Showing papers on "Ionic liquid published in 2019"

Planar perovskite solar cells with long-term stability using ionic liquid additives

Abstract: Solar cells based on metal halide perovskites are one of the most promising photovoltaic technologies(1-4). Over the past few years, the long-term operational stability of such devices has been gre ...

Molecular Dynamics Simulations of Ionic Liquids and Electrolytes Using Polarizable Force Fields.

Abstract: Many applications in chemistry, biology, and energy storage/conversion research rely on molecular simulations to provide fundamental insight into structural and transport properties of materials with high ionic concentrations. Whether the system is comprised entirely of ions, like ionic liquids, or is a mixture of a polar solvent with a salt, e.g., liquid electrolytes for battery applications, the presence of ions in these materials results in strong local electric fields polarizing solvent molecules and large ions. To predict properties of such systems from molecular simulations often requires either explicit or mean-field inclusion of the influence of polarization on electrostatic interactions. In this manuscript, we review the pros and cons of different treatments of polarization ranging from the mean-field approaches to the most popular explicit polarization models in molecular dynamics simulations of ionic materials. For each method, we discuss their advantages and disadvantages and emphasize key assumptions as well as their adjustable parameters. Strategies for the development of polarizable models are presented with a specific focus on extracting atomic polarizabilities. Finally, we compare simulations using polarizable and nonpolarizable models for several classes of ionic systems, discussing the underlying physics that each approach includes or ignores, implications for implementation and computational efficiency, and the accuracy of properties predicted by these methods compared to experiments.

Construction of a sp 3 /sp 2 Carbon Interface in 3D N-Doped Nanocarbons for the Oxygen Reduction Reaction

Abstract: The development of highly efficient metal-free carbon electrocatalysts for the oxygen reduction reaction (ORR) is one very promising strategy for the exploitation and commercialization of renewable and clean energy, but this still remains a significant challenge. Herein, we demonstrate a facile approach to prepare three-dimensional (3D) N-doped carbon with a sp3 /sp2 carbon interface derived from ionic liquids via a simple pyrolysis process. The tunable hybrid sp3 and sp2 carbon composition and pore structures stem from the transformation of ionic liquids to polymerized organics and introduction of a Co metal salt. Through tuning both composition and pores, the 3D N-doped nanocarbon with a high sp3 /sp2 carbon ratio on the surface exhibits a superior electrocatalytic performance for the ORR compared to that of the commercial Pt/C in Zn-air batteries. Density functional theory calculations suggest that the improved ORR performance can be ascribed to the existence of N dopants at the sp3 /sp2 carbon interface, which can lower the theoretical overpotential of the ORR.

Advances of Ionic Liquids in Analytical Chemistry.

Abstract: Ionic liquids (ILs) are a highly unique class of non-molecular solvents that possess melting points below 100 ºC.1 ILs that have melting points below room temperature are often referred to as room temperature ionic liquids (RTILs). ILs possess a wide variety of unique physico-chemical properties, including low or negligible vapor pressure at room temperature, high thermal and electrochemical stability, and high conductivity.2.

Water-Soluble Triazolium Ionic-Liquid-Induced Surface Self-Assembly to Enhance the Stability and Efficiency of Perovskite Solar Cells

Abstract: Despite being a promising candidate for next-generation photovoltaics, perovskite solar cells (PSCs) exhibit limited stability that hinders their practical application. In order to improve the humidity stability of PSCs, herein, a series of ionic liquids (ILs) “1-alkyl-4-amino-1,2,4-triazolium” (termed as RATZ; R represents alkyl chain, and ATZ represents 4-amino-1,2,4-triazolium) as cations are designed and used as additives in methylammonium lead iodide (MAPbI3) perovskite precursor solution, obtaining triazolium ILsmodified PSCs for the first time (termed as MA/RATZ PSCs). As opposed to from traditional methods that seek to improve the stability of PSCs by functionalizing perovskite film with hydrophobic molecules, humidity-stable perovskite films are prepared by exploiting the self-assembled monolayer (SAM) formation of water-soluble triazolium ILs on a hydrophilic perovskite surface. The mechanism is validated by experimental and theoretical calculation. This strategy means that the MA/RATZ devices exhibit good humidity stability, maintaining around 80% initial efficiency for 3500 h under 40 ± 5% relative humidity. Meanwhile, the MA/RATZ PSCs exhibit enhanced thermal stability and photostability. Tuning the molecule structure of the ILs additives achieves a maximum power conversion efficiency (PCE) of 20.03%. This work demonstrates the potential of using triazolium ILs as additives and SAM and molecular design to achieve high performance PSCs.

A safe and non-flammable sodium metal battery based on an ionic liquid electrolyte

Abstract: Rechargeable sodium metal batteries with high energy density could be important to a wide range of energy applications in modern society. The pursuit of higher energy density should ideally come with high safety, a goal difficult for electrolytes based on organic solvents. Here we report a chloroaluminate ionic liquid electrolyte comprised of aluminium chloride/1-methyl-3-ethylimidazolium chloride/sodium chloride ionic liquid spiked with two important additives, ethylaluminum dichloride and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide. This leads to the first chloroaluminate based ionic liquid electrolyte for rechargeable sodium metal battery. The obtained batteries reached voltages up to ~ 4 V, high Coulombic efficiency up to 99.9%, and high energy and power density of ~ 420 Wh kg−1 and ~ 1766 W kg−1, respectively. The batteries retained over 90% of the original capacity after 700 cycles, suggesting an effective approach to sodium metal batteries with high energy/high power density, long cycle life and high safety. Na metal batteries offer compelling merits; however, the safety issue remains to be overcome. Here, the authors report an ionic liquid electrolyte based on NaCl-buffered AlCl3/[EMIm]Cl with two additives including EtAlCl2 and [EMIm]FSI which serve to stabilize SEI for reversible Na plating/stripping.

Highly Dense Packing of Chromophoric Linkers Achievable in a Pyrene-Based Metal–Organic Framework for Photoelectric Response

Abstract: Highly dense packing of chromophoric linkers is achieved in a novel pyrene-based metal-organic framework (MOF), [Zn(TBAPy)1/2(H2O)2], induced by an ionic liquid. This MOF displays a quick response to visible-light irradiation (photocurrent density of up to 4.492 μA cm-2) and is capable of repetitive on-off photocurrent switching with a large on-off ratio (37.55).

Which is the best food emerging solvent: IL, DES or NADES?

Abstract: Background Bioactive compounds have been intensely studied because of their biological properties that provide health benefits. However, for chemical or biological applications, these compounds are obtained mostly by using organic solvents. Emergent technologies consider the combination of methods and process optimization to improve the utilization of raw material, decreasing process costs, time and energy consumption. Additionally, due to the arising interest for green processes, alternative solvents have been developed. Ionic liquids (IL), deep eutectic solvents (DES) and, recently, natural deep eutectic solvents (NADES) can show high ability to extract organic, inorganic and polymeric bio-compounds. Overall, these promising solvents are environmentally friendly and less toxic than conventional extraction solvents. Scope and approach This review summarizes the use of IL, DES, and NADES for the extraction of bioactive compounds from natural products, presenting their evolution, process variables, target compounds, extraction techniques employed and future perspectives. Key findings and conclusions The use of these emerging solvents for extraction process has shown to be promising. Besides its high solvation ability and versatility, these solvents may present low or none toxicity. Particularly, it is allowed the use of NADES in food and pharmaceutical formulations, however, some DES and IL are in need of further investigation. IL, DES, and NADES are recyclables and can be related to sustainable processes. Therefore, to expand the applications of these emerging solvents for the recovery of bioactive compounds, the extraction mechanisms involved need to be proper elucidated.

A versatile functionalized ionic liquid to boost the solution-mediated performances of lithium-oxygen batteries.

Abstract: Due to the high theoretical specific energy, the lithium–oxygen battery has been heralded as a promising energy storage system for applications such as electric vehicles. However, its large over-potentials during discharge–charge cycling lead to the formation of side-products, and short cycle life. Herein, we report an ionic liquid bearing the redox active 2,2,6,6-tetramethyl-1-piperidinyloxy moiety, which serves multiple functions as redox mediator, oxygen shuttle, lithium anode protector, as well as electrolyte solvent. The additive contributes a 33-fold increase of the discharge capacity in comparison to a pure ether-based electrolyte and lowers the over-potential to an exceptionally low value of 0.9 V. Meanwhile, its molecule facilitates smooth lithium plating/stripping, and promotes the formation of a stable solid electrolyte interface to suppress side-reactions. Moreover, the proportion of ionic liquid in the electrolyte influences the reaction mechanism, and a high proportion leads to the formation of amorphous lithium peroxide and a long cycling life (> 200 cycles). In particular, it enables an outstanding electrochemical performance when operated in air. Li-O2 batteries are promising candidates for the next generation of rechargeable batteries, but the side reactions and poor cycling stability limit their applications. Here, the authors show a versatile ionic liquid with functional groups that can address both issues for cells operated in oxygen and air.

Hybrid Chloroantimonates(III): Thermally Induced Triple-Mode Reversible Luminescent Switching and Laser-Printable Rewritable Luminescent Paper

Abstract: Two hybrid chloroantimonates(III), [Bzmim]3 SbCl6 (1, Bzmim=1-benzyl-3-methylimidazolium, Tm1 =410 K) and [Bzmim]2 SbCl5 (2, Tm2 =348 K) are presented. 1 exhibits green emission (quantum efficiency of 87.5 %); 2 exhibits blue and red emissions under the irradiation of 310 and 396 nm light, respectively. Using different cooling methods, crystalline 1 and IL@2 (IL=ionic liquid of [Bzmim]Cl) could be generated from the molten 1. Reversible structural and PL transformation triggered by moisture or heat was observed between 1 and IL@2. Such PL switching, combined with the crystallization-induced PL properties of 1 and 2, resulted in the firstly reported triple-mode reversible PL switching, that is, on-off (T>Tm1 ), color switching (T

Green solvents for the extraction of bioactive compounds from natural products using ionic liquids and deep eutectic solvents

Abstract: Green technology is moving from an option to a must in modern industrial processing. Solvents are the core of the food, pharmaceutical, cosmetic, agrochemical, chemical, and biotechnological process technologies. In the past two decades, supercritical fluids, ionic liquids, and deep eutectic solvents became the most actively investigated as potential green solvents, especially in the field associated with food, flavors, fragrances, and medicinal plants processing. This review assesses recent information about the novel solvent technologies.

Reversible Ion-Conducting Switch in a Novel Single-Ion Supramolecular Hydrogel Enabled by Photoresponsive Host-Guest Molecular Recognition.

Abstract: A novel ion-conducting supramolecular hydrogel with reversible photoconductive properties in which the azobenzene motif, α-cyclodextrin (α-CD), and ionic liquid are grafted onto the gel matrix is reported. Host-guest interactions with different association constants between α-CD and azobenzene or the anionic part of the ionic liquid can be readily tuned by photoinduced trans-cis isomerization of the azobenzene unit. When irradiated by 365 nm light, α-CD prefers to form a complex with the anionic part of the ionic liquid, resulting in decreased ionic mobility and thus high resistance of the hydrogel. However, under 420 nm light irradiation, a more stable complex is again formed between α-CD and trans-azobenzene, thereby releasing the bound anions to regenerate the low-resistive hydrogel. As such, remote control of the ionic conductivity of the hydrogel is realized by simple host-guest chemistry. With the incorporation of a logic gate, this hydrogel is able to reversibly switch an electric circuit on and off by light irradiation with certain wavelengths. The concept of photoswitchable ionic conductivity of a hydrogel mediated by competitive molecular recognition is potentially promising toward the fabrication of optoelectronic devices and applications in bioelectronic technology.

Plasmonic photosynthesis of C 1 –C 3 hydrocarbons from carbon dioxide assisted by an ionic liquid

Abstract: Photochemical conversion of CO2 into fuels has promise as a strategy for storage of intermittent solar energy in the form of chemical bonds. However, higher-energy-value hydrocarbons are rarely produced by this strategy, because of kinetic challenges. Here we demonstrate a strategy for green-light-driven synthesis of C1–C3 hydrocarbons from CO2 and H2O. In this approach, plasmonic excitation of Au nanoparticles produces a charge-rich environment at the nanoparticle/solution interface conducive for CO2 activation, while an ionic liquid stabilizes charged intermediates formed at this interface, facilitating multi-step reduction and C–C coupling. Methane, ethylene, acetylene, propane, and propene are photosynthesized with a C2+ selectivity of ~50% under the most optimal conditions. Hydrocarbon turnover exhibits a volcano relationship as a function of the ionic liquid concentration, the kinetic analysis of which coupled with density functional theory simulations provides mechanistic insights into the synergy between plasmonic excitation and the ionic liquid.

Efficient molecular doping of polymeric semiconductors driven by anion exchange

Abstract: The efficiency with which polymeric semiconductors can be chemically doped—and the charge carrier densities that can thereby be achieved—is determined primarily by the electrochemical redox potential between the π-conjugated polymer and the dopant species1,2. Thus, matching the electron affinity of one with the ionization potential of the other can allow effective doping3,4. Here we describe a different process—which we term ‘anion exchange’—that might offer improved doping levels. This process is mediated by an ionic liquid solvent and can be pictured as the effective instantaneous exchange of a conventional small p-type dopant anion with a second anion provided by an ionic liquid. The introduction of optimized ionic salt (the ionic liquid solvent) into a conventional binary donor–acceptor system can overcome the redox potential limitations described by Marcus theory5, and allows an anion-exchange efficiency of nearly 100 per cent. As a result, doping levels of up to almost one charge per monomer unit can be achieved. This demonstration of increased doping levels, increased stability and excellent transport properties shows that anion-exchange doping, which can use an almost infinite selection of ionic salts, could be a powerful tool for the realization of advanced molecular electronics. The limitations of conventional chemical doping of polymeric semiconductors can be overcome by adding a second ionic species into the system, leading to enhanced doping, electrical conductivity and stability.

MOF-derived nanoporous multifunctional fillers enhancing the performances of polymer electrolytes for solid-state lithium batteries

Abstract: Polymer electrolytes usually suffer from low ionic conductivity and poor stability against the lithium electrode. Taking advantage of nanostructured metal–organic frameworks (MOFs), novel nanoporous fillers, i.e., UIO/Li-IL, are developed for polymer electrolytes; in UIO/Li-IL, a Li-containing ionic liquid (Li-IL) is absorbed in UIO-66 MOFs. These fillers are multifunctional: high ionic conductivity and capability to suppress the crystallinity and to improve the stability of polyethylene oxide (PEO) against the lithium electrode. PEO-n-UIO composite polymer electrolytes are formed by dispersing the multifunctional fillers in PEO; the conductivity of the PEO-n-UIO solid electrolytes is increased by a factor of ∼37 to 1.3 × 10−4 S cm−1 at 30 °C with 40% UIO/Li-IL, and the current density for stable Li plating/stripping in PEO-n-UIO solid electrolytes is enhanced to 500 μA cm−2 at 60 °C. Solid-state lithium batteries based on the PEO-n-UIO solid electrolyte show an initial discharge capacity of ∼151 mA h g−1 with a capacity retention of 95% after 100 cycles at 0.5C and 60 °C. Our work pioneers novel multifunctional fillers to boost the performances of composite polymer electrolytes for high energy density, safe and long lifetime energy storage systems.

Self-assembled nanostructures in ionic liquids facilitate charge storage at electrified interfaces

Abstract: Driven by the potential applications of ionic liquids (ILs) in many emerging electrochemical technologies, recent research efforts have been directed at understanding the complex ion ordering in these systems, to uncover novel energy storage mechanisms at IL–electrode interfaces. Here, we discover that surface-active ILs (SAILs), which contain amphiphilic structures inducing self-assembly, exhibit enhanced charge storage performance at electrified surfaces. Unlike conventional non-amphiphilic ILs, for which ion distribution is dominated by Coulombic interactions, SAILs exhibit significant and competing van der Waals interactions owing to the non-polar surfactant tails, leading to unusual interfacial ion distributions. We reveal that, at an intermediate degree of electrode polarization, SAILs display optimum performance, because the low-charge-density alkyl tails are effectively excluded from the electrode surfaces, whereas the formation of non-polar domains along the surface suppresses undesired overscreening effects. This work represents a crucial step towards understanding the unique interfacial behaviour and electrochemical properties of amphiphilic liquid systems showing long-range ordering, and offers insights into the design principles for high-energy-density electrolytes based on spontaneous self-assembly behaviour. Understanding molecular interactions between ionic liquids and interfaces is crucial for electrochemical device applications. Self-assembled amphiphilic nanostructures in surface-active ionic liquids are shown to exhibit enhanced charge storage at electrified surfaces.

Green solvents in analytical chemistry

Abstract: Current trends in incorporating the principles of green chemistry in analytical methods have led to the design and usage of new solvents to replace conventional organic solvents, which characterize by their high volatility, flammability, and toxicity. Among the alternatives that have emerged, amphiphilic solvents, ionic liquids, and deep eutectic solvents are the most explored candidates in this research field. Taking advantage of the solvation properties of these new solvents, together with the synthetic versatility in the case of ionic liquids and deep eutectic solvents, a wide variety of applications of these solvents within green analytical chemistry appear in the recent literature. The aim of this article is to provide a quick summary of the state of the art on the usage of these new green solvents in analytical chemistry, particularly in liquid-phase microextraction methods (within sample preparation) and as additives or pseudostationary phases in liquid chromatography (within analytical separation methods).

Ionic liquid-decorated COF and its covalent composite aerogel for selective CO2 adsorption and catalytic conversion

Abstract: Atmospheric CO2 is closely related to the greenhouse effect. Therefore, new practical materials and techniques for highly selective CO2 adsorption and catalytic conversion are imperative. Covalent composites of covalent organic frameworks (COFs) with polymers (oligomers) might be a promising approach to meeting the multifaceted requirements of CO2 treatment. Herein, a novel COF–chitosan composite aerogel (COF-IL@chitosan) was designed and fabricated by chemical crosslinking of an allyl-imidazolium ionic liquid-decorated COF (COF-IL) with a thiol-attached chitosan (chitosan–SH) binder via a photoinduced thiol–ene reaction. The crystalline structure, highly selective CO2 adsorption and catalytic conversion features of COF-IL were found to be well maintained in the composite aerogel. The generated covalently coupled COF–chitosan composite material COF-IL@chitosan was found to be robust, uniform and processable even with a remarkably high COF loading (up to 80 wt%). More importantly, the processable COF-IL@chitosan aerogel could be readily shaped into a simplified fixed-bed reactor model via a facile templated freeze-drying procedure, and a scaled-up recyclable CO2 cycloaddition reaction was realized.

Synergistic design of a N, O co-doped honeycomb carbon electrode and an ionogel electrolyte enabling all-solid-state supercapacitors with an ultrahigh energy density

Abstract: Significantly boosting the energy densities of supercapacitors without compromising their power densities is of paramount importance for practical applications, but still faces great challenges. Herein, we report an ultrahigh-energy-density solid-state supercapacitor enabled by synergistical design of a N, O co-doped honeycomb porous carbon (HPC) electrode and an ionogel electrolyte. HPC is synthesized through the co-assembly of melamine/formaldehyde with silica spheres, and shows an ultrahigh surface area (2379 m2 g−1) coupled with a 3D interconnected macro-, meso- and microporous structure, and high-level redox-active N/O dopants (6.90 and 10.17 wt%). Benefiting from such merits, the HPC electrode yields an extremely high capacitance of 533 F g−1 at 0.5 A g−1 in an alkaline electrolyte, together with superior cycling stability with 92.1% capacitance retention after 20 000 cycles at 5 A g−1. HPC assembled supercapacitors deliver energy outputs of 12.8 and 26.6 W h kg−1 using KOH and Na2SO4 electrolytes, respectively. More attractively, a HPC-fabricated all-solid-state symmetric device based on the use of a well-designed, polymer-gel supported ionic liquid electrolyte achieves an ultrahigh energy density of 94.1 W h kg−1, which is the highest value among those of previously reported supercapacitors of the same type, and an excellent cycling stability (91.5% retention over 10 000 cycles). This study highlights promising prospects of developing solid-state energy storage systems of high energy-power supply.

Deep eutectic solvents (DESs) for cellulose dissolution: a mini-review

Abstract: Deep eutectic solvents (DESs), which are a novel class of sustainable designer solvents, have attracted considerable attentions in the field of cellulose chemistry. Due to their low cost and analogous physico-chemical properties to ionic liquids, DESs are expected to be alternative solvents for dissolving cellulose. However, at present, the solubility of cellulose in DESs is much lower than in most ionic liquids. In this mini-review, we briefly summarize the current state of knowledge about cellulose dissolution in DESs. By comparing with similar solvents, it was found that the components of current DESs are usually involved in hydrogen bond interaction making difficult their interaction with the hydrogen bond network of cellulose. Accordingly, we propose a strategy that the components which have good hydrogen bond accepting ability, such as Cl-, OAc-, HCOO-, (MeO)2PO2-, morpholine and imidazole, are promising choices to form DESs for cellulose dissolution. Ultrasound-assisted treatment and adding a surfactant are effective ways to promote cellulose solubility by enhancing the permeability of DESs.