Highly Reversible Cuprous Mediated Cathode Chemistry for Magnesium Batteries

Sluggish kinetics and poor reversibility of cathode chemistry is the major challenge for magnesium batteries to achieve high volumetric capacity. Introduction of the cuprous ion (Cu⁺) as a charge carrier can decouple the magnesiation related energy storage from the cathode electrochemistry. Cu⁺ is generated from a fast equilibrium between copper selenide electrode and Mg electrolyte during standing time, rather than in the electrochemical process. A reversible chemical magnesiation/de‐magnesiation can be driven by this solid/liquid equilibrium. During a typical discharge process, Cu⁺ is reduced to Cu and drives the equilibrium to promote the magnesiation process. The reversible Cu to Cu⁺ redox promotes the recharge process. This novel Cu⁺ mediated cathode chemistry of Mg battery leads to a high reversible areal capacity of 12.5 mAh cm^?2 with high mass loading (49.1 mg cm^?2) of the electrode. 80 % capacity retention can be achieved for 200 cycles after a conditioning process.     

A standardless method for the local electrochemical analysis of homogeneous alloys

A standardless method is proposed for the local electrochemical analysis of homogeneous alloys. The method is verified by examples of unlimited solid solutions (Au-Ag, Cu-Ni) and limited solid solutions, as well as intermediate phases with a wide homogeneity range (In-Pb). It is shown that the composition of a homogeneous alloy can be determined from polarization curves of the alloy and its pure components or from polarization curves of the phases at the boundary with the homogeneity region, without a calibration curve.     

Various strategies to tune the ionic/electronic properties of electrode materials

This Perspective highlights, through several snapshot examples, the importance of electrochemically-driven redox reactions in tuning the electronic/ionic as well as magnetic properties of 3d-metal-based inorganic compounds through a careful control of the metal oxidation state. Although such redox reactions usually imply the electron-ionic duality, they can be extended to insulating compounds (LiFePO(4)) or semiconductors (CoO) as long as we can combine electrochemistry at the nanoscale to reduce diffusion and migration limitations, and provide the compounds with electrons through metallic coating techniques. A thorough investigation of the composition-structure-property relationships of the Li(x)CoO(2) system, through the assembly of LiCoO(2)/Li electrochemical cells has led to the identification of the CoO(2) phase, whose property and stability are discussed in terms of cationic-anionic redox competition, thus bearing some similarity with the high T(c) cuprate superconductors. Such a d-sp redox competition could have structural and electronic consequences. Encouraged by the recently reported superconductivity in Na(x)CoO(2);yH(2)O phase, the room temperature Li(x)CuO(2) phase diagram was reinvestigated through Li-driven electrochemical reactions. A solid solution domain was unravelled but superconductivity was not evident. With Cu-based materials such as Cu(2.33)V(4)O(11), we have shown the feasibility of a new reversible Li electrochemically-driven copper extrusion/insertion process, owing to the enhanced copper diffusion within the structure.     

钠盐溶液中U(Ⅵ)的电化学电子转移与晶化研究

采用循环伏安法分析钠盐溶液中U(Ⅵ)的电化学行为,恒电位电化学还原处理U(Ⅵ),利用交流阻抗谱分析电化学还原反应中的过程动力学特性,利用X射线衍射、扫描电子显微镜和电子能谱等方法分析了U(Ⅵ)的电化学晶化.结果表明,在钠盐溶液中,U(Ⅵ)可通过电化学反应先还原成低价的U(V)并进一步还原为U(Ⅳ),U(Ⅳ)一步氧化为U(Ⅵ),U(Ⅳ)/U(Ⅵ)之间的电化学转化过程受扩散控制,且U(Ⅵ)的电化学电子转移易受环境p H值的影响;恒电位还原4 h时,溶液中U(Ⅵ)的去除率可达90%,U(Ⅵ)的结晶固化产物主要以固态的(UO2)6O2(OH)8·6H2O(水铀矿)和UO2的形式附着在工作电极上.     

Kinetics of crystallization processes in some glass ceramic products

The paper presents the kinetic study of the crystallization processes which take place in basalt glasses containing variable amount of nucleation agent (CaF₂, 310%). The activation energies have been calculated using Kissinger's equation and verified with the Ozawa-Flynn-Wall equation. In this order, the DTA curves have been registered with different heating rates, between 4 and 20 degrees/min. A correlation equation between the activation energy and the amount of nucleation agent (% of CaF₂) was established. By X-ray diffraction it was proved that the crystalline phase formed in the crystallization process represents a pyroxenic solid solution, Ca(Mg,Fe)SiO₃. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetic study of the crystallization processes of some glass ceramics based on basalt,via thermal analysis

The paper presents the kinetic study of the crystallization processes which take place at the obtaining of some glass ceramics, starting from two basalt glasses with different oxide composition. The activation energies have been calculated using Kissinger's equation and verified with the Ozawa's equation. In this order, the DTA curves have been registered with different heating rates, between 4 and 20°C min^-1. By X-ray diffraction it was established that the crystalline phase formed in the crystallization process represent a pyroxenic solid solution, Ca(Mg,Fe)SiO₃. This revised version was published online in July 2006 with corrections to the Cover Date.     

Univocal demonstration of the electrochemically mediated binding of Pb2+ by a modified surface incorporating a TTF-based redox-switchable ligand

A tetrathiafulvalene-based redox-switchable ligand with unprecedented electrochemical recognition properties for a metallic cation is described and is chemically immobilized onto a solid surface. The recognition properties for Pb2+ are maintained at the solid-liquid interface. Evidence of the modulation of the binding affinity of the modified surface, as a function of the potential applied, is given by EQCM analyses and by direct measurements of residual Pb2+ concentration in solution by atomic absorption.     

钠盐溶液中U(Ⅵ)的电化学电子转移与晶化研究

采用循环伏安法分析钠盐溶液中U(Ⅵ)的电化学行为, 恒电位电化学还原处理U(Ⅵ), 利用交流阻抗谱分析电化学还原反应中的过程动力学特性, 利用X射线衍射、 扫描电子显微镜和电子能谱等方法分析了U(Ⅵ)的电化学晶化. 结果表明, 在钠盐溶液中, U(Ⅵ)可通过电化学反应先还原成低价的U(V)并进一步还原为U(Ⅳ), U(Ⅳ)一步氧化为U(Ⅵ), U(Ⅳ)/U(Ⅵ)之间的电化学转化过程受扩散控制, 且U(Ⅵ)的电化学电子转移易受环境pH值的影响; 恒电位还原4 h时, 溶液中U(Ⅵ)的去除率可达90%, U(Ⅵ)的结晶固化产物主要以固态的(UO₂)₆O₂(OH)₈·6H₂O(水铀矿) 和UO₂的形式附着在工作电极上.     

Determination of traces of impurities in high-purity sodium chloride by differential pulse polarography and flame spectrometry

Summary Detection limits for the determination of a number of elements in solid sodium chloride by differential pulse polarography, flame absorption and emission spectrometry were established. These methods were used for a quantitative investigation on the distribution of ppm quantities of Cu, Pb, Cd, Zn, Mn, Mg, Sr and Ba between the crystallizate and the mother solution obtained in a partial crystallization of sodium chloride from its saturated solution. Recoveries of the crystallization process, calculated from the results of the analysis, vary from 86% for Pb to 115% for Sr.

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Bestimmung von Spurenverunreinigungen in reinstem Natriumchlorid durch Differential-Pulspolarographie und Flammenspektrometrie

Zusammenfassung Die Nachweisgrenzen für die Bestimmung einer Zahl von Elementen im festen Natriumchlorid wurden mit Differential-Pulspolarographie, Absorptions- und Emissions-Flammenspektrometrie bestimmt. Diese Methoden wurden benutzt zur quantitativen Untersuchung der Verteilung von ppm-Mengen Cu, Pb, Cd, Zn, Mn, Mg, Sr und Ba zwischen kristallisiertem Salz und Mutterlösung bei teilweiser Kristallisation vom Natriumchlorid aus seiner gesättigten Lösung. Die Ausbeuten des Kristallisationsprozesses, berechnet aus den Analysenergebnissen, schwanken von 86% für Pb bis 115% für Sr.

Lecture presented at Euroanalysis I Conference, 28. 8.–1. 9. 1972 in Heidelberg, Germany.     

Electrochemically-driven conformational shift in mono- and di-copper constrained macrotricyclic cyclen receptors

An electrochemical study of mono- and di-copper constrained cyclen macrotricycles is presented. Electrochemical data in DMF solution indicate that the reduction of dinuclear complexes occurs in two steps in the -0.4 to -0.8 V vs.AgCl/Ag potential range yielding CuII CuI and CuI CuI species further reduced to Cu metal at highly negative potentials. Mononuclear complexes are reduced in two steps to CuI and Cu metal. Electrochemical data suggest that reduction of both mononuclear and dinuclear complexes approach a square scheme involving electrochemically-driven conformational shifts for metal ions. The presence of endo- and exo-forms of the complexes are revealed by changes in the electrochemical response of the complexes in the presence of tetraethylammonium chloride, 1-azabicyclo[2.2.2]octane and diazabicyclo[2.2.2]octane competing ligands.     

Multiple regioselective functionalizations of quinolines via magnesiations

A wide range of polyfunctionalized quinolines was prepared via chemo- and regioselective magnesiation reactions using appropriate Mg reagents, such as i-PrMgCl.LiCl, MesMgBr.LiCl, Mes2Mg.2LiBr, TMPMgCl.LiCl, and TMP2Mg.2LiCl. An application to the total synthesis of the biologically active compound talnetant was performed (six steps, 28%).     

Processing and characterization of Pb(Mg,Nb)O3-PbTiO3 thin films from metal alkoxide-derived gels

The sol-gel processing is one of promising methods to fabricate well-derived integrated thin films at relatively low temperature. Ferroelectric niobates films do afford the possibilities for adding the values by the hybridization with semiconductor and/or electro-optic systems. The molecular level designing of the precursor solution was stressed as well as the control of key processing factors. The advantages of this sol-gel have been extended to prepare the ferroelectric Pb(Mg, Nb)O₃-PbTiO₃ solid solution films integrated on Si wafers. The crystallization of the films with desired crystal structure could be promoted by the controlled partial hydrolysis of designed alkoxide solution in the intermediate state and the pre-heated treatment of alkoxide-derived films in flow of water vapor and oxygen gas mixture.     

Chemistry of borate in salt lake brine (XXXIV) ——Phase diagram of thermodynamic nonequilibrium state of MgO-B_2O_3-18%MgCl_2-H_2O system at 20℃

The crystallization processes of hydrated Mg-borates, boric, magnesium hydroxide and Mg-oxychloride from MgO-B2O3-18%MgCl2-H2O supersaturated solution at 20℃ have been studied by kinetic method. The crystallization solid phases were characterized by X-ray powder diffraction, IR spectra, thermal analysis and chemical analysis. The liquid-solid phase diagram of ther-modynamic nonequilibrium state has been given. In this phase diagram, there exist eight crystallization fields, boric acid(H3BO3), trigomagneborite(MgO · 3B2O3 · 7.5H2O, MgO · 3B2O3 · 7H2O), hungchaoite(MgO ·2B2O3 ·9H2O), inderite(2MgO ·3B2O3 · 15H2O), chloropinnoite(2MgO ·2B2O3 · MgCl2 · 14H2O), magnesium hydroxide(Mg(OH)2) and magnesium oxychloride (5Mg(OH)2 · MgCl2·8H2O).     

Effect of the Heating Rate on Crystallization Kinetics of Mg84Ni12.5Y3.5 Amorphous Ribbons

Crystallization kinetics of Mg₈₄Ni_12.5Y_3.5 amorphous ribbons produced by the melt-spinning method, was studied by DSC analysis and X-ray diffraction. The effect of heating rate (from 2 to 240 K min^–1) was investigated in the temperature range from 298 to 673 K. The results showed that the crystallization process took place in two stages: a) crystallization of part of the amorphous matrix to an intermediate phase and hcp-Mg, and b) transformation of the intermediate phase and the remaining amorphous material to Mg₂Ni+Mg (solid solution of Y in Mg). Increasing the heating rate from 2 to 240 K min^–1 results in increases of the temperature difference between the two-step crystallization of the first stage transformation processes from 33 to 56 K and in increases of the temperature difference between the two-stage transformation from 62 to 97 K.This revised version was published online in November 2005 with corrections to the Cover Date.     

Microstructural Exploration of the High Capacitance in RuO_2-ZrO_2 Coating

A high capacitance RuO₂-ZrO₂ coating was prepared by thermal decomposition method.Extended X-ray absorption fine structure(EXAFS),X-ray diffraction(XRD),high-resolution transmission electron microscope(HRTEM)and ab initio calculations were applied to understand the role of the microstructure in the acquisition of high specific capacitance of RuO₂-based oxides.The results show that the RuO₂-ZrO₂ oxide prepared at critical crystallization temperature can be considered to be quasi-amorphous or microcrystalline(A short-range ordered crystal structure can be seen from the TEM image,but no diffraction peaks can be seen from the XRD diffraction patterns).And this RuO₂-ZrO₂ was identified as a solid solution with high solid solubility.It referred to herein as a quasi-amorphous solid solution.Such a special microstructure was conducive for"synergistic catalysis"owing to the cationic interaction and thus could gain high"active site density"and high"active surface",thus developing high specific capacitance.     

Ni_(0.67)Mg_(0.33)O贮锂性能的研究

通过溶胶-凝胶法制备了Ni-Mg-O及作为对照物的NiO样品,研究了其电化学嵌锂性能,并对样品进行了XRD结构表征,Rietveld精化以及贮锂性能测试.结果表明:Ni-Mg-O电极由于Mg的掺入而抑制了其中Ni2+的还原,导致材料的比容量降低.但同时又因该样品形成均一的固溶体使得NiO分散效果较好,从而改善其循环性能.     

The study on microstructure and electrochemical properties of Al–Mg–Sn–Ga–Pb alloy anode material for Al/AgO battery

The microstructure of Al–Mg–Sn–Ga–Pb quinary aluminum alloy anode material and the influences of its electrochemical properties and self-corrosion rate in 4 mol/l NaOH +10 g/l Na₂SnO₃ medium were studied. The microstructure and morphology were characterized by metallographic microscope, transmission electron microscope, and scanning electron microscopy. The electrochemical properties were tested by electrochemical workstation, and the self-corrosion rate of Al alloy anode was studied by methods of recovery H₂ gas by discharge water. The results show that homogenization has not much impact on the electrochemical properties and the corrosion rate of the cast aluminum alloy anode material; besides, return annealing treatment of the cold-rolled Al–Mg–Sn–Ga–Pb quinary aluminum alloy anode material can reduce the rate of self-corrosion and make Al anodic potential shift negative steadily and improve the properties of the material.

     

Electrochemical and structural characterization of sputter-deposited Mg–Nb and Mg–Nb–Al–Zn alloy films

Nanocrystalline Mg–Nb and Mg–Nb–Al–Zn alloy films were deposited by dc magnetron sputtering on glass and quartz substrates in a wide range of niobium concentrations from 6 to 80 at.%. Structural, electrochemical and corrosion properties of the films were studied by X-ray diffraction, dc voltammetry, electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance. Development of body-centred cubic Nb structure in the Mg–Nb alloy matrix yielded the effects of lattice contraction, grain refining and electrochemical passivity. The measurements showed high corrosion resistance of the films in alkaline solutions when niobium content was one third or more. An increased corrosion resistance was achieved by introducing minor amounts of Al (ca. 2 at.%). In particular, such Al effect was pronounced at lower Nb concentrations (20 to 30 at.%). Semiconductor properties of spontaneously formed oxide on Mg–Nb alloy were studied by Mott–Schottky plots, which indicated highly doped n-type oxide structures on Mg–Nb surface. The paper fills some gap in understanding of niobium–magnesium systems, which show potential for applications in hydrogen storage, switchable mirrors and corrosion protection.     

Highly efficient adsorbents of poly(o-phenylenediamine) solid and hollow sub-microspheres towards lead ions: a comparative study

Two kinds of different-shaped poly(o-phenylenediamine) (PoPD) polymers: solid and hollow sub-microspheres with both size of about 700 nm synthesized by a solution route without any additional directing agents, were employed as efficient adsorbents for removal of Pb(??) ions from water. Firstly, chemical structures of PoPD sub-microspheres were performed by Fourier-transform infrared (FT-IR), UV-vis, (1)H NMR spectra, X-ray diffraction (XRD) and GPC analysis. When used as adsorbents, both PoPD hollow and solid sub-microspheres showed high adsorptivity and adsorption capacity towards Pb(??) ions in water, and mechanisms of adsorption behaviors were revealed by XRD and X-ray photoelectron spectra (XPS). It was found that the pH and concentration of Pb(??) ion solution, as well as contact time and adsorbent dosage affect the degree of adsorption. Adsorption isotherms and kinetics of Pb(??) ions onto PoPD sub-microspheres were also investigated according to experimental data. Comparative investigations of adsorption behaviors revealed that hollow sub-microspheres showed enhanced adsorptivity adsorption capacity towards Pb(??) ions as compared with solid sub-microspheres typical at low adsorbent dosage. PoPD hollow sub-microspheres also showed good adsorptivity for other heavy-metal ions, such as Hg(??), Cd(??) and Cu(??), which implied their potential applications as effective adsorbents for heavy-metal ions in water.     

First principles simulations of the electrochemical lithiation and delithiation of faceted crystalline silicon

Silicon is of significant interest as a next-generation anode material for lithium-ion batteries due to its extremely high capacity. The reaction of lithium with crystalline silicon is known to present a rich range of phenomena, including electrochemical solid state amorphization, crystallization at full lithiation of a Li(15)Si(4) phase, hysteresis in the first lithiation-delithiation cycle, and highly anisotropic lithiation in crystalline samples. Very little is known about these processes at an atomistic level, however. To provide fundamental insights into these issues, we develop and apply a first principles, history-dependent, lithium insertion and removal algorithm to model the process of lithiation and subsequent delithiation of crystalline Si. The simulations give a realistic atomistic picture of lithiation demonstrating, for the first time, the amorphization process and hinting at the formation of the Li(15)Si(4) phase. Voltages obtained from the simulations show that lithiation of the (110) surface is thermodynamically more favorable than lithiation of the (100) or (111) surfaces, providing an explanation for the drastic lithiation anisotropy seen in experiments on Si micro- and nanostructures. Analysis of the delithiation and relithiation processes also provides insights into the underlying physics of the lithiation-delithiation hysteresis, thus providing firm conceptual foundations for future design of improved Si-based anodes for Li ion battery applications.