Sodium diffusion in ionic liquid-based electrolytes for Na-ion batteries: the effect of polarizable force fields.

Understanding the transport of sodium ions in ionic liquids is key to designing novel electrolyte materials for sodium-ion batteries. In this work, we combine molecular dynamics simulation and experiments to study how molecular interactions and local ordering affect relevant physico-chemical properties. Ionic transport and local solvation environments are investigated in electrolytes composed of sodium bis(fluorosulfonyl)imide, (Na[FSI]), in N,N-methylpropylpyrrolidinium bis(fluorosulfonyl)imide, [CCpyr][FSI], at different salt concentrations.

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

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.

Molecular dynamics simulations of polyethers and a quaternary ammonium ionic liquid as CO absorbers.

The properties of mixtures of butyltrimethylammonium bis(trifluoromethylsulfonyl)imide, [N][NTf], with poly(ethyleneglycol) dimethyl ether, PEO, were described as a function of PEO chain size by molecular dynamics simulations. Both PEO chain size and mixture composition revealed to play a significant role in determining the structure and the dynamics of the fluids. The remarkably higher viscosity observed for mixtures composed by 0.

Polycyclic aromatic hydrocarbons as model solutes for carbon nanomaterials in ionic liquids.

The aim of this work is to understand the details of the interactions of ionic liquids with carbon nanomaterials (graphene and nanotubes) using polyaromatic compounds as model solutes. We have combined the measurements of thermodynamic quantities of solvation with molecular dynamics simulations to provide a microscopic view. The solubility of five polycyclic aromatic hydrocarbons (naphthalene, anthracene, phenanthrene, pyrene and coronene) was determined in seven ionic liquids ([CCim][C(CN)], [CCpyrr][Ntf], [CCim][Ntf], [CCim][C(CN)], [CCim][Ntf], [CCpyrr][N(CN)] and [CCim][N(CN)]) at 298 K.

Liquids with permanent porosity.

Porous solids such as zeolites and metal-organic frameworks are useful in molecular separation and in catalysis, but their solid nature can impose limitations. For example, liquid solvents, rather than porous solids, are the most mature technology for post-combustion capture of carbon dioxide because liquid circulation systems are more easily retrofitted to existing plants. Solid porous adsorbents offer major benefits, such as lower energy penalties in adsorption-desorption cycles, but they are difficult to implement in conventional flow processes.

Solubility of n-butane and 2-methylpropane (isobutane) in 1-alkyl-3-methylimidazolium-based ionic liquids with linear and branched alkyl side-chains.

The solubility of n-butane and 2-methylpropane (isobutane) in three ionic liquids - 1-(2-methylpropyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [(2mC3)C1im][Ntf2], 1-(3-methylbutyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [(3mC4)C1im][Ntf2] and 1-methyl-3-pentylimidazolium bis(trifluoromethylsulfonyl)imide [C5C1im][Ntf2] - has been measured at atmospheric pressure from 303 to 343 K. Isobutane is less soluble than n-butane in all the ionic liquids. Henry's constant values range from 13.

Interactions between water and 1-butyl-1-methylpyrrolidinium ionic liquids.

We report experimental results on the diffusivity of water in two ionic liquids obtained using the pulsed-gradient spin-echo NMR method. Both ionic liquids have the same cation, 1-butyl-1-methylpyrrolidinium, but different trifluoromethyl-containing anions. One has a strongly hydrophobic anion, bis(trifluoromethylsulfonyl)amide, while the second has a hydrophilic anion, trifluoromethylsulfonate.

Preliminary study on suitability of ionic liquids as potential passive-sampling media of polyaromatic-hydrocarbon (PAH) analyses in water.

Recently, ionic liquids (ILs) have been regarded as an attractive water-immiscible phase in liquid-liquid extraction. Because ILs have a wide range of polarity irrespective of their miscibility with water, the possibility of using them as an effective extraction phase for a broad range of contaminants means they are starting to be of particular interest. In this study we investigated a wide variety of ionic liquids, which are known to be hydrolytically stable and of a hydrophobic character, for their potential suitability as passive-sampling media for monitoring selected polyaromatic hydrocarbons.

Solvation of a Cellulose Microfibril in Imidazolium Acetate Ionic Liquids: Effect of a Cosolvent.

The solvation and the onset of dissolution of a cellulose I(β) microcrystal in ionic liquid media are studied by molecular simulation. Ionic liquids can dissolve large amounts of cellulose, which can later be regenerated from solution, but their high viscosity is an inconvenience. Hydrogen bonding between the anion of the ionic liquid and cellulose is the main aspect determining dissolution.

Glass transition of ionic liquids under high pressure.

The glass transition pressure at room temperature, pg, of six ionic liquids based on 1-alkyl-3-methylimidazolium cations and the anions [BF4](-), [PF6](-), and bis(trifluromethanesulfonyl)imide, [NTf2](-), has been obtained from the pressure dependence of the bandwidth of the ruby fluorescence line in diamond anvil cells. Molar volume, Vm(pg), has been estimated by a group contribution model (GCM) developed for the ionic liquids. A density scaling relation, TV(γ), has been considered for the states Vm(pg, 295 K) and Vm(Tg, 0.

Effect of unsaturation on the absorption of ethane and ethylene in imidazolium-based ionic liquids.

The influence of the presence of imidazolium side chain unsaturation on the solubility of ethane and ethylene was studied in three ionic liquids: 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide-saturated alkyl side-chain in the cation; 1-methyl-3-(buten-3-yl)imidazolium bis(trifluorosulfonyl)imide-double bond in the side-chain of the cation; and 1-methyl-3-benzylimidazolium bis(trifluorosulfonyl)imide-benzyl group in the side-chain of the cation. The solubility of both gases decreases when the side-chain of the cations is functionalized with an unsaturated group. This can be explained by a less favorable enthalpy of solvation.

Preparation of microfibers from wood/ionic liquid solutions.

Two types of ionic liquids, 1-ethyl-3-methylimidazolim acetate and 1-ethyl-3-methylimidazolium lactate, were employed for the direct processing of pine wood into microfibers. The concentration of 5 wt.% of wood in ionic liquids was rated as the most appropriate for electrospinning.

Effect of water on the carbon dioxide absorption by 1-alkyl-3-methylimidazolium acetate ionic liquids.

The absorption of carbon dioxide by the pure ionic liquids 1-ethyl-3-methylimidazolium acetate ([C(1)C(2)Im][OAc]) and 1-butyl-3-methylimidazolium acetate ([C(1)C(4)Im][OAc]) was studied experimentally from 303 to 343 K. As expected, the mole fraction of absorbed carbon dioxide is high (0.16 at 303 K and 5.

Ligand effect on the catalytic activity of ruthenium nanoparticles in ionic liquids.

Suspensions of small sized (1-2.5 nm) ruthenium nanoparticles (RuNPs) have been obtained by decomposition, under H(2), of (η(4)-1,5-cyclooctadiene)(η(6)-1,3,5-cyclooctatriene)ruthenium(0), [Ru(COD)(COT)], in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(4)Im][NTf(2)], and in the presence of different compounds acting as ligands: C(8)H(17)NH(2), PPhH(2), PPh(2)H and H(2)O. Previous and new liquid NMR experiments showed that the ligands are coordinated or in the proximity to the surface of the RuNPs.

Relevant parameters for assessing the environmental impact of some pyridinium, ammonium and pyrrolidinium based ionic liquids.

Several physico-chemical properties relevant to determine the environmental impact of ionic liquids - aqueous solubility, octanol/water partition coefficient, chromatographically derived lipophilicity and infinite dilution diffusion coefficients in water - were measured in ionic liquids based on pyridinium, ammonium and pyrrolidinium cations with bis(trifluoromethylsulfonyl)imide anions. The influence of the presence of hydroxyl or ester groups in the physico-chemical properties of these liquids was checked. It appeared that the presence of functional oxygenated moieties reduces the lipophilicity of ionic liquids and so decreases the risk of bioaccumulation in environment.

Using ethane and butane as probes to the molecular structure of 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide ionic liquids.

In this work, we have studied the solubility and the thermodynamic properties of solvation, between 298 and 343 K and at pressures close to atmospheric, of ethane and n-butane in several ionic liquids based on the bis[(trifluoromethyl) sulfonyl]imide anion and on 1-alkyl-3-methylimidazolium cations, [CnC1Im] [NTf2], with alkyl side-chains varying from two to ten carbon atoms. The solubility of butane is circa one order of magnitude larger than that of ethane with mole fractions as high as 0.15 in [C10C1Im][NTf2] at 300 K.

Glycine in 1-butyl-3-methylimidazolium acetate and trifluoroacetate ionic liquids: effect of fluorination and hydrogen bonding.

The solvation of glycine in two ionic liquids (ILs), namely, 1-butyl-3-methylimidazolium acetate, [C(1)C(4)Im][OAc], and 1-butyl-3-methylimidazolium trifluoroacetate, [C(1)C(4)Im][TFA], was studied by a combination of experimental and theoretical methods. The solubility of glycine in both ILs was determined at 333.15 K to be (8.

Phase behaviour, interactions, and structural studies of (amines+ionic liquids) binary mixtures.

We present a study on the phase equilibrium behaviour of binary mixtures containing two 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide-based ionic liquids, [C(n)mim] [NTf(2)] (n=2 and 4), mixed with diethylamine or triethylamine as a function of temperature and composition using different experimental techniques. Based on this work, two systems showing an LCST and one system with a possible hourglass shape are measured. Their phase behaviours are then correlated and predicted by using Flory-Huggins equations and the UNIQUAC method implemented in Aspen.

Influence of oxygen functionalities on the environmental impact of imidazolium based ionic liquids.

Several physico-chemical properties relevant to determine the environmental impact of ionic liquids - aqueous solubility, octanol-water partition coefficient and diffusion coefficients in water at infinite dilution - together with toxicity and biodegradability of ionic liquids based on 1-alkyl-3-methylimidazolium cations with or without different oxygenated functional groups (hydroxyl, ester and ether) are studied in this work. The presence of oxygen groups on the imidazolium cation reduces the toxicity of ionic liquids 1-alkyl-3-methylimidazolium with bis(trifluoromethylsulfonyl)imide or octylsulfate anions and simultaneously decreases the value of their octanol-water partition coefficient. The presence of ester functions renders the ionic liquids more easily biodegradable, especially for long alkyl side-chains in the cation but leads to hydrolysis with the formation of reaction products that accumulate.

Influence of ionic association, transport properties, and solvation on the catalytic hydrogenation of 1,3-cyclohexadiene in ionic liquids.

The influence of the nature of two different ionic liquids, namely 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(4)Im][NTf(2)], and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(1)C(4)Im][NTf(2)], on the catalytic hydrogenation of 1,3-cyclohexadiene with [Rh(COD)(PPh(3))(2)][NTf(2)] (COD = 1,5-cyclooctadiene) was studied. Initially, the effect of different concentrations of 1,3-cyclohexadiene on the molecular interactions and on the structure in two ionic liquids was investigated by NMR and by molecular dynamic simulations. It was found that in both ionic liquids 1,3-cyclohexadiene is solvated preferentially in the lipophilic regions.

Effect of alkyl chain length and hydroxyl group functionalization on the surface properties of imidazolium ionic liquids.

Properties of the surface of ionic liquids, such as surface tension, ordering, and charge and density profiles, were studied using molecular simulation. Two types of modification in the molecular structure of imidazolium cations were studied: the length of the alkyl side chain and the presence of a polar hydroxyl group at the end of the side chain. Four ionic liquids were considered: 1-ethyl-3-methylimidazolium tetrafluoroborate, [C(2)C(1)im][BF(4)]; 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate, [C(2)OHC(1)im][BF(4)]; 1-octyl-3-methylimidazolium tetrafluoroborate, [C(8)C(1)im][BF(4)] and 1-(8-hydroxyoctyl)-3-methylimidazolium tetrafluoroborate, [C(8)OHC(1)im][BF(4)].

Ruthenium nanoparticles in ionic liquids: structural and stability effects of polar solutes.

Ionic liquids are a stabilizing medium for the in situ synthesis of ruthenium nanoparticles. Herein we show that the addition of molecular polar solutes to the ionic liquid, even in low concentrations, eliminates the role of the ionic liquid 3D structure in controlling the size of ruthenium nanoparticles, and can induce their aggregation. We have performed the synthesis of ruthenium nanoparticles by decomposition of [Ru(COD)(COT)] in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(4)Im][NTf(2)], under H(2) in the presence of varying amounts of water or 1-octylamine.

Polarity, viscosity, and ionic conductivity of liquid mixtures containing [C4C1im][Ntf2] and a molecular component.

In this study, we have focused on binary mixtures composed of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)-imide, [C(4)C(1)im][Ntf(2)], and a selection of six molecular components (acetonitrile, dichloromethane, methanol, 1-butanol, t-butanol, and water) varying in polarity, size, and isomerism. Two Kamlet-Taft parameters, the polarizability π* and the hydrogen bond acceptor β coefficient were determined by spectroscopic measurements. In most cases, the solvent power (dipolarity/polarizability) of the ionic liquid is only slightly modified by the presence of the molecular component unless large quantities of this component are present.

Influence of ester functional groups on the liquid-phase structure and solvation properties of imidazolium-based ionic liquids.

The incorporation of ester functions in the side chains in 1-alkyl-3-methylimidazolium cations seems to increase the biodegradability of these ionic liquids. We study here how the presence of ester functional groups affects the liquid-state structure (namely, the microphase segregation between polar and nonpolar domains in these ionic liquids) and the way in which the solvation of gases can be understood in these solvents. We use molecular simulation to study the structure of the ionic liquids 3-methyl-1-(pentoxycarbonylmethyl)imidazolium octylsulfate, [C(1)COOC(5)C(1)im][C(8)SO(4)]; and 3-methyl-1-(pentoxycarbonylmethyl)imidazolium bis(trifluoromethylsulfonyl)imide, [C(1)COOC(5)C(1)im][NTf(2)] in the liquid phase and to assess the molecular mechanisms of solvation of carbon dioxide and ethane.