Chloride/sulfate ion exchange kinetics at high solution concentration

Kinetics of chloride-sulfate exchange and reverse exchange and sulfate self-exchange at high salinity on three acrylate-base anion exchange resins with quaternary ammonium, tertiary amine, and secondary amine groups, respectively, have been examined. In all cases, evidence points to rate control by intra-particle diffusion. At low conversion, rates are slightly lower than predicted on the basis of the Nernst-Planck equations; this is attributed to initial retardation by film diffusion. For forward and reverse exchange (sulfate and chloride, respectively, taken up by the resin), but not for isotopic sulfate exchange, rates at high conversion tend to be somewhat higher than predicted; this is tentatively attributed to changes in water content of the resins in the course of conversion.     

Study of lithium glassy solid electrolyte/electrode interface by impedance analysis

Cells of lithium ion conducting glassy electrolyte Li ₂SO₄-Li₂O-B₂O₃ with different combinations of electrodes (stainless steel blocking electrode, lithium non-blocking electrode and TiS₂ electrode) have been prepared. The a.c. impedance measurements of the cells have been studied at elevated temperature as a function of time. The circuit elements such as bulk resistance, double layer capacitance and charge transfer resistance have been inferred and their time dependence studied. The results show that the electrolyte and the interface are chemically very stable with the different types of electrodes studied here.     

Triplet-state photoexcitation dipole-jump relaxation method to observe adsorption/desorption kinetics at a reversed-phase silica/solution interface

Electronic excitation of a probe chromophore can lead to a change in dipole moment that influences its activity or solubility in solution and changes its relative affinity for partitioning between two phases. Photoexcitation of a probe molecule can, therefore, perturb a sorption equilibrium, and the relaxation kinetics of the probe to the new equilibrium conditions can be monitored in a time-resolved luminescence experiment. The adsorption/desorption kinetics of rose bengal, distributed between a C-18 derivatized porous-silica surface and a liquid mobile-phase solution, were investigated. These kinetics were determined by observing their effect on the phosphorescence decay of the triplet state of rose bengal and its quenching by ferricyanide. The methanol/water solvent compositions were varied to alter the fraction of adsorbed rose bengal. The adsorption rate constant for the triplet state was determined from the dependence of the phosphorescence relaxation rate on dye concentration in solution. The results indicate that the adsorption kinetics are diffusion controlled and that the relaxation is influenced by efficient triplet-energy transfer between excited- and ground-state rose bengal at the C-18 silica/solution interface.     

Investigation of conformation of polyvinyl alcohol chain at oxide/electrolyte interface

An attempt to evaluate the surface area of hematite and rutile occupied by an adsorbed molecule of polyvinyl alcohol(PVA) was made. The surface area occupied by a PVA molecule was evaluated from the changes of surface charge density of the oxides before and after PVA addition in the presence of Cs⁺, Mg²⁺, and Ca²⁺ ions. The desorption of an inorganic ion caused by PVA adsorption was taken into account. The configuration of the PVA chain at the solid — liquid interface is also discussed in the light of the results obtained.     

Surface charge and adsorption of sodium ions at the controlled porosity glasses/electrolyte interface

Controlled porosity glasses (CPGs) are used as adsorbents, supports or catalysts. Their properties depend on the amount of surface boron and sodium concentration. The surface boron and sodium concentration can be changed by proper thermal treatment. The presented paper deals with the change of charge surface density and pH of point zero charge of the thermally treated CPG. The surface reaction constants according to the site binding theory of the electric double layer were calculated on the basis of the surface charge data. The results of Na⁺ adsorption on the CPGs are presented.     

Dimples due to dislocations at the superfluid/solid interface of4He

On vicinal planes the surface stiffness is quite anisotropic and a crystal defect, terminating at the interface, is predicted to produce a 10...50 nm deep dimple with macroscopic lateral extent (up to a few mm). We have searched for such depressions using high resolution interferometry. Sometimes our measured interferograms of the super fluid/solid interface display unexpectedly large dimples. The volume and shape of the observed objects suggest that these dimples are caused by bundles of about 10 dislocations.     

Assembly of nanoscale building blocks at solution/solid interfaces

A chemical strategy has been purposely designed to hierarchically assemble nanoscale building blocks at the interface of solution/solid. Typically, a solution containing precursor of one component and a metal foil as metal source of another component were employed, on the basis of proposed chemical reactions on expected interfaces. Proper reaction parameters including temperature, pH value etc. were selected to adapt both chemical reactions in solution and on the metal surface. Consequently, at the interface of solution and metal foil, two kinds of nanoscale building blocks deposited simultaneously leading to the current hierarchical assembly. This strategy has been applied to the fabrication of a series of functional materials, including Nb₂O₅/TiO₂, Nb₂O₅/LiF and ZnO/Co₃O₄. The current strategy provides a convenient one-step route to achieve complex functional structures, which may have potential applications in a variety of fields such as solar cells, Li-ion batteries, electrochemical supercapacitors, catalysts as well as chemical, gas, and bio-sensors.     

碳纳米管膜/电解液界面的整流效应

对碳纳米管(CNT)膜/电解液(电解质溶液)界面的整流效应进行了研究。实验所用的碳纳米管用热灯丝化学气相沉积法(CVD)合成,整流效应通过分析其伏安特性来研究。结果发现,在室温下与一定浓度的电解液中,碳纳米管膜/电解液界面呈现出较强的整流效应,且该效应随电解液温度和浓度的增大而增强,重点讨论了碳纳米管膜/电解液界面整流效应的产生机制。     

Ice nucleation at the silver iodide-aqueous solution interface

The ability of a solid substrate to activate ice nucleation in supercooled water depends on the extent to which it effects the orientation of the adsorbed water molecules into the ice like structure. The nucleating activity of silver iodide in supercooled water depends upon the potential determining silver and iodide ions. In order to find the influence of silver ion, nucleation experiments were conducted with varying concentration of silver ion from 10^?2 to 10^?12 M. The highest nucleating activity was observed at pAg6. The addition of isobutyl, n-butyl and n-propyl alcohols improved the nucleation temperature to ?3°C. In addition to that the higher values of pAg were found to be more active than the lower pAg values in the presence of aliphatic alcohols. The exposition of AgI sols to ultra violet radiation affected the nucleation temperature depending upon the time of exposure. The mechanism of these effects is discussed in detail.     

Phase transition kinetics at the interface of two extended masses

The motion of a phase interface is examined in the case of two semiinfinite rods of the same material, one in the solid and the other in the liquid state. The variation of temperature at the phase interface is calculated.     

锂金属电池中复合固态电解质与负极界面的研究进展

与传统锂离子电池相比,全固态锂金属电池因其安全性好、能量密度高的特点备受关注.但是电极与固态电解质的固固接触带来较大的界面阻抗,而锂金属较为活泼易与固态电解质发生反应,造成了界面不稳定.界面问题已经成为制约全固态电池发展的关键因素之一.有机-无机复合固态电解质兼顾无机固态电解质和有机固态电解质的优势,具有较高离子电导率和一定的力学强度,展现出优异的实用化前景.本文综述了近年来复合固态电解质与金属锂负极界面改性的研究进展,总结了当前界面改性的主要研究思路:包括在界面构筑"软接触"、调节固态电解质的力学性能以及调控界面处锂离子的沉积动力学过程等.同时,也对今后界面改性的研究趋势进行了展望.     

On the kinetics of Cu(I) transfer through the solid CuI-Cu interface

The Cu(I) transfer through the Cu/γ,β, α-CuI interface was studied by a galvanostatic transient technique. From the experimental activation energies obtained for both the anodic and cathodic processes, two different steps are postulated as rate controlling according to the temperature range:

• 1.a) the ion incorporation into the CuI solid electrolyte for the Cu/γ,β-CuI interface
• 2.b) the ion transfer from the metallic side to the electrolyte surface at the Cu/γ -CuI interface. A theoretical calculation of the energy barrier for the ion transfer is also presented.

     

The determination of Gibbs energy of the exchange reaction of sulphides using beta-alumina solid electrolyte

EMF measurements of the cell Na (l) |-alumina | Na₂S + A9₂S + Ag were carried out in the temperature range of 463.4 to 843.7 K. The results were represented by the equationE/V (±0.00057) = 1.75793(±0.00086) – 4.452(±0.014) × 10^–4(T) where 463.4 < T < 737.7 K. The Gibbs energy of the exchange reaction 1/2Ag₂S(s) + Na(l) 1/2Na₂S(s) + Ag(s) was determined from the EMFs. The standard Gibbs energy of formation of Na₂S in the reaction 2Na(l) + 1/2S₂(g) = Na₂S(s) was obtained from the values of EMF and in the literature as (J mol^–1 ± 1160) = –427940 + 124.92T where 463.4 < T < 737.7 K. The eutectic temperature of the Ag₂S-Na₂S system was estimated to be 738 ± 5 K.     

Electric field induced enhancement in the interfacial charge transfer kinetics of a solid polymer electrolyte

A novel electrostatic method for preparing modified solid polymer electrolytes (SPEs) is reported. Application of an electric field on an evaporating mixture of KYNAR, ethylene carbonate (EC), propylene carbonate (PC) and LiPF₆ dissolved in tetra hydro furan (THF) resulted in a solid polymer electrolyte whose charge transfer resistance was at least an order of magnitude lower than that formed without the application of an electric field. We believe that the observed enhancement is probably due to an electric field induced orientation of dipoles in the polymer chain.     

Atomically controlled electrochemical nucleation at superionic solid electrolyte surfaces

Electrochemical equilibrium and the transfer of mass and charge through interfaces at the atomic scale are of fundamental importance for the microscopic understanding of elementary physicochemical processes. Approaching atomic dimensions, phase instabilities and instrumentation limits restrict the resolution. Here we show an ultimate lateral, mass and charge resolution during electrochemical Ag phase formation at the surface of RbAg(4)I(5) superionic conductor thin films. We found that a small amount of electron donors in the solid electrolyte enables scanning tunnelling microscope measurements and atomically resolved imaging. We demonstrate that Ag critical nucleus formation is rate limiting. The Gibbs energy of this process takes discrete values and the number of atoms of the critical nucleus remains constant over a large range of applied potentials. Our approach is crucial to elucidate the mechanism of atomic switches and highlights the possibility of extending this method to a variety of other electrochemical systems.     

Dissolution and reprecipitation of barium at the particulate BaTiO3-aqueous solution interface

The electrokinetic behavior of BaTO₃ particles in an aqueous medium exhibited a hysteresis loop with titration direction. As BaTiO₃ suspension was titrated toward acidic pH, the amount of Ba²⁺ dissolution strongly increased, and in the subsequent titration toward alkaline pH, Ba²⁺ adsorbed and/or reprecipitated on the Ba-depleted BaTiO₃ surface. This dissolution-reprecipitation cycle results in the observed hysteresis behavior. An attempt was made to identify the responsible species of the adsorbed/reprecipitated compound by XPS in conjunction with electrokinetic titrations.     

Electroanalytical behavior of poly-L-lysine dendrigrafts at the interface between two immiscible electrolyte solutions

In this work, the electrochemical behavior of nonredox-active poly-L-lysine dendrigraft molecules of four different generations was investigated at the interface between two immiscible electrolyte solutions (ITIES). The influence of the dendrigraft generation on the electrochemical response, sensitivity of the calibration curves, and limit of detection was studied. Cyclic voltammetry at the ITIES revealed that the sensitivity increased (1840 to 25?800 nA μM(-1)) and the limit of detection decreased (11.10 to 0.65 μM) as the dendrigraft generation increased from generation G2 through to generation G5, respectively. The results are compared to those for protein voltammetry at the ITIES. Our studies suggest that the sensitivity expected for a synthetic ionized macromolecule can be predicted on the basis of its net charge and its diffusion coefficient. However, electrochemistry at the ITIES demonstrates a greater sensitivity toward proteins, which is attributed to their tertiary structure.     

Mechanism of arsenate coprecipitation at the solid/liquid interface of ferrihydrite: A perspective review

Arsenate (As(V)) is a toxic element in acid mine drainage and has to be removed during the neutralization process. Coprecipitation with ferrihydrite is the main mechanism for As(V) removal from acid mine drainage. To improve treatment efficiency, a quantitative understanding of the coprecipitation mechanism is required. Coprecipitation can incorporate more As(V) into ferrihydrite than adsorption. The results of XRD (X-ray Diffraction) and XANES (X-ray Adsorption Near Edge Structure) analysis confirmed that the formation of poorly crystalline ferric arsenate increased when the initial As/Fe molar ratio increased in the coprecipitation with ferrihydrite. EXAFS (Extended X-ray Adsorption Fine Structure) analysis at the iron K-edge showed that the proportion of octahedral structures in ferrihydrite increased when the initial As/Fe molar ratio increased. Moreover, EXAFS analysis at the arsenic K-edge, assuming three kinds of surface complexes for the AsFe bond, revealed that the coordination number for AsFe with an atomic distance of 2.85 × 10⁻¹⁰ m increased and that for As-Fe with an atomic distance of 3.24 × 10⁻¹⁰ m decreased as the initial As/Fe molar ratio increased. Thus, for more efficient wastewater treatment, active control of coprecipitation phenomena according to mechanistic details is essential.