Pulse radiolysis of alkali metal cations in isopropylamine: Correlation of optical absorption spectra with electron spin resonance data

Pulse radiolysis of alkali metal cations in isopropylamine indicates the formation of three distinct optical bands attributed to solvated electrons, e^?_s, ion-pairs (M⁺, e^?_s) and alkali anions M^?. It is found that the ion-pair spectra exhibit a distinct blue shift from that of e^?_s. Comparisons with results obtained in ethylamine, tetrahydrofuran and other solvents demonstrate that the position of the ion-pair band can be correlated with the percent atomic character observed by ESR for the “monomer” species in alkali metal solutions. Results are presented for the alkali metal series, Li, Na, K, Rb and Cs.     

Coated-wire ion-selective electrodes

Coated-wire ion-selective electrodes were first developed in 1971, and comprise a film of polyvinyl chloride or other suitable polymeric matrix substrate containing a dissolved electroactive species, coated on a conducting substrate (generally a metal, although any material with conductivity substantially higher than that of the film can be used). Electrodes of this sort are simple, inexpensive, durable and capable of reliable response in the concentration range of 10^?1 to 10^?6 M for a wide variety of both organic and inorganic cations and anions. The principles on which these electrodes are based, as well as their application to a variety of analytical problems, will be discussed.     

Tough Gel Electrolyte Using Double Polymer Network Design for the Safe,Stable Cycling of Lithium Metal Anode

The growth of lithium dendrites and low coulombic efficiency restrict the development of Li metal anodes. Polymer electrolytes are expected to be promising candidates to solve the issue, but ways to obtain a polymer electrolyte that integrates high ionic conductivity and high mechanical toughness is still challenging. By introducing a double polymer network into the electrolyte design to reshape it, a tough polymer electrolyte was developed with high conductivity, and stable operation of lithium metal anodes was further realized. The double network (DNW) gel electrolyte has high modulus of 44.3 MPa and high fracture energy of 69.5 kJ m^?2. The conductivity of DNW gel is 0.81 mS cm^?1 at 30 °C. By using this gel electrolyte design, the lithium metal electrode could be cycled more than 400 times with a coulombic efficiency (CE) as high as 96.3 % with carbonate‐based electrolytes.     

Concentrated Electrolyte for the Sodium–Oxygen Battery: Solvation Structure and Improved Cycle Life

Alkali metal–oxygen batteries are of great interests for energy storage because of their unparalleled theoretical energy densities. Particularly attractive is the emerging Na–O₂ battery because of the formation of superoxide as the discharge product. Dimethyl sulfoxide (DMSO) is a promising solvent for this battery but its instability towards Na makes it impractical in the Na–O₂ battery. Herein we report the enhanced stability of Na in DMSO solutions containing concentrated sodium trifluoromethanesulfonimide (NaTFSI) salts (>3 mol kg^?1). Raman spectra of NaTFSI/DMSO electrolytes and ab initio molecular dynamics simulation reveal the Na⁺ solvation number in DMSO and the formation of Na(DMSO)₃(TFSI)‐like solvation structure. The majority of DMSO molecules solvating Na⁺ in concentrated solutions reduces the available free DMSO molecules that can react with Na and renders the TFSI anion decomposition, which protects Na from reacting with the electrolyte. Using these concentrated electrolytes, Na–O₂ batteries can be cycled forming sodium superoxide (NaO₂) as the sole discharge product with improved long cycle life, highlighting the beneficial role of concentrated electrolytes for Na‐based batteries.     

Ultrathin 2D Graphitic Carbon Nitride on Metal Films: Underpotential Sodium Deposition in Adlayers for Sodium‐Ion Batteries

Efficient and low‐cost anode materials for the sodium‐ion battery are highly desired to enable more economic energy storage. Effects on an ultrathin carbon nitride film deposited on a copper metal electrode are presented. The combination of effects show an unusually high capacity to store sodium metal. The g‐C₃N₄ film is as thin as 10 nm and can be fabricated by an efficient, facile, and general chemical‐vapor deposition method. A high reversible capacity of formally up to 51 Ah g^?1 indicates that the Na is not only stored in the carbon nitride as such, but that carbon nitride activates also the metal for reversible Na‐deposition, while forming at the same time an solid electrolyte interface layer avoiding direct contact of the metallic phase with the liquid electrolyte.     

Adsorption of alkali metal cations and halide anions on metal oxides: prediction of Hofmeister series using 1-pK triple layer model

Adsorption of electrolyte ions on metal oxides significantly affects the interfacial charge distribution. The general procedure for the prediction of surface charge on oxides in salt solutions was given by Sverjensky for the 2-pK Triple Layer Model (2-pK TLM) (Sverjensky, Geochim. Cosmochim. Acta 69:225–257, 2005). Based on his parameters values and by assuming parameters transferability (Piasecki, J. Colloid Interface Sci. 302:389–395, 2006) we have predicted the adsorption constants for three monovalent ions (Rb⁺, F^?, Br^?) for eight oxides within the framework of the 1-pK Triple Layer Model (1-pK TLM). The obtained parameters values along with the previously reported ones (Piasecki, J. Colloid Interface Sci. 302:389–395, 2006) allowed us to compare the adsorption affinities of alkali metal cations and halide anions, and construct the following Hofmeister series for the cations (Cs⁺≈ Rb⁺≈ K⁺< Na⁺< Li⁺) and for the anions (F^?? Cl^?≈ Br^?< I^?) for investigated oxides. The same lyotropic series was predicted by the 2-pK TLM. It indicates that Hofmeister series is invariable during parameter transfer between surface complexation models.     

One decade of research on ion-selective electrodes in Iran (1996–2006)

This review presents a general overview about the development of ion-selective electrodes in Iran during the past decade (1996–2006). All of the reported ion-selective sensors (for cations, anions and organic species) are cited in this review. Sensors for 39 cations, 12 anions, and 23 organic compounds and drugs have been reported in this reivew. Some of the main group cations (e.g. beryllium) as well as most of the lanthanide ion (i.e., presidium, erbium, lutetium, cerium, neodymium, europium, gadolinium, terbium, dysprosium, holmium, ytterbium, and thulium) sensors have been reported for the first time. It is noticable that the best reported sensors for HPO₄ ^2?, SO₄ ^2?, Cl^?, ClO₄ ^?, Br^?, and I₃ ^? have been designed and constructed by the Iranian researchers.     

A TTF–TCNQ Electrode as a Voltammetric Analogue of an Ion‐Selective Electrode

A TTF‐TCNQ/PVC composite electrode is proposed as a voltammetric cation and anion sensor. The electrode relies on the principle that, during redox processes involving the TCNQ^0/? couple for cations and the TTF^+/0 couple for anions, electrolyte ions are included into lattice sites in the charge neutralization process. This voltammetric ion‐sensor provides results that are similar to those of sensors based on two electrodes (viz. one modified with TCNQ for cations and another modified with TTF for anions) but with some practical advantages over them.     

The Application of Cryptand 22 as a Bifunctional Stationary Phase for Ion Chromatography

Poly (styrene/divinyl benzene) with cryptand 22 as an anchoring group was synthesized and applied as a bifunctional packing material for the separation of both cations and anions. At pH < 2, the resin can be protonated and applied as an anion exchanger for the separation of anions; with water as eluent, inorganic anions such as F^?, Cl^?, Br^?, NO₃^?”, I^? were well separated. After deprotonation at pH> 10, the resin became a cation exchanger and successfully separated alkali metal ions such as Li⁺, K⁺ and Cs⁺ with methanol as eluent. The effects of solvents, flow rate and temperature on the separation of various ions were also investigated.     

Catalysis of the reduction of dioxygen by poly(xylylviologen) coatings on graphite electrodes

At graphite electrodes coated with poly(xylylviologen), PXV, the reduction of dioxygen to hydrogen peroxide proceeds at potentials somewhat more positive than those where the reduction occurs at uncoated electrodes. Coated electrodes were used as rotating disks to evaluate the kinetics of the reduction. The data indicate that only one to two monolayers of the PXV coatings participate in the catalysis. Electrons can be delivered from the electrode surface to the catalytically active viologen sites rapidly enough for the catalytic current to be limited by the rate of the cross reaction between viologen radical cations and dioxygen. The rate constant for this heterogeneous reaction at the polymer—electrolyte interface was estimated to be ca. 10⁶M^?1s^?1.     

Manipulating Coulombic Efficiency of Cathodes in Aqueous Zinc Batteries by Anion Chemistry

Electrolyte environments, including cations, anions, and solvents are critical for the performance delivery of cathodes of batteries. Most works focused on interactions between cations and cathode materials, in contrast, there is a lack of in-depth research on the correlation between anions and cathodes. Here, we systematically investigated how anions manipulate the coulombic efficiency (CE) of cathodes of zinc batteries. We take intercalation-type V₂O₅ and conversion-type I₂ cathodes as typical cases for profound studies. It was found that electronic properties of anions, including charge density and its distribution, can tune conversion or intercalation reactions, leading to significant CE differences. Using operando visual Raman microscopy and theoretical simulations, we confirm that competitive coordination between anions and I⁻ can regulate CEs by modulating polyiodide diffusion rates in Zn−I₂ cells. In Zn−V₂O₅ cells, anion-tuned solvation structures vastly affect CEs through varying Zn²⁺ intercalation kinetics. Conversion I₂ cathode achieves a 99 % CE with highly electron-donating anions, while anions with preferable charge structures that interact strongly with Zn²⁺ afford an intercalation V₂O₅ a nearly 100 % CE. Understanding the mechanism of anion-governed CEs will help us evaluate compatibility of electrolytes with electrodes, thus providing a guideline for anion selection and electrolyte design for high-energy, long-cycling zinc batteries.     

VOCl as a Cathode for Rechargeable Chloride Ion Batteries

A novel room temperature rechargeable battery with VOCl cathode, lithium anode, and chloride ion transporting liquid electrolyte is described. The cell is based on the reversible transfer of chloride ions between the two electrodes. The VOCl cathode delivered an initial discharge capacity of 189 mAh g^?1. A reversible capacity of 113 mAh g^?1 was retained even after 100 cycles when cycled at a high current density of 522 mA g^?1. Such high cycling stability was achieved in chloride ion batteries for the first time, demonstrating the practicality of the system beyond a proof of concept model. The electrochemical reaction mechanism of the VOCl electrode in the chloride ion cell was investigated in detail by ex situ X‐ray diffraction (XRD), infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS). The results confirm reversible deintercalation–intercalation of chloride ions in the VOCl electrode.     

The short-term cycling properties of Na/PVdF/S battery at ambient temperature

The Na/PVdF/S cells were composed of solid sodium, sulfur, and polyvinylidene fluoride–hexafluoropropene (PVdF) gel polymer electrolyte. The PVdF polymer electrolyte was prepared form tetraglyme plasticizer and NaCF₃SO₃ salt, and its electrochemical properties were studied using CV and impedance analysis. The interfacial resistance between sodium and polymer electrolyte increase with storage time, which might be associated with passivation layer. Solid-state sodium/sulfur cell using a PVdF gel polymer electrolyte has been tested. The Na/PVdF/S cell with 0.288 mA cm^?2 shows a high discharge capacity of 392 mAh g^?1 and 36 mAh g^?1 after 20 cycles. The cycle performance of Na/GPE/S cell operating at 25 °C is worse than Na/S cell at a high temperature.     

Polymerization of Acrylonitrile-Metal Halide Complexes in the Frozen State. V. Comparison of Metal Cations and Halogen Anions in Radiation-Induced Polymerization of Acrylonitrile-Metal Halide Complexes

The radiation-induced polymerization of acrylonitrile in the frozen aqueous solutions of various metal chlorides and zinc halides was studied to compare the accelerating effect of metal cations and halogen anions. Among metal chlorides examined, zinc, stannous, manganese, and nickel cations gave greater rates and degrees of polymerization. Of the halogen anions, the rate of polymerization decreased in the order, Br^?, CI^?, SCN^? ? I^?, CH₃CO₂ ^?, and the degree of polymerization decreased in the order, Br^?, SCN^? ? CI^? ? I^? ? CH₃CO₂ ^?. The increase of the rate and the degree of polymerization was confirmed below the eutectic temperatures of the hydrated metal chlorides and ice. This suggests that the increment of the rate and the degree of polymerization is attributed to formation of hydrated metal chloride-acrylonitrile complexes accompanied by their solidification in eutectic mixtures with ice. The radioactivation analysis of polymers obtained in frozen dilute aqueous zinc bromide solution reveals appreciable contribution of water to generation of initiating species.     

Fluoroethylene Carbonate Enabling a Robust LiF‐rich Solid Electrolyte Interphase to Enhance the Stability of the MoS2 Anode for Lithium‐Ion Storage

As a high‐capacity anode for lithium‐ion batteries (LIBs), MoS₂ suffers from short lifespan that is due in part to its unstable solid electrolyte interphase (SEI). The cycle life of MoS₂ can be greatly extended by manipulating the SEI with a fluoroethylene carbonate (FEC) additive. The capacity of MoS₂ in the electrolyte with 10 wt % FEC stabilizes at about 770 mAh g^?1 for 200 cycles at 1 A g^?1, which far surpasses the FEC‐free counterpart (ca. 40 mAh g^?1 after 150 cycles). The presence of FEC enables a robust LiF‐rich SEI that can effectively inhibit the continual electrolyte decomposition. A full cell with a LiNi_0.5Co_0.3Mn_0.2O₂ cathode also gains improved performance in the FEC‐containing electrolyte. These findings reveal the importance of controlling SEI formation on MoS₂ toward promoted lithium storage, opening a new avenue for developing metal sulfides as high‐capacity electrodes for LIBs.     

Concurrent determination and separation of inorganic cations and anions in microchip electrophoresis with precisely controlled high‐voltage

An improved method for the concurrent determination and separation of cations and anions by microchip electrophoresis with capacitively coupled contactless conductivity detection (ME‐C⁴D) is described. Two kinds of microchip structures were designed. The first microchip has a long bent separation channel. And for the defects of the first microchip, the second microchip with a Y‐type separation channel has been proposed. The background electrolyte (BGE) composed of 20 mm His/MES and 0.01 mm CTAB was optimized for inhibiting the electroosmotic flow (EOF). Due to the low electroosmotic flow, the cations and anions migrate in opposite directions and can be separated from each other. With the precisely controlled high‐voltage, cations and anions can be migrated in microchannels according to our requirements and sequentially detected by a C⁴D detector built in‐house. Samples containing K⁺, Na⁺, Li⁺, Cl⁻, F⁻ and PO₄³⁻ were analyzed simultaneously in a single run (within 140 s) by both methods. The reproducibility obtained by both methods remained below 5% for migration time and within 3.5–9.1% for peak areas. The proposed concurrent determination methods are inexpensive, simple, fast, ease of operation, high degree of integration.     

Activity coefficients of electrolytes from the E.M.F. of liquid membrane cells. I. The method—Test measurements on KCl

A new electrochemical cell is described, in which two permselective liquid membranes, one anionic the other cationic, are interposed between the subsidiary electrodes and the solution of the electrolyte under examination By means of this kind of cell it is possible to measure activity coefficients of salts of cations and anions for which reversible electrodes are not available, with great accuracy even at high dilutions never accessible before (down to ≊10⁻⁴ mol-dm⁻³). The cell performance has been tested by measuring the activity coefficients of KCl for which accurate data are available in literature.     

Aluminium‐27 NMR investigation of the influence of cation type on aluminosilicate solutions

The effects of tetraalkylammonium (TAA) and alkali metal cations on the equilibrium distribution of aluminosilicate oligomers in aqueous alkaline aluminosilicate solutions were investigated using ²⁷Al NMR spectra and their evolution with time. The results indicate that there are no differences in the initial equilibria involving solutions containing both TAA and alkali metal cations on the one hand and those containing alkali metal cations only. However, re‐equilibration of the aluminosilicate species for TAA/Na aluminosilicates is slow (usually not detectable on the time‐scale of the experiments), whereas when purely alkali metal cations are used, the spectra alter over a period of ～1 h, such that resolution is degraded substantially. In the latter case, it is suggested that the anions aggregate into larger systems, although the solutions are still clear. ²⁹Si NMR evidence for slow equilibration of silicate and aluminosilicate solutions at higher concentrations is also discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Determination of tin in indium by neutron activation with pre-irradiation separation

A method has been developed for chemical control of a short-lived radiopharmaceutical,⁵²Fe. The optimum conditions have been investigated for the simultaneous determination of microgram amounts of nickel, iron and chromium in an admixture. The method developed is applicable for the determination of 0.01 to 20 μg·ml^?1 of nickel, 0.01 to 50 μg·ml^?1 of iron and 0.05 to 50 μg·ml^?1 of chromium. A study has been made of the mutual interference of these elements at different concentrations, and also of the interference by various other cations and anions. A list has been given of the other elements that can be analysed using the supporting electrolyte. A method of routine analysis is described.     

Enhancing the Hydrogen Evolution Reaction Activity of Platinum Electrodes in Alkaline Media Using Nickel–Iron Clusters

Herein, we demonstrate an easy way to improve the hydrogen evolution reaction (HER) activity of Pt electrodes in alkaline media by introducing Ni–Fe clusters. As a result, the overpotential needed to achieve a current density of 10 mA cm^?2 in H₂‐saturated 0.1 m KOH is reduced for the model single‐crystal electrodes down to about 70 mV. To our knowledge, these modified electrodes outperform any other reported electrocatalysts tested under similar conditions. Moreover, the influence of 1) Ni to Fe ratio, 2) cluster coverage, and 3) the nature of the alkali‐metal cations present in the electrolyte on the HER activity has been investigated. The observed catalytic performance likely originates from both the improved water dissociation at the Ni–Fe clusters and the subsequent optimal hydrogen adsorption and recombination at Pt atoms present at the Ni–Fe/Pt boundary.