Valence Of Ions Research Articles

Counterion Distribution in the Stern Layer on Charged Surfaces.

Counterion adsorption at the solid-liquid interface affects numerous applications. However, the counterion adsorption density in the Stern layer has remained poorly evaluated. Here we report the direct determination of surface charge density at the shear plane between the Stern layer and the diffuse layer. By the Grahame equation extension and streaming current measurements for different solid surfaces in different aqueous electrolytes, we are able to obtain the counterion adsorption density in the Stern layer, which is mainly related to the surface charge density but is less affected by the bulk ion concentration. The charge inversion concentration is further found to be sensitive to the ion type and ion valence rather than to the charged surface, which is attributed to the ionic competitive adsorption and ion-ion correlations. Our findings offer a framework for understanding ion distribution in many physical and chemical processes where the Stern layer is ubiquitous.

Adsorption studies of methylene blue on cation-modified graphene oxide and graphene oxide/MXene membranes

Membranes prepared from graphene oxide (GO) have greater advantages over traditional materials for water treatment, while MXene is a good candidate for pollutant removal. However, the effect of different cations introduced into the prepared GO membranes on their adsorption performance must be further explored. In this study, a series of cation-modified GO and GO/MXene membranes were prepared based on the self-assembly of GO. Na+-modified membranes were found to be more effective at removing methylene blue (MB) than multivalent cation-modified GO membranes. However, the cation-modified GO/MXene membranes improved the MB adsorption efficiency, and the higher the ionic valence, the more pronounced the effect. In addition, the effects of the pH, temperature, contact time and initial concentration of MB on the adsorption performance of the membranes were investigated. The best removal of MB was achieved under neutral conditions, and the adsorption process was consistent with quasi-secondary kinetics and Langmuir isotherm models. The fitting results of the Langmuir isotherm model showed that the maximum adsorption capacities of the cation-modified GO membranes for MB were 654.9, 319.8, and 246.3 mg/g, respectively. The maximum adsorption capacities of the cation-modified GO/MXene membranes for MB were 687.3, 497.6, and 772.4 mg/g, respectively. Furthermore, the results of the intraparticle diffusion model revealed that the entire adsorption process was controlled by both external and internal diffusion. The thermodynamic analysis results indicated that the entire adsorption process was a heat-absorbing process and could proceed spontaneously. That the findings suggest that the Na+-modified GO and Al3+-modified GO/MXene membranes demonstrate the best adsorption effects and are promising adsorbents for MB removal.

Molecular control via dynamic bonding enables material responsiveness in additively manufactured metallo-polyelectrolytes

Metallo-polyelectrolytes are versatile materials for applications like filtration, biomedical devices, and sensors, due to their metal-organic synergy. Their dynamic and reversible electrostatic interactions offer high ionic conductivity, self-healing, and tunable mechanical properties. However, the knowledge gap between molecular-level dynamic bonds and continuum-level material properties persists, largely due to limited fabrication methods and a lack of theoretical design frameworks. To address this critical gap, we present a framework, combining theoretical and experimental insights, highlighting the interplay of molecular parameters in governing material properties. Using stereolithography-based additive manufacturing, we produce durable metallo-polyelectrolytes gels with tunable mechanical properties based on metal ion valency and polymer charge sparsity. Our approach unveils mechanistic insights into how these interactions propagate to macroscale properties, where higher valency ions yield stiffer, tougher materials, and lower charge sparsity alters material phase behavior. This work enhances understanding of metallo-polyelectrolytes behavior, providing a foundation for designing advanced functional materials.

Molecular Insights into Redox-Active Polymer Interfaces: Solvation and Ion Valency Effects on Metal Oxyanion Selectivity

Chemical separations are responsible for 10-15% of the world’s energy consumption. Minimizing energy and materials inputs in selective separations is imperative for a sustainable future. Ion-electrosorption mediated by redox-active metallopolymer interfaces has the unique advantage of selectively capturing and releasing metal oxyanions in a switchable manner by adjusting the applied potential, without any regenerants. Electrosorption addresses the need for selective separation approaches with low chemical and energy inputs. Previous studies on ferrocene metallopolymers have demonstrated the role of polymer structure and applied potential on selectivity—however, the ubiquitous role of solvation in redox-polymers has remained unexplored. Here, we investigate how solvation and ion valency influence selectivity of ReO4 - vs MoO4 2- for two redox-metallopolymers, poly(vinyl ferrocene) (PVFc) and poly(3-ferrocenylpropyl methacrylamide) (PFPMAm). Both polymers display time-dependent Re/Mo selectivity, with PVFc having higher selectivity compared to PFPMAm. Operando neutron reflectometry, ellipsometry, and electrochemical quartz-crystal microbalance show that both PVFc and PFPMAm swell in the presence of ReO4 - (with PFPMAm having higher solvation), but do not swell in contact with MoO4 2-. We find that the less solvated anion (ReO4 -) is preferably adsorbed by the more hydrophobic redox-polymer (PVFc). We expect that a deeper understanding of solvation and valency effects on selectivity mechanisms in redox interfaces will expedite the development of targeted selective ion-electrosorption systems. Figure 1

Sr and Fe-Substituted LaMnO3 Perovskite for High-Rate Asymmetric Hybrid Supercapacitors

Perovskite has been getting significant attention in solar cells, photocatalysts, and hybrid supercapacitors. The symmetry or structural stability of ABO3-type perovskite oxides depends mainly on the size of ‘A’ and ‘B’ cations, which determines the material properties. The partial substitution of these cations may be used to tune these properties. The ionic sizes and valence states of the cations play an important role in improving the properties of perovskite. In this study, the substitution of La3+ with Sr2+ with a larger ionic radius and Mn3+ with Fe3+ with a similar ionic radius favored both the crystal symmetry and the mixed ionic-electronic conductivity of the perovskite. Electrodes based on La0.7Sr0.3Mn0.5Fe0.5O3 (LSMFO55) exhibited a faradaic behavior with a specific capacity of 330 C g-1 (92 mAh g-1) at a 12C rate, while this electrode maintained a capacity of 259 C g-1 at 240C (charge or discharge in 15s). Additionally, exohedral carbon nano-onions (CNO) were introduced as a negative electrode to design an asymmetric hybrid supercapacitor (AHS) with a widened cell voltage. The use of CNO as a negative electrode in the AHS improved the rate capability drastically compared to rGO. This device maintained a good energy density even at an extra-high charging rate (600C), owing to its outstanding rate capability. The high-rate performance of the LSMFO55//CNO AHS can be elucidated by successful fabrication with a mixed ionic-electronic conductive positive electrode and a CNO negative electrode. Tuning the electronic and ionic conductivities by cationic substitution and introducing CNO negative electrodes can provide a practical high-rate hybrid device using various perovskites.

Effects of B- and A/B-sites Codoping on lattice distortion and defect concentration for high electromechanical response of lead-free piezoelectrics

Effects of different thermal conditions on lead-free (Bi0.65Ba0.35)(Fe0.65Ti0.35)O3 ceramics were studied to reduce secondary phase formation, regulate bismuth vacancies and resulting oxygen vacancies, and Fe ions valence transition during the heat treatment process. The optimal thermal conditions led to a higher d33 = 200 pC/N and a d33* = 420 pm/V. A/B-sites ions replacement in BF35BT, BF35BT-Zr, and BF35BTSZ ceramics were prepared to reveal the effects of different Zr or Sr-Zr-contents. A maximum tetragonality (cT/aT) was estimated for the single doping (Zr) and co-doping (Sr and Zr) cases. For Zr = 0.02, the electric field-induced strain reached its maximum value of d33* = 562 pm/V. Similarly, a strain of d33* = 701 pm/V was observed for Sr-Zr = 0.02. Additionally, the d33* improved to 870 pm/V (90 °C) in Zr = 0.02 and 1130 pm/V (120 °C) in Sr-Zr=0.02. The presence of local structural heterogeneity causes the domain size to decrease as it moves from the micro to the nanoscale. The results demonstrate that improved performance can be associated with reduced concentration of oxygen vacancies, nanodomains by local structural heterogeneity, high lattice anisotropy, higher relative density, and appropriate grain size.

Probing the thermophysical property mechanism of Mg2+-doped high-entropy oxide ceramics

To create thermal barrier coatings (TBCs) with superior thermal characteristics and high-temperature stability, understanding the microscopic process of heat transfer in high-entropy solid solutions is crucial. In this study, novel (Zr0.2(1-x)Ce0.2(1-x)Pr0.2(1-x)Y0.2(1-x)Ho0.2(1-x)Mgx)O2-δ single-phase high-entropy fluorite-structured oxides with varying Mg elemental contents were successfully synthesized at 1600 °C. Given the unique ionic radius and valence nature of Mg2+, the effects of varying the Mg doping amount on the thermophysical properties and microstructures were explored. Furthermore, the mechanism influencing high-temperature thermal conductivity was studied at the microscopic scale using first-principles calculations to clarify the nature of the thermal conductivity behavior. On one hand, an increase in oxygen vacancies leads to an enhancement of the lattice distortion degree and phonon scattering level. On the other hand, divalent Mg2+ activates the lattice via unequal substitutions, thereby reducing the thermal conductivity. The experimental and simulation results revealed that as Mg doping increases, the content of oxygen vacancies significantly increases, the degree of lattice distortion increases, phonon scattering is enhanced (19.54–21.37 THz), high-temperature thermal conductivity progressively decreases (1.91-1.20 w·m−1·K−1), and the coefficient of thermal expansion progressively increases (11.70 × 10−6-12.31 × 10−6 K−1). These results offer a novel approach for designing doped high-entropy strategies that can satisfy the performance requirements of TBCs.

Effects of high valency and polarizability ion (W6+) on the phase evolution of CaZr1–2xLn2xTi2–xWxO7 zirconolite-based solid solution (Ln = Nd, Sm, Gd, Ho, Yb)

Zirconolite-based structures have served as robust matrices for the incorporation of minor actinide-rich high-level waste (HLW). The co-doping effects are critical for exploring the phase evolution of zirconolite-based structures, thereby providing a guide for HLW immobilization. Nevertheless, few studies have studied the synergistic effect of high valent ion W6+ and Lanthanides (Ln, surrogates to minor actinides) co-doping. This study proposed a systematical study on the Ln-W (Ln = Nd, Sm, Gd, Ho, Yb) co-doping in zirconolite-derived structure using X-ray diffraction (XRD) and scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDX). The results showed that near-single-phase zirconolite-2M was recorded for samples with low level doping of Ln-W (Nd–W, Sm–W and Gd–W with x = 0.05; Ho–W and Yb–W with x = 0.05–0.1), and its structure underwent a moderate expansion along the c-axis, as revealed by a Pawley refinement method. One key finding is that near-single-phase zirconolite-2M was recorded for samples with low level doping of Ln-W (Nd–W, Sm–W and Gd–W with x = 0.05; Ho–W and Yb–W with x = 0.05–0.1), and its structure underwent a moderate expansion along the c-axis, as revealed by a Pawley refinement method. Notably, in addition to a transformation from zirconolite-2M to pyrochlore, a pseudo-yellow phase CaWO4 was also noted with increasing co-doping contents. This work demonstrates that the high charge compensator W6+ and lanthanides can be simultaneously incorporated into zirconolite structure, and a different phase transformation was revealed compared to that in low valent element doping system, which gives a new insight into the optimization of HLW immobilization route.

Magnetic capacity in manganese sulfides with rare earth substitution Mn<sub>1–x</sub>Re<sub>x</sub>S

Polycrystalline samples Mn1–xGdxS and Mn1–xYbxS with a concentration x = 0.2, near the concentration of ion flow through the fcc lattice, are studied in order to determine fluctuations in the valence of the ytterbium ion on dielectric properties. Dielectric constant and dielectric losses were determined from measurements of capacitance and loss tangent in the frequency range 102–106 Hz at temperatures of 80–500 K without a magnetic field and in a magnetic field. The magnetic capacity and dielectric losses in the magnetic field of the sample were determined from the relative change in the real and imaginary parts of the dielectric constant of the sample in a magnetic field H = 12 kOe applied parallel to the capacitor plates. A temperature range with a sharp increase in dielectric constant and with a maximum dielectric loss has been discovered, which shifts with increasing frequency and magnetic field. An increase in dielectric constant and dielectric losses in a magnetic field above 170 K was found in Mn1-xYbxS. The increase in dielectric losses is explained by an increase in relaxation time, as a result of local deformations near ytterbium ions during valence fluctuations. The mechanism for reducing reactance in a magnetic field in Mn1–xYbxS at low frequencies due to capacitance, and at high frequencies due to inductance, has been determined. In the Mn0.8Gd0.2S compound, the imaginary part of the dielectric constant has two maxima. The low-temperature maximum shifts in a magnetic field towards high temperatures and is described in the model of localized electrons with freezing of dipole moments. Dielectric losses decrease in a magnetic field. The magnetic capacity decreases by an order of magnitude in Mn0.8Gd0.2S compared to Mn0.8Yb0.2S. The dielectric constant in both compounds is described in the Debye model with the activation dependence of the relaxation time on temperature, where the activation energies differ for ytterbium and gadolinium ions.

Neuronal regulated cell death in aging-related neurodegenerative diseases: key pathways and therapeutic potentials.

Regulated cell death (such as apoptosis, necroptosis, pyroptosis, autophagy, cuproptosis, ferroptosis, disulfidptosis) involves complex signaling pathways and molecular effectors, and has been proven to be an important regulatory mechanism for regulating neuronal aging and death. However, excessive activation of regulated cell death may lead to the progression of aging-related diseases. This review summarizes recent advances in the understanding of seven forms of regulated cell death in age-related diseases. Notably, the newly identified ferroptosis and cuproptosis have been implicated in the risk of cognitive impairment and neurodegenerative diseases. These forms of cell death exacerbate disease progression by promoting inflammation, oxidative stress, and pathological protein aggregation. The review also provides an overview of key signaling pathways and crosstalk mechanisms among these regulated cell death forms, with a focus on ferroptosis, cuproptosis, and disulfidptosis. For instance, FDX1 directly induces cuproptosis by regulating copper ion valency and dihydrolipoamide S-acetyltransferase aggregation, while copper mediates glutathione peroxidase 4 degradation, enhancing ferroptosis sensitivity. Additionally, inhibiting the Xc- transport system to prevent ferroptosis can increase disulfide formation and shift the NADP + /NADPH ratio, transitioning ferroptosis to disulfidptosis. These insights help to uncover the potential connections among these novel regulated cell death forms and differentiate them from traditional regulated cell death mechanisms. In conclusion, identifying key targets and their crosstalk points among various regulated cell death pathways may aid in developing specific biomarkers to reverse the aging clock and treat age-related neurodegenerative conditions.

Effects of inorganic salt ions on the wettability of deep coal seams: Insights from experiments and molecular simulations

Coal wettability plays a significant role in the efficiency of coalbed methane (CBM) extraction since it determines fluid transport and distribution. Deep coal seam aqueous fluids have a high salinity. Consequently, coal wettability experiments utilizing fresh water are not representative for those coal seams. Therefore, the effect of aqueous fluids with inorganic salt ions on coal wettability needs to be investigated. In this study, both experiments and molecular simulations are conducted to unravel the wetting behaviour and mechanisms of saline fluids on coal surfaces, investigating different fluid salt concentrations, temperatures, valence states, and coal pore sizes. The results reveal that a more saline fluid displays a more hydrophobic behaviour on the coal surface. Microscopically, water molecules have a tendency to assemble around cations and anions as hydration shells and gradually detach from the coal surface, leading to a gradual transition from hydrophilicity to hydrophobicity. A change in wettability with fluid salinity can be caused by two mechanisms. On the one hand, an increase in ion concentration constrains the diffusion of water molecules through hydration, weakening the mobility of water molecules. On the other hand, a higher ion concentration weakens the interaction between water molecules and oxygen-containing functional groups, reducing the affinity of the water molecules with the pore wall. Moreover, at higher temperatures, ion valence states, and for coal with smaller pores, the impact of inorganic salt ions in fluids on the wetting behaviour of coal surfaces becomes more significant. The coal wettability influences the capillary pressure of coal pores. This study provides new insights on the effect of saline fluids on coal wettability which may help address challenges of fracturing fluid loss and water-blocking in CBM production activities.

Calciothermic Reduction Reaction Behavior and Samarium Ion Valence Evolution of SmF3

Calciothermic Reduction Reaction Behavior and Samarium Ion Valence Evolution of SmF3

Parameter-Fitting-Free Continuum Modeling of Electric Double Layer in Aqueous Electrolyte.

Electric double layers (EDLs) play fundamental roles in various electrochemical processes. Despite the extensive history of EDL modeling, there remain challenges in the accurate prediction of its structure without expensive computation. Herein, we propose a predictive multiscale continuum model of EDL that eliminates the need for parameter fitting. This model computes the distribution of the electrostatic potential, electron density, and species' concentrations by taking the extremum of the total grand potential of the system. The grand potential includes the microscopic interactions that are newly introduced in this work: polarization of solvation shells, electrostatic interaction in parallel plane toward the electrode, and ion-size-dependent entropy. The parameters that identify the electrode and electrolyte materials are obtained from independent experiments in the literature. The model reproduces the trends in the experimental differential capacitance with multiple electrode and nonadsorbing electrolyte materials (Ag(110) in NaF, Ag(110) in NaClO4, and Hg in NaF), which verifies the accuracy and predictiveness of the model and rationalizes the observed values to be due to changes in electron stability. However, our calculation on Pt(111) in KClO4 suggests the need for the incorporation of electrode/ion-specific interactions. Sensitivity analyses confirmed that effective ion radius, ion valence, the electrode's Wigner-Seitz radius, and the bulk modulus of the electrode are significant material properties that control the EDL structure. Overall, the model framework and findings provide insights into EDL structures and predictive capability at low computational cost.

Exploring the Impact of Steric Effects on Ion Removal of Water Solutions under the Influence of an Electric Field

In this study, we examine the movement of ions that are in a water solution which flows along a duct, due to the existence of an electric field, taking into account the size of the ions, a phenomenon known as the steric effect. We compare the results from the above model with the classical one (the one that uses the Boltzmann distribution where ions are considered dimensionless) for various parameters such as surface charge density, electric field and differential capacitance. It is shown that for dilute water solutions (1019–1024 ions/m3 final concentration at the center of the duct), with ions of valence z=1 (let us say saline water), steric effects become important for potentials greater than 1 V, and the phenomenon is more pronounced at higher concentrations. Furthermore, the steric effect model is applied to the calculation of the percentage of reduction in ion concentration in the main volume of the solution as a function of duct width for various electrode potentials and initial ion concentrations. Removal times are also calculated using Modified PNP equations which take into account steric effects. It is found that with a potential of 2.6 V, a 96% reduction in ions is achieved in the main volume of the solution for duct width 0.1 mm for 1021 ions/m3 final concentration at the center of the duct within approximately 1.6 s, while the percentage drops to 80% for duct width 1 mm. For smaller potentials, no noticeable decrease in concentration is observed, while for higher potentials, there are more impressive results, but we must be very careful because there is the case of other electrochemical phenomena taking place. The results are better when reducing the width of the duct, but relatively large widths are considered for the method to be practically applicable. With the increase in the concentration of the ions, their reduction percentage in the main volume of the solution decreases but remains significant up to 1023 ions/m3 final concentration at the center of the duct. In addition, the completion time is shown to be proportional to the duct width. Therefore, for example, with the other parameters the same (2.6 V, 1021 ions/m3) but with L~1 mm, the completion time can be estimated to be approximately 16 s. This observation enables us to estimate the completion time for different duct widths, eliminating the need for repeated numerical computation of the MPNP equations.

Influence of nitrogen stoichiometry and the role of Sm 5d states in SmN thin films

We report a comprehensive study of the synthesis of epitaxial SmN thin films on LaAlO3 (100) by molecular beam epitaxy under slow-growth conditions. By carefully tuning the substrate temperature and the molecular nitrogen partial pressure, we are able to control the nitrogen content of our samples and produce near-stoichiometric, well-ordered SmN thin films. The influence of nitrogen defects on the samarium ion valence and the electronic structure is investigated by x-ray absorption and photoelectron spectroscopy, suggesting that the empty Sm 5d states may act as a charge reservoir stabilizing the 4f5 configuration in the nitrogen-deficient compound. The spectra also reveal a significant hybridization of the Sm 4f and N 2p states. Published by the American Physical Society 2024

Comparative study of polystyrene microplastic transport behavior in three different filter media: Quartz sand, zeolite, and anthracite

Microplastics (MPs) are emerging contaminants that are attracting increasing interest from researchers, and the safety of drinking water is greatly affected by their transportation during filtration. Polystyrene (PS) was selected as a representative MPs, and three filter media (quartz sand, zeolite, and anthracite) commonly found in water plants were used. The retention patterns of PS-MPs by various filter media under various background water quality conditions were methodically investigated with the aid of DLVO theory and colloidal filtration theory. The results show that the different structures and elemental compositions of the three filter media cause them to exhibit different surface roughnesses and surface potentials. A greater surface roughness of the filter media can provide more deposition sites for PS-MPs, and the greater surface roughness of zeolite and anthracite significantly enhances their ability to inhibit the migration of PS-MPs compared with that of quartz sand. However, surface roughness is not the only factor affecting the migration of MPs. The lower absolute value of the surface potential of anthracite causes the DLVO energy between it and PS-MPs to be significantly lower than that between zeolite and PS-MPs, which results in stronger retention of PS-MPs by anthracite, which has a lower surface roughness, than zeolite, which has a higher surface roughness. The transport of PS-MPs in the medium is affected by the combination of the surface roughness of the filter media and the DLVO energy. Under the same operating conditions, the retention efficiencies of the three filter materials for PS-MPs followed the order of quartz sand < zeolite < anthracite. Additionally, the conditions of the solution markedly influenced the transport ability of PS-MPs within the simulated filter column. The transport PS-MPs in the simulated filter column decreased with increasing solution ionic strength and cation valence. Naturally, dissolved organic matter promoted the transfer of PS-MPs in the filter layer, and humic acid had a much stronger facilitating impact than fulvic acid. The study findings might offer helpful insight for improving the ability of filter units ability to retain MPs.

Polarization loss in rutile TiO2 doped with acceptor ions for microwave absorption

With an increase in electromagnetic (EM) pollution, inducing polarization loss using lattice defects has become one of the main strategies for the design and optimization of a new generation of microwave absorbers. In this study, point defects in TiO2 absorbers are designed and controlled using a sol–gel method. The influences of the electronegativity difference and the ionic valence states of the dopant ions on the microwave absorption (MA) performance of rutile TiO2 composites are investigated. The results show that the defects such as oxygen vacancy (VO∙∙) and Ti3+ can be adjusted continuously at a high-temperature sintering process. Cu2+, which has a larger electronegativity than Ti4+ (Cu2+χ = 1.90 > Ti4+χ = 1.54) promotes the localization of electrons. Furthermore, compared with Ag+, which has a similar electronegativity (Ag+χ = 1.93 ≈ Cu2+χ = 1.90), polyvalent copper ions (Cu2++e→Cu+) enhance the electron-hopping process. The formed electron-pinning defect dipole clusters (TiTi′, VO∙∙, CuTi″, CuTi″′, Ti3+→VO∙∙←Ti3+, Ti3+→VO∙∙←Cu2++e, Cu2++e→Cu+, Ti4++e→Ti3+) produce a stronger polarization relaxation process, which regulates the MA performance of TiO2 absorbers. Therefore, this study provides an essential reference for refining the EM wave attenuation performance of simple oxide absorbers.

Designing a three-dimensional CoFe2O4 cross-frame wrapped with carbon nanotubes for monitoring the environmental pollutant nitrobenzene

In this study, we employ a catalytic system derived from a zeolitic imidazolate framework (ZIF), comprising carbon nanotube-wrapped CoFe2O4 with a modified 3D cross morphology. The seamless transition between ionic valence states in CoFe2O4 contributes to enhanced material conductivity, illustrating a significant synergistic coupling effect. The 3D matrix has the capacity to generate a greater number of active sites and exhibit a high surface area. The generation of nanotubes provides additional channels for electron transport, thereby improving the charge transfer efficiency and enhancing the electrochemical sensing capability of the system. The synthesized material demonstrates outstanding electrochemical sensing capabilities for nitrobenzene, exhibiting impressive sensitivity with a remarkably low limit of detection at 0.013 μM and a broad linear response range (0.06–414.9 μM), heightened sensitivity, excellent repeatability, and superior selectivity. Furthermore, the quantification of trace nitrobenzene in water samples demonstrates a recovery rate within the range of 96.0 %–102.8 %. Consequently, this material presents itself as a promising catalyst for electrochemical analysis and introduces a novel approach for detecting low concentrations of nitrobenzene.

Effect of cation species on pressure-driven electrokinetic energy conversion in charged conical nanochannels

Electrokinetic energy conversion (EEC) offers a promising avenue for transforming elusive natural energy into electric power, showing a wide application spectrum. Unlike prevalent studies that chiefly utilize symmetrical electrolyte solution (e.g., KCl) and uniformly structured negatively charged nanochannels for EEC, this paper delves into a thorough examination of EEC characteristics—streaming current, streaming potential, and output power—in both positively and negatively charged conical nanochannels with symmetrical and asymmetric (CaCl2 and LaCl3) electrolytes solutions. Operating under the assumption that the electrolyte solutions (KCl, CaCl2, and LaCl3) possess equivalent ionic strength and, thereby, a common Debye length, our findings reveal a significant dependency of EEC characteristics and their regulation parameters on the electrolyte type, nanochannel charge polarity, and ionic strength. As the ionic strength increases, both the streaming current and output power initially rise to a peak before subsequently declining, with the ionic strength at the peak being influenced by the cation valence: lower valence leads to lower ionic strength. In asymmetric electrolyte scenarios, optimal EEC characteristic is observed in positively charged conical nanochannels under a reverse pressure difference, attributed to the ion-selective and ionic concentration distribution in the charged conical nanochannels. Moreover, the complex behaviors of the regulation parameters of EEC characteristics are unveiled. Notably, a tri-valent electrolyte's regulation parameters exceed those of a bi-valent electrolyte, indicating that ionic valence asymmetry enhances the regulation effects on EEC in conical nanochannels.

Local structure and entropic stabilization of Ca‐based molten salt electrolytes

Here molten salt electrolytes (MSEs) and specifically their physico‐chemical properties as a function of composition are reported on, with a special emphasis on the compositional entropy and targeting calcium battery application. By using MSEs, several problematic issues associated with organic electrolytes, such as the blocking of Ca2+ transfer at the electrode/electrolyte interfaces and electrolyte flammability, are avoided. Ca(FSI)2 salt in combination with the analogous Li‐, Na‐, and KFSI salts are used in equimolar compositions to first create several ternary MSEs, melting at ca. 60‐75 ◦C, a melting temperature which is further reduced to ca. 55 ◦C for the unique quaternary MSE. This is ascribed to an increased entropy of mixing, which also contributes to an improved stability vs. (re‐)crystallization, as shown by Raman spectroscopy. Furthermore, molecular dynamics simulations of the quaternary MSE alongside density functional theory calculations targeting the ion‐ion interactions are used to elucidate the local structure in more detail, demonstrating that both the ionic radii and valence influence the coordination and solvation of the cations. These MSEs are stepping‐stones towards completely solvent‐free, semi‐solid, and ideally room‐temperature Ca‐conducting electrolytes.