酸性AlCl3-BMIC离子液体中的铝阳极溶解

采用线性扫描伏安法研究了Lewis 酸性AlCl₃-BMIC (BMIC: 1-butyl-3-methylimidazolium chloride)离子液体中铝电极的溶解. 铝电极在阳极极化时出现了钝化现象, 钝化是由于在铝电极表面形成了固体AlCl₃钝化膜造成的. 铝的电化学溶解过程可以依次分为三个区: 电化学控制区、过渡区和钝化区. 在电化学控制区, 铝的电化学溶解速率随着电位的正移而逐渐增加; 在过渡区, 由于电极表面AlCl₄^-和Al₂Cl₇^-浓度发生改变而析出固体AlCl₃使得铝电化学溶解速率随着电位的正移而逐渐减小; 当钝化膜形成之后, 铝的电化学溶解速率不再随着电位的正移而发生改变, 铝溶解进入钝化区. 增加搅拌、升高温度、降低离子液体AlCl₃摩尔分数都可以增加铝溶解阳极极限电流密度.     

在LiCl-KCl-AlCl3熔盐中直接电化学还原Sm2O3及Al-Sm合金的形成

在803 K LiCl-KCl熔盐中, 研究了通过添加助剂AlCl₃直接电化学还原Sm₂O₃和Al-Sm合金的形成。以SmCl₃为原料作为参照, 采用循环伏安和方波伏安方法, 研究了Sm₂O₃在LiCl-KCl-AlCl₃熔盐体系中的电化学行为。通过对比发现在两个体系中, 峰的数量和位置基本一致, 这说明在LiCl-KCl熔盐中, 加入AlCl₃之后, 可以将Sm₂O₃有效氯化。计时电位结果表明, 当阴极电流比-139.8 mA·cm^-2更负时, Al和Sm共同还原。为了提取Sm, 采用恒电流从LiCl-KCl-AlCl₃-Sm₂O₃熔盐中电解得到Al-Sm合金样品, 并进行XRD表征, 结果表明可以通过调节AlCl₃和Sm₂O₃的浓度得到不同相的Al-Sm合金。     

Acid-Base and Anion Binding Properties of Tetrafluorinated 1,3-Benzodiazole, 1,2,3-Benzotriazole and 2,1,3-Benzoselenadiazole

The influence of fluorination on the acid-base properties and the capacity of structurally related 6–5 bicyclic compounds – 1,3-benzodiazole 1 , 1,2,3-benzotriazole 2 and 2,1,3-benzoselenadiazole 3 to σ-hole interactions, i. e. hydrogen ( 1 and 2 ) and chalcogen ( 3 ) bondings, is studied experimentally and computationally. The tetrafluorination increases the Brønsted acidity of the diazole and triazole scaffolds and the Lewis acidity of selenadiazole scaffold decreases the basicity. Increased Brønsted acidity facilitates anion binding via the formation of hydrogen bonds; particularly, tetrafluorinated derivative of 1 (compound 4 ) binds Cl⁻. Increased Lewis acidity of tetrafluorinated derivative of 3 (compound 10 ), however, is not enough for binding with Cl⁻ and F⁻ via chalcogen bonds in contrast to previously studied Te analog of 10 . It is suggested that the maximum positive values of molecular electrostatic potential at the σ-holes, V_S,max, can be a reasonable metric for design and synthesis of new anion receptors with selenadiazole-diazole/triazole hybrids as a special target. Related chlorinated compounds are also discussed.     

The effect of water on the anodic dissolution of aluminum in non-aqueous electrolytes

The influence of water concentration on the electrochemical behavior of Al anodes in Al/active-non-aqueous electrolytes is investigated. Normally passive, Al exhibits facile electrochemical oxidation in both AlCl₃/γ-butyrolactone (AlCl₃/BLA) and (C₂H₅)₄NCl acetonitrile (TEAC/ACN) electrolytes. However, in these two electrolytes, the influence of water on Al oxidation shows opposite effects. Incremental increase from 0 to 1.5 M H₂O (0 to 3% water by volume) hinders Al oxidation in 1 M AlCl₃/BLA, increasing polarization loss from 100 to 400 mV cm² mA⁻¹. Yet in 0.3 M TEAC/ACN, Al is passive in the absence of water, exhibiting currents only in the μA cm⁻² domain, equivalent to oxidative polarization losses of over 1000 mV cm² mA⁻¹. This polarization loss is alleviated by water addition, and decreases from 20 to 7 mV cm² mA⁻¹ as water is increased from 0.3 to 1.5 M. FT-IR spectroscopy, linear voltammetry, galvanostatic reduction, surface microscopy and electrolytic conductivity measurements were conducted to probe competing water activation or water passivation effects on organic-phase Al electrochemistry.     

A Computational Study of a Single‐Walled Carbon‐Nanotube‐Based Ultrafast High‐Capacity Aluminum Battery

Exploring suitable electrode materials is a fundamental step toward developing Al batteries with enhanced performance. In this work, we explore using density functional theory calculations the feasibility of single‐walled carbon nanotubes (SWNTs) as a cathode material for Al batteries. Carbon nanotubes with hollow structures and large surface area are able to overcome the difficulty of activating the opening of interlayer spaces as observed in graphite electrode during the first intercalation cycle. Our results show that AlCl₄ binds strongly with the SWNT to result in an energetically and thermally stable AlCl₄‐adsorbed SWNT system. Diffusion calculations show that the SWNT system allows ultrafast diffusion of AlCl₄ with a more favorable inner surface diffusion than outer surface diffusion. Our charge‐density difference and Bader atomic charge analysis confirm the oxidation of SWNT upon adsorption of AlCl₄, which shows a similar behavior to the previously studied graphite cathode. The average open‐circuit voltage and AlCl₄ storage capacity increases with increasing SWNT diameter and can be as high as 1.96 V and 275 mA h g⁻¹ in (25,25) SWNT relative to graphite (70 mA h g⁻¹). All of these properties show that SWNTs are a potential cathode material for high‐performance Al batteries and should be explored further.     

Electrochemistry of lanthanides in molten chloroaluminates: Part I. The electrochemical behaviour of Eu(III), Yb(III) and Sm(III)

The electrochemical behaviour of Eu(III), Yb(III,II) and Sm(III,II) has been investigated in NaCl-AlCl₃ mixtures, in a temperature range between 150 and 250°C. Principal investigation methods are cyclic voltammetry, pulse polarography and chronoamperometry. The three tervalent lanthanides can be reduced reversibly and solutions of divalent oxidation states are stable. E_1/2 potentials measured with respect to an Al electrode in a saturated melt are located respectively at 2.295 V (Eu), 1.630 V (Yb) and 1.080 V (Sm). In acidic chloroaluminates, the three investigated lanthanides are more oxidizing than in other more complexing solvents. If the acidity of the melt is decreased, precipitation of the trichloride (or the dichloride) occurs and the solubility product of the different species is directly related to the cationic size.     

Electrochemical Performance of Graphitic Multi-walled Carbon Nanotubes with Different Aspect Ratios as Cathode Materials for Aluminum-ion Batteries

Graphitic multi-walled carbon nanotubes (MWCNTs) can function as high-performance cathode materials for rechargeable Al-ion batteries with well-defined discharging plateaus and reasonable charge/discharge C-rates. However, the main intercalation/deintercalation or adsorption/desorption path of AlCl₄⁻ anions into or onto G-MWCNTs has not been elucidated. Herein, we used battery cells comprised of G-MWCNTs with different aspect ratios, Al metal, and AlCl₃/1-ethyl-3-methylimidazolium chloride ionic liquid as the cathode, anode, and electrolyte, respectively. The electrochemical performance of the Al||G-MWCNT cell increased as the aspect ratio of the G-MWCNT cathode increased (i. e., longer and thinner). The degree of defects of the G-MWCNTs was similar (0.15–0.22); hence, the results confirm that the main and alternate paths for the AlCl₄⁻ intercalation/de-intercalation or adsorption/desorption into/from or onto/from the G-MWCNT are the basal and edge planes, respectively. The step-like structures of defects on the basal plane provide the main reaction site for AlCl₄⁻ anions.     

在LiCl-KCl-AlCl3熔盐中直接电化学还原Sm2O3及Al-Sm合金的形成

在803 K LiCl-KCl熔盐中,研究了通过添加助剂AlCl3直接电化学还原Sm2O3和Al-Sm合金的形成。以SmCl3为原料作为参照,采用循环伏安和方波伏安方法,研究了Sm2O3在LiCl-KCl-AlCl3熔盐体系中的电化学行为。通过对比发现在两个体系中,峰的数量和位置基本一致,这说明在LiCl-KCl熔盐中,加入AlCl3之后,可以将Sm2O3有效氯化。计时电位结果表明,当阴极电流比-139.8 mA.cm-2更负时,Al和Sm共同还原。为了提取Sm,采用恒电流从LiCl-KCl-AlCl3-Sm2O3熔盐中电解得到Al-Sm合金样品,并进行XRD表征,结果表明可以通过调节AlCl3和Sm2O3的浓度得到不同相的Al-Sm合金。     

Electrochemical investigation of the redox couple Sm(III)/Sm(II) on a tungsten electrode in molten LiF–CaF2–SmF3

This article is focused on the electrochemical investigation (cyclic voltammetry and related studies) of the redox couple Sm(III)/Sm(II) in an eutectic LiF–CaF₂ melt containing SmF₃. The first step of reduction for Sm(III) ions involving one electron exchange in soluble/soluble Sm(III)/Sm(II) system was found on a tungsten electrode. The study of the Sm(II)/Sm(0) electrode reaction was not feasible, due to insufficient electrochemical stability of LiF–CaF₂. The first step was found reversible at temperatures 1,075 and 1,125 K up to polarization rate 1 V/s and at temperature 1,175 K the process was reversible at all sweep rates applied in this study. The diffusion coefficients (D) of Sm(II) and Sm(III) ions were determined by cyclic voltammetry, showing that D decreases when oxidation state increase, while the activation energy of diffusion (E _a) increases. The standard rate constants of charge transfer (k _s) were calculated for the redox couple Sm(III)/Sm(II) at 1,075 and 1,125 K based on the data of cyclic voltammetry.     

Extraction of ytterbium via co-reduction of Al(III) and Yb(III) from LiCl–KCl melt on W electrode

Anhydrous ytterbium chloride was obtained via solid-phase reaction from Yb₂O₃ with AlCl₃ as a chlorination agent. The electrochemical behavior of the chloridized Yb₂O₃ was investigated on W electrodes in LiCl–KCl and LiCl–KCl–AlCl₃ melts by cyclic voltammetry and square wave voltammetry. The results showed that the reduction/reoxidation of Yb(III)/Yb(II) was reversible and controlled by diffusion. The signals related to the formation of two Al–Yb intermetallic compounds were detected in LiCl–KCl–AlCl₃ melt. Potentiostatic electrolysis was carried out in LiCl–KCl–AlCl₃–YbCl₃ melt on W electrodes at 943 K at different potentials and Al₃Yb, Al₂Yb, AlLi and Al₂Li₃ phases were detected in deposits. Then, the extraction of ytterbium was performed. The currents evolution was recorded by square wave voltammetry and the extraction efficiency was evaluated via inductive coupled plasma atomic emission spectrometer analysis during electrolysis. The initial extraction rate is much higher than that at longer times. The extraction efficiency was about 98.0 % for Yb(III) after potentiostatic electrolysis for 60 h at ?1.84 V in LiCl–KCl–AlCl₃–YbCl₃ melt.     

Structure and stability of solid and molten complexes in the MgCl2-AlCl3 system

A visual determination of the phase diagram of the MgCl₂-AlCl₃ system reveals the formation of two intermediate compounds. One of these compounds is MgAl₂Cl₈ crystallizing with a monoclinic unit cell, space group I2/c, with dimensions a = 12.873(1)Å, b = 7.8959(7)Å, c = 11.617(1)Å, β = 92.348(8)° and z = 4. The two crystal modifications of anhydrous magnesium chloride and the lattice parameters of aluminium chloride have been reexamined. Lattice energies for α- and β-MgCl₂ have been measured, respectively, as 661(1) and 646(4) kcal mol⁻¹. The liquidus curve on the acidic side has been used to estimate the activity of aluminium chloride. Fourier-transform IR spectra of melts with compositions ranging from 0 to 30 mol% MgCl₂ have been interpreted in terms of Al₂Cl₆, strongly perturbed Al₂Cl₇⁻ and AlCl₄⁻ entities. In particular, the tetrachloroaluminate ion acts as both a tri- and a bidentate ligand towards Mg²⁺. Neutral species, e.g. Mg(AlCl₄)₂ and Mg(Al₂Cl₆)(AlCl₄)Cl, dominate in the melt. Ab initio molecular-orbital calculations have been performed to obtain a better understanding of the Mg²⁺ —d AlCl₄⁻ interaction.     

Tris(trichlorosilyl)tetrelide Anions and a Comparative Study of Their Donor Qualities

Trichlorosilylated tetrelides [(Cl₃Si)₃E]⁻ have been prepared by adding 1 equiv of a soluble Cl⁻ salt to (Cl₃Si)₄Si (E=Si) or 4 Si₂Cl₆/GeCl₄ (E=Ge). To assess their donor qualities, the anions [(Cl₃Si)₃E]⁻ (E=C, Si, Ge) have been treated with BCl₃, AlCl₃, and GaCl₃. Both BCl₃ and GaCl₃ give 1:1 adducts with the anionic centers. AlCl₃ leads to Cl⁻ abstraction from [(Cl₃Si)₃E]⁻ with formation of (Cl₃Si)₄E (E=Si or Ge). (Cl₃Si)₄Ge is cleanly converted to the perhydrogenated (H₃Si)₄Ge by use of Li[AlH₄]. Another case of Cl⁻ abstraction was observed for [(Cl₃Si)₃Ge ⋅ GaCl₃]⁻, which reacts with GaCl₃ to afford the neutral dimer [(Cl₃Si)₃Ge−GaCl₂]₂.     

Stereocontrol during the radical polymerization of methyl methacrylates with combined Lewis acids: Aluminium trichloride (AlCl3) and iron dichloride tetrahydrate

The radical polymerization of methyl methacrylate (MMA) was carried out in the presence of combined Lewis acids of the AlCl₃-FeCl₂ system. Compared with the polymerization produced in the presence of single Lewis acids, AlCl₃ or FeCl₂, the MMA polymerization in the presence of AlCl₃-FeCl₂ composite in CHCl₃ or 1-butanol produced a polymer with a higher isotacticity and in toluene produced a polymer with a much higher isotacticity (mm = 50%). The molecular weight and polydispersity of PMMA in the presence of Lewis acids were similar with those in the absence of Lewis acids, although Lewis acids decelerate the polymerization of MMA. The effects of the Lewis acids were greater in a solvent with a lower polarity. A possible stereocontrol mechanism of the polymerization was proposed. The Lewis acid composite of AlCl₃-FeCl₂ readily formed a complex with growing species. These complexes possessed apparent bulkiness that changes the direction of monomer addition to the growing radical center.     

Synthese und Kristallstruktur des Lewis‐Säure/Base‐Addukts AlCl3·C3N3Cl3

Synthesis and Crystal Structure of the Lewis Acid‐Base Adduct AlCl₃·C₃N₃Cl₃ The reaction between cyanuric chloride (C₃N₃Cl₃) and the strong Lewis acid AlCl₃ yielded colorless crystals of the adduct AlCl₃·C₃N₃Cl₃. The crystal structure was determined by single crystal X‐ray diffraction at room temperature and was solved in the space group with Z = 4, a = 7.3802(7) Å, b = 9.688(1) Å, c = 16.272(2) Å, α = 72.80(1)°, β = 89.97(1)°, γ = 87.23(1)°, and V = 1110.0(2) ų. In the crystal structure, AlCl₃ is closely associated to the triazine ring with Al–N distances of 2.042(3) Å and 2.067(4) Å, respectively. The AlCl₃·C₃N₃Cl₃ units are connected with each other via intermolecular N···Cl donor–acceptor interactions, forming tape‐like arrangements in the ac‐plane, with tapes running parallel to the a‐axis.     

Vergleichende Untersuchungen zur Struktur von 4‐Dimethylaminopyridin‐Addukten

Comparative Structural Studies on 4‐Dimethylaminopyridine‐Adducts Lewis acid‐base adducts of the type dmap—MMe₃ (M = Al 1 , Ga 2 , In 3 , Tl 4 ) as well as dmap—AlCl₃ ( 6 ) and dmap—Al(t‐Bu)₃ ( 7 ) were synthesized by reaction of MR₃ with 4‐dimethylamino‐pyridine (dmap) whereas dmap—AlH₃ ( 5 ) was obtained from AlH₃·Et₂O. 1 — 7 were characterized by means of NMR (¹H, ¹³C{¹H}) and mass spectrometry and elemental analysis. In addition, their solid state structures were determined by single crystal X‐ray diffraction studies. A comparison of the structural parameters reveales the influence of both electronic (Lewis acidity of the group 13 atom) and steric interactions on the structure and stability of as prepared Lewis acid‐base adducts.     

Nuclear magnetic resonance study of aluminum chloride-n-Butylpyridinium chloride melts

High resolution proton and ¹³C-NMR measurements were used to follow the variation of the n-butylpyridinium (BP⁺) cation spectra in BP⁺Cl^?AlCl₃ molten mixtures. The mole fraction of AlCl₃ was varied between 0.45 and 0.60. It was found that chemical shifts and proton coupling constants are significantly affected by the BP⁺-Cl^? and BP⁺ -AlCl^?₄ associations. Analysis of the NMR results shows that in the melts the ionic association into ion pairs is essentially quantitative. Lithium-7 NMR of BPCl-AlCl₃-LiCl melt shows that when the mole-fraction of AlCl₃ is < 0.50 (basic melt) LiCl₂^? ion is formed, while in the acidic melts the Li⁺ ion probably interacts with two AlCl₄^? ions to form LiAl₂Cl^?₈ ion.     

Solubility Behaviour of TiCl4, ZrCl4, and HfCl4 in Chloroaluminate Ionic Liquids

The solubility of NbCl₅, TaCl₅, TiCl₄, ZrCl₄, and HfCl₄ in neutral [BMIM][AlCl₄] (BMIM = 1‐butyl‐3‐methylimidazolium) was determined. While TiCl₄ was immiscible with the neutral ionic liquid, 0.80 molar equivalents of ZrCl₄ and stoichiometric amounts of HfCl₄ dissolved in the melt at ambient temperature. The crystal structures and the unit cell parameters of [BMIM]₂[Ti₂Cl₁₀], [BMIM]₂[Zr₂Cl₁₀], and [PhNMe₃][Hf₂Cl₉] were determined. [BMIM]₂[Ti₂Cl₁₀], and [BMIM]₂[Zr₂Cl₁₀] were crystallised from basic chloroaluminate melts. With a trimethylanilinium cation, [PhNMe₃][Hf₂Cl₉] crystallised from an equimolar composition of PhNMe₃Cl, AlCl₃, and HfCl₄. Obviously, HfCl₄ abstracted a chloride ligand from [AlCl₄]^– to give highly Lewis acidic [Al₂Cl₇]^– anions.     

Synthesis of Pure Al35Cl3 and Al37Cl3

Chemically and isotopically pure Al³⁵Cl₃ and Al³⁷Cl₃ are synthesized from Al (s) and HCl (g). The yield is quantitative and no measurable decrease in isotopic content from HCl to AlCl₃ takes place.     

Metallampullen als Mini‐Autoklaven: Synthese und Kristallstrukturen der Ammoniakate [Al(NH3)4Cl2][Al(NH3)2Cl4] und (NH4)2[Al(NH3)4Cl2][Al(NH3)2Cl4]Cl2

Metal Ampoules as Mini‐Autoclaves: Syntheses and Crystal Structures of [Al(NH₃)₄Cl₂][Al(NH₃)₂Cl₄] and (NH₄)₂[Al(NH₃)₄Cl₂][Al(NH₃)₂Cl₄]Cl₂ The salts [Al(NH₃)₄Cl₂]⁺[Al(NH₃)₂Cl₄]^–≡AlCl₃ · 3 NH₃ ( 1 ) and (NH₄⁺)²[Al(NH₃)₄Cl₂]⁺[Al(NH₃)₂Cl₄]^–(Cl^–)₂≡ AlCl₃ · 3 NH₃ · (NH₄)Cl ( 2 ) have been obtained as single crystals during the reactions of aluminum and aluminum trichloride, respectively, with ammonium chloride in sealed Monel metal containers. The crystal structure of 1 was determined again [triclinic, P‐1; a = 574.16(10); b = 655.67(12); c = 954.80(16) pm; α = 86.41(2); β = 87.16(2); γ = 84.89(2)°], that of 2 for the first time [monoclinic, I2/m; a = 657.74(12); b = 1103.01(14); c = 1358.1(3) pm; β = 103.24(2)°].     

Electrochemical studies of iodine in an aluminium chloride-butylpyridinium chloride ionic liquid part II. Neutral and basic solvent composition

The electrochemical behavior of iodine in an ambient temperature molten salt system, aluminum chloride-N-(1-butyl)pyridinium chloride (BuPyCl), have been studied in basic (excess BuPyCl) and neutral (1.0:1.0 AlCl₃: BuPyCI mole ratio) melt compositions. Acid-base interactions of iodine in different oxidation states with the ionic solvent are observed. High stability of triiodide ion in neutral butylpyridinium tetrachloroaluminate indicates relatively weak intermolecular interactions in this solvent. In basic solutions polyhalogen equilibria involving iodine in different oxidation states and chloride ions are established. In iodine and tetraethylammonium triiodide solutions a mixture of ICI₂^?, I₂Cl^?, I₃^? and I^? ions forms. The formation constants of I₂Cl^? and I₃^? and the equilibrium constant for I₂Cl^? disproportionation are estimated.