Aqueous Solutions Of KCl Research Articles

Novel High‐Pressure Potassium Chloride Monohydrate and Its Implications for Water‐Rich Planetary Bodies

AbstractSaline water is a common fluid on the Earth‘s surface and in ice planets. Potassium chloride (KCl) is a common salt and is expected to be a ubiquitous solute in salt water in the Universe; however, few studies investigated the behavior of KCl‐H2O system at high pressures and temperatures. In this study, powder and single‐crystal X‐ray diffraction (SC‐XRD), Raman and Brillouin scattering combined with diamond anvil cells were used to investigate the phase relation in the KCl‐H2O system for different KCl concentrations at 0–4 GPa and 298–405 K. The results of powder X‐ray diffraction and Raman scattering demonstrate that a novel KCl hydrate is formed when KCl aqueous solutions transform to solid ice‐VI and ice‐VII at high pressure. Simultaneously, the single‐crystal of KCl hydrate is synthesized from a supersaturated KCl solution at 298 K and 1.8 GPa. The structure is solved by SC‐XRD, indicating a KCl monohydrate with the P21/n space group is formed. We have verified the phase stability of KCl monohydrate by using Raman spectroscopy and density functional theory. Our results indicate that KCl monohydrate is a stable phase under pressure and temperature conditions between 1.6 and 2.4 GPa and 298–359 K. By considering the thermal profile and composition of icy moons, we hypothesize that the formation and decomposition of KCl monohydrate might induce mantle convection in these moons.

Experimental investigation of hydrogen production performance of various salts with a chlor-alkali method

In this experimental study, the hydrogen production performance of aqueous solutions of NaCl, KCl, and CaCl2 salts via an electrochemical method through a chlor-alkali reactor is investigated. For this purpose, a laboratory-scale reactor consisting of anode and cathode compartments is built. The compartments of the reactor are separated by a cation exchange membrane which prevents the mixing of anolyte and catholyte solutions and also allows positive ions (Na+, K+, and Ca2+) and some water to pass through. Electrodes made of 316 stainless steel are used in the compartments of the reactor due to their economic efficiency. While the anode compartment of the reactor is fed with the aqueous solutions of NaCl, KCl, and CaCl2 salts one by one, the cathode compartment is fed with one of the diluted aqueous solutions of NaOH, KOH, and Ca(OH)2 bases depending on the type of salt used. Experiments are carried out at three different cell voltages (3, 4, and 5 V) and three different cell temperatures (30, 50, and 70 °C), and five different electrolyte flows (0.4, 0.6, 0.8, 1.0, and 1.2 g/s). Since the reactor dimensions are very small, experiments are also carried out with small changes in the electrolyte mass flow rate. It is observed that active chlorine gas causes serious contamination in the anode compartment and erosion on the electrode in this compartment. Therefore, the expected chlorine gas output from the anode compartment of the reactor is not observed. Luckily, a significant amount of hydrogen gas output is observed from the cathode compartment of the reactor. The minimum hydrogen production rate is 37.23 mL/h when the aqueous solution of CaCl2 is used with a mass flow rate of 0.4 g/s and cell voltage of 3 V at the cell temperature of 30 °C. The maximum hydrogen production rate is 437.72 mL/h when KCl salt solution is used with a mass flow rate of 1.2 g/s and cell voltage of 5 V at the cell temperature of 70 °C.

Effect of Ion Size on Pressure-Induced Infiltration of a Zeolite-Based Nanofluidic System.

A nanofluidic system consists of a nano-porous medium and functional liquid, which demonstrates a higher energy absorption density compared to conventional systems for energy absorption. Alterations in the composition of the functional liquid can significantly impact the properties of a nanofluidic system. In this paper, the widely used zeolite ZSM-5 was chosen as the porous medium to establish a nanofluidic system. Three distinct electrolyte solutions, namely KCl aqueous solutions, NaCl aqueous solutions and MgCl2 aqueous solutions were employed as functional liquids while pure water served as the reference condition for configuring four kinds of nanofluidic systems. Pressure-induced percolation experiments were performed on the four zeolite-based systems. The difference in the infiltration process between the electrolyte solution systems and the deionized water system has been ascertained. The effect of the ion size on the infiltration and defiltration process has been determined. The results show that the introduction of ions induces a hydration effect, resulting in a higher critical infiltration pressure of the electrolyte solution system compared to an aqueous solution system. The magnitude of cation charge directly correlates with the strength of the hydration effect and the corresponding increase in critical infiltration pressure. Upon entering the nanochannel, the liquid infiltrates primarily in the form of ions rather than a cation hydration form. The larger the ion size, the shallower the penetration depth after entering the nanopore channel and the larger the corresponding relative outflow rate. The present work will provide valuable theoretical complementary and experimental data support for nanofluidic system applications.

Aqueous electrolytes at the charged graphene Surface: Electrode-Electrolyte coupling

Electrochemical energy sources support the growth in performance and portability of consumer electronics. Further sustainable development assumes an atomistically precise understanding of how the electrolyte binds to the electrode in the charged and uncharged states of the supercapacitors and Li-ion batteries. The present work investigates electrode–electrolyte interactions at the cathode using ab initio molecular dynamics simulations and representative energy-minimized ion-molecular configurations. Graphene is chosen as a material for the cathode, whereas the aqueous solutions of LiCl, NaCl, and KCl are model electrolytes. The study reveals a few fundamentally new physical insights regarding the performance of a supercapacitor. First, the graphene-ions coordination regularities are qualitatively different at charged and uncharged cathode. It is, therefore, essential to account for the effect of charging when studying the physical chemistry of supercapacitors. Second, the energy capacity offered by the aqueous Na-ion electrolyte is worse than those of the aqueous Li-ion and K-ion electrolytes. This observation is a result of an interplay between the dehydration energies and adsorption energies at the cathode energies. Third, the role of cation-solvent binding represents a cornerstone contribution to the capacity of an energy storage device in addition to the well-recognized cation-cathode binding thermodynamics. The reported results are fundamentally important to thoughtfully designing electrolyte compositions and electrode materials for supercapacitors and alkali-ion batteries.

Computation of Electrical Conductivities of Aqueous Electrolyte Solutions: Two Surfaces, One Property.

In this work, we computed electrical conductivities under ambient conditions of aqueous NaCl and KCl solutions by using the Einstein-Helfand equation. Common force fields (charge q = ±1 e) do not reproduce the experimental values of electrical conductivities, viscosities, and diffusion coefficients. Recently, we proposed the idea of using different charges to describe the potential energy surface (PES) and the dipole moment surface (DMS). In this work, we implement this concept. The equilibrium trajectories required to evaluate electrical conductivities (within linear response theory) were obtained by using scaled charges (with the value q = ±0.75 e) to describe the PES. The potential parameters were those of the Madrid-Transport force field, which accurately describe viscosities and diffusion coefficients of these ionic solutions. However, integer charges were used to compute the conductivities (thus describing the DMS). The basic idea is that although the scaled charge describes the ion-water interaction better, the integer charge reflects the value of the charge that is transported due to the electric field. The agreement obtained with experiments is excellent, as for the first time electrical conductivities (and the other transport properties) of NaCl and KCl electrolyte solutions are described with high accuracy for the whole concentration range up to their solubility limit. Finally, we propose an easy way to obtain a rough estimate of the actual electrical conductivity of the potential model under consideration using the approximate Nernst-Einstein equation, which neglects correlations between different ions.

Salinity Gradient-Induced Power Generation in Nanochannels: The Role of pH-Sensitive Polyelectrolyte Layers.

By varying the pH values (pHR) and types of salt solution, we investigate the salinity gradient-induced electrical and mechanical flow energies inside a reservoir-connected charged nanochannel with a grafted pH-sensitive polyelectrolyte layer (PEL) on the inner surfaces. The aqueous solutions of KCl, LiCl, BaCl2, BeCl2, AlCl3, and Co(en)3Cl3 salts are used as the working fluid in the current investigation. We examine the associated ionic transport and flow field, aiming to understand the underlying physics behind the generation of electrical and hydraulic energy through alterations in pHR and types of salt solution. Our results reveal that the PEL space charge density decreases with increasing pHR at lower values, while it remains almost insensitive to higher pHR values. The electrical conductance and maximum pore power of the Co(en)3Cl3 solution are significantly higher compared to salts with monovalent and divalent cations. Furthermore, the magnitude of these two parameters decreases with lower pHR and becomes insensitive to higher pHR values. The results illustrate that the maximum electrical energy conversion efficiency enhances with pHR, reaching its highest level for the Co(en)3Cl3 solution. We expect that the findings of the current work will have a significant bearing on the design and development of a state-of-the-art salinity gradient-based energy convertor as a potential candidate for renewable energy sources.

Analytical treatment of ion-exchange permselectivity and transport number measurements for high accuracy

We analyse electromotive force measurements of concentration cells using non-equilibrium thermodynamics, and determine the transference coefficients of ion-exchange membranes in aqueous KCl solutions. By taking advantage of the analytical expression for the permselectivity, we extract transport coefficients with high accuracy. The transport number of K+ and the transference coefficient of water in the Selemion CMVN cation-exchange membrane are found to be 100tK+=99.59±0.56 and tw=3.69±0.40 respectively, while for the Selemion AMVN anion-exchange membrane they are 100tCl−=100.21±0.37 and tw=−3.75±0.27. These results suggest that the membranes are perfectly selective to the target ion, and that each ion carries 3-4 water molecules through the membrane, which reduces the membrane permselectivity. In these concentration cells, the electrical potential contribution of the membrane alone was more easily isolated with bare Ag/AgCl electrodes without reference solutions and liquid junction plugs. Additionally, we find a large contribution to the measured concentration cell voltage from concentration gradients across the porous plug of the reference electrode, which cannot be explained by Henderson’s equation alone. For most of the concentration range, the transport number of the porous plug is determined to be 100tK+=49.43±0.78 with negligible water transport, similar to literature values for bulk electrolyte. In dilute electrolyte solutions with concentrations below 0.1 mol kg−1, the plug shows anomalous behaviour consistent with an increase in K+ selectivity and water co-transport.

Determination of the error of measurements obtained by the optical micrometry

We present the results of measuring the volume of polyvinyl alcohol polymer granules crosslinked with epichlorohydrin in water and in aqueous solutions of KCl, MgCl2 and their mixtures, obtained by optical micrometry, and consider the main sources of errors in the measurement errors. The purpose of this study is to analyze and evaluate the effect of the main sources of errors on the accuracy of determining the relative volumes of granules, as well as to search for techniques that can minimize the resulting measurement errors. The diameters of the granules were determined using specialized software implementing machine vision algorithms from the images obtained by optical microscopy. Their volumes were calculated using the formula for the volume of the ellipsoid of revolution. The maximum accuracy of volume determination is known to be achieved when the measured granule has a sphere shape. It is shown that deviation from this shape, for example, in case of an ellipsoid, gives errors in determining the third axis of the ellipsoid, invisible in the image, which creates an error in determining the relative volume of the granule. The instrument error is determined and a statistical estimate of the error attributed to the non-sphericity of the granules is given. It is shown that a typical instrument error in determining the relative volumes of granules is 0.4%. The non-sphericity of the measured granules increases the measurement error up to 3.5%. The error for a single granule can be reduced to 2.3% by combination of methodological techniques and statistical processing of the results, whereas and for an ensemble of at least 5 granules — up to 1.5%. The reproducibility of the properties of polymer granules in cyclic measurements was studied. It is shown that the degree of swelling the granules is reproduced with an error of 1%, which allows the sensor to be used repeatedly. The results obtained can be used in experiments and data processing for analytical applications.

Fast Ion Transfer Associated with Dehydration and Modulation of Hydration Structure in Electric Double-Layer Capacitors Using Molecular Dynamics Simulations and Experiments

Carbon materials, such as graphite and activated carbon, have been widely used as electrodes in batteries and electric double-layer capacitors (EDLCs). Graphene, which has an extremely thin sheet-like structure, is considered as a fundamental carbon material. However, it was less investigated as an electrode material than graphite and activated carbons. This is because graphene is a relatively new material and is difficult to handle. However, using graphene electrodes can enhance the performance of nanodevices. Here, the performance of EDLCs based on single-layer and bilayer graphene electrodes in LiCl, NaCl, and KCl aqueous electrolyte solutions was evaluated using cyclic voltammetry, and the charging mechanism was evaluated using molecular dynamics simulations. KCl aqueous solution provided the highest capacitance compared to LiCl and NaCl aqueous solutions in the case of single-layer graphene electrodes. In contrast, the dependence of the capacitance on the ion species was hardly observed in the case of bilayer graphene. This indicates that Li and Na ions also contributed to the capacitances. The high EDLC performance can be attributed to the fast ion transfer promoted by the dehydration and modification of the second hydration shell on the bilayer graphene because of the relatively strong interaction of ions with the bilayer graphene.

Tough and stretchable all-κ-carrageenan hydrogel based on the cooperative effects between chain conformation transition and stepwise mechanical training

The traditional κ-carrageenan (κCG)-based hydrogel obtained from hot water can rupture easily under mechanical loading. To address this vulnerability, here we presented a robust all-κCG hydrogel without employing the second synthetic network. By simply regulating the polymer chains from random coil to stiff chain conformation in NaOH/urea solvent system via the freeze-thawing process, the as-prepared hydrogel with homogeneous structure can display an enhanced stretchability from 42.1 to 156 %, while maintaining the similar fracture stress. Moreover, upon the stepwise mechanical training and subsequent incubation in KCl aqueous solution, more helical segments of κCG were aligned and involved into the association domains, thus leading to the increment in both the crystallinity and anisotropy. Consequently, a fast self-strengthening behavior occurred, and a more stretchable (fracture strain up to 396 %), strong (stress ∼ 0.55 MPa) and tough (∼1.52 MJ m−3) κCG hydrogel was obtained. In comparison to the traditional one, the fracture strain and toughness are increased by 8.5 and 11.5 times, respectively. In addition, this κCG hydrogel can demonstrate good recovery and shape-memory behaviors under medium deformation. Hence, this tough all-κCG hydrogel is expected to be tailored into the biomaterials as the wearable device, artificial tendon, and cartilage in the future.

Effect of aqueous solutions of KCl, MgCl2, Dextrose and Urea on solvation behavior of aqueous myo-Inositol

Owing to the indispensable role of myo-Inositol (MI), a cyclic polyol, in biological, pharmaceutical and food industries, in this investigation, we herewith report the systematic data of densities (ρ) and speed of sound (u) of MI in water, aqueous electrolytic (0.06 mol∙kg−1 KCl/MgCl2) and non-electrolytic (0.06 mol∙kg−1 Dextrose/Urea) solutions at seven different temperatures T/K (=288.15–318.15) and ambient pressure over the dilute concentration range of (0.03–0.2) mol∙kg−1. The experimental data of density (ρ) and speed of sound (u) were further processed to obtain respective derived parameters, such as apparent molar volume of solute Vϕ, isentropic compressibility of solution κs and apparent molar isentropic compression of the solute Ks,ϕ. The limiting values of apparent molar volume Vϕ0, apparent molar isentropic compression Ksϕ0 and apparent molar expansibility Eϕ0 of solute have been computed. Further, the coefficient of thermal expansion α∗, second order derivative of limiting apparent molal volume ∂2Vϕ0/∂T2, hydration number (nH) and transfer properties (ΔtrVϕ0andΔtrKs,ϕ0) of MI have also been obtained. An attempt has been made to analyse the molecular interactions through the coulomb attenuated hybrid exchange–correlation density functional theory (DFT) by gaussian tool. The effect of temperature and the studied electrolytic and non-electrolytic moieties (i.e., KCl, MgCl2, Dextrose and Urea) have been discussed in the light of prevailing interactions between solute-co-solute and solvent molecules on the basis of co-sphere overlap model.

Identification of Ion Pairs in Aqueous NaCl and KCl Solutions in Combination with Raman Spectroscopy, Molecular Dynamics, and Quantum Chemical Calculations

This work summarizes a theoretical analysis of the perturbation on Raman spectra in aqueous NaCl and KCl solutions with the aim to detect ion pairs. The experimental Raman spectra, both polarized and depolarized, are perturbed by these ions to a comparable extent or somewhat less by KCl than NaCl. This result appears to be contrary to the molecular dynamics (MD) simulation showing that the isolated and separated ions of KCl should have a larger perturbation than NaCl, as the solvation shell of K+ is larger than that of Na+. The apparent discrepancy signifies the ion pair formation which is more substantial for KCl than NaCl. The MD simulations and quantum chemical calculations revealed that KCl forms ion pairs more than NaCl and that the ion pair formation reduces the perturbation on the Raman spectra more for KCl. The present analysis shows that the perturbed Raman spectra provide a useful sign to evaluate the ion pair formation in aqueous solutions.

Amorphous aluminosilicates as efficient ion exchangers for ammonium cation removal from aqueous solutions

The efficient removal of ammonium cation, one of the main causes of the eutrophication of water sources, has been achieved by using amorphous aluminosilicates as low-cost ion exchangers. The materials with a Si/Al ratio that varied from 1 to 5 were prepared by the coprecipitation method just by mixing an acidic aluminium sulphate solution with a basic sodium silicate solution, and the products were characterized by XRD, SEM and 27Al MAS NMR spectroscopy. All the amorphous solids presented a higher cation exchange capacity (CEC) than a synthetic mordenite (Si/Al = 9.5) and a natural zeolite (Si/Al = 4.6). The ammonium uptake was investigated as a function of contact time and initial ammonium concentration; additionally, the presence of Na+ and K+ as coexisting cations in the solutions was also evaluated. Langmuir and Freundlich models were applied to describe the data obtained in the ammonium exchange isotherms. The amorphous aluminosilicate with Si/Al = 3 was regenerated with a KCl aqueous solution and was reused 5 times keeping a stable removal efficiency. The reusability of the amorphous aluminosilicate combined with the superior cation exchange capacity manifests the promising use of this type of materials as ion exchangers to remove ammonium cations from wastewater.

Electrolytic conductivity measurements for ten ionic liquids

Electrolytic conductivity measurements for a total of ten ionic liquids (ILs) (four N-alkyl-N-methyl pyrrolidinium cations [Cnmpyr] and six 1-(methyl)benzyl-3-alkyl imidazolium cations ([Bnmim] or [MeBnCnmim]), all paired with bistriflimide [Tf2N] anions) are reported at p = 0.1 MPa over T = 293.15 – 323.15 K. All samples were thoroughly dried under vacuum and their water content before and after measurements was determined by Karl Fischer titration. For the conductivity measurements, an impedance bridge technique was used in conjunction with a sealed cell equipped with platinum black electrodes. The cell constant (Kcell = 101 m − 1) was determined with standard aqueous KCl solutions before and after measurements. The results show that electrolytic conductivity increases with increasing temperature in both families of ILs, while conductivity decreases as the length of the IL side chain increases, which is associated with increase in IL viscosity. Conductivities of the pyrrolidinium ILs were consistent with other data for these compounds already reported in the literature. The conductivities of the 1-(methyl)benzyl-3-alkyl imidazolium ILs are reduced by ∼70-90% compared to the analogous 1-alkyl-3-methylimidazolium ILs

A new experimental approach to understanding microscopic details of the electrode/electrolyte interface

The article contributes to understanding the microscopic details of the electrochemical interphase and the electron transfer mechanism in a real experiment. The dynamic responses of the electrical phase interface were monitored via cyclic voltammetry of [Fe(CN)6]3-/4− on a pencil graphite electrode in an aqueous KCl solution, and the CV recordings were evaluated using elimination linear scan voltammetry (EVLS). The voltammetric data processing EVLS software, derived primarily for the reversible system, is capable of describing and distinguishing the diffusion, capacitance, and kinetic contributions of these current components. Based on the EVLS functions which eliminate the diffusion and charging current components or the diffusion and kinetic current components, we performed a detailed analysis of the state where the electronics meet the ionics. An emphasis was placed on the relationship between the dynamic response of the electric double layer and (a) the material of the graphite electrode, (b) the concentration of the [Fe(CN)6]3-/4−, (c) the concentration of the KCl, and (d) the presence or absence of oxygen in the solution. Our new approach to evaluating voltammetric data is characterized by experiments that promote understanding the electrochemical processes, influenced especially by changes in the electrical double layer. The results open a perspective of further research to facilitate a rational clarification and optimization of electrode processes.

Fine analysis of the component effect on the microstructure of LiCl solution

Lithium resources are abundant in Chinese salt lakes, but the high Mg/Li ratio in such aqueous natural sources has brought difficulties to the separation and purification of lithium. Crystallization processes are highly affected by the solution microstructure, which, in turn, depends on its composition. Synchrotron X-ray scattering, Raman spectroscopy, and molecular dynamics simulation methods were used to study the microstructure of aqueous LiCl solutions with different concentrations. In the reduced structure function, F(Q), the double peak around the scattering vector Q = 2.5 Å−1 becomes a single peak, which indicates the addition of LiCl changes the tetrahedral hydrogen bond structure in the aqueous solution. The deconvolution fitting of the Raman spectra show that the DDAA-type (double donor-double acceptor) hydrogen bonds tend to be transformed into DA-type (single donor–single acceptor) hydrogen bonds, confirming that the addition of LiCl breaks the tetrahedral hydrogen bond structure. This hydrogen-bond transformation was confirmed by pair distribution function analysis from molecular dynamics simulations of aqueous KCl solutions. In addition, considering the large number of magnesium ions coexisting with LiCl in the Salt Lake, the microstructure of mixed LiCl-MgCl2 solution was also studied. According to the X-ray scattering results, the peak in the reduced pair distribution function G(r) near r = 3.25 Å shifted from 3.25 Å to 3.10 Å with increased Mg/Li ratio. This change is likely to result from the Cl-O and OO interactions in the mixed aqueous solution. The deconvolution fitting results of Raman spectra show that the DDAA type hydrogen bond increases with the Mg/Li ratio, while the DA + DDA type hydrogen bond decreases. The molecular dynamics results showed that chlorine ions have a higher tendency to form contact ion pairs with Mg2+ than Li+. We propose this to be one of the processes retarding the separation of pure LiCl crystal from mixed LiCl-MgCl2 systems.

Energy conversion in Textus Bioactiv Ag membrane dressings using Peusner's network thermodynamic descriptions.

The Textus Bioactiv Ag membrane is an active dressing for the treatment of chronic wounds such as venous stasis ulcers and burns. Determination of the transport and internal energy conversion properties of the Textus Bioactiv Ag membrane using the Kedem-Katchalsky-Peusner model. This model introduces the coefficients Lij necessary to calculate the degree of coupling (lij, QL), energy conversion efficiency (eij), dissipated energy (S-energy), free energy (F-energy), and internal energy (U-energy). The research material was the Textus Bioactiv Ag membrane that is used as an active dressing in the treatment of difficult-to-heal wounds, and KCl aqueous solutions. The research methods employed Peusner's formalism of network thermodynamics and Kedem and Katchalsky's thermodynamics of membrane processes. To calculate the Lij coefficients, we used hydraulic conductivity (Lp), diffusion conductivity (ů) and reflection (ó) coefficients to perform experimental measurements in different conditions. The Lp coefficient for the Textus Bioactiv Ag membrane is nonlinearly dependent on the average concentrations of the solutions. In turn, the ů and ó coefficients are nonlinearly dependent on the differences in osmotic pressures (Äđ). An increase in the Äđ causes the Textus Bioactiv Ag membrane to become more permeable and less selective for KCl solutions. The coefficients of Peusner (Lij), couplings (lij, QL), energy conversion efficiency (eij), S-energy, F-energy, and U-energy also depend nonlinearly on Äđ. Our results showed that for higher concentrations of KCl solutions transported through the Textus Bioactiv Ag membrane, the coupling and energy conversion coefficients were greater for larger Äđ up to their maximum values for large Äđ. Coupling of the membrane structure with the electrolyte flux through the membrane is observed for Äđ greater than 10 kPa. Textus Bioactiv Ag membrane dressings possess the properties of a solution component separator as well as an internal energy converter.

Application Characteristics of Zeolite-Based Stuffing for Nanofluidic Packer Rubber

Aiming at obtaining the application characteristics of more nanofluidic stuffing to enrich the database of nanofluidic packer rubber, three zeolite-based nanofluidic types of stuffing with water, glycerin, and a saturated aqueous solution of KCl (hereinafter referred to as saturated KCl solution) as the functional liquids were studied using experiments. The results showed that all the three zeolite-based nanofluidic stuffing types could be applied as stuffing for nanofluidic packer rubber. The setting pressure ranges for zeolite/water, zeolite/glycerin, and zeolite/saturated KCl solution stuffing were 21.71 to 30.62 MPa, 15.31 to 23.57 MPa, and 27.50 to 38.83 MPa, and the specific deformation quantities of the three stuffing types were 72.76, 102.07, and 77.54 mm3∙g−1, respectively. In zeolite/saturated KCl solution stuffing, the number of liquid molecules retained in the nanochannels was the minimum; thus, this stuffing type was the most stable during application. The order of the equivalent surface tensions of the three zeolite-based stuffing types in the confined nanochannels was consistent with the order of the gas–liquid surface tensions in the bulk phase. The equivalent surface tension, which reflected the interaction between liquid–solid phases, dominated the pressure threshold, the deformation capacity, and the stability of nanofluidic stuffing. This research study provided data support for the application of nanofluidic packer rubber.

Photo-controllable Ion-Gated Metal-Organic Framework MIL-53 Sub-nanochannels for Efficient Osmotic Energy Generation.

By closing and opening ion channels, electric eels are able to convert ion concentration gradients into electricity. Inspired by electric eels, considerable artificial sub-nanoscale ion channels with high ion selectivity and transportation efficiency have been designed for harvesting the osmotic energy between ionic solutions of different salinities, but constructing smart ion-gated sub-nanochannels for effective ion transport is still a huge challenge. Herein, photo-controllable sub-nanochannels of metal-organic framework (MOF) NH2-MIL-53 encapsulated with spiropyrans (SP-MIL-53) were fabricated by a facile in situ growth strategy. Interestingly, the highly ordered sub-nanochannels of SP-MIL-53 were switched on and off to efficiently regulate the ion flux by the light-driven isomerization of SP, which made it a smart ionic gate with a high on-off ratio of 16.2 in 10 mM KCl aqueous solution via UV irradiation. Moreover, the ion-gated sub-nanochannel membrane yielded a high power density of 8.3 W m-2 under a 50-fold KCl concentration gradient in the open state. Density functional theory calculations revealed that K+ ions in SP-MIL-53 sub-nanochannels had a higher mobility constant (3.61 × 10-2) with UV irradiation than without UV illumination (2.33 × 10-22). This work provides an effective way to develop smart ion-gating sub-nanochannels for capturing salinity gradient power.

Effects of pyridinic N of carboxylic acid on the polymerization of polyaniline and its supercapacitor performances

Phthalic acid and 2,3-pyrazinedicarboxylic acid doped PANI were synthesized on carbon felt electrode by a simple hydrothermal method. A systematic study was done to show the effect of carboxylic acid groups and pyrazine moiety on the energy storage properties of polyaniline and the obtained electrodes were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, Fourier Transform Infrared spectroscopy, Thermogravimetric analysis, Brunauer–Emmett–Teller surface area analysis and Scanning Electron Microscopy. Better specific capacitance of polyaniline (PANI) was observed in the presence of 2,3-pyrazinedicarboxylic (Pzdc) acid. The strengthening of electron delocalization of the PANI structure with pyridine N, the increase of π-π interactions and the formation of hydrogen bonds with the effect of carboxyl groups in the 2,3 pyrazine dicarboxylic acid contributed to the improvement of the energy storage properties of PANI. (Strengthening electron delocalization of the PANI structure with pyridine N, increased π-π interactions, and the formation of hydrogen bonds under the influence of carboxyl groups in the 2,3 pyrazine dicarboxylic acid contributed to the improvement of the energy storage properties of PANI.)Moreover, the study focused on showing the effect of the 2,3-pyrazinedi carboxylic acid ratio on its charge storage properties. Electrochemical measurements were carried out in 3.0 M KCl aqueous electrolyte solution. The results show that the high specific capacitance of 882.0 F g−1 is observed for Pzdc(0.02)/PANI electrode at the current density of 7 A g−1. Further, the supercapacitor electrode performed a good cycling test (96.7 %) after 2000 cycles with a high operating potential of 1.5 V. The fabricated symmetrical supercapacitor device has high cyclic stability and good electrochemical performance (energy density of 27.2 Wh kg−1 and 81.7 % at 2500 cycles).