Conductivity Of Deep Eutectic Solvents Research Articles

Predicting the properties of deep eutectic solvents based on choline chloride and carboxylic acids and their mixtures with water using QSPR approach

Deep eutectic solvents (DES) are increasingly popular materials in various fields of chemistry. The set of properties of a particular DES determines the range of its applicability for a certain task. Tailoring these properties to meet the needs of various applications can be tedious, as it may require a large amount of experimental work. Here we propose the use of quantitative structure-property relationship (QSPR) approach to model DES properties. Using choline chloride and six carboxylic acids as a case study we attempted to construct regression models relating molecular descriptors of carboxylic acids and the properties of corresponding solvents. Statistically meaningful correlations were established between the descriptors of the acids and density, viscosity and conductivity of DES. The impact of different descriptors on these properties was analyzed based on the regression coefficients. Taking into account rather limited dataset a rigorous validation of the regression models was performed using double loop cross-validation.

Deep eutectic solvents based on N, N, N-trimethyl propylsulphonate ammonium hydrosulfate-urea as potential electrolytes for proton exchange membrane fuel cell

Deep eutectic solvents (DESs) have been synthesized by using N, N, N-trimethyl propylsulphonate ammonium hydrosulfate as the hydrogen bond acceptor (HBA) and urea as hydrogen bond donor (HBD) in capricious molar ratios. Fourier transform infrared spectrum, the proton nuclear magnetic resonance and carbon-13 nuclear magnetic resonance are employed to confirmed the chemical structures of N, N, N-trimethyl propylsulphonate ammonium hydrosulfate. The synthesized DESs are characterized by thermogravimetric analysis and Fourier transform infrared spectrum. The synthesized DESs exhibit excellent thermal stability, making them suitable electrolytes for proton exchange membrane fuel cell. The viscosity and conductivity of DESs are significantly affected by the molar ratio between HBD and HBA. The four samples are used as electrolytes to evaluate the fuel cell performance. The results indicate that the power density of the four samples decreases in the following order: DES with a molar ratio of HBA/HBD of 1:1 > DES with a molar ratio of HBA/HBD of 2:1 >N, N, N-trimethyl propylsulphonate ammonium hydrosulfate > DES with a molar ratio of HBA/HBD of 1:2. The DES with a molar ratio of HBA/HBD of 1:1 exhibits a significantly higher peak power density of 92.5 mW · cm−2 compared to the peak power density (48.5 mW · cm−2) observed without the addition of urea at 50 °C, while DES with a molar ratio of HBA/HBD of 1:2 displays a much lower peak power density of only 8.7 mW · cm−2 at 30 °C. The proton diffusion coefficient D is a critical factor that significantly impacts fuel cell performance. DESs as proton conducting media is a promising approach to improve cell performance in the proton exchange membrane fuel cell.

Molecular-based artificial neural network for predicting the electrical conductivity of deep eutectic solvents

Due to their unique features, deep eutectic solvents (DESs) are well-known as promising and environmentally friendly solvents. Their use in various processes has recently become the focus of several research groups. However, designing DESs with optimal properties for a particular application requires many resources and is time-consuming. Therefore, it is crucial to develop predictive models to estimate the properties of DESs, which will save resources and time. Electrical conductivity is one of the most critical factors for the design, control and optimization of electrochemical processes. In this work, a model capable of estimating the electrical conductivity of DESs is presented. The model combines the Quantitative Structure-Property Relationships (QSPR) approach with artificial neural networks (ANNs) and COSMO-RS-based molecular parameters known as Sσprofiles.. The QSPR-ANN training set consists of 2,266 data points from 191 DES mixtures with 334 compositions prepared from 8 anions, 26 cations, and 73 hydrogen bond donors (HBDs) measured at various temperatures ranging from 218 to 403 K. The coefficient of determination (R2) for the QSPR-ANN developed was 0.993 in training and 0.984 in testing. In conclusion, the proposed approach can reliably estimate the electrical conductivity of DESs and can be used to determine appropriate DESs with the desired electrical conductivity for various electrochemical applications.

Comprehensive physicochemical evaluation of deep eutectic solvents: quantum-chemical calculations and electrochemical stability

The focus of the investigation is physicochemical properties (electrical conductivity, electrochemical window) and theoretical study of stability of the formed deep eutectic solvents (DESs). Quantum-chemical calculations have been performed to predict the formation of solvents with higher stability. The reported results reveal a complete description of fluid’s characteristics which of the components is the most effective donor for creation hydrogen bond with hydrogen bond acceptor. Two DESs have been synthesized by using of choline chloride as hydrogen bond acceptors (HBAs) and Urea and Lactic acid as hydrogen bond donors (HBDs). Also, DES have been synthesized by using of Lactic acid as hydrogen bond acceptors (HBAs) and Sodium Acetate as hydrogen bond donors (HBDs). The electrical conductivity of deep eutectic solvents was measured and the width of electrochemical window was evaluated using cycling voltammetry depending on water content in the solvent (0–25%).

ELECTROCHEMICAL PROPERTIES OF NATURAL IONIC LIQUIDS OF NEW GENERATION

Nowadays, the development of modern chemical technology and engineering is aimed at the concept of greening and implementation of "green" technologies. Therefore, the study of deep eutectic solvents (DES), which arecheap and environmentally friendly, is of particular importance. DES are a class of novel green solventswith a wide range of properties and applications. In the work, 6 solvents were synthesized using choline chloride, lactic acid, proline, betaine, propanol, and urea. These constituents jointly determine the nature of the synthesized DESs and their electrochemical behavior. The knowledge of physicochemical, electrochemical properties of DESs is also valuable to DESs practical applications. Electrical conductivity indicates the strength with which DESs can conduct electricity. The focus of the investigation is physicochemical properties (electrical conductivity, electrochemical window) deep eutectic solvents (DESs). The formation of hydrogen bonds between the components was confirmed and the electrochemical characteristics of the synthesized ionic liquids were determined. The conducted studies showed that urea and lactic acid arethe most suitable compounds for the formation of DES. DESs have been synthesized using choline chloride, Betaine and Proline as hydrogen bond acceptors (HBAs). Choline chloride-urea, Choline chloride-lactic acid, Sodium acetate-lactic acid, Choline chloride-propanediol, Proline-lactic acid, Betaine-lactic acid were synthesized. The electrical conductivity of deep eutectic solvents was measured and the width of the electrochemical window was evaluated using cycling voltammetry. FTIR-ATR was carried out to confirm the formation of the DESs. FT-IR results confirmed that H-bonds, occurring between two components in DES, were the main force leading to the eutectic formation. Adding water in quantity 1...25% leads to a decrease in the width of the electrochemicalwindow from 1.33to 1.21 V and increase in electrical conductivity from 0.39 to 2.07 S/m.

Prediction of Electrical Conductivity of Deep Eutectic Solvents Using COSMO-RS Sigma Profiles as Molecular Descriptors: A Quantitative Structure–Property Relationship Study

This work presents the development of molecular-based mathematical models for the prediction of electrical conductivity of deep eutectic solvents (DESs). Two new quantitative structure–property relationship (QSPR) models based on conductor-like screening model for real solvent (COSMO-RS) molecular charge density distributions (Sσ-profiles) were developed using the data obtained from the literature. The data comprise 236 experimental electrical conductivity measurements for 21 ammonium- and phosphonium-based DESs, covering a wide range of temperatures and molar ratios. First, the hydrogen-bond acceptors (HBAs) and hydrogen-bond donors (HBDs) of each DES were successfully modeled using COSMO-RS. Then, the calculated Sσ-profiles were used as molecular descriptors. The relation between the conductivity and the descriptors in both models has been expressed via multiple linear regression. The first model accounted for the structure of the HBA, the HBD, the molar ratio, and temperature, whereas the second model additionally incorporated the interactions between the molecular descriptors. The results showed that by accounting for the interactions, the regression coefficient (R2) of the predictive model can be increased from 0.801 to 0.985. Additionally, the scope and reliability of the models were further assessed using the applicability domain analysis. The findings showed that QSPR models based on Sσ-profiles as molecular descriptors are excellent at describing the properties of DESs. Accordingly, the obtained model in this work can be used as a useful guideline in selecting DESs with the desired electrical conductivity for industrial applications.

Green aerobic oxidative desulfurization of diesel by constructing an Fe-Anderson type polyoxometalate and benzene sulfonic acid-based deep eutectic solvent biomimetic cycle

A unique redox-coupled biomimetic system was developed, in which Fe-Anderson type polyoxometalates (POMs) were employed as electron transfer mediators (ETMs) and benzenesulfonic acid (BSA)-based deep eutectic solvents (DESs) were used as electron-donors for aerobic oxidative desulfurization (AODS) of diesel fuel. Different compositions of DESs were used and the polyethylene glycol 2000 (PEG2000)/2.5BSA system showed the highest desulfurization activity, with the removal of dibenzothiophene (DBT) at 60 °C reaching 95% in 60 min. The excellent desulfurization activity of the system is due to the in situ formation of peroxysulfonate via a biomimetic process. By constructing a coupled redox system, Fe-Anderson type POMs as ETMs reduce the activation energy of oxygen-activated sulfonate. The physical characteristics of four different DESs were tested. The results show that the conductivity of DESs is correlated with the composition of BSA-based DESs. However, there is no similar trend in viscosity testing at the same temperature, and the maximum viscosity value is obtained for the PEG2000/2.5BSA system at 60 °C, which may be associated with the stronger hydrogen bonds. It is worth noting that the PEG2000/2.5BSA system also possesses the best desulfurization activity, which suggests that the activity of the desulfurization system is related to the strength of the hydrogen bond in DESs. Finally, the biomimetic desulfurization system exhibits excellent performance and good stability under mild reaction conditions (60 °C, atmospheric pressure, oxygen as the oxidant).

Thermal conductivity of deep eutectic solvents

We have reported the thermal conductivities of three deep eutectic solvents (DESs). We have used choline chloride, N,N-diethyl ethanol ammonium chloride and urea, N,N-diethylthiourea, to prepare three DESs. The thermal conductivities of three DESs have measured over the temperature range from 298 to 343 K at atmospheric pressure. We have observed that the thermal conductivities of DESs are slightly decreased with increase in temperature. In all systems, linear correlations were found between thermal conductivities with temperature. Out of three, DESs studied the thermal conductivities of DES-I (prepared from urea and choline chloride) and DES-II (prepared from urea and N,N-diethyl ethanol ammonium chloride) were found to be higher than some ionic liquids reported in the literature. We have measured the sound velocity of DES at 298 K. The trend of sound velocity in these three DESs is same as thermal conductivity. We have also reported viscosity of DES-III (prepared from thiourea and choline chloride) in the temperature range from 288 to 333 K.

Ionic conductivity of deep eutectic solvents: the role of orientational dynamics and glassy freezing.

We have performed a thorough examination of the reorientational relaxation dynamics and the ionic charge transport of three typical deep eutectic solvents, ethaline, glyceline and reline, by using broadband dielectric spectroscopy. Our experiments cover a broad temperature range from the low-viscosity liquid down to the deeply supercooled state, allowing us to investigate the significant influence of glassy freezing on the ionic charge transport in these systems. In addition, we provide evidence for a close coupling of the ionic conductivity in these materials to reorientational dipolar motions, which should be considered when searching for deep eutectic solvents optimized for electrochemical applications.