Ionic Liquid Species Research Articles

Enhancement of Electrochemical Properties of Carboxylate-Based Single-Ion Conducting Polymers through Complexation with Ionic Liquids for Lithium-Ion Batteries

[Introduction] Single-ion conducting (SIC) polymers, wherein anions are covalently bonded to the polymer chain, selectively facilitate the movement of lithium ions, making them promising polymer electrolytes for lithium-ion batteries (LIBs) due to their high lithium-ion transference number. However, in the application of highly basic carboxylate-based SIC polymer electrolytes, there is a drawback of difficultly in dissociating Li+ ions. In this study, the complexation with ionic liquids (ILs) was investigated to promote the dissociation of Li+ ions.[Experiment] The carboxylate-based SIC polymer (MAA-St) was synthesized through a 1:1 radical copolymerization of methacrylic acid derivatives and styrene. A polymer electrolyte was fabricated by compounding the obtained polymer with ILs, and its electrochemical properties were evaluated.[Results and Discussion] Electrochemical evaluations were conducted on the polymer electrolyte, which was a composite of MAA-St and ILs. In the absence of ILs, the ionic conductivity (σ = 7.13×10–4 mS cm–1 at room temperature) and critical current density (CCD) were extremely low because of the high basicity and difficulty in dissociating Li+ ions. However, the incorporation of ILs led to a significant improvement in electrochemical properties (σ = 7.13×10–4 → 1.98 mS cm–1, critical current density = 0.1 → 2.1 mA cm–2). Furthermore, ionic conductivity and CCD were substantially enhanced with an increase in the quantity of ILs (Figure 1). The addition of ILs weakened the interaction between the SIC polymer and Li ions, facilitating the dissociation of Li ions.The effect of ionic species of ILs on electrochemical properties was investigated. To examine the dependence on anion species, the cation of the IL was fixed to (N-butyl-N-methylpyrrolidinium: P14 +) and five different anions (PF6, TFSA, FSA, OTf, and N(CN)2) were used for evaluation. As a result, it was observed that the CCD varied significantly according to the donor number (DN) of the anion species. On the other hand, the impact of cation species on CCD was minimal because they interacted with the anionic part of the SIC polymer.The interaction between SIC polymer and ILs was observed through IR measurements, and the peak of the polymer-derived carbonyl group (C=O) underwent significant changes upon the addition of ILs (1680 cm–1: substantial decrease, 1572 cm–1: red-shift). Additionally, the movement of the anion species of the IL was confirmed by Raman spectroscopy, revealing distinct movements based on the DN of the anion species. Consequently, it became evident that the interaction between SIC polymer and ILs results in the dissociation of Li+ ions and the counteranions. Figure 1

Effects of Anion or Cation Structures on the Interaction of Ionic Liquid with Cu3(BTC)2 Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are a class of porous materials with highly periodic nanopores and enormous specific surface area, which allow us to achieve gas adsorption and catalytic applications superior to those based on conventional porous materials [1]. However, the structural degradation due to moisture absorption and fragility in many MOFs led to challenges for practical application. We have found a solution to inhibit this moisture degradation by filling ionic liquid (IL) into the nanopores of MOF; the composite materials are referred to as IL@MOF. In addition, in IL@MOF, it was also clarified that the fragility was improved while keeping the crystal structure [2]. However, the reason is still unclear.In this study, we focus on the interaction of IL with MOF and the effects of IL types on the crystal structure of MOF. IL@MOF samples were prepared by filling imidazolium-based [Cnmim][Tf2N] with different cation alkyl side chain lengths (n = 2, 4, 8) into single crystal HKUST-1 MOF (Cu3(BTC)2), which was synthesized by the solvothermal method [3]. Here, the sample was given a name according to the cation alkyl side chain length, i.e., Cu3(BTC)2 filled with [C2mim][Tf2N] is named C2@ Cu3(BTC)2. X-ray photoelectron spectroscopy (XPS) was used to analyze the binding energy (B.E.) of MOF frames, and X-ray diffraction (XRD) was used to measure the lattice spacing of MOF.XPS spectra of C 1s, O 1s, Cu 2p3/2 for Cu3(BTC)2 and C4@Cu3(BTC)2 are presented in Figs. 1(a), (b), and (c). The XPS spectra were corrected so that the peaks corresponding to the C–C (285 eV) for both Cu3(BTC)2 and C4@Cu3(BTC)2, confirmed by peak separation, became the same, as shown in Fig. 1(a). It was found that the B.E. of Cu 2p3/2 and O 1s decreased with IL filling. The decrease in B.E. from B.E. of Cu3(BTC)2 was larger for shorter alkyl side chain lengths (Fig. 1(d)). This may be attributed to the coordination of the anions of the ILs to Cu, which effectively decreased the oxidation number of Cu. The decrease in the oxidation number of Cu is expected to reduce the Cu–O interactions and elongate the Cu–O bonds. This was verified by the result of XRD measurement shown in Fig. 1(e), indicating that the lattice spacing of the (222) plane of Cu3(BTC)2 increased after IL filling. The increase in the lattice spacing by IL filling is larger for shorter alkyl side chain lengths. These results suggest that IL filling elongates the Cu–O bonds in Cu3(BTC)2, and that the effect is more significant for shorter side chain lengths. We will discuss the IL species dependence of the MOF framework modulation including anions in detail in the presentation.[1] YU, Jia, et al., Materials Horizons, 2017, 4.4: 557.[2] S. G. Koh, et al., J. Phys. Chem. C 2022, 126, 6736[3] L. Li, F. Sun, J. Jia, T. Borjigina, and G. Zhu, CrystEngComm, 2013, 15, 4094. Figure 1

Correlation-Based Predictions of Gas Solute Diffusivity in Ionic Liquid Solvents Based on Solvent-Accessible Surface Area.

In our prior study [Olowookere, F. V.; Turner, C. H. J. Phys. Chem. B 2023, 127(42), 9144-9154], we introduced a new scaling relationship to predict gas solute diffusion at challenging conditions, focusing on CO2 and SO2 diffusion in multivalent ionic liquid (IL) solvents. This work extends our initial exploratory study into a much broader array of systems, encompassing additional solutes (N2, CH4, C2H6, C3H8, C3H8O, and H2O) and a variety of different ionic liquid species ([Bzmim3]3+, [Bzmim4]4+, [BMIM]+, [EMIM]+, [HMIM]+, [NapO2]2-, [BzO3]3-, [BF4]-, [Tf2N]-, and [PF6]-). Our study demonstrates a remarkably robust logarithmic correlation between solute diffusion and solvent accessible surface area (SA) across 20 different additional systems. We perform comprehensive analyses of the underlying molecular phenomena responsible for this correlation, including solute lifetime distributions, void space dynamics, and Voronoi tessellation, in order to elucidate a stronger mechanistic understanding of this behavior. Our findings highlight a direct link between the solvent accessible SA and the size of the void domains. Overall, our scaling approach provides an efficient and reliable approach for predicting diffusion from analyses of short simulations at higher temperatures.

A comparative study on the solubility of CH3SH and H2S in imidazolium-based ionic liquids: A connectionist approach between free volume and thermodynamics

Sulfur contaminants in industrial gas streams, such as hydrogen sulfide and mercaptans, must be eliminated due to safety and environmental considerations. Ionic liquids, as a new class of chemical compounds, are an alternative to conventional aqueous alkanolamine solutions currently used in absorption gas treatment processes. In this work, the solubilities of methyl mercaptan (CH3SH) and hydrogen sulfide gases in 1-butyl-3-methylimidazolium-based ionic liquids with tetrafluoroborate ([C4mim][BF4]), hexafluorophosphate ([C4mim][PF6]), trifluoromethanesulfonate ([C4mim][OTf]), and bis(trifluoromethylsulfonyl)imide ([C4mim][Tf2N]) anions have been studied using molecular dynamics (MD) simulation and a recently developed OPLS all-atom (OPLS-AA-0.8) force field. A new concept, the induced free volume, has been introduced in this work, which provides a realistic and precise connection between the thermodynamic entropic contributions to the dissolution process of CH3SH and H2S in the ionic liquids, on one hand, and the microscopic free/void volume induced as a result of the entrance of a gas solute molecule into the liquid structure, on the other hand. The thermodynamic energetic contributions were correlated to the CH3SH/H2S interaction with the ionic species of the ionic liquids. Quantum chemical energy decomposition analysis (EDA) was employed to calculate and analyze the binding interaction and nature of CH3SH/H2S interactions with the ionic species of ionic liquids. It was found that the van der Waals contributions to the interaction of CH3SH with ionic liquids are more significant compared to that of H2S, while the opposite conclusion could be deduced for the corresponding electrostatic contributions. Both CH3SH and H2S established equivalent hydrogen bonding interactions with the ionic liquids studied in this work. The diffusion coefficients of the ionic species, as well as the excess chemical potentials and Henry’s constants for the dissolution of CH3SH and H2S in the ionic liquids, were calculated by free energy perturbation technique (FEP) and compared with the MD simulated and experimental data, reported in the literature. It was concluded that the OPLS-AA-0.8 force field yields Henry’s constants and diffusivities that are in better agreement with the reliable experimental data corresponding to other OPLS versions reported to date.

Improvement of X-ray Photoelectric Conversion Performance of MAPbI3 Perovskite Crystals by Ionic Liquid Treatment

Although perovskite has great potential in optoelectronic devices, the simultaneous satisfaction of material stability and high performance is still an issue that needs to be solved. Most perovskite optoelectronic devices use quantum dot spin coating or the gas-phase growth of perovskite thin films as the photoelectric conversion layer. Due to stability limitations, these materials often experience a significant decrease in photoelectric conversion efficiency when encountering liquid reagents. The self-assembled growth of hybrid perovskite crystals determines superior lattice ordering and stability. There are three types of ionic liquids—[Emim]BF4, EMIMNTF2, and HMITFSI—that can effectively enhance the X-ray photoelectric conversion performance of hybrid perovskite crystal CH3NH3PbI3 (MAPbI3), and the enhancement in the photocurrent leads to an improvement in the sensitivity of X-ray detectors. We soak the perovskite crystals in an ionic liquid and perform two treatment methods: electrification and dilution with ETOH solution. It is interesting to find that MAPbI3 perovskite single crystal materials choose the same optimized ionic liquid species in X-ray detection and photovoltaic power generation applications, and the effect is quite the opposite. Compared with untreated MAPbI3 crystals, the average photocurrent density of Electrify-HMITFSI MAPbI3 increased by 826.85% under X-ray excitation and the sensitivity of X-ray detectors made from these treated MAPbI3 crystals significantly increased by 72.6%, but the intensity of the PL spectrum decreased to 90% of the untreated intensity.

CuPd bimetallic nanoparticles supported magnetic ionic liquid-derived N-doped carbon as a highly efficient heterogeneous catalyst for the one-pot oxidative multicomponent reactions

BackgroundMulticomponent reactions often rely on aldehydes as the reactants, limiting their widespread use. To enhance the versatility and scope of these reactions, aldehydes can be replaced with alcohols. MethodsIn this study, nitrogen-doped magnetic carbon nanostructures modified with imidazolium-based ionic liquid (Fe3O4@NC-IL) were prepared. These nanostructures were synthesized by a one-pot hydrothermal carbonization method using ferric chloride in the presence of glucose, urea, epichlorohydrin and 1-methylimidazole as carbon source, nitrogen source, linker and ionic liquid, respectively. Then, CuPd bimetallic nanoparticles were immobilized on the synthesized nanostructures by a wet chemical reduction process. Significant findingsThe catalytic activity of the nanostructures was evaluated in the oxidation of alcohol under base-free conditions. The results indicate that the CuPd bimetallic catalyst exhibited better catalytic performance than both Cu and Pd monometallic catalysts, suggesting a synergistic effect between copper and palladium. Also, a non-ionic liquid-based catalyst was synthesized and used in the model reaction to study the effect of imidazolium ionic liquid species on the catalytic activity. The results showed that these species enhanced the catalytic activity. Finally, the catalytic activity of the synthesized structure was evaluated through a one-pot tandem oxidative synthesis of dihydropyrimidinones (Biginelli reaction) and dihydropyridines (Hantzsch reaction).

Enhancing CO2 adsorption capacity of hydroxypyridine-based ionic liquids using fluorinated graphene as carrier Material: A density functional theory study

Graphene carriers can improve the properties of ionic liquids and enhance their CO2 capture performance. Density functional theory calculations were employed to evaluate the feasibility of utilizing graphene as a carrier material to enhance the CO2 adsorption capacity of hydroxypyridine-based ionic liquids (ILs). The results indicated that BN co-doped fluorinated graphene represented a promising carrier material capable of weakening the interaction between cations and anions while enhancing the charges of O and N in the anionic species of ILs, thereby increasing the adsorption capacity of ionic liquids for CO2. Furthermore, the microstructure and properties of the graphene-ILs composites were explored. Doping atoms in graphene were found to induce alterations in the distribution of surface electrostatic potential, influencing the adsorption sites of ionic liquids and their properties. Compared to hydrogen-terminated graphene, fluorinated graphene was a more stable carrier material due to its higher binding energy with hydroxypyridine-based ILs. The higher binding energy was not derived from the direct interaction between doped atoms and ILs, but rather from the impact of doped atoms on the electronic structure of graphene. In methanol solvent, the adsorption of ILs on various graphene surfaces was a spontaneous exothermic process, indicating the feasibility of material preparation.

Survey of the multi-stage mass spectrometry of common ionic liquid cations and some polyfluorinated ions

Ionic liquids are useful for many applications and the structural diversity as a class is ever increasing. Knowledge of gas-phase dissociation pathways can inform analytical method development for the characterization of novel syntheses, degradation products, or environmental contaminants, and can inform our knowledge of the fate of ionic liquid species in the gas phase (e.g., after ejection by electrospray spacecraft thrusters). In this work, the N-heterocyclic (NHC) ions:1-butyl-1-methylpiperidinium (BMPi), 1-methyl-1-propylpiperidinium (MPPi), 1-butyl-1-methylpyrrolidinium (BMPyr), 1-ethyl-1-methylpyrrolidinium (EMPyr), 1-butylpyridinium (BPy), and 1-Butyl-1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) imidazolium (BFIm) were studied. An additional fluorinated anion, nonafluorobutanesulfonate (NFBS), was also studied. Collision-induced dissociation mass spectrometry (CID-MS), as MS2 and MS3 using an ion trap mass spectrometer and energy-resolved breakdown curves using a quadrupole time-of-flight mass spectrometer, were used to determine dissociation patterns. Assignment of proposed dissociation pathways were made based on the experimental results and complementary computational chemistry. It was observed that for aromatic NHCs, cleavage at the C–N bond was preferred, to generate alkene-based neutral losses. Non-aromatic NHCs typically generated both alkane- and alkene-based neutral losses. Breakdown curves, supported by theoretical thermodynamic calculations, suggest that the loss of the alkane is the favorable dissociation pathway. Additionally, some ring-opening and ring contraction reactions via C–C bond cleavage were observed in non-aromatic species, whereas the intact aromatic NHC is typically a stable terminal ion. The polyfluorinated imidazolium fragmented via the breaking of C–N, C–C, and C–F bonds. The fluorinated anion, NFBS, fragmented by C–C and C–S bond cleavage to generate fluoroalkene, sulfur dioxide, and sulfur trioxide neutral losses. Beyond these broad stroke findings, the dissociation pathways of the seven ionic liquid ions were mapped using evidence from MS3, breakdown curves, and computational chemistry together assigning product ions as either arising from competitive or sequential pathways and proposing tentative structures. Some of the ionic liquid ions showed class-based product ions which will be useful in analytical development for their characterization. Finally, these results were contextualized within previous literature reports on other ionic liquid species.

Chemical accuracy prediction of molecular solvation and partition in ionic liquids with educated estimators

Ionic liquids (ILs) derivatives as novel green solvents are widely employed in laboratory and industrial applications. Many computational tools have been developed to compute various physiochemical properties of ILs species, e.g., mass density and viscosity. However, despite their central role as solvents, predictive tools for the solvation of external agents and the partition between water and ILs phases are rather limited. Common selections are atomistic simulations, especially the alchemical method. However, the relatively high computational costs could be harmful to large-scale applications. In this work, we develop a series of low-cost machine-learning estimators to exploit further the chemical-accuracy frontier. 1764 solvation and 1764 water-ILs transfer free energies involving 120 gaseous or drug-like solutes and many commonly applied ILs families are gathered from experimental references to form the dataset with a diverse coverage of chemical spaces. The best-performing tree-based method could predict simultaneously solvation and water-ILs biphasic partition thermodynamics with a state-of-the-art performance of ∼ 0.13 kcal/mol MAE, ∼0.25 kcal/mol RMSE, ∼0.98 Pearson r and ∼ 0.94 Kendall τ, beating transferable tools such as alchemical free energy calculations in a series of face-to-face comparisons.

Phosphonium-Based Polyelectrolytes: Preparation, Properties, and Usage in Lithium-Ion Batteries.

Phosphorous is an essential element for the life of organisms, and phosphorus-based compounds have many uses in industry, such as flame retardancy reagents, ingredients in fertilizers, pyrotechnics, etc. Ionic liquids are salts with melting points lower than the boiling point of water. The term "polymerized ionic liquids" (PILs) refers to a class of polyelectrolytes that contain an ionic liquid (IL) species in each monomer repeating unit and are connected by a polymeric backbone to form macromolecular structures. PILs provide a new class of polymeric materials by combining some of the distinctive qualities of ILs in the polymer chain. Ionic liquids have been identified as attractive prospects for a variety of applications due to the high stability (thermal, chemical, and electrochemical) and high mobility of their ions, but their practical applicability is constrained because they lack the benefits of both liquids and solids, suffering from both leakage issues and excessive viscosity. PILs are garnering for developing non-volatile and non-flammable solid electrolytes. In this paper, we provide a brief review of phosphonium-based PILs, including their synthesis route, properties, advantages and drawbacks, and the comparison between nitrogen-based and phosphonium-based PILs. As phosphonium PILs can be used as polymer electrolytes in lithium-ion battery (LIB) applications, the conductivity and the thermo-mechanical properties are the most important features for this polymer electrolyte system. The chemical structure of phosphonium-based PILs that was reported in previous literature has been reviewed and summarized in this article. Generally, the phosphonium PILs that have more flexible backbones exhibit better conductivity values compared to the PILs that consist of a rigid backbone. At the end of this section, future directions for research regarding PILs are discussed, including the use of recyclable phosphorus from waste.

An unusual Microdomain Factor Controls Interaction of Organic Halides with the Palladium Phase and Influences Catalytic Activity in the Mizoroki-Heck Reaction.

In this work, using a combination of scanning and transmission electron microscopy (SEM and TEM), the transformations of palladium-containing species in imidazolium ionic liquids in reaction mixtures of the Mizoroki-Heck reaction and in related organic media are studied to understand a challenging question of the relative reactivity of organic halides as key substrates in modern catalytic technologies. The microscopy technique detects the formation of a stable nanosized palladium phase under the action of an aryl (Ar) halide capable of forming microcompartments in an ionic liquid. For the first time, the correlation between the reactivity of the aryl halide and the microdomain structure is observed: Ar-I (well-developed microdomains) > Ar-Br (microphase present) > Ar-Cl (minor amount of microphase). Previously, it is assumed that molecular level factors, namely, carbon-halogen bond strength and the ease of bond breakage, are the sole factors determining the reactivity of aryl halides in catalytic transformations. The present work reports a new factor connected with the nature of the organic substrates used and their ability to form a microdomain structure and concentrate metallic species, highlighting the importance of considering both the molecular and microscale properties of the reaction mixtures.

A Metal-Organic Framework Based Quasi-Solid-State Electrolyte Enabling Continuous Ion Transport for High-Safety and High-Energy-Density Lithium Metal Batteries.

Solid-state lithium metal batteries are promising next-generation rechargeable energy storage systems. However, the poor compatibility of the electrode/electrolyte interface and the low lithium ion conductivity of solid-state electrolytes are key issues hindering the practicality of solid-state electrolytes. Herein, rational designed metal-organic frameworks (MOFs) with the incorporation of two types of ionic liquids (ILs) are fabricated as quasi-solid electrolytes. The obtained MOF-IL electrolytes offer continuous ion transport channels with the functional sulfonic acid groups serving as lithium ion hopping sites, which accelerate the Li+ transport both in the bulk and at the interfaces. The quasi-solid MOF-IL electrolytes exhibit competitive ionic conductivities of over 3.0 × 10-4 S cm-1 at room temperature, wide electrochemical windows over 5.2 V, and good interfacial compatibility, together with greatly enhanced Li+ transference numbers compared to the bare IL electrolyte. Consequently, the assembled quasi-solid Li metal batteries show either superior stability at low C rates or improved rate performance, related to the species of ILs. Overall, the quasi-solid MOF-IL electrolytes possess great application potential in high-safety and high-energy-density lithium metal batteries.

Bi-functional phosphonium poly(ionic liquid)s catalyzed CO2-promoted hydration of ethylene oxide

The highly selective production of monoethylene glycol (MEG) from ethylene oxide (EO) is desirable at low H2O/EO molar ratio, however, the development of an efficient heterogeneous catalyst for the reaction is a challenge. Herein, a series of bi-functional poly(ionic liquid)s (BF-PILs) were successfully synthesized by radical copolymerization of polymerizable phosphonium/ammonium ionic liquids, N-vinyl imidazole and cross-linker divinylbenzene (DVB). The structure and thermal stability of BF-PILs were characterized by NMR, FT-IR, elemental analysis and TGA. These BF-PILs could be swollen in the H2O and MEG mixture and the swelling ratio (Q) increased with the increase of the MEG mole fraction. Under swelling in the H2O and MEG mixture (1:1), BF-PILs presented an irregular channel structure with the diameter of 1–20 μm observed by the cryo-scanning electron microscope (cryo-SEM). BF-PILs were applied to catalyze the CO2-promoted hydration of EO at a low H2O/EO ratio of 1.5:1. The catalytic activities of phosphonium BF-PILs were superior to ammonium BF-PILs, and poly[(Ph)3VBPBr-VIm] with the greatest Q in the H2O and MEG mixture (1:1) gave highest yield (96.1%) and selectivity (97.3%) of MEG. The CO2-promoted hydration of EO involved the cycloaddition of EO with CO2 to produce ethylene carbonate (EC), and followed by the hydrolysis of EC to produce MEG. Kinetic experiments confirmed that phosphonium ionic liquid species mainly catalyzed CO2 cycloaddition and imidazole catalyzed hydrolysis of EC. Furthermore, poly[(Ph)3VBPBr-VIm] exhibited good generality and could be reused up to eight times without significant decrease of its initial activity.

Ionic liquid supported on mesoporous Pd/SBA-15 during the manufacture of 1,3-butadiene using ethanol at lower temperature reaction

Investigating the heterogeneous organo-catalysts such as 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate upon SBA-15, which includes one percent palladium, and their ability to produce 1,3-butadiene from ethanol while supporting them on mesoporous materials. SBA-15 and metal precursors were mixed together and crushed in solid state. By using the TGA, N2 adsorption–desorption, TEM, and XRD procedures, the produced catalysts were studied. Once an organic motif was added to SBA-15, the solid-state grinding procedure produced more accessible acid sites on the catalyst and increased the dispersion of Pd metal. In a fixed-bed reactor, the catalytic performance was assessed, and a selectivity of up to 82% for 1,3-butadiene was achieved. This is brought on by the coupling activity of Pd and ionic liquid species in the porous structure of SBA-15, where the ionic liquid catalyst promotes ethanol dehydrogenation while Pd promotes aldol condensation The solvent-free method also served as the inspiration for a fresh way of synthesizing catalysts for the formation of 1,3-butadiene using ethanol.

Fabrication Strategy of MXenes through Ionic-Liquid-Based Microemulsions toward Supercapacitor Electrodes.

With rapid development and broad application of MXenes, it is important to dedicate efforts to explore the preparation of MXenes from MAX phases, owing to the strict policies of energy conservation and environmental protection. Therefore, a new synthesis strategy for MXenes through ionic-liquid-based microemulsions was proposed successfully for the first time here. Because of the unique interface reaction feature of microemulsions, it could improve the etching conditions of MAX phases, thereby enhancing the reaction efficiency. Effects of the temperature, acid, and ionic liquid species on the etching reaction were investigated in detail. MXenes were prepared successfully within 24 h through 1-hexyl-3-methylimidazolium hexafluorophosphate- or 1-hexyl-3-methylimidazolium tetrafluoroborate-based microemuslions at a temperature of 30 °C and pH of 0.3. MXenes with or without annealed treatment were used to make supercapacitor electrodes for evaluating their electrochemical performances. In comparison to unannealed MXenes, the specific capacitance of annealed MXenes was higher, owing to the lower resistance. The optimal MXenes exhibited a specific capacitance of 46.5 F/g at a current density of 40 mA/g and high stability after 500 charge/discharge cycles (100 mA/g), which is comparable to other reports. Through this work, it can open a new window for the preparation of MXenes, which helps to further promote their development and application in research of electrode materials.

Investigations on the electrochemistry and reactivity of tantalum species in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide using X-ray photoelectron spectroscopy (in situ and ex-situ XPS)

Tantalum is a metal whose properties enable it to be used in a wide range of technological applications. In the present work, the underlying electrochemical processes of tantalum species in ionic liquids (ILs) are investigated using in situ X-ray photoelectron spectroscopy (XPS) in ultra-high vacuum. For this purpose electrochemical deposition of tantalum on a gold wire from 0.1 mol/L TaF5 in a 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4]TFSI) electrolyte was studied by in situ electrochemical XPS. The cyclic voltammogram shows two reduction peaks and one oxidation peak, indicating a complex electrochemical behaviour. The electrochemical in situ XPS gives evidence of a reduction reaction, although no metallic tantalum could be detected on the gold wire. In order to investigate the reactivity of tantalum in more detail, thin IL films were prepared on tantalum by physical vapor deposition and these were examined by XPS. Decomposition reactions were observed with the formation of subhalides, oxyfluorides, or tantalum sulfides, showing the decomposition of the ionic liquid. The decomposition products indicate the splitting of the C-F bond of the TFSI anion.

Revealing the roles of hydrogen bond and Al2Cl7− anion species and kinetics for ionic liquid catalyzed transesterification of ethylene carbonate with methanol

The co-production of dimethyl carbonate (DMC) and ethylene glycol (EG) from the transesterification of ethylene carbonate (EC), which is synthesized from CO2 and ethylene oxide, with methanol has received researchers’ attention. Herein, this transformative process catalyzed with metal chloride-based ionic liquids (ILs) was investigated by employing spectroscopic characterizations in combination with kinetic studies. The interaction between cation and methanol via hydrogen bond and activation of carbonyl group in EC (or 2-hydroxyethyl methyl carbonate, HEMC) by metal chloride-contained anion were identified to show synergistic effects on catalytic transesterification. The chain length of alkyl group substituted at the 1-position N atom in imidazole ring affected the reaction rates due to the steric hindrance effect. Not AlCl4− but Al2Cl7− anion species in AlCl3-based IL exhibited activity in this transesterification, and the content of Al2Cl7− species was observed to show linear relationship with the transformative rates of both EC and HEMC. The kinetic studies also elucidated that the rates of both EC (or HEMC) and methanol are first-order dependent on their concentrations, and the formation of HEMC intermediate was the kinetic-relevant step with the activation barrier of 92 kJ/mol. As a result, the yield and selectivity of DMC (or EG) could reach up to around 95 % and 97 % with catalysis of [MDMIM]Cl/AlCl3 with AlCl3 molar fraction of 0.67 after 12 h reaction at 140 °C, which showed higher performance than any other tested metal chloride-based IL. Besides, no decay in catalytic activity and selectivity of this IL was observed after 10 times’ recycling.

Adsorption, thermodynamic, and quantum chemical investigations of an ionic liquid that inhibits corrosion of carbon steel in chloride solutions

The purpose of this work lies in the use of ionic liquids as corrosion inhibitors due to the difficulty in some oil fields with the solubility of corrosion inhibitors and these materials can be miscible with water and thus provide a solution to such problems in the industry. The second purpose is concerned with the lower toxicity of these compounds compared with the most common corrosion inhibitors. The study covered the corrosion inhibition performance of the ionic liquid 1-butyl-3-methylimidazolium trifluoromethyl sulfonate ([BMIm]TfO) for carbon steel in 3.5% NaCl solutions. The study comprised electrochemical, adsorption, and quantum chemical investigations. The results manifested that [BMIm]TfO can be considered a promising corrosion inhibitor and the inhibition efficacy intensifies as the concentration rises. The observed inhibitive effect can be correlated to the adsorption of the ionic liquid species and the creation of protecting films on the surface. The mode of adsorption follows the Langmuir adsorption isotherm. The polarization results showed that the ionic liquid [BMIm]TfO functions as a mixed inhibitor. Reliance of the corrosion influence on the temperature in the existence and absence of [BMIm]TfO was demonstrated in the temperature range of 303–333 K using polarization data. Activation parameters were determined and discussed. The observed inhibition performance of [BMIm]TfO was correlated with the electronic properties of the ionic liquid using a quantum chemical study.

(Digital Presentation) Reservoir Computing Device Using Faradaic Current of Electroactive Species in Ionic Liquids

Physical Reservoir Computing (PRC) has recently attracted significant attention as a computational method suitable for the edge AI computing, which requires both the high performance of information processing and energy conservative operation. There are two standard methods for evaluating PRC performance: the short-term memory (STM) task for the memory capacity and the parity check (PC) task for the nonlinear conversion capacity. We have developed PR device utilizing Faradaic currents generated by the redox reaction of metal ions in ionic liquids (ILs) and the impact of metal ions in ILs on the STM characteristics has been evaluated by comparing the RC device using metal-ion doped IL with that using non-doped (pure) IL [1]. In this study, we investigated the effect of Faradaic current on the STM and PC tasks by extracting the Faradaic current from the output signal when the triangular shaped input voltage pulse was applied to the PR device. It was found out that the peak shaped Faradaic current in the output signal improves not only the memory capacity but also the nonlinear conversion capability.A reservoir device with a transverse Pt/SiO2/Pt structure was prepared (Fig. 1) and solvated IL, Cu(Tf2N)2-Glyme(G3)=1:1 [2], was provided between the Pt electrodes as a reaction field where electrochemical reaction of Cu actively takes place. In order to prevent unnecessary copper deposition on the top surface of the Pt electrode, all areas other than the Pt electrode tip was covered with SiO2. As a result, a structure that allows deposition only between the terminals was realized. Furthermore, to prevent the migration of the IL by the application of an electric field, an IL pool surrounded by a resist wall was formed by patterning a spin-coated photoresist AZ5214E with a thickness of 2 µm. Au/Ti (100/10 nm) was deposited as the contact pad. The device characteristics were evaluated by cyclic voltammetry. In addition, a response of the device to the triangular pulses was investigated by using the B1530A WGFMU (waveform generator / fast measurement unit). STM and PC tasks were used to evaluate the time series data processing ability.In the present study, an artificial time-series data consisting of randomly connected binary data (0 and 1) was input to one of the Pt electrodes as the triangular shaped voltage pulse stream, while the other electrode was grounded. The positive and negative voltages were defined as 2bit data, ‘1’ and ‘0’, respectively. As shown in Fig. 2, triangular voltage pulse streams shown by the blue line were input to the reservoir device, and output current shown by red line was observed. Current peak appears when the polarity of the input signal is switched from positive to negative and vice versa (black arrow), but the peak intensity decreases when application of voltage pulses with the same polarity are continuously repeated. In addition, Cu deposition on the Pt electrode was observed. These results indicate that the origin of the peak is the Faradaic current generated by the electroactive species near the electrode. We divided output current data into two parts; the first half (yellow region), the latter half (green region). The first half corresponds to the rising part of the triangular pulse and involves the Faradaic current. On the other hand, the latter half corresponds to the descending part of the triangular pulse and is more featureless compared with the first half. We found that the accuracy of STM task was much higher when the first half was used. This tendency was also confirmed for the PC task. In PRC based on the concept of virtual nodes using a single physical device [3], the output signal complexity is considered to be related to the multidimensional transformation capability, which is one of indispensable property for PRC [4]. The present results suggest that the redox reaction of electroactive species in the IL increases the complexity of the output signal and improves the ability to extract time-series features.We thank Mr. Hiroshi Sato for supporting device fabrication processes. A part of this work was supported by "Nanotechnology Platform Program", Grant Number JPMXPF21NM0006.[1] D. Sato et al., MEMRISYS 2021, 4A-7 (2021).[2] H. Yamaoka et al., Chem. Lett., 46, 1832-1835 (2017).[3] L. Appeltant et al., Nat. Commun., 2, 468 (2011).[4] L. Appeltant et al., Sci. Rep., 4, 3629 (2014). Figure 1

Poly(ionic liquid)‐Based Energy and Electronic Devices

Comprehensive SummaryPoly(ionic liquid)s (PILs) refer to a polymeric architecture with repeating ionic liquid species in each unit. They are attracting rapidly increasing interest because of their diverse structures and facial processability. Our group focused on the design and synthesis of PILs for various applications in the past decade, including polyelectrolytes, biomedical materials, and other related fields. In this review, we briefly summarized our recent studies on the application of PILs for energy and electronic devices, emphasizing the controllable synthesis and regulation of specific structures and functions. The unique properties and designable structures of PILs will inspire further investigation in an extensive variety of potential applications. What is the most favorite and original chemistry developed in your research group?Synthesis and application of poly(ionic liquid)s for various applications, including polyelectrolytes for energy devices, smart windows, as well as biomedical applications.How do you get into this specific field? Could you please share some experiences with our readers?About 15 years ago, I was attracted by the novel properties of ionic liquids, which encouraged me to engage in ionic liquids with polymer science. Keep curiosity, keep learning and hard‐working are very important.How do you supervise your students?I always encourage my students to innovate and enjoy their scientificresearch. I would like to see motivated and determined characters from my students.What is the most important personality for scientific research?I think the most important personality for scientific research is keeping curiosity, innovative spirit and persistence.How do you keep balance between research and family?Both research and family are important in my life. I work hard during working hours while spending time with my family as much as possible after work.Who influences you mostly in your life?My parents and Prof. Gi Xue.