Aqueous Electrolyte Solutions Research Articles

MoS2 thin film decorated TiO2 nanotube arrays on flexible Ti foil for solar water splitting application

MoS2/TiO2 nanostructure provides a lot of advantages in photoelectrochemical (PEC) applications due to the absorption of the wide spectrum solar radiation, more catalytically active sites, proper band alignment, and better separation of photogenerated charge carriers. Here we report PEC water splitting studies of MoS2 thin film grown by chemical vapor deposition on TiO2 nanotubes fabricated on flexible thin Ti foil. Raman and x-ray diffraction analysis confirmed the polycrystalline growth of a few layers MoS2 on TiO2/Ti through their characteristic peaks. Field emission scanning electron microscopy revealed the nanotube surface morphology of TiO2 having a diameter in the range of 200–300 nm. The chemical and electronic composition of MoS2 and TiO2 were investigated by x-ray photoelectron spectroscopy. PEC measurements performed in 0.5 M Na2SO4 aqueous electrolyte solution under 100 mW cm−2 (AM 1.5G) simulated sunlight revealed 2-fold improved photocurrent density for MoS2/TiO2 heterostructure (∼135.7 μA cm−2) compared to that of bare TiO2 (∼70 μA cm−2). This is attributed to extended light absorption and more catalytically active surface area resulting from MoS2 functionalization of the TiO2 nanotubes, which results in better PEC activity. This study provides a new insight to explore the performance of thin metal foil-based photoelectrode in PEC applications that can be beneficial to develop roll-to-roll device fabrication to advance futuristic flexible electronics.

Molten salt-shielded synthesis of Ti3AlC2 as a precursor for large-scale preparation of Ti3C2Tx MXene binder-free film electrode supercapacitors.

MXenes are a group of two-dimensional materials that are promising for many applications, including as film electrode supercapacitors. When synthesizing such materials, special attention is paid to the conditions for obtaining the MAX phase, the chemical, morphological and structural features of which determine the functional properties of the final product. In this study, the Ti3AlC2 precursor is proposed to be obtained using a technologically simple and accessible method of synthesis in molten salt. This method allows reducing the reaction temperature and creating an antioxidant atmosphere. Ti3C2Tx MXene electrode films are produced by the easily scalable blade coating method without a binder. The synthesized materials were studied by X-ray phase analysis and scanning electron microscopy. Electrochemical testing of Ti3C2Tx film electrodes was carried out in a three-electrode configuration in aqueous solutions of 1M H2SO4, 6M KOH, 1M LiOH and 1M Na2SO4 electrolytes. The maximum specific capacity value for Ti3C2Tx MXene binder-free film electrode supercapacitors is obtained in 1M H2SO4 electrolyte (480 F g-1 at a scan rate of 1 mV s-1). The simple, low-cost and scalable production technology and promising electrochemical characteristics of the Ti3C2Tx MXene binder-free film electrode make it an excellent candidate for new-generation supercapacitors.

Properties of aqueous electrolyte solutions at carbon electrodes: effects of concentration and surface charge on solution structure, ion clustering and thermodynamics in the electric double layer.

Surfaces are able to control physical-chemical processes in multi-component solution systems and, as such, find application in a wide range of technological devices. Understanding the structure, dynamics and thermodynamics of non-ideal solutions at surfaces, however, is particularly challenging. Here, we use Constant Chemical Potential Molecular Dynamics (CμMD) simulations to gain insight into aqueous NaCl solutions in contact with graphite surfaces at high concentrations and under the effect of applied surface charges: conditions where mean-field theories describing interfaces cannot (typically) be reliably applied. We discover an asymmetric effect of surface charge on the electric double layer structure and resulting thermodynamic properties, which can be explained by considering the affinity of the surface for cations and anions and the cooperative adsorption of ions that occurs at higher concentrations. We characterise how the sign of the surface charge affects ion densities and water structure in the double layer and how the capacitance of the interface-a function of the electric potential drop across the double layer-is largely insensitive to the bulk solution concentration. Notably, we find that negatively charged graphite surfaces induce an increase in the size and concentration of extended liquid-like ion clusters confined to the double layer. Finally, we discuss how concentration and surface charge affect the activity coefficients of ions and water at the interface, demonstrating how electric fields in this region should be explicitly considered when characterising the thermodynamics of both solute and solvent at the solid/liquid interface.

Water molecules mute the dependence of the double-layer potential profile on ionic strength.

We present the results of molecular dynamics simulations of a nanoscale electrochemical cell. The simulations include an aqueous electrolyte solution with varying ionic strength (i.e., concentrations ranging from 0-4 M) between a pair of metallic electrodes held at constant potential difference. We analyze these simulations by computing the electrostatic potential profile of the electric double-layer region and find it to be nearly independent of ionic concentration, in stark contrast to the predictions of standard continuum-based theories. We attribute this lack of concentration dependence to the molecular influences of water molecules at the electrode-solution interface. These influences include the molecular manifestation of water's dielectric response, which tends to drown out the comparatively weak screening requirement of the ions. To support our analysis, we decompose water's interfacial response into three primary contributions: molecular layering, intrinsic (zero-field) orientational polarization, and the dipolar dielectric response.

Nanoshell Formation at the Electrically Charged Gas-Water Interface of Collapsing Microbubbles: Insights from Atomic Force Microscopy Imaging.

AFM imaging has revealed intriguing features when bulk nanobubbles were deposited on a positively charged substrate. Numerous spherical objects, each less than 20 nm in diameter, were observed on the substrate. These objects were adorned with noticeable, tiny protrusions, each measuring a few nanometers. These findings suggest the presence of solid shells contributing to the stability of the gas bodies. Furthermore, electrically charged microbubbles appear to play a critical role in the formation of these solid shells. The collapse of microbubbles in an electrolyte aqueous solution containing iron ions leads to a condensing ionic cloud, creating conditions necessary for solid nucleation at the interface. At the end of the collapsing process, concurrent multinucleation may result in the deposition of solid material on the interface, forming solid shells with specific structures on the surfaces. This study illuminates the phenomenon of electrically charged gas-water interfaces during microbubble collapse and highlights the generation of stabilized nanoshells in aqueous solutions without the need for chemical stabilizers.

Surfactants as Performance-Enhancing Additives in Supercapacitor Electrolyte Solutions—An Overview

Wetting the surface area of an electrode material as completely as possible is desirable to achieve optimum specific capacity of an electrode material. Keeping this surface area utilized even at high current densities and even when inside pores is required for high capacitance retention. The addition of surfactants at very small concentrations to aqueous supercapacitor electrolyte solutions has been suggested as a way to improve performance in terms of capacitance, capacitance retention at increased current density and stability. Effects are pronounced with carbon materials used in electrochemical double-layer capacitors; they are also observed with redox materials. The causes of the observed improvements and mode of operation of the added surfactants seem to need further investigation; they are inconclusive beyond the obvious statement of increased wetting. Reported examples and the current state of understanding are reviewed.

Electropolymerization of acrylic acid on steel for enhanced joining by plastic deformation

Resource-efficient electrochemical polymerization of acrylic acid (AA) on steel (DC04), from mildly acid Zn2+/ AA-containing aqueous solutions, is presented as an effective and sustainable thin film technology which allows for a precise control of the polymer thickness and morphology. The steel substrates were potentiostatically polarized to -1.4 V (vs. Ag/AgCl) or cycled between +0.1 to -1.4 V (vs. Ag/AgCl) in a degassed 2.0 M AA and 0.2 M ZnCl2-containing aqueous electrolyte solution at pH 6. FE-SEM, AFM, FT-IRRAS, XPS, and electrochemical measurements shed light on the structural and chemical features exhibited by the as-prepared polyacrylic acid (PAA) thin films. When PAA-modified DC04 plates are joined to Al EN AW-1050A H24 specimens by plastic deformation using cold pressure welding (CPW), tensile strength testing unveiled the macroscopic interfacial adhesion-promoting capabilities exhibited by PAA layers to the opposing aluminum oxide surfaces. Carboxylate moieties present in the PAA are shown to form stable chemical bonds with metal oxide surfaces and with amine-epoxy-based resins. Interestingly, higher maximum shear force values are obtained for the PAA films when Zn metallic deposits are not present in the organic layer, but, when these welded specimens are heated up to 200 °C in a N2 atmosphere, it occurred exactly the opposite: Zn particle-containing PAA films showed the highest maximum shear force values for the same deposition time.

Biomass-derived Co, N and P co-doped 3D porous carbon as an effective electrocatalyst for oxygen reduction reaction

Fuel cells are an important and promising energy system which has attracted lots of attention. The research on non precious metal catalysts is extremely important for the development of fuel cells. In this work, we fabricated metal organic hybrids (MOH) from chitosan, phytic acid, and CoCl2 through a simple chemical method, and further obtained the Co, N, and P co-doped 3D porous carbon material, with the Co atoms exhibiting good monodispersity on the surface. Due to the size effect brought by the single atom doping of Co and the influence of N and P doping on the microenvironment of the active center, the obtained Co-NPC-6 M exhibits excellent catalytic performance for ORR in the alkaline aqueous electrolyte solution.

Thin-Film Electrodes Based on Conjugated Polyelectrolytes for High-Performance Pseudocapacitance in Aqueous Media

Conjugated polyelectrolytes (CPEs) are an emerging class of materials that exhibits competitive pseudocapacitive performances in their hydrogel form due to their mixed electronic/ionic conductive nature. Interest in developing solid-state electrodes based on CPEs for practical applications is needed. However, the water-soluble nature of the CPEs hinders their thin-film stability in aqueous media. Herein, we report that the slow-dried drop-casted CPE-K thin films formed a solid-state electrode insoluble in aqueous electrolyte solutions when the salt concentration is higher than 0.1 M. XRD measurements revealed that slow-dried, drop-casted CPE-K film possesses a more ordered macromolecular structure when compared to its pre-deposited powder form. DLS measurements revealed that the extent of CPE-K aggregation increases as a function of salt concentration, which enhances the stability of the films in the electrolyte solutions. In addition, AFM imaging suggests well-ordered and uniform nanostructures. As a result, it is possible to use CPE-K thin-film as a pseudocapacitive electrodes capable to maintain 85% (71 F g-1 ) of its original capacitance (84 F g-1) at a specific current of 500 A g-1. In addition, CPE-K film electrodes exhibit good cycling stability where a capacitance retention of 93% after 100,000 cycles at a current density of 35 A g-1 was obtained. To our knowledge, such high charge/discharge rates and stabilities are greater than those reported for state-of-the-art CP in any form. Further electrochemical characterization revealed that surface-controlled pseudocapacitive behavior dominates the charge-storing mechanism of the CPE-K electrodes. In addition, our electrochemical analysis suggests that facile ionic diffusion attributed to the presence of an ionic lattice in the ordered structure of the CPE-K films is responsible for the unprecedented charging and cycling performances. These findings provide a new strategy to obtain solid-state electrodes based on CPEs without the need for binders or additives. Additional advantages such as water processability, low cost, and bio-compatibility may allow CPE-K to be a sustainable solution for the future of electrochemical energy storage.

Deconvoluting the Role of Electrolyte pH, Structural Sensitivity, and Electric Field Effects on the Electrochemical Hydrogenation of Phenol

Traditional thermochemical hydrogenation (TCH) methods that are used in the U.S. chemical and petroleum industries to produce value-added fuels are highly energy intensive. To achieve hydrogenation, they require high temperature and pressure, along with an external source of hydrogen that usually comes from steam methane reformation. Electrochemical hydrogenation (ECH) is an attractive alternative that replaces the thermal driving force with an applied electrical potential, allowing ECH to operate near ambient conditions. The participating protons come from the aqueous electrolyte solution rather than externally produced hydrogen. These features of ECH lower its energy demand compared to TCH and result in less greenhouse gas emissions. ECH is also promising for the processing of biomass feedstocks and could be powered directly by renewable energy, further minimizing the environmental impact.The addition of an aqueous electrolyte and electric field means that insights from TCH should not be directly translated to ECH systems, however, this is often the case in the literature. Fundamental studies on ECH of aromatic hydrocarbons (AHs) are necessary to address current limitations including: competition with the hydrogen evolution reaction (HER) resulting in lower faradaic efficiency, low rates compared to TCH, and little control over selectivity and degree of hydrogenation. For instance, the role of electrolyte pH on phenol ECH remains poorly understood. While some groups have reported negligible phenol turnover rates in electrolytes of pH 10 and above on Pt/C and Pd/C catalysts [1], Song et al. have shown that turnover rates and efficiency are highest on Rh/C at pH 10 [2]. Yet, the idea that low pH (3-5) is best has persisted and the source of the pH dependence remains unknown.In this work we use phenol as a simple representative AH for lignocellulosic bio-oil. We have shown with rotating disk electrode voltammetry that the presence of phenol in electrolytes of pH ~10 enhances HER rates on Pt, Pd, and Au catalysts. Considering that the pKa of phenol is also 10.0, we propose that interfacial phenol molecules channel protons to the catalyst surface by way of facile proton dissociation/reassociation, lowering the barrier for adsorbed H formation in alkaline electrolytes. While this may explain, in part, the low phenol turnover rates observed at higher pH, we further investigate why the opposite is observed on Rh/C catalysts. The role of atomic surface structure is also critical to the adsorption geometry and coverage of AHs. We use well-defined, low-index Pt single crystals to identify the true structural sensitivity for the ECH of AHs. We show with select stepped single crystal surfaces that there is a synergetic role between terrace width/step density that defines activity, balancing coverage of AH molecules, formation of surface adsorbed H, and transfer of that H to AH reactants. We use a low-volume, membrane-separated flow cell for chrono-amperometry followed by product analysis to correlate pH, structural sensitivity, and applied potential to phenol ECH rates and faradaic efficiency. With an understanding of the role of atomic surface structure and the true source of pH dependence, we propose strategies for enhancing phenol turnover rates at lower overpotentials, improving faradaic efficiency, and controlling selectivity.

Soft X-Ray Operando Characterization of Electrochemical Interfaces

HIPPIE is a high-flux, high-resolution soft x-ray beamline at MAX IV Laboratory (Sweden) with a new dedicated experimental setup for operando studies of electrochemical interfaces.[1] Such experiments utilize the dip-and-pull method to form a thin liquid meniscus on the surface of the working electrode in a three-electrode cell with a liquid electrolyte solution. Both the liquid film itself and the electrode-electrolyte interface can then be probed using X-ray photoelectron spectroscopy (PES) whilst maintaining full electrochemical control. The technique can be used to probe oxidation state changes, chemical shifts, electronic structure and electrochemical potentials in-situ.In this talk we will discuss status of spectroelectrochemical PES using soft X-rays, discussing the merits of the various different approaches to cell design. We will present three case studies on the topics of molecular redox reactions, battery interfaces and metal corrosion, all of which can be studied using dip-and-pull.[2-4] We will primarily aim to provide an introduction to the dip-and-pull method for those interested in this genre of advanced operando characterization. We will additionally outline the experimental realities and challenges that any potential new user of the dip-and-pull method should be aware of before applying for beamtime to conduct an experiment.The three case studies were all measured at HIPPIE, where the beamline operates in the 250-2000 eV range, providing access to the L absorption edges of many transition metals and the K edges of light elements. The dip-and-pull PES experiments are realized with an ambient-pressure hemispherical electron analyzer allowing measurements in vapor pressures up to 25 mbar. Electrochemical cells can therefore use aqueous electrolyte solutions as well as some organic solvents, including many of those common in batteries. An argon/nitrogen atmosphere glove box can be attached to the measurement chamber such that air sensitive materials can be studied. Typically foils or thin films are used for the working electrode. This apparatus therefore provides one of the most flexible platforms for electrochemical studies using soft-X-ray spectroscopy.

Anode Reaction Control for a Single-Compartment Electrochemical CO2 Reduction Reactor with a Surface-Activated Diamond Cathode.

The electrochemical reaction of carbon dioxide (CO2 ) in aqueous electrolyte solutions is attracting increasing attention for sustainable chemical production. Boron-doped diamond (BDD) electrodes have been previously shown to be very effective for the stable electrochemical production of formic acid from CO2 . Typically, the electrochemical production of formic acid by CO2 reduction (CO2 R) reaction is performed with a dual-compartment flow reactor equipped with a membrane separator. The problems caused by the membrane separator, such as scaling-up, complicated operational control and materials costs can be solved using a membrane free single-compartment reactor. Here we demonstrate anode reaction control for a single-compartment CO2 R flow reactor using a surface-activated BDD cathode and achieve a Faradaic efficiency for formic acid production of over 70 %.

Study of the short-range order of Co-W alloys electrodeposited using pulse current

Pulsed electrodeposition modes allowed to obtain amorphous Co-W alloys. Using X-ray phase and spectral analysis methods, it was established that the deposition modes and the concentration of the amorphizing component (sodium tungstate salts) in an aqueous electrolyte solution affect the amorphization of alloys. The short-range atomic order was studied by X-ray diffraction analysis and the sizes of the regions of ordered arrangement of atoms were determined in X-ray amorphous Co-W alloys obtained by pulsed electrodeposition. The radial distribution function of atoms was analysed. The assumption is made that cobalt and tungsten atoms combine into configurations that are irregular polyhedrons.

Modeling gypsum (calcium sulfate dihydrate) solubility in aqueous electrolyte solutions using extreme learning machine

Due to various operational conditions, experimental determination of gypsum solubility in water-based systems comprising multiple ionic compounds is often impractical or costly. In this regard, computer-based intelligent approaches can provide highly effective and economical alternatives. In this study, after providing a database with 2288 experimental data-points gathered from 31 various literatures, four advanced artificial intelligence techniques were developed: Adaptive Boosting-Support Vector Regression (AdaBoost-SVR), Extreme Learning Machine (ELM), Gradient Boosting-Support Vector Regression (GB-SVR), and Multivariate Adaptive Regression Splines (MARS). The aim of these techniques was to predict the gypsum solubility in aqueous electrolyte solutions as a function of the solutions' temperature and 22 distinct salts' Molal concentrations. After performing various statistical and graphical analyses, it was observed that the ELM model has a more accurate prediction capability for gypsum solubility in aqueous electrolyte solutions compared to the other three models. For this model, the highest Coefficient of Determination (R2 = 0.9926) and the lowest Root Mean Square Error (RMSE = 0.00373) were obtained. Furthermore, after conducting a sensitivity analysis to calculate the relevancy factors of the ELM model's input and output variables, the variation trend of gypsum solubility was evaluated. According to the multiple evaluations, the ELM model predictions reasonably agreed with the experimental data on gypsum solubility in the chosen solutions and temperature ranges. The ELM model can be implemented in numerical modeling frameworks for improving the treatment and reclamation operations of saline water sources, optimizing the oil and gas recovery and production processes, and controlling the complicated geotechnical issues.

Anomalous Concentration Dependence of Viscosity: Hidden Role of Cross-Correlations in Aqueous Electrolyte Solutions.

The viscosity of aqueous electrolyte solutions exhibits well-known composition-dependent anomalies that show certain definitive trends and universal features. The viscosity of LiCl and NaCl solutions increases with concentration in a monotonic fashion, while solutions of KCl, RbCl, and CsCl exhibit a more complex behavior. Here, the viscosity first decreases and then increases with increasing concentration, with a rather broad minimum at intermediate concentrations (ca. 1-3 m). To unearth the origin of such puzzling behavior, we carried out detailed molecular-level analyses by interrogating the exact Green-Kubo expression of viscosity in terms of the stress-stress time correlation function (SS-TCF). The total SS-TCF can be decomposed into a collection of three self- and three cross-SS-TCFs arising from the three constituent components (water, cations, and anions). Mode coupling theory (MCT) analysis for the friction on ions and the viscosity of the solution suggests the possible importance of two-particle static and time-dependent cross-correlations between water and the ions. We calculate the viscosity and other dynamical properties for all five electrolyte (LiCl, NaCl, KCl, RbCl, and CsCl) solutions over a range of concentrations, using two models of water (SPC/E and TIP4P/2005). The total viscosity derives non-negligible contributions from all of the terms. The cross-correlations are found to be surprisingly large and seen to play a hidden role in the concentration dependence. However, the importance of cross-correlations is often not discussed. Our study leads to a theoretical understanding of the microscopic origin of the observed anomalies in the composition dependence of viscosity across all five electrolytes.

Modeling of dilution enthalpies within implicit-solvent models for electrolytes

This work deals with the calculation of dilution enthalpies for strong aqueous electrolyte solutions when their thermodynamic properties are described within implicit-solvent models. The solution is modeled as a collection of charged hard spheres in a continuum solvent. A new general expression is obtained that accounts for the variation of the solution permittivity, of the size of the ions, and of the specific volume of the solution, with temperature and concentration. This expression is used to compute the enthalpies of LiCl aqueous solutions at temperatures in the range of 25∘C to 100∘C for concentrations up to 6 mol kg−1. The mean spherical approximation (MSA) model with implicit continuum solvent is employed to describe the thermodynamic properties of these solutions.

Structure of aqueous alkali metal halide electrolyte solutions from molecular simulations of phase-transferable polarizable models

The structure of aqueous solutions of alkali metal halides is studied under ambient thermodynamic conditions and concentrations from infinite dilution to supersaturation using molecular dynamics simulations of phase-transferable polarizable models. The results of the solution densities, radial distribution functions, 3D spatial distribution functions, the properties of hydrogen and other noncovalent bonds in solutions, hydration numbers, coordination numbers, numbers of contact cation-anion pairs, and other statistics of the number of ions hydrated simultaneously by a shared water molecule are systematically presented. In particular, the results show and quantify how the strengths of the hydration bonds of different ions vary and how the hydration numbers decrease with increasing concentration in parallel with an increase in the number of contact cation-anion pairs. In most cases, they completely compensate for the loss of water-ion bonds by an increase in cation-anion bonds. An exception are solutions based on the Li+ cation, which retain a solid hydration shell even at high concentrations. This behavior is conceptualized on the basis of three imaginary driving forces: the first dominating at low concentrations and causing full hydration of the ions, the second representing a lack of water necessary for full hydration of the ions and increasing with increasing concentration, and the third attracting counterions to the water-unoccupied sites of the hydration shells and also increasing with concentration. This concept can be used not only to understand the structural behavior of homogeneous electrolytes in thermodynamic equilibrium but also to study phenomena that involve preferential adsorption of ions on electrodes, in nanochannels, or porous materials. The data obtained for the number and strength of hydration bonds and ion pairs can also be used in further studies to elucidate the diffusion behavior, viscosity, and conductivity of aqueous electrolyte solutions.

Further extension of the Madrid-2019 force field: Parametrization of nitrate (NO3−) and ammonium (NH4+) ions

The importance of nitrate and ammonium salts both in the environment and in biological processes cannot be questioned. In this work, using the TIP4P/2005 water model, aqueous solutions of nitrate and ammonium electrolytes are parametrized using scaled charges while keeping a rigid structure and nonpolarizable charge distributions. The models are optimized by systematically testing a set of properties for twelve electrolytes—eight nitrate and four ammonium salts—thus, enlarging the number of potential chemical species encompassed within the Madrid-2019 force field for ions. The capacity of the force field for predicting densities, ion–ion and ion–solvent structures, and transport properties of the solutions comprised by the trial batch of salts was tested and discussed. Both the dependence of the densities with the salt concentration and the solution structure were nicely reproduced by the models in the whole concentration range without any trace of precipitating events and with improved accuracy in comparison with recently reported models, while the agreement of the simulated transport properties with experimental data ranges from good to reasonable, depending on the ion/counterion pair. These scaled charge models might be considered as force fields embodying a reasonable compromise between exactness and general applicability and also as an important step in the development of accurate models for polyatomic ions.

On the Elusive Links between Solution Microstructure, Dynamics, and Solvation Thermodynamics: Demystifying the Path through a Bridge over Troubled Conjectures and Misinterpretations.

We build a fundamentally based bridge between the solute-induced microstructural perturbation of the species environment and the dynamic as well as thermodynamic responses of the fluid system, regardless of the state conditions, composition, nature of the solvent, and either the magnitude or the type of solute-solvent intermolecular-interaction asymmetries. For that purpose, we advance a fluctuation-based solvation formalism of fluid mixtures to provide meaningful descriptors of solvation phenomena, the microstructural signatures of their solute-solvent intermolecular interaction asymmetry, and the thermodynamic manifestations linked to the solution nonideality. The rigorous foundations afford us to address some crucial issues frequently invoked in the literature including the microstructural perturbation domain, its proper identification and molecular-based meaning toward the interpretation of the solvation process, and the potential impact of the local differential behavior between anions and cations on the actual salt-induced perturbation of the solvent microstructure. Indeed, we link the precisely characterized species solvation behavior to fundamental thermodynamic residual-property relations, and the dynamics associated with either the viscous flow or diffusive behavior of the solvent, to finally illustrate their outcome with experimental data of aqueous electrolyte solutions from the available literature. Ultimately, this effort provides a highly desirable unambiguous identification of the cause-effect connections between the microstructurally perturbed domains and the experimentally measured macroscopic solvation properties, including their effect on the dynamics of the solvent environment. More importantly, it lends a well-established solvation framework to bridge rigorously the microstructural details of the mixture, its dynamics, and its solvation thermodynamics to enhance our understanding of well-defined ranked Hofmeister series, i.e., by avoiding ad hoc conjectures and unsupported microscopic interpretations of solvation phenomena.

Effect of ionic polarization on the static permittivity of electrolyte aqueous solutions

AbstractWe developed a theoretical model with two separate components for the description of the static permittivity of aqueous electrolytes versus concentration and temperature. The first component is due to the water molecular polarization, whereas the second component is governed by the ionic polarization. We found that the permittivity part due to the ionic polarization effect is comparable to that come from the water molecule polarization for aqueous electrolytes at ambient temperatures. The microdynamic mechanism of the phenomenon, which the static permittivity of sodium chloride aqueous solution with concentration of 2.8 mol/L holds constant with the change of temperature, is clarified. The equilibrium compensation between the decrement of the permittivity part due to the water molecular polarization and the increase of that originated from the ionic polarization as increasing temperature is responsible for this phenomenon. The dipole moment reduction of water molecules as rising temperature is also confirmed by the model.