dye-sensitized solar cells (DSSCs). The precise roles played by DES components and whether they simply represent a benign medium for mobilizing charge carriers or present beneficial functionality that impacts device performance remain unclear. To begin to address this deficiency in understanding, we performed a comprehensive characterization of the three "canonical" choline chloride-based DESs (i.e., reline, ethaline, and glyceline) as DSSC electrolytes hosting the iodide-triiodide (I-/I3 -) redox couple. The measurement of electrolyte viscosities, determination of triiodide diffusion coefficients, and photovoltaic performances assessed for water contents up to 40 wt. % allow the emergence of several important insights. A comparison to the observed photovoltaic performance arising from the individual components aids in further clarifying the impact of DES chemistry and solution viscosity on photovoltaic and charge carrier diffusion characteristics. Finally, we introduce the DES guaniline-consisting of a 1:1 molar ratio mixture of choline chloride with guanidinium thiocyanate-demonstrating it to be a superior DSSC electrolyte over those formulated from the three most widely studied canonical DESs at all water contents investigated.