Use Of Ionic Liquids Research Articles

Extraction of lignin-containing nanocellulose fibrils from date palm waste using a green solvent

Lignin-containing nanocellulose (LNC) is a compelling alternative to traditional nanocellulose (NC), it offers enhanced yields and a reduction in the demand for toxic chemicals. This research involves the isolation of LNC from date palm waste using a green hydrolysis process and its subsequent characterization. The potential of using ionic liquids (ILs) as green solvents to isolate LNC has not yet been explored. Our findings suggest that 1-ethyl-3-methylimidazolium chloride ([Emim]Cl) can hydrolyze partially delignified and unbleached lignocellulose, achieving LNC synthesis. The obtained LNC showed a higher yield than its NC counterpart and exhibited rod-shaped fibers with nanoscale diameters and micrometer lengths, indicating a high aspect ratio. Dynamic Light Scattering (DLS) results indicate average particle sizes of 143.20 nm for NC and 282.30 nm for LNC, with a narrow particle size distribution conforming their monodisperse behavior. Thermogravimetric analysis and differential scanning calorimetry revealed high thermal stability (initial degradation temperature = 222.50 °C and glass transition temperature = 84.45°C) of LNC. Moreover, the obtained LNC fibers were crystalline (crystallinity index = 52.76 %). Their activation energy (124.95 kJ/mol) was determined using the Coats–Redfern method by employing eight solid-state diffusion models. Overall, this study motivates the use of ILs as green solvents to produce lignocellulose derivatives that are suitable for various applications.

Ionic Liquid-promoted the Synthesis of Structurally Diverse Pyrans, Pyran-annulated Heterocycles, and Spiropyrans

Abstract: During the last two decades, non-conventional solvents, especially various ionic liquids, have been utilized as efficient reaction media as they can play a dual role as solvents and promoters. The use of ionic liquids as a medium increases the efficiency of the reactions due to their inherent features like high thermal stability, ability to act as a catalyst, non-volatility, high polarity, reusability, ability to dissolve a large number of organic and inorganic compounds, etc. Under this direction, various structurally diverse ionic liquids have been employed as efficient reaction media for various organic transformations. On the other hand, among many other important synthetic scaffolds, during the last two decades, the synthesis of pyrans, pyran-annulated heterocyclic scaffolds, and spiropyrans have gained huge attention as they possess a wide range of significant biological efficacies, which include antibacterial, anticancer, antimycobacterial, antioxidant, xanthine oxidase inhibitory, etc. activities. Almost every day, many new methods are being added to the literature related to synthesizing pyrans, pyran- annulated heterocyclic scaffolds, and spiropyrans. Among many other alternatives, various ionic liquids have also played an efficient role as promoters for synthesizing structurally diverse pyrans, pyran-annulated heterocyclic scaffolds, and spiropyrans. In this review, we have summarized a large number of literature reported during the last two decades related to the ionic liquid-promoted synthesis of pyrans, pyran-annulated heterocyclic scaffolds, and spiropyran derivatives.

Unraveling the emulsifying activity of bio-based ionic liquids in the formation and stabilization of oil-in-water emulsions

Bio-based ionic liquids (ILs), especially those derived from fatty acids (FAs) have been considered promising compounds for the agri-food and bioproduct industries, due to their sustainable appeal, possibly low or non-toxic effect and the nutritional value of FAs. However, studies have been mainly focused on the use of ILs as greener solvents. This work investigated the application of ILs derived from FAs and diethanolamine as emulsifiers to form and stabilize oil-in-water emulsions using ultraturrax (PM) and high-pressure homogenization (H). The influence of the IL type obtained from different FAs (stearic or oleic acids), and vegetable oil type (sunflower or olive oil) and concentration (30:70 or 70:30, oil:water phase ratio) on the formation and stabilization of emulsions was evaluated. This study was focused on the zeta potential of IL aqueous solutions in different pH conditions, interfacial tension between vegetable oils and IL aqueous solutions at different concentrations, kinetic stability, droplet size and size distribution, optical microscopy, viscosity profile and rheological behavior of the emulsions. ILs presented highly negative ZP charge (−12.97–−74.81), high emulsifying ability at low concentrations (1 %) and led to emulsions with high kinetic stability (>30 days). The electrostatic stabilization mechanism may predominate over the steric in IL-based emulsions. The stabilization of emulsions with ILs was associated to lower oil droplet size (D3,2 = 0.60–4.09 µm, D4,3 = 0.95–9.91 μm) and emulsion viscosity (4.8 mPa·s-1.13 Pa·s), which were related to the IL molecular structure, oil type and concentration, and process. Emulsions prepared with stearic-based IL and sunflower oil by PM+H presented higher kinetic stability. The proposed ILs are presented as highly effective emulsifiers with potential application in the agri-food, pharmaceutical and cosmetic industries.

High-resolution performance of pillar[6]arene functionalized with imidazolium ionic liquids for gas chromatography

Pillar[n]arenes (P[n]A, n = 5–10) have attracted much attention because of their highly symmetric pillar-shaped architecture with π-electron rich cavity. Nevertheless, the use of ionic liquid functionalized P[n]A in chromatography has not been reported up to data. This work reports the investigation of the imidazolium ionic liquids functionalized pillar[6]arene (P6A-C10-IM-C8[NTf2]) as the stationary phase for gas chromatography (GC). The statically coated P6A-C10-IM-C8[NTf2] column (0.25 mm i.d.) showed moderate polarity and high column efficiency of 4733 plates/m determined by n-dodecane at 120 °C (k = 2.29). Owing to its unique amphiphilic conformation, the P6A-C10-IM-C8[NTf2] showed good column inertness and resolving capability for a wide range of analytes and isomers. Particularly, the P6A-C10-IM-C8[NTf2] column exhibited distinctly advantageous performance for the challenging isomers of halogenated benzenes, benzaldehydes, phenols and anilines over the common commercial columns, namely 5% phenyl methyl polysiloxane (HP-5) and 35% phenyl methyl polysiloxane (HP-35). In addition, it exhibited good column repeatability and reproducibility with RSD values on the retention times less than 0.05% for run-to-run, 0.38% for day-to-day and 2.94% for column-to-column, respectively. This work demonstrates the promising future of ionic liquid P[n]A stationary phases for chromatographic separations.

Pyrylium- and Pyridinium-Based Ionic Liquids as Friction Modifiers for Greases.

The use of ionic liquids (ILs) as lubricants or additives has been studied extensively over the past few decades. However, the ILs considered for lubricant applications have been part of a limited structural class of phosphonium- or imidazolium-type compounds. Here, new pyrylium- and pyridinium-based ILs bearing long alkyl chains were prepared and evaluated as friction- and wear-reducing additives in naphthenic greases. The physical properties of the synthetic ILs and additized naphthenic grease were measured. The tribological performance of the greases was measured by using standard benchtop tests. The addition of ILs was detrimental to wear, causing an increase in the amount of material removed by sliding relative to the base greases in most cases. In contrast, the friction performance improved under nearly all conditions tested due to the IL additives. The compatibility of the synthetic ILs with the naphthenic greases and its potential influence upon miscibility and tribological performance are tentatively proposed to be a result of the molecular structure.

Metal-Free Activation of Molecular Oxygen by Quaternary Ammonium-Based Ionic Liquid: A Detail Mechanistic Study.

Most oxidation processes in common organic synthesis and chemical biology require transition metal catalysts or metalloenzymes. Herein, we report a detailed mechanistic study of a metal-free oxygen (O2) activation protocol on benzylamine/alcohols using simple quaternary alkylammonium-based ionic liquids to produce products such as amide, aldehyde, imine, and in some cases, even aromatized products. NMR and various control experiments established the product formation and reaction mechanism, which involved the conversion of molecular oxygen into a hydroperoxyl radical via a proton-coupled electron transfer process. Detection of hydrogen peroxide in the reaction medium using colorimetric analysis supported the proposed mechanism of oxygen activation. Furthermore, first-principles calculations using density functional theory (DFT) revealed that reaction coordinates and transition state spin densities have a unique spin conversion of triplet oxygen leading to formation of singlet products via a minimum energy crossing point. In addition to DFT, domain-based local pair natural orbital coupled cluster, (DLPNO-CCSD(T)), and complete active space self-consistent field, CASSCF(20,14) methods complemented the above findings. Partial density of states analysis showed stabilization of π* orbital of oxygen in the presence of ionic liquid, making it susceptible to hydrogen abstraction in a mild, metal-free condition. Inductively coupled plasma atomic emission spectroscopic (ICP-AES) analysis of reactant and ionic liquids clearly showed the absence of any significant transition metal contamination. The current results described the origin of O2 activation within the context of molecular orbital (MO) theory and opened up a new avenue for the use of ionic liquids as inexpensive, multifunctional and high-performance alternative to metal-based catalysts for O2 activation.

Application of ionic liquids in ion-selective electrodes and reference electrodes: A review.

Ionic liquids (ILs) are organic chemical compounds that are composed only of ions, a large organic cation and a smaller inorganic or organic anion. These are salts whose melting point is lower than the boiling point of water. ILs have many interesting properties, thanks to which they find great practical applications in analytics, electrochemistry, separation techniques, catalysis and others. One of the many areas of application of ionic liquids is sensors especially electrochemical sensors including ion-selective electrodes. In this case, the properties of ILs that are particularly useful include very good electrical conductivity, high electrochemical stability, good extraction properties, hydrophobic character and compatibility with other materials, e. g. polyvinyl chloride plasticizers or carbon nanomaterials. ILs were used as components of ion-selective membranes, both polymeric ones based on PVC and membranes in carbon paste electrodes. ILs performed various functions in these membranes, including lipophilic ionic additive, ionophore/ion exchanger, plasticizer, transducer media and matrix. They were also used as a component of the intermediate layer in solid contact ISEs. The last chapter presents examples of the use of ILs in reference electrodes. This review discusses the use of ionic liquids in ion-selective electrodes (ISEs) and reference electrodes over the last ten years.

Efficient Extraction of Sericin Protein from Mulberry and Non‐Mulberry Silk Fibers: Utilizing Aqueous Ionic Liquid Solutions as Green Solvents

AbstractProtein extraction from silk is a unique area of research and the foremost need is the efficient extraction of the silk proteins namely fibroin and sericin from the silk fibres, which is conventionally done using chemicals. In this work, we show that Ionic liquids (ILs) can be employed as a green and alternative method for degumming sericin from both mulberry (B. mori) and non‐mulberry (A. assamensis and P. ricini) silk. Six different ILs with varying tail lengths were studied for their degumming efficiencies. The interaction between silk proteins and IL ions involves a complex ionic disruption of hydrogen bonds, non‐polar interactions, and electrostatic effects. We have found that 1‐Butyl‐3‐methylimidazolium chloride (BMIM.Cl), 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIM.BF4) and Tetraethylammonium bromide (TEAB) bring in higher weight loss % in silk fibres compared to other ILs, indicating that it can be used in better sericin removal without significant damage to the silk fibre. TEAB emerged as a potential candidate for sericin extraction due to its promotion of protein destabilization. Additionally, no drastic changes in the structure of the extracted silk protein sericin were observed, as evident from the FTIR spectra and SEM images. This work highlights for the first time, the use of ILs for extraction of non‐mulberry silk sericin and also proves that ILs can be a potential green solvent for sericin extraction.

Enhanced Physical Stability of L-Ascorbic Acid in an Ionic Liquid.

Ionic liquid (IL) technology was used to enhance the stability of L-ascorbic acid (AA). Pyridoxine was selected as the counter cation for anionic AA in IL. After AA was dissolved in water at 40 °C, its ratio decreased to 3.2% after 7 d. In contrast, the IL formulation showed negligible degradation, with almost no loss of AA even after 28 d. These results suggest that the use of IL enhances the stability of AA.

Is the carotenoid production from Phaffia rhodozyma yeast genuinely sustainable? a comprehensive analysis of biocompatibility, environmental assessment, and techno-economic constraints

Microorganisms, such as yeasts, filamentous fungi, bacteria, and microalgae, have gained significant attention due to their potential in producing commercially valuable natural carotenoids. In recent years, Phaffia rhodozyma yeasts have emerged as intriguing non-conventional sources of carotenoids, particularly astaxanthin and β-carotene. However, the shift from academic exploration to effective industrial implementation has been challenging to achieve. This study aims to bridge this gap by assessing various scenarios for carotenoid production and recovery. It explores the use of ionic liquids (ILs) and bio-based solvents (ethanol) to ensure safe extraction. The evaluation includes a comprehensive analysis involving Life Cycle Assessment (LCA), biocompatibility assessment, and Techno-Economic Analysis (TEA) of two integrated technologies that utilize choline-based ILs and ethanol (EtOH) for astaxanthin (+β-carotene) recovery from P. rhodozyma cells. This work evaluates the potential sustainability of integrating these alternative solvents within a yeast-based bioeconomy.

Ionic Liquid@ HT- Clay Combination for Baylis -Hillman Reaction and Lactone Ceramide Analog Synthesis

Abstract: This study investigates the use of ionic liquids (ILs) immobilized on HT-clay as catalysts for the Baylis-Hillman reaction. The catalytic system comprised three different types of ILs ([HIM]Im, [BIM]Im, [EIM]Im) and exhibited high reactivity, and the B-H products were obtained in good yield, which is superior to previously reported catalytic systems, whether they were heterogeneous or homogeneous. The HT-clay immobilized with ILs also allowed for easy recovery from the reaction mass and could be recycled for up to 7 consecutive runs with only a slight decrease in activity. Moreover, the scope of our catalytic system was extended to synthesize biologically active lactone ceramide analogs using the Baylis-Hillman reaction at room temperature with (S-) Garner aldehyde and methyl acrylate. The synthesis was successful, and we obtained good yields of the desired products, highlighting the versatility of the ionic liquid immobilized HT-clay catalytic system. This study demonstrates the potential of ionic liquid immobilized HT-clay as a promising catalyst for various organic reactions. Our findings emphasize the importance of developing efficient and environmentally friendly methods for synthesizing valuable organic compounds. The results obtained from this study provide a significant contribution to the ongoing research in the field of catalysis and will be useful for developing new approaches to the synthesis of complex organic molecules.

Synthetization and Characterization of Zinc Oxide Nanoparticles by X- Ray Diffractometry (XRD), Fourier Transforms, Infra-Red Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Antibacterial Activity Test

Purpose: Nanomaterials with their derivable potentials offer wide obtain ability and have recently aroused much attention for biomedical applications. Nowadays, nanomaterials-based colorimetric sensing is a quickly emerging field of sensing applications. Nanomaterials are considered as the main component of colorimetric determination of hydrogen peroxide to replace the natural enzyme-based sensors because of some associated intrinsic drawbacks. Considering the advantageous properties of ionic liquid (IL) for various applications, significant attention has been made to the use of ionic liquid stabilized metal NPs which may serve as a regulator to enhance the catalytic performance of the metal nanoparticles in the different IL reaction medium. 
 Methodology: The peroxidase-like activity of IL coated metal NPs (IL-MNPs) have been considered for the catalytic oxidation reaction of chromogenic substrate 3,3,5,5- tetramethylbenzidine (TMB) in the presence of H2O2 at an estimated wavelength of 652 nm.
 Results: The synthesized metal nanoparticles (Ag) were produced using a chemical reduction method. Various characterization techniques like FTIR, UV-Visible spread Reflectance Spectroscopy [UV-VIS DRS], were employed, which verified the structure, nano-size and successful combination of metal dopant ion into the samples. The molecular structure of ionic liquid with varying cations was produced and confirmed by 1H-NMR spectroscopy. The ionic liquid was coated on metal nanoparticles to enhance their conductivity. 
 Unique Contribution to Theory, Practice and Policy: Optimized reaction conditions like pH, temperature and catalyst dosage affect catalytic activity and color sensing properties. The coating of [Min] Ac on Ag achieved low detection limits and colorimetric detection of [Pyr] based Ag.

Monoketone Curcuminoids: An Updated Review of Their Synthesis and Biological Activities

Curcumin (or diferuloylmethane), a component of Curcuma longa L. rhizomes, displays various biological and pharmacological activities. However, it is poorly bioavailable and unstable in physiological pH. In this review, we cover papers published between 2019 and 2023 on the synthesis and biological activities of more stable and effective curcumin analogs known as monoketone curcuminoids (MKCs) or “monocarbonyl curcuminoids.” Recent advances in Claisen–Schmidt condensation, the standard procedure to synthesize MKCs, including the use of ionic liquids, are addressed. MKCs’ antimicrobial, anticancer, antioxidant, and antiparasitic actions, as well as other less common MKC biological and pharmacological activities, have been shown to be similar or higher than curcumin. The promising biological and pharmacological activities, combined with the attractive synthetic aspects (e.g., good yields and an easiness of product isolation) to obtain MKCs, make this class of compounds an interesting prospect for further antimicrobial, anticancer, and antiparasitic drug discovery.

Choline-based Deep Eutectic Solvent for Extractive Oxidative Desulfurization of Model Oil

One of the hardest processes encountered by petroleum refining is sulfur elimination from fuel oil. There are many traditional methods executed but they caused drawbacks such as poor selectivity of sulfur compounds and toxic raw materials. Extractive oxidative desulfurization (EODS) caught the interest of researchers due to high selectivity of sulfur compounds and great desulfurization. Currently, researchers are investigating the use of ionic liquids (ILs) as green extractant, unfortunately they are expensive. This research is proposing and comparing the use of cheap biodegradable solvents called deep eutectic solvents (DESs), as extractants in removing sulfur from fuel oil. The DESs are synthesized through a combination of choline chloride - orcinol and choline chloride - ethylene glycol, and their structure is confirmed through FTIR. Their thermal properties are characterized by DSC and TGA. Their desulfurization performance is evaluated by type of DESs, different ratios of DES and model oil, different ratios of oxidant and sulfone and various temperatures which these factors are found to influence the result. The optimum conditions are found to be at 1:1 for DES and model oil ratio, 4 for O/S ratio and temperature at 85 °C with the extraction efficiency of 99.98%. In conclusion, this DES has high potential to be the cheap green alternative to the conventional extractant for extractive oxidative desulfurization process.

Ionic liquids for the green synthesis of 1,2,3-triazoles: a systematic review

This review focuses on the use of ionic liquids (ILs) in green synthesis of 1,2,3-triazoles which critically screened, and summarized in two sections i.e., from alkynes and substrates other than alkynes using ILs as solvent, as catalyst and as both.

Use of ionic liquids in amidation reactions for proteolysis targeting chimera synthesis.

Selective degradation of disease-causing proteins using proteolysis targeting chimeras (PROTACs) has gained great attention, thanks to its several advantages over traditional therapeutic modalities. Despite the advances made so far, the structural chemical complexity of PROTACs poses challenges in their synthetic approaches. PROTACs are typically prepared through a convergent approach, first synthesizing two fragments separately (target protein and E3 ligase ligands) and then coupling them to produce a fully assembled PROTAC. The amidation reaction represents the most common coupling exploited in PROTACs synthesis. Unfortunately, the overall isolated yields of such synthetic procedures are usually low due to one or more purification steps to obtain the final PROTAC with acceptable purity. In this work, we focused our attention on the optimization of the final amidation step for the synthesis of an anti-SARS-CoV-2 PROTAC by investigating different amidation coupling reagents and a range of alternative solvents, including ionic liquids (ILs). Among the ILs screened, [OMIM][ClO4] emerged as a successful replacement for the commonly used DMF within the HATU-mediated amidation reaction, thus allowing the synthesis of the target PROTAC under mild and sustainable conditions in very high isolated yields. With the optimised conditions in hand, we explored the scalability of the synthetic approach and the substrate scope of the reaction by employing different E3 ligase ligand (VHL and CRBN)-based intermediates containing linkers of different lengths and compositions or by using different target protein ligands. Interestingly, in all cases, we obtained high isolated yields and complete conversion in short reaction times.

Liquid-liquid phase of imidazolium-based ionic liquids in n-butyl acetate + n-butanol mixtures: Experimental measurements, quality testing, phase stability, thermodynamic modeling

The ester n-butyl acetate is an important chemical compound produced by esterification with n-butanol and used as solvent for pigments, vegetable oils and fats, and in the production of varnishes, coatings, waxes and resins. This work investigated the use of ionic liquids (ILs) as solvents in separation processes involving these substances. The ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]) was synthesized, while 1-ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) were purchased. The liquid–liquid equilibrium (LLE) was analyzed based on the experimental measurements (binodal curve, tie-lines), σ-profiles analysis (COSMOTherm), experimental data quality tests, phase stability and thermodynamic modeling with NRTL for the n-butyl acetate + n-butanol + IL ([BMIM][Cl], [EMIM][EtSO4], [EMIM][BF4]) systems at 298.15 K and 101.3 kPa. Experimental results indicated that the studied systems had the LLE phase behavior of type I. Experiments and calculations showed that [EMIM][EtSO4] and [BMIM][Cl] had the best capacities to separate the azeotrope n-butanol and n-butyl acetate. All systems showed separation factors values higher than unity. Low deviations, in the compositions of both liquid phases, indicate that the NRTL model was able to analyze the phase stability and model the phase behavior of the n-butyl acetate + n-butanol + IL systems using gamma-gamma approach.

Engineered ionic liquids supported on activated carbon as a sustainable and selective catalyst for viable fixation of CO2 into valuable chemicals

The use of ionic liquids (ILs) based materials in catalysis, especially for CO2 conversion has been attracted great scientific attention due to green catalytic approach and eco-friendliness of the material. In this effort, especially engineered NH2-functionalized imidazolium based ILs with different anions were prepared to develop new covalent ILs functionalized activated carbon (AC) catalysts. All different AC-ILs namely AC-IL-Br, AC-IL-BF4, AC-IL-NTf2 and AC-IL-HSO4 was successfully synthesized by metathesis reaction, and characterized using various analytical and spectroscopic techniques. With the maximum immobilization of the NH2-functionalized ILs on the AC support, the immobilized AC-ILs showed superior structural advantages such as high thermal stability and appreciable surface area. The newly developed AC-ILs as bi-functional catalysts were applied in the fixation of CO2 into epoxide and it displayed high catalytic activity during the catalytic screening. Various reaction variables were surveyed wherein especially, 10.0 wt% of AC-IL-NTf2 catalyst demonstrated the best catalytic activity with 100 % conversion of styrene oxide and 83 % selectivity towards styrene carbonate at 120 °C, 20 bar CO2 pressure in 13 h under solvent-free conditions. The enhanced performance by AC-IL-NTf2 catalyst was achieved as a result of least co-ordination of the NTf2− anion with the NH2-functionalized imidazolium cation which helped in the opening and stabilization of epoxide ring and increased the reaction rate. The best performing AC-IL-NTf2 catalyst was found to be compatible with a broad substrate scope and could effectively produce the respective cyclic carbonates in good to quantitative yields with different substituted epoxides. Most significantly, AC-IL-NTf2 catalyst could be easily separated from the reaction mixture and recycled it for number of cycles. It maintained its catalytic activity without any evident leaching and structural damage up to six recycles. Additionally, plausible reaction mechanism also has been proposed with AC-IL-NTf2 catalyst with the help of catalytic activity results and characterization support.

Use of Ionic Liquid as Crystallization Inhibitor in Water-Lithium Bromide Absorption Chiller

Chillers are used in commercial buildings and industrial plants to provide air conditioning, refrigeration, and process fluid cooling. There are two basic types of chiller cycles: vapor compression and sorption. Sorption chillers are available as either absorption or adsorption designs, depending on the state of the sorbent. Absorption chillers use fluid refrigerants and absorbents (liquid or dissolved), while adsorption chillers employ a solid sorbent (typically silica gel) in combination with a fluid refrigerant. Among the former category, the use of highly hygroscopic LiBr salt as absorbent in combination with H2O as refrigerant comprises LiBr-H2O absorption chillers. Such chillers possess cooling capacities ranging from a few kilowatts (kW) to megawatts (MW) which match with small residential to large scale commercial or even industrial cooling needs. One of the major debilitating factors associated with LiBr-H2O absorption chillers is crystallization. A crystallization event causes a loss of cooling and requires de-crystallization by applying external heat, which results in extensive down-time and requires redundancy designed into a chiller plant. We investigated the use of the imidazolium-based ionic liquid, 1-butyl-3-methylimidazolium bromide ([BMIm]-Br), as crystallization inhibitor additive to LiBr-H2O in the ratio 1:19 [BMIm]-Br:LiBr. It was found that under the operating boundary conditions of 27°C/9°C (cooling water inlet temperature/chilled water outlet temperature), the LiBr-H2O absorption chiller can be operated without modifications and with around 10 K higher heating water inlet temperatures when adding [BMIM]-Br before crystallization occurs compared to pure LiBr-H2O solution. When using the [BMIM]-Br ionic liquid, the refrigeration capacity of the absorption chiller under the above operating conditions and at 85°C heating water inlet temperature exhibited 10% increase after optimizing the solution flow, that lead to higher outputs, such as lower cooling water temperatures. By adding the [BMIM]-Br to the aqueous lithium bromide solution the operating range of the absorption refrigeration system could also be extended to resorption mode, which allows refrigeration below 0 °C. Thus, there is an excellent potential for a significant extension of the application range of LiBr-H2O chillers, e.g. in the field of food cooling and refrigeration processes. Figure 1

Role of Ionic Liquids As Modifiers of Ru-Based Catalysts for Water Electrolysis

The generation of hydrogen through electrocatalytic water splitting has attracted tremendous attention in the past years [1,2]. Although water electrolysis has been already established in industrial settings, a large amount of research is still being carried out to further improve the catalytic efficiency and stability to exploit the full potential of this technology. One approach in this endeavor is the utilization of ionic liquids (ILs) as modifiers of electrocatalysts and electrode surfaces [3, 4]. The special physicochemical properties of the IL can affect and ideally improve the characteristics of the electrocatalyst, e.g., in terms of mass and electron transport [3]. Furthermore, the hydrophilic nature of certain ILs can in addition influence gas bubbles removal on the working electrode and improve the stability of the catalysts (e.g., Ru) by acting as a monomer-like binder [4].In this study, we compared the effect of four different ILs that are based on the same cation chain (1-butyl-3-(4-methylphenethyl)-1H-imidazol-3-ium) but different anions (-OAc, -NTf2, -Br, and -MeSO3) on Ru nanoparticles as catalysts for hydrogen and oxygen evolution reactions (HER and OER). To this end, carbon nanotubes were functionalized using different ILs and subsequently decorated with 1-2 nm Ru nanoparticles (Ru NPs) following an established organometallic approach [5]. We analyze how the catalytic activity/stability for HER, as well as OER, is influenced by the metal-ILs combination by established electrochemical methods utilizing a rotational disc electrode setup, with a particular focus on the different hydrophilic natures (depending on the anion) of the four ILs. To obtain a more comprehensive picture of how the different ILs affect Ru dissolution during the reaction, the IL/catalyst systems are additionally investigated by inductively coupled plasma-optical emission spectroscopy (ICP-OES) in a flow cell setup, as well as by electrochemical quartz crystal microbalance (EQCM) measurements.In this work, we discuss the use of ILs as modifiers for catalyst/electrode systems in water-splitting reactions, highlighting the importance of careful IL selection as well as the necessity for more future research in this field to fully explore the potential of IL/NPs-systems in electrochemistry.