Search query: "coulomb" "ionic liquid"

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abstract: Ionic liquids are room temperature molten salts, composed mostly of organic ions that may undergo almost unlimited structural variations. This review covers the newest aspects of ionic liquids in applications where their ion conductivity is exploited; as electrochemical solvents for metal/semiconductor electrodeposition, and as batteries and fuel cells where conventional media, organic solvents (in batteries) or water (in polymer electrolyte membrane fuel cells) fail. Biology and biomimetic processes in ionic liquids are also discussed. In these decidedly different materials, some enzymes show activity that is not exhibited in more traditional systems, creating huge potential for bioinspired catalysis and biofuel cells. Our goal in this review is to survey the recent key developments and issues within ionic liquid research in these areas. As well as informing materials scientists, we hope to generate interest in the wider community and encourage others to make use of ionic liquids in tackling scientific challenges.
author_names: Michel Armand

Frank Endres

Douglas R Macfarlane

Hiroyuki Ohno

Bruno Scrosati
title: Ionic liquid materials for the electrochemical challenges of the future.
venue: Nature materials
year: 2009

abstract: Applications of ionic liquids at electrified interfaces to energy storage systems, electrowetting devices, or nanojunction gating media cannot proceed without a deep understanding of the structure and properties of the interfacial double layer. This article provides a detailed critique of the present work on this problem. It promotes the point of view that future considerations of ionic liquids should be based on the modern statistical mechanics of dense Coulomb systems, or density functional theory, rather than classical electrochemical theories which hinge on a dilute solution approximation. The article will, however, contain more questions than answers. To trigger the discussion, it starts with a simplified original result. A new analytical formula is derived to rationalize the potential dependence of double layer capacitance at a planar metal ionic liquid interface. The theory behind it has a mean field character, based on the Poisson Boltzmann lattice gas model, with a modification to account for the finite volume occupied by ions. When the volume of liquid excluded by the ions is taken to be zero (that is, if ions are extremely sparsely packed in the liquid) the expression reduces to the nonlinear Gouy Chapman law, the canonical result typically used to describe the potential dependence of capacitance in electrochemical double layers. If ionic volume exclusion takes more realistic values, the formula shows that capacitance potential curves for an ionic liquid may differ dramatically from the Gouy Chapman law. Capacitance has a maximum close to the potential of zero charge, rather than the familiar minimum. At large potenials, capacitance decreases with the square root of potential, rather than increases exponentially. The reported formula does not take into account the specific adsorption of ions, which, if present, can complicate the analysis of experimental data. Since electrochemists use to think about the capacitance data in terms of the classical Gouy Chapman theory, which, as we know, should be good only for electrolytes of moderate concentration, the question of which result is "better" arises. Experimental data are sparse, but a quick look at them suggests that the new formula seems to be closer to reality. Opinions here could, however, split. Indeed, a comparison with Monte Carlo simulations has shown that incorporation of restricted volume effects in the mean field theory of electrolyte solutions may give results that are worse than the simple Gouy Chapman theory. Generally, should the simple mean field theory work for such highly concentrated ionic systems, where the so called ion correlation effects must be strong? It may not, as it does not incorporate a possibility of charge density oscillations. Somehow, to answer this question definitely, one should do further work. This could be based on density functional theory (and possibly not on what is referred to as local density approximation but rather "weighted density approximation" field theory methods for the account of fluctuations in the calculation of partition function, heuristic integral equation theory extended to the nonlinear response, systematic force field computer simulations, and, most importantly, experiments with independently determined potentials of zero charge, as discussed in the paper.
author_names: Alexei A Kornyshev
title: Double layer in ionic liquids: paradigm change?
venue: The journal of physical chemistry. B
year: 2007

abstract: We combine old, unpublished data on ionic liquids containing quaternary ammonium cations with new data on salts of aromatic cations containing a variety of anions, to demonstrate the existence for ionic liquids of an unexpectedly wide range of liquid fragilities. The pattern is one now familiar for other liquids. Here, the pattern is important in determining the relative fluid properties at ambient temperatures. We find that the optimization of ionic liquids for ambient temperature applications requiring low vapor pressure fluid phases involves the proper interplay of both cohesive energy and fragility factors. The cohesive energy is discussed in terms of the coulomb and van der Waals contributions to the attractive part of the pair potential. On the basis of the relation between the glass transition temperature and the molar volume for salts with less polarizable anions, we find evidence for a broad minimum in the ionic liquid cohesive energy at an internuclear separation of ca. 0.6 nm. This minimum lies.
author_names: Wu Xu

Emanuel I Cooper

C Austen Angell
title: Ionic liquids: Ion mobilities, glass temperatures, and fragilities
year: 2003

abstract: Small and salty CO2 reduction scheme Most artificial photosynthesis approaches focus on making hydrogen. Modifying CO2, as plants and microbes do, is more chemically complex. Asadi et al. report that fashioning WSe2 and related electrochemical catalysts into nanometer scale flakes greatly improves their activity for the reduction of CO2 to CO. An ionic liquid reaction medium further enhances efficiency. An artificial leaf with WSe2 reduced CO2 on one side while a cobalt catalyst oxidized water on the other side. Science, this issue p. 467 Nanostructuring tungsten diselenide enhances catalytic activity for carbon dioxide conversion to carbon monoxide in an ionic liquid medium. Conversion of carbon dioxide (CO2) into fuels is an attractive solution to many energy and environmental challenges. However, the chemical inertness of CO2 renders many electrochemical and photochemical conversion processes inefficient. We report a transition metal dichalcogenide nanoarchitecture for catalytic electrochemical CO2 conversion to carbon monoxide (CO) in an ionic liquid. We found that tungsten diselenide nanoflakes show a current density of 18.95 milliamperes per square centimeter, CO faradaic efficiency of 24% and CO formation turnover frequency of 0.28 per second at a low overpotential of 54 millivolts. We also applied this catalyst in a light harvesting artificial leaf platform that concurrently oxidized water in the absence of any external potential.
author_names: Mohammad Asadi

Kibum Kim

Cong Liu

Aditya Venkata Addepalli

Pedram Abbasi

Poya Yasaei

Patrick J Phillips

Amirhossein Behranginia

Jose M Cerrato

Richard T Haasch

Peter Zapol

Bijandra Kumar

Robert F Klie

J T Abiade

Larry A Curtiss

Amin Salehi-Khojin
title: Nanostructured transition metal dichalcogenide electrocatalysts for CO2 reduction in ionic liquid
venue: Science
year: 2016

abstract: We review recent works on the synthesis and application of poly(ionic liquid)s (PILs) Novel chemical structures, different synthetic strategies and controllable morphologies are introduced as a supplement to PIL systems already reported. The primary properties determining applications, such as ionic conductivity, aqueous solubility, thermodynamic stability and electrochemical/chemical durability, are discussed. Furthermore, the near term applications of PILs in multiple fields, such as their use in electrochemical energy materials, stimuli responsive materials, carbon materials, and antimicrobial materials, in catalysis, in sensors, in absorption and in separation materials, as well as several special interest applications, are described in detail. We also discuss the limitations of PIL applications, efforts to improve PIL physics, and likely future developments.
author_names: Wenjing Qian

John Texter

Feng Yan
title: Frontiers in poly(ionic liquid)s: syntheses and applications.
venue: Chemical Society reviews
year: 2017

abstract: This Review covers the recent developments (2005 2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state of the art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal containing compounds (metallomesogens) but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.
author_names: Karel Goossens

Kathleen Lava

Christopher W Bielawski

Koen Binnemans
title: Ionic Liquid Crystals: Versatile Materials.
venue: Chemical reviews
year: 2016

abstract: Ionic liquid gel materials offer a way to further utilise ionic liquids in technological applications. Combining the controlled and directed assembly of gels, with the diverse applications of ionic liquids, enables the design of a heady combination of functional tailored materials, leading to the development of task specific/functional ionic liquid gels. This review introduces gels and gel classification, focusing on ionic liquid gels and their potential roles in a more sustainable future. Ionic liquid gels provide the ability to build functionality at every level, the solid component, the ionic liquid, and any incorporated active functional agents. This allows materials to be custom designed for a vast assortment of applications. This diverse class of materials has the potential to yield functional materials for green and sustainable chemistry, energy, electronics, medicine, food, cosmetics, and more. The discussion of the development of ionic liquid gel materials for applications in green and sustainable chemistry centres on uses of ionic liquid gels in catalysis and energy.
author_names: Patricia C Marr

Andrew Craig Marr
title: Ionic liquid gel materials: applications in green and sustainable chemistry
year: 2016

abstract: The IR and Raman spectra and conformations of the ionic liquid 1 ethyl 3 methyl 1H imidazolium tetrafluoroborate, [EMIM][BF4] (6) were analyzed within the framework of scaled quantum mechanics (SQM) It was shown that SQM successfully reproduced the spectra of the ionic liquid. The computations revealed that normal modes of the EMIM+ BF4 ion pair closely resemble those of the isolated ions EMIM+ and BF4 except for the antisymmetric BF stretching vibrations of the anion, and the out of plane and stretching vibrations of the H C(2) moiety of the cation. The most plausible explanation for the pronounced changes of the latter vibrations upon ion pair formation is the H bonding between H C(2) and BF4 However, these weak H bonds are of minor importance compared with the Coulomb interactions between the ions that keep them closely associated even in dilute CD2Cl2 Solutions. According to the 'gas phase' computations, in these associates, the BF4 anion is positioned over the imidazolium ring of the EMIM+ cation and has short contacts not only with the H C(2) of the latter, but also with a proton of the Me N(3) group.
author_names: Sergey A Katsyuba

Paul J Dyson

Elena E Vandyukova

Alla V Chernova

Ana Vidis
title: Molecular Structure, Vibrational Spectra, and Hydrogen Bonding of the Ionic Liquid 1 Ethyl 3 methyl 1H imidazolium Tetrafluoroborate
year: 2004

abstract: We calculate the heats of vaporisation for imidazolium based ionic liquids [C(n)mim][NTf(2) with n=1, 2, 4, 6, 8 by means of molecular dynamics (MD) simulations and discuss their behavior with respect to temperature and the alkyl chain length. We use a force field developed recently. The different cohesive energies contributing to the overall heats of vaporisations are discussed in detail. With increasing alkyl chain length, the Coulomb contribution to the heat of vaporisation remains constant at around 80 kJ mol( 1) whereas the van der Waals interaction increases continuously. The calculated increase of about 4.7 kJ mol( 1) per CH(2) group of the van der Waals contribution in the ionic liquid exactly coincides with the increase in the heats of vaporisation for n alcohols and n alkanes, respectively. The results support the importance of van der Waals interactions even in systems completely composed of ions.
author_names: Thorsten Koddermann

Dietmar Paschek

Ralf Ludwig
title: Ionic liquids: dissecting the enthalpies of vaporization.
venue: Chemphyschem a European journal of chemical physics and physical chemistry
year: 2008

abstract: Precise coexistence curves are reported for the liquid liquid phase transition of binary solutions of the room temperature ionic liquid (RTIL) 1 methyl 3 hexylimidazolium tetrafluoroborate (C6mim+BF4 in a series of alcohols (1 butanol, 1 pentanol, 2 butanol, and 2 pentanol) The phase diagrams are determined by measuring the temperature dependence of the refractive index in the two phases of samples of critical composition. The critical data of the systems are in the region predicted for the model fluid of equal sized, charged, hard spheres in a dielectric continuum, the so called restricted primitive model (RPM) Therefore, the phase transition can be classified as essentially driven by Coulomb interactions. The effective exponents beff determined are close to the universal Ising value, where the deviations are found to be negative, when the volume fraction or the mass fraction are chosen as concentration variable. The negative values of the first Wegner correction indicate non uniform crossover from Ising to mean field criticality. The diameter of the coexistence curves shows the non analytic temperature dependence typical for Ising systems.
author_names: Monika Wagner

Olimpiu Stanga

Wolffram Schrer
title: The liquid?liquid coexistence of binary mixtures of the room temperature ionic liquid 1 methyl 3 hexylimidazolium tetrafluoroborate with alcoholsElectronic supplementary information (ESI) available: Temperatures and corresponding refractive index data in the one phase region and in the coexisting ph
year: 2004