Thiocyanate Ionic Liquids Research Articles

Trialkylsulfonium Thiocyanate Ionic Liquids: Investigation on Temperature‐Dependent Ignition Behavior of Green Hypergolic Propellants

AbstractThree trialkylsulfonium thiocyanate ionic liquids (ILs) are presented as fuel candidates for novel green hypergolic propellants. The physical and chemical properties such as density, viscosity, melting point and decomposition temperature as well as the enthalpy of formation of the ILs were determined. Further, the research focused on the potential of the ILs as fuel components for hypergolic propellants with highly concentrated hydrogen peroxide as oxidizer. For this, the theoretical maximum specific impulses of the propellants were calculated with NASA CEA. To evaluate the ignition delay times of the hypergolic propellants, drop tests were carried out. These were conducted not only at ambient conditions but also at lower levels of fuel temperature. It was found that all three propellant combinations still ignited reliably at temperature levels down to −25°C, however, the average ignition delay increased at lower temperatures. Overall, not only three promising hypergolic fuels were identified, but also important insights into the temperature‐dependent ignition behavior of hypergolic ionic liquid‐based propellants with thiocyanate anions were obtained.

Investigation of the double layer structure of 1-butyl-3-methylimidazolium thiocyanate at the air-water interface using sum-frequency generation vibrational spectroscopy.

The interfacial structure and adsorption behavior of 1-butyl-3-methylimidazolium thiocyanate ionic liquids (ILs) aqueous solutions were investigated using sum-frequency generation vibrational spectroscopy (SFG-VS) and surface tension measurements. Polarization-dependent measurements revealed a dramatic increase in the SFG signal for both CH and CN stretching modes with increasing ILs concentration, reaching a maximum at a mole fraction of 0.01. This concentration dependence was accompanied by a dramatic drop in surface tension. Upon further increasing the concentration, surface tension varied slightly and reached a constant value, while the SFG signal decreased significantly. Quantitative polarization analysis showed that as the bulk concentration increased, the apparent molecular orientation of the SCN- transition dipole at the interface changed from 51° to 46°, and the tilt angle of CH3 group of the butyl chain attached to the imidazole cationic ring changed from 18° to 32°. The decrease in the SFG signal can be explained by the formation of a double layer adsorption structure at the air/water interface. It was also demonstrated that the anions were adsorbed at the interface simultaneously with the cationic group, rather than by successive adsorption as proposed in a previous study. Using the Shereshefsky model, the thermodynamic Gibbs free energy of adsorption deduced from surface tension data was compared with SFG results.

Reducing surficial and interfacial defects by thiocyanate ionic liquid additive and ammonium formate passivator for efficient and stable perovskite solar cells

Reducing surficial and interfacial defects by thiocyanate ionic liquid additive and ammonium formate passivator for efficient and stable perovskite solar cells

Protic thiocyanate ionic liquids as fuels for hypergolic bipropellants with hydrogen peroxide

The combination of ionic liquids (ILs) and hydrogen peroxide is one of the most promising approaches for the substitution of conventionally used hypergolic bipropellants consisting of nitrogen tetroxide and hydrazines. In this work, protic ionic liquids with imidazolium-based cationic structures and thiocyanate anions are presented as new fuels for green hypergolic bipropellants for the first time. All seven presented substances are hypergolic with hydrogen peroxide and surpass the density specific impulse of the previously mentioned conventional bipropellant. One of them stands out in particular, as no other transition metal-, hydride- and boron-free ionic liquid with an ignition delay time as short as 7.3 ms was found with hydrogen peroxide so far. This extremely good ignition behavior of the, at room temperature solid, IL offers great potential not only for hybrid propellants, but also for liquid hypergolic bipropellant combinations: out of a mixture of 35 wt% [Him][SCN] and 65 wt% [Emim][SCN], a remarkable new liquid bipropellant combination (named HIM_35) is formed with a very low ignition delay time of 16.7 ms and a particularly high maximum density specific impulse ρ Isp of 429 s·g·cm−3.

Thermodynamics Properties and Internal Interactions of Ether-Group Functionalized Thiocyanate Ionic Liquid 1-(2-Methoxyethyl)-3-Methylimidazolium Thiocyanate and Its Mixtures with 1,4-Butyrolactone or Propylene Carbonate

In this paper, thermodynamic properties such as density, conductivity, and viscosity of an ether-based-functionalized ionic liquid (IL) 1-(2-methoxyethyl)-3-methylimidazole thiocyanate [MOEMIM][SCN] was measured at temperatures from (288.15 to 343.15) K and at atmospheric pressure (101 KPa). Then, the mixture systems blends of [MOEMIM][SCN] + 1,4-butyrolactone (GBL) or propylene carbonate (PC) were also prepared and measured over the whole composition range at the same temperature and pressure conditions. The Vogel–Fulcher–Tamman (VFT) equation was employed to describe the temperature dependence of transport properties (viscosity and conductivity). The Casteel–Amis four-parameter (C–A) equation was used to explain the mole fraction dependence of ILs on the electrical conductivity. From the experimental density and viscosity, the excess molar volume (VE) and viscosity deviation (Δη) were obtained, and fitting results of the Redlich–Kister (R–K) polynomial equation showed that the changes of the excess properties were reasonable for the mixtures. Combined with the COSMO–RS model based on DFT calculation, the intermolecular interaction situations of the mixture systems were evaluated. Further, the σ-profile can provide the computational aspect of specific interactions between molecules or between solvent through H-bond donors and H-bond acceptors.

Triethylammonium thiocyanate ionic liquid electrolyte-based supercapacitor fabricated using coconut shell-derived electronically conducting activated charcoal electrode material

Organic solvents are commonly used as commercial electrolytes in supercapacitors, but they have several drawbacks, such as high volatility, toxicity, and environmental issues. To overcome these problems, ionic liquids are used though their high costs hamper commercial applications. In this study, a novel and low-cost ionic liquid based on triethylammonium cation and thiocyanate anion were synthesized and used as the electrolyte in a low-cost supercapacitor fabricated using electronically conducting activated carbon derived from cleaned coconut shells as electrode material. The temperature dependence of electrolyte conductivity was investigated, in the frequency range of 1 Hz-500 kHz, using AC impedance analysis, in the temperature range from 30 °C - 90 °C in ten-degree increments and found to be in the range of 4.5 to 14.4 mS cm−1. The ion transport kinetics behaves according to the Vogel-Tammann-Fulcher (VTF) model with an activation energy (Ea) and the pre-exponential factor (AσT) of 0.0158 eV and 114.9 S m−1 K1/2, respectively. The activated carbon material developed has a high porosity and high electronic conductivity. The electrode fabrication methodology was optimized by varying the polyvinylpyrrolidone (PVP) binder amount with respect to the mass of activated carbon on a titanium sheet as a function of heat treatment temperature. The supercapacitor that gives the highest specific capacitance is based on the electrode constructed using 5 % w/w PVP in 0.50 g of activated carbon deposited on a titanium sheet by heat treating at 200 °C for 20 min. At the scan rate of 5 mV s−1, two-electrode CV studies revealed a specific capacitance of 36.8 F g−1 for the optimized supercapacitor assembly. The electrolyte triethylammonium thiocyanate (TAT) demonstrated good electrochemical stability and a large operating voltage window of 1.8 V and high stability, with 94.4 % capacity retention after 1000 cycles. The AC impedance studies also gave comparable results. Prime novelty statementThe manuscript describes a method to prepare a novel and low-cost ionic liquid material triethylammoniumthiocyanate starting from triethylamine and ammonium thiocyanate, and its application as the ionic liquid electrolyte in a low-cost supercapacitor. The electrode material used in the supercapacitor was fabricated using electronically conducting activated carbon derived from cleaned coconut shells, which were deposited firmly adhering to titanium sheets using polyvinylpyrrolidone binder under optimized heat treatment conditions. As such, both the ionic liquid electrolyte and the activated carbon electrode material are novel and attractive materials for the commercial production of low-cost supercapacitors.

Three‐Component Solid Polymer Electrolytes Based on Li‐Ion Exchanged Microporous Silicates and an Ionic Liquid for Solid‐State Batteries

Solid polymer electrolytes (SPEs) represent one of the most suitable options to overcome durability and safety issues. Herein, three‐component SPEs based on poly(vinylidene fluoride‐co‐hexafluoropropylene) as a binder, the 1‐butyl‐3‐methylimidazolium thiocyanate ionic liquid as an ionic conductive component, and zeolites, to improve SPE ionic conductivity and electrochemical stability, are prepared and characterized. Different zeolite and zeolite‐like structures (clinoptilolite, ETS‐4, and ETS‐10) are used, and the effect of lithium‐ion exchange in their structures is evaluated. A clear influence of the ion exchange process on the crystallinity of the prepared samples is observed, which plays a key role in the conduction mechanisms. The ionic conductivity of the samples at room temperature is of the order of 10−3 S cm−1, making them suitable for battery applications. The assembled batteries show promising results at room temperature, proving that the ion exchange has a positive effect on battery performance. The ion‐exchanged clinoptilolite sample presents the best performance at a prolonged cycle number, with an initial discharge capacity of about 130 mAh g−1 at C/10, and a capacity retention of 70% after 50 cycles. Thus, it is proved that the ion exchange process in microporous silicates represents a suitable strategy to develop high‐performance solid‐state lithium‐ion batteries (LIBs).

Lithium-Ion Battery Solid Electrolytes Based on Poly(vinylidene Fluoride)-Metal Thiocyanate Ionic Liquid Blends.

Solid polymer electrolytes (SPEs) are required to improve battery safety through the elimination of the liquid electrolyte solution in current batteries. This work is focused on the development of a hybrid SPE based on poly(vinylidene fluoride), PVDF, and 1-butyl-3-methylimidazolium cobalt(II) isothiocyanate, [BMIM]2[(SCN)4Co] magnetic ionic liquid (MIL), and its battery cycling behavior at room temperature. The addition of MIL in filler contents up to 40 wt % to the PVDF matrix does not influence the compact morphology of the samples obtained by solvent casting. The polar β-phase of PVDF increases with increasing MIL content, whereas the degree of crystallinity, thermal degradation temperature, and mechanical properties of the MIL/PVDF blends decrease with increasing MIL content. The ionic conductivity of the MIL/PVDF blends increases both with temperature and MIL content, showing the highest ionic conductivity of 7 × 10-4 mS cm-1 at room temperature for the MIL/PVDF blend with 40 wt % of MIL. The cathodic half-cells prepared with this blend as SPE show good reversibility and excellent cycling behavior at different C-rates, with a discharge capacity of 80 mAh g-1 at a C/10-rate with a Coulombic efficiency of 99%. The developed magnetic SPE, with excellent performance at room temperature, shows potential for the implementation of sustainable lithium-ion batteries, which can be further tuned by the application of an external magnetic field.

High-conductivity thiocyanate ionic liquid interface engineering for efficient and stable perovskite solar cells.

A high-conductivity thiocyanate ionic liquid (EMIMSCN) was introduced into perovskite solar cells for the first time. The high conductivity of EMIMSCN ensures an adequate supply of free SCN- anions and EMIM+ cations, so as to multifunctionally passivate the I vacancy and Pb-I antisite defects and realize an optimized interfacial energy level. Consequently, the devices with EMIMSCN treatment achieve a high PCE of 22.55% with substantial enhancement in stability. This simple and efficient strategy provides new insights into the selection of passivation agents for efficient and stable PSCs.

The Impact of Cation Structures on Hypergolicity of Thiocyanate Ionic Liquids with Hydrogen Peroxide

The Impact of Cation Structures on Hypergolicity of Thiocyanate Ionic Liquids with Hydrogen Peroxide

From lab and up: superior and economic heat transfer performance of ionanofluids containing long carbon nanotubes and 1-ethyl-3-methylimidazolium thiocyanate

The optimization of energy systems and the efficiency enhancement of energy conversion processes are still huge challenges. The ionanofluids (INFs) composed of the long multi-walled carbon nanotubes (MWCNTs) and 1-ethyl-3-methylimidazolium thiocyanate ionic liquid ([C2C1im][SCN]) are innovative systems with proven remarkably enhanced thermal conductivity and attractive rheological characteristics. Therefore, as an extension of our previous study, this work aims to examine the overall heat transfer performance of these INFs as working fluids for energy conversion processes and design sustainable energy systems. The new measuring set was designed and constructed to determine the convective heat transfer coefficient and pressure drop during the flow of INFs, using the heat exchanger with saturated steam at 100°C. The obtained results showed that the heat transfer of INFs is prevailed by the convection mechanism. According to a new thermo-economic efficiency-price index proposed in this work, the amalgamation of MWCNTs with [C2C1im][SCN] is justified from both thermophysical and economic points of view.

Green bipropellant development – A study on the hypergolicity of imidazole thiocyanate ionic liquids with hydrogen peroxide in an automated drop test setup

Conventional hypergolic propellant combinations, using hydrazine and its derivatives as fuels and dinitrogen tetroxide based oxidizers, have been applied in spacecraft for attitude and roll control systems for more than 50 years. However, due to their high toxicity and carcinogenic potential, investigations into alternative green propellants are an active field in current research efforts. Promising alternative propellant candidates are combinations of hydrogen peroxide and suitable hypergolic room-temperature ionic liquids. In this work, imidazole thiocyanate ionic liquids are tested in drop tests with hydrogen peroxide. For this purpose, a newly developed automated drop test setup was designed and implemented. As a result, 1-ethyl-3-methylimidazolium thiocyanate (EMIM SCN) and 1-butyl-3-methylimidazolium thiocyanate (BMIM SCN) turned out to be hypergolic with highly concentrated hydrogen peroxide (96.1%). The ignition delay time on average is 31.7 ms for EMIM SCN and 45 ms for BMIM SCN. Theoretical performance of the two ionic liquids was calculated with NASA CEA and compared to a conventional hypergolic propellant combination (monomethyl hydrazine/dinitrogen tetroxide). The specific impulse of the green propellants is nearly 5% lower, but the density specific impulse is increased by 10%. Furthermore, the ignition delay time was reduced by dissolving a catalytic additive, copper thiocyanate, in the EMIM SCN. The lowest average ignition delay time of 13.9 ms was achieved for EMIM SCN and 5 wt% of copper thiocyanate. For higher copper concentration the ignition delay time is not further reduced. The fuel with EMIM SCN and 5 wt% of copper thiocyanate and the pure EMIM SCN were further characterized by thermal and spectroscopic methods. Fluid properties like density, viscosity and surface tension were also determined in laboratory investigations.

Viscosity of binary mixtures of 1-(2-methoxyethyl)-3-ethylimidazolium thiocyanate ionic liquid with short-chain alcohols

In this paper, a ether-group functionalized ionic liquid 1-(2-methoxyethyl)-3-ethylimidazolium thiocyanate [C22O1IM][SCN] was synthesized and characterized by 1H NMR, 13C NMR, ESI mass spectrometry and elemental analysis, and the viscosities of [C22O1IM][SCN] and of binary mixtures with monohydric alcohols (ethanol, 1-propanol, isopropanol and 1-butanol) were measured over the entire range of mole fraction in the temperature range from 288.15 K to 318.15 K and atmospheric pressure. The Arrhenius equation was used to describe the changing trends of viscosity with temperature. To investigate the internal interactions of the mixtures, the viscosity deviations, Δη, and the Gibbs energy of activation for viscous flow of the relative viscosity for the mixture, ΔG≠r, were calculated based on the experimental viscosity, they were all negative values indicating that the hydrogen bond formation between ionic liquid and alcohol. In addition, the related entropies and enthalpies were also calculated and discussed.

The highly stable air-operating ionic polymer metal composite actuator with consecutive channels and its potential application in soft gripper

In this study, a highly stable air-operating ionic polymer–metal composite (IPMC) actuator with consecutive channels suitable for transportation of the cations and anions of ionic liquids was prepared by introducing and removing copper foam. The electromechanical properties of this novel porous IPMC were investigated. Scanning electron microscopy observation showed that channels and pores ranging in size from ∼100 nm to ∼50 μm were distributed in the Nafion membrane. The porous IPMC was doped with 1-ethyl-3-methylimidazolium thiocyanate ionic liquid. A larger capacitance (285.00 mF cm−2) was obtained, which can be attributed to the electric double layer generated at the interface between the ionic polymer membrane and platinum electrode under the input voltage. The fast ion migration channels, high conductivity, and large capacitance enabled high strain of 0.051%–0.666%, a relatively large blocking force of 17.63 mN, and excellent actuation durability for more than 180 000 cycles to be achieved. Furthermore, a soft gripper consisting of a bio-inspired micropillar dry adhesive glued on one surface of the porous IPMC assembled with a mobile mechanical arm was fabricated, and the soft gripper successfully grabbed objects with various features.

Inorganic AlCl3-alkali metal thiocyanate ionic liquids as electrolytes for electrochemical Al technologies.

A series of inorganic AlCl3-alkali metal thiocyanate (AMSCN: AM = Li, Na, K) ionic liquids (ILs) are demonstrated as electrolytes for Al electrodeposition and Al-anion rechargeable batteries (AARBs) at 303-363 K. Al deposits with a unique flake nanostructure are obtained in these electrolytes. The assembled AARBs show a stable cyclability over 250 cycles with a reversible capacity of ca. 70 mA h (g-graphite)-1 at 363 K. These inorganic ILs inherit the advantages of conventional chloroaluminate ILs (applicability at near-ambient temperature) and molten salts (cost effectiveness), making them promising electrolyte candidates for industrializable electrochemical Al technologies.

1-Ethyl 3-methylimidazolium thiocyanate ionic liquid as corrosion inhibitor of API 5L X52 steel in H2SO4 and HCl media

The corrosion inhibition behavior of 1-ethyl 3-methylimidazolium thiocyanate, (EMIM)+(SCN)− ionic liquid (IL), on API 5 L X52 steel immersed in 0.5 M H2SO4 and 0.5 M HCl aqueous solutions were studied. The kinetic corrosion parameters were determined using a gravimetrical method and electrochemical tests (polarization curves, electrochemical impedance spectroscopy). The (EMIM)+(SCN)− exhibited good inhibition efficiency, IE, (82.9% and 77.4% for H2SO4 (75 ppm) and HCl (100 ppm) solutions) properties in both solutions acting as a mixed-type inhibitor. In H2SO4 the IE increased with increasing IL concentration and temperature, while in HCl IE decreased with the temperature increase. The IL adsorption mechanism followed the Langmuir isotherm, presenting a competition between the physical and chemical interactions. Surface analysis techniques (energy dispersive spectroscopy and X-ray photoelectron spectroscopy) indicate that the inhibitor formed a protective film on the steel surface, evidencing the adsorption of the cation (EMIM)+ and the anion (SCN)− of the IL on the steel surface, which corroborates that both the (EMIM)+ and the (SCN)− of IL interact with the substrate. The evaluation of interactions of (EMIM)+(SCN)− molecules with H2SO4 and HCl in the presence of water on different surfaces of iron Fe and Fe2O3 (110) plane was performed, using molecular dynamics to determine the inhibitor adsorption energies in both acid media. The simulation results are in close agreement with the experimental observations that the inhibition efficiency is better in H2SO4 solution in comparison with that in HCl due to the higher adsorption energy values obtained in H2SO4 medium.

Synthesis, microstructure and volumetry of novel metal thiocyanate ionic liquids with [BMIM] cation

We present a new family of ionic liquids (ILs) with a common cation, 1-butyl-3-methyl imidazolium, the popular [BMIM]+ (also written C4C1Im+) and a variety of anionic complexes (also called adducts) based in thiocyanate (SCN)−: one blank compound, BMIM(SCN), and ten doped with metals having different oxidation states: Al+3, Mn+2, Fe+3, Cr+3, Ni+2, Hg+2, Zn+2, Co+2, Cd+2 and Cu+, forming, respectively, [BMIM]3[Al(SCN)6], [BMIM]4 Mn(SCN)6, [BMIM]3 Fe(SCN)6, [BMIM]3 Cr(SCN)6, [BMIM]4 Ni(SCN)6, [BMIM]2 Hg(SCN)4, [BMIM]2 Zn(SCN)4, [BMIM]2 Co(SCN)4, [BMIM]2 Cd(SCN)4 and [BMIM]3 Cu(SCN)4. All of them were synthesized by us, except the blank IL and the Co thiocyanate, which are commercial. Obtained products have been characterized by NMR, and also by electrospray ionization, MS-ES, which allows the determination of the new ILs purities. Then, compounds have been analyzed using FT-IR and Raman spectroscopy. In addition, magnetic susceptibility and refractive index measurements were performed in some of the compounds studied, as well as thermal characterization using DSC and TGA. Finally, experimental measurements of density on all those ILs have been performed, and for some of the samples in a broad temperature range (about 100 K). In spite of being very similar compounds from the chemical point of view, they present quite different physical properties, including optical, thermal and magnetic ones… Also, they show different oxidation states (one with +1, six with +2 and other three with +3). We guess that this family of ILs will have interesting applications, mainly for photonic devices.

Solvation properties of 1-alkyl-3-methylimidazolium thiocyanate ionic liquids in the presence of lithium halide salts in N-methyl-2-pyrrolidone

Recently, ionic liquids in design and optimization of the membrane technology were applied. Thiocyanate based ionic liquids as green and fluorine-free solvents were used effectively in the preparation of membranes that were used in separation and purification. In this work, 1-alkyl-3-methylimidazolium thiocyanate, [RMIM][SCN] (R = butyl, hexyl, and octyl), were synthesized and some of the thermophysical properties of (IL + LiX (X = Cl, Br) + N-methyl-2-pyrrolidone) ternary solutions including density, speed of sound and viscosity data have been determined at T = 298.15 K. Also, the standard partial molar volumes Vφ0, partial molar isentropic compressibility κφ0 and viscosity B-coefficients have been calculated. The scaled particle theory (SPT) was used to determining of different contributions of the Vφ0. The obtained quantities were used to interpret the influence of lithium halide salts on the solute-solvent interactions in the studied IL solutions.

Microwave Synthesis of Fused Pyrans by Humic Acid Supported Ionic Liquid Catalyst and Their Antimicrobial, Antioxidant, Toxicity Assessment, and Molecular Docking Studies

A series of fused quinolinyl and quinolonyl pyrans were synthesized via a one‐pot reaction of quinolinyl and quinolonyl carbaldehydes, malononitrile, and a 1,3‐diketone. The reactions were catalyzed by a new humic acid supported 1‐butyl‐3‐methyl imidazolium thiocyanate ionic liquid under microwave irradiation conditions. Antimicrobial, antioxidant, and toxicity studies displayed various biological activities depending on structure of the pyrans.

Yttrium and europium separation by solvent extraction with undiluted thiocyanate ionic liquids.

An yttrium/europium oxide obtained by the processing of fluorescent lamp waste powder was separated into its individual elements by solvent extraction with two undiluted ionic liquids, trihexyl(tetradecyl)phosphonium thiocyanate, [C101][SCN], and tricaprylmethylammonium thiocyanate, [A336][SCN]. The best extraction performances were observed for [C101][SCN], by using an organic-to-aqueous volume ratio of 1/10 and four counter-current extraction stages. The loaded organic phase was afterwards subjected to scrubbing with a solution of 3 mol L−1 CaCl2 + 0.8 mol L−1 NH4SCN to remove the co-extracted europium. Yttrium was quantitatively stripped from the scrubbed organic phase by deionized water. Yttrium and europium were finally recovered as hydroxides by precipitation with ammonia and then calcined to the corresponding oxides. The conditions thus defined for an efficient yttrium/europium separation from synthetic chloride solutions were afterwards tested on a leachate obtained from the dissolution of a real mixed oxide. The purity of Y2O3 with respect to the rare-earth content was 98.2%; the purity of Eu2O3 with respect to calcium was 98.7%.