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Ionic Liquids for Materials and Energy

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Molecular Liquids".

Deadline for manuscript submissions: closed (30 March 2021) | Viewed by 47502

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Dr. Paul Nancarrow

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Department of Chemical Engineering, American University of Sharjah, P.O. Box 26666, Sharjah, United Arab Emirates
Interests: ionic liquids technology; reaction engineering; nanomaterials processing; pharmaceutical process development and predictive modeling of liquid systems
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Special Issue Information

Dear Colleagues,

In recent decades, ionic liquids have emerged as novel fluids, with unique physical and chemical properties, for a wide range of potential industrial applications. Initially, the focus was on using ionic liquids as replacements for industrial solvents due to their excellent solvation properties and nonvolatility. While some success has been achieved in this area, their relatively high cost has inhibited widespread uptake. As a result, the focus has shifted towards the exploitation of these designer liquids for targeted high-value applications such as materials and energy technology.

The aim of this Special Issue is to present a collection of articles reporting on the most recent research and developments in the use of ionic liquids for materials and energy technology. In particular, we welcome original contributions reporting on the application of ionic liquids in following areas: materials synthesis; nanomaterials; smart materials; immobilized ionic liquid materials; composite polymer–ionic liquid materials; functionalized ionic liquids for materials applications; electrolytes for lithium ion batteries; electrolytes for fuel cells; superconductor technology; thermal energy storage; heat transfer fluids; nanofluids; photovoltaic and solar energy technology; biorefineries for materials; and renewable energy. We also highly encourage contributions on other current topics relevant to ionic liquids for materials and energy.

Assoc. Prof. Dr. Paul Nancarrow
Guest Editor

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Keywords

ionic liquids
materials synthesis
nanomaterials
composite materials
renewable energy
energy storage

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Published Papers (10 papers)

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Research

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33 pages, 5386 KiB

Open AccessArticle

Group Contribution Estimation of Ionic Liquid Melting Points: Critical Evaluation and Refinement of Existing Models

by Dhruve Kumar Mital, Paul Nancarrow, Samira Zeinab, Nabil Abdel Jabbar, Taleb Hassan Ibrahim, Mustafa I. Khamis and Alnoman Taha

Molecules 2021, 26(9), 2454; https://doi.org/10.3390/molecules26092454 - 22 Apr 2021

Cited by 11 | Viewed by 4335

Abstract

While several group contribution method (GCM) models have been developed in recent years for the prediction of ionic liquid (IL) properties, some challenges exist in their effective application. Firstly, the models have been developed and tested based on different datasets; therefore, direct comparison based on reported statistical measures is not reliable. Secondly, many of the existing models are limited in the range of ILs for which they can be used due to the lack of functional group parameters. In this paper, we examine two of the most diverse GCMs for the estimation of IL melting point; a key property in the selection and design of ILs for materials and energy applications. A comprehensive database consisting of over 1300 data points for 933 unique ILs, has been compiled and used to critically evaluate the two GCMs. One of the GCMs has been refined by introducing new functional groups and reparametrized to give improved performance for melting point estimation over a wider range of ILs. This work will aid in the targeted design of ILs for materials and energy applications. Full article

(This article belongs to the Special Issue Ionic Liquids for Materials and Energy)

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32 pages, 5973 KiB

Open AccessArticle

Effect of Increased Ionic Liquid Uptake via Thermal Annealing on Mechanical Properties of Polyimide-Poly(ethylene glycol) Segmented Block Copolymer Membranes

by Gokcen A. Ciftcioglu and Curtis W. Frank

Molecules 2021, 26(8), 2143; https://doi.org/10.3390/molecules26082143 - 8 Apr 2021

Cited by 3 | Viewed by 2600

Abstract

Proton exchange membranes (PEMs) suffer performance degradation under certain conditions—temperatures greater than 80 °C, relative humidity less than 50%, and water retention less than 22%. Novel materials are needed that have improved water retention, stability at higher temperatures, flexibility, conductivity, and the ability to function at low humidity. This work focuses on polyimide-poly(ethylene glycol) (PI-PEG) segmented block copolymer (SBC) membranes with high conductivity and mechanical strength. Membranes were prepared with one of two ionic liquids (ILs), either ethylammonium nitrate (EAN) or propylammonium nitrate (PAN), incorporated within the membrane structure to enhance the proton exchange capability. Ionic liquid uptake capacities were compared for two different temperatures, 25 and 60 °C. Then, conductivities were measured for a series of combinations of undoped or doped unannealed and undoped or doped annealed membranes. Stress and strain tests were performed for unannealed and thermally annealed undoped membranes. Later, these experiments were repeated for doped unannealed and thermally annealed. Mechanical and conductivity data were interpreted in the context of prior small angle X-ray scattering (SAXS) studies on similar materials. We have shown that varying the compositions of polyimide-poly(ethylene glycol) (PI-PEG) SBCs allowed the morphology in the system to be tuned. Since polyimides (PI) are made from the condensation of dianhydrides and diamines, this was accomplished using components having different functional groups. Dianhydrides having either fluorinated or oxygenated functional groups and diamines having either fluorinated or oxygenated diamines were used as well as mixtures of these species. Changing the morphology by creating macrophase separation elevated the IL uptake capacities, and in turn, increased their conductivities by a factor of three or more compared to Nafion 115. The stiffness of the membranes synthesized in this work was comparable to Nafion 115 and, thus, sufficient for practical applications. Full article

(This article belongs to the Special Issue Ionic Liquids for Materials and Energy)

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8 pages, 1824 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Electropolishing of Aluminum in a Deep Eutectic Medium and Acidic Electrolyte

by Tarek M. Abdel-Fattah and J. Derek Loftis

Molecules 2020, 25(23), 5712; https://doi.org/10.3390/molecules25235712 - 3 Dec 2020

Cited by 15 | Viewed by 4548

Abstract

Research advances in electropolishing, with respect to the field of metalworking, have afforded significant improvements in the surface roughness and conductivity properties of aluminum polished surfaces in ways that machine polishing and simple chemical polishing cannot. The effects of a deep eutectic medium as an acid-free electrolyte were tested to determine the potential energy thresholds during electropolishing treatments based upon temperature, experiment duration, current, and voltage. Using voltammetry and chronoamperometry tests during electropolishing to supplement representative recordings via atomic force microscopy (AFM), surface morphology comparisons were performed regarding the electropolishing efficiency of phosphoric acid and acid-free ionic liquid treatments for aluminum. This eco-friendly solution produced polished surfaces superior to those surfaces treated with industry standard acid electrochemistry treatments of 1 M phosphoric acid. The roughness average of the as-received sample became 6.11 times smoother, improving from 159 nm to 26 nm when electropolished with the deep eutectic solvent. This result was accompanied by a mass loss of 0.039 g and a 7.2 µm change in step height along the edge of the electropolishing interface, whereas the acid treatment resulted in a slight improvement in surface roughness, becoming 1.63 times smoother with an average post-electropolishing roughness of 97.7 nm, yielding a mass loss of 0.0458 g and a step height of 8.1 µm. Full article

(This article belongs to the Special Issue Ionic Liquids for Materials and Energy)

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16 pages, 1541 KiB

Open AccessArticle

Thermal Conductivities of Choline Chloride-Based Deep Eutectic Solvents and Their Mixtures with Water: Measurement and Estimation

by Taleb H. Ibrahim, Muhammad A. Sabri, Nabil Abdel Jabbar, Paul Nancarrow, Farouq S. Mjalli and Inas AlNashef

Molecules 2020, 25(17), 3816; https://doi.org/10.3390/molecules25173816 - 21 Aug 2020

Cited by 29 | Viewed by 4043

Abstract

The thermal conductivities of selected deep eutectic solvents (DESs) were determined using the modified transient plane source (MTPS) method over the temperature range from 295 K to 363 K at atmospheric pressure. The results were found to range from 0.198 W·m⁻¹·K⁻¹ to 0.250 W·m⁻¹·K⁻¹. Various empirical and thermodynamic correlations present in literature, including the group contribution method and mixing correlations, were used to model the thermal conductivities of these DES at different temperatures. The predictions of these correlations were compared and consolidated with the reported experimental values. In addition, the thermal conductivities of DES mixtures with water over a wide range of compositions at 298 K and atmospheric pressure were measured. The standard uncertainty in thermal conductivity was estimated to be less than ± 0.001 W·m⁻¹·K⁻¹ and ± 0.05 K in temperature. The results indicated that DES have significant potential for use as heat transfer fluids. Full article

(This article belongs to the Special Issue Ionic Liquids for Materials and Energy)

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14 pages, 2962 KiB

Open AccessArticle

Influence of Tethered Ions on Electric Polarization and Electrorheological Property of Polymerized Ionic Liquids

by Fang He, Bo Wang, Jia Zhao, Xiaopeng Zhao and Jianbo Yin

Molecules 2020, 25(12), 2896; https://doi.org/10.3390/molecules25122896 - 23 Jun 2020

Cited by 16 | Viewed by 3119

Abstract

Polymerized ionic liquids (PILs) show potential to be used as new water-free polyelectrolyte-based electrorheological (ER) material. To direct ER material design at the molecular level, unveiling structure-property relationships is essential. While a few studies compare the mobile ions in PILs there is still a limited understanding of how the structure of tethered counterions on backbone influences ER property. In this study, three PILs with same mobile anions but different tethered countercations (e.g., poly(dimethyldiallylammonium) P[DADMA]⁺, poly(benzylethyl) trimethylammonium P[VBTMA]⁺, and poly(1-ethyl-4-vinylimidazolium hexafluorophosphate) P[C₂VIm]⁺) are prepared and the influence of tethered countercations on the ER property of PILs is investigated. It shows that among these PILs, P[DADMA]⁺ PILs have the strongest ER property and P[C₂VIm]⁺ PILs have the weakest one. By combining dielectric spectra analysis with DFT calculation and activation energy measurement, it can clarify that the influence of tethered counterions on ER property is mainly associated with ion-pair interaction energy that is affecting ionic conductivity and interfacial polarization induced by ion motion. P[DADMA]⁺ has the smallest ion-pair interaction energy with mobile ions, which can result in the highest ionic conductivity and the fastest interfacial polarization rate for its strongest ER property. Full article

(This article belongs to the Special Issue Ionic Liquids for Materials and Energy)

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Review

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33 pages, 13355 KiB

Open AccessReview

Pyrrolidinium Containing Ionic Liquid Electrolytes for Li-Based Batteries

by Louise M. McGrath and James F. Rohan

Molecules 2020, 25(24), 6002; https://doi.org/10.3390/molecules25246002 - 18 Dec 2020

Cited by 24 | Viewed by 5576

Abstract

Ionic liquids are potential alternative electrolytes to the more conventional solid-state options under investigation for future energy storage solutions. This review addresses the utilization of IL electrolytes in energy storage devices, particularly pyrrolidinium-based ILs. These ILs offer favorable properties, such as high ionic conductivity and the potential for high power drain, low volatility and wide electrochemical stability windows (ESW). The cation/anion combination utilized significantly influences their physical and electrochemical properties, therefore a thorough discussion of different combinations is outlined. Compatibility with a wide array of cathode and anode materials such as LFP, V₂O₅, Ge and Sn is exhibited, whereby thin-films and nanostructured materials are investigated for micro energy applications. Polymer gel electrolytes suitable for layer-by-layer fabrication are discussed for the various pyrrolidinium cations, and their compatibility with electrode materials assessed. Recent advancements regarding the modification of typical cations such a 1-butyl-1-methylpyrrolidinium, to produce ether-functionalized or symmetrical cations is discussed. Full article

(This article belongs to the Special Issue Ionic Liquids for Materials and Energy)

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27 pages, 2276 KiB

Open AccessReview

Application of Ionic Liquids for Chemical Demulsification: A Review

by Nahid Hassanshahi, Guangji Hu and Jianbing Li

Molecules 2020, 25(21), 4915; https://doi.org/10.3390/molecules25214915 - 23 Oct 2020

Cited by 82 | Viewed by 6857

Abstract

In recent years, ionic liquids have received increasing interests as an effective demulsifier due to their characteristics of non-flammability, thermal stability, recyclability, and low vapor pressure. In this study, emulsion formation and types, chemical demulsification system, the application of ionic liquids as a chemical demulsifier, and key factors affecting their performance were comprehensively reviewed. Future challenges and opportunities of ionic liquids application for chemical demulsification were also discussed. The review indicted that the demulsification performance was affected by the type, molecular weight, and concentration of ionic liquids. Moreover, other factors, including the salinity of aqueous phase, temperature, and oil types, could affect the demulsification process. It can be concluded that ionic liquids can be used as a suitable substitute for commercial demulsifiers, but future efforts should be required to develop non-toxic and less expensive ionic liquids with low viscosity, and the demulsification efficiency could be improved through the application of ionic liquids with other methods such as organic solvents. Full article

(This article belongs to the Special Issue Ionic Liquids for Materials and Energy)

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19 pages, 3582 KiB

Open AccessReview

Ionic Liquids as Antifungal Agents for Wood Preservation

by Catalin Croitoru and Ionut Claudiu Roata

Molecules 2020, 25(18), 4289; https://doi.org/10.3390/molecules25184289 - 18 Sep 2020

Cited by 16 | Viewed by 4293

Abstract

Ionic liquids represent a class of highly versatile organic compounds used extensively in the last decade for lignocellulose biomass fractionation and dissolution, as well as property modifiers for wood materials. This review is dedicated to the use of ionic liquids as antifungal agents for wood preservation. Wood preservation against fungal attack represents a relatively new domain of application for ionic liquids, emerging in the late 1990s. Comparing to other application domains of ionic liquids, this particular one has been relatively little researched. Ionic liquids may be promising as wood preservatives due to their ability to swell wood, which translates into better penetration ability and fixation into the bulk of the wood material than other conventional antifungal agents, avoiding leaching over time. The antifungal character of ionic liquids depends on the nature of their alkyl-substituted cation, on the size and position of their substituents, and of their anion. It pertains to a large variety of wood-colonizing fungi, both Basidiomycetes and Fungiimperfecti. Full article

(This article belongs to the Special Issue Ionic Liquids for Materials and Energy)

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30 pages, 7078 KiB

Open AccessReview

Key Applications and Potential Limitations of Ionic Liquid Membranes in the Gas Separation Process of CO₂, CH₄, N₂, H₂ or Mixtures of These Gases from Various Gas Streams

by Salma Elhenawy, Majeda Khraisheh, Fares AlMomani and Mohamed Hassan

Molecules 2020, 25(18), 4274; https://doi.org/10.3390/molecules25184274 - 18 Sep 2020

Cited by 30 | Viewed by 5250

Abstract

Heightened levels of carbon dioxide (CO₂) and other greenhouse gases (GHGs) have prompted research into techniques for their capture and separation, including membrane separation, chemical looping, and cryogenic distillation. Ionic liquids, due to their negligible vapour pressure, thermal stability, and broad electrochemical stability have expanded their application in gas separations. This work provides an overview of the recent developments and applications of ionic liquid membranes (ILMs) for gas separation by focusing on the separation of carbon dioxide (CO₂), methane (CH₄), nitrogen (N₂), hydrogen (H₂)_, or mixtures of these gases from various gas streams. The three general types of ILMs, such as supported ionic liquid membranes (SILMs), ionic liquid polymeric membranes (ILPMs), and ionic liquid mixed-matrix membranes (ILMMMs) for the separation of various mixed gas systems, are discussed in detail. Furthermore, issues, challenges, computational studies and future perspectives for ILMs are also considered. The results of the analysis show that SILMs, ILPMs, and the ILMMs are very promising membranes that have great potential in gas separation processes. They offer a wide range of permeabilities and selectivities for CO₂, CH₄, N₂, H₂ or mixtures of these gases. In addition, a comparison was made based on the selectivity and permeability of SILMs, ILPMs, and ILMMMs for CO₂/CH₄ separation based on a Robeson’s upper bound curves. Full article

(This article belongs to the Special Issue Ionic Liquids for Materials and Energy)

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24 pages, 4528 KiB

Open AccessEditor’s ChoiceReview

Insights into the Properties and Potential Applications of Renewable Carbohydrate-Based Ionic Liquids: A Review

by Bartłomiej Gaida and Alina Brzęczek-Szafran

Molecules 2020, 25(14), 3285; https://doi.org/10.3390/molecules25143285 - 20 Jul 2020

Cited by 38 | Viewed by 5667

Abstract

Carbohydrate-derived ionic liquids have been explored as bio-alternatives to conventional ionic liquids for over a decade. Since their discovery, significant progress has been made regarding synthetic methods, understanding their environmental effect, and developing perspectives on their potential applications. This review discusses the relationships between the structural properties of carbohydrate ionic liquids and their thermal, toxicological, and biodegradability characteristics in terms of guiding future designs of sugar-rich systems for targeted applications. The synthetic strategies related to carbohydrate-based ionic liquids, the most recent relevant advances, and several perspectives for possible applications spanning catalysis, biomedicine, ecology, biomass, and energy conversion are presented herein. Full article

(This article belongs to the Special Issue Ionic Liquids for Materials and Energy)

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