KCl-LiCl-MgCl2熔盐体系中共电沉积制备Mg-Li合金及理论分析

在670 ℃的KCl-LiCl-MgCl₂熔盐体系中通过共电沉积方法制备了Mg-Li合金,并进行了理论分析。循环伏安表明：670 ℃时,锂在镁上(镁预先沉积到钼丝上)的欠电位沉积形成了液态的Mg-Li合金;当MgCl₂质量分数为10%时,出现了Mg-Li合金成核。极化曲线表明：在含有5% MgCl₂的熔盐中,MgCl₂的极限电流密度为0.35 A·cm^-2,超过此值时,Mg和Li就能产生共电沉积。对沉积物进行X射线衍射和电感耦合等离子体发射光谱(ICP)分析表明：通过恒电流电解得到了3种不同相的Mg-Li合金。在电流密度为6.21 A·cm^-2电解2 h条件下,只有当MgCl₂质量分数小于10%时,才能得到Mg-Li合金。并通过Nernst和浓差极化方程讨论了MgCl₂浓度对于Mg-Li合金形成的影响。Mg-Li合金中锂的含量能够通过熔盐中的MgCl₂浓度配比和电解参数来控制。实验证明这种直接从原料入手,通过共电沉积制备Mg-Li合金的新方法是可行的。     

钇离子在氯化物熔盐中的电化学还原

利用循环伏安法、计时电位法和卷积伏安法研究了钇离子在LiCl-KCl熔盐体系中,钼电极上的阴极过程。结果表明,钇离子的电化学还原反应是简单的一步反应,阴极过程在较低扫描速度下接近于可逆过程,且受扩散控制。阴极产物为固态钇。     

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。     

氯化物熔盐体系中Gd的电化学行为及提取效率的评估

研究了773 K时GdCl₃在LiCl-KCl熔盐体系中在Mo和Al 电极上的电化学行为和热力学特性. 利用开路计时电位曲线得到了Gd(III)/Gd(0)体系在723-873 K温度范围的平衡电极电位和表观电极电位. 结果表明: 平衡电极电位和表观电极电位随着温度的升高而变正. 通过吉布斯自由能变进一步计算得到了GdCl₃在LiCl-KCl熔盐体系中不同温度下的活度系数. 结合稳态极化曲线, 求得去极化值, 并通过热力学计算, 求得773 K时Gd的理论提取效率. 在773 K时, 在LiCl-KCl-GdCl₃体系中, 以Al 为工作电极在-1.5 V左右通过恒电位电解提取Gd, 电解20 h后实际电解提取效率为94.22%. 对电解沉积物进行X射线衍射(XRD)分析, 检测到了Al₃Gd合金相.     

在LiCl-KCl共晶熔体中电化学制备钬镍金属间化合物

采用循环伏安、方波伏安和开路计时电位等研究了Ho(Ⅲ)离子在LiCl-KCl共晶熔体中的电化学行为及Ho-Ni合金化机理。在惰性W电极上,Ho(Ⅲ)离子在-2.06 V(vs Ag/AgCl)发生电化学还原,该还原过程为3个电子转移的一步反应。与惰性W电极上的循环伏安相比,Ho(Ⅲ)离子在活性Ni电极的循环伏安曲线上还出现了3对氧化还原峰,是Ho与Ni形成了金属间化合物,导致了Ho(Ⅲ)离子在活性Ni电极发生了欠电位沉积。在不同的电位进行恒电位电解制备的3个不同的Ho-Ni合金,采用X-射线衍射(XRD)和扫描电子显微镜-能谱仪(SEM-EDS)等测试手段进行表征,结果表明:制备的3种合金分别是Ho₂Ni₁₇,HoNi₅ 和 HoNi₂ 3种合金化合物。     

LiCl-KCl熔盐体系中镨(Ⅲ)在镍电极上的电化学行为

采用循环伏安、 方波伏安、 计时电位和开路计时电位等电化学方法研究了Pr(Ⅲ)离子在共晶LiCl-KCl熔盐中Ni电极上的电化学行为及Pr-Ni合金化机理. 结果表明, Pr(Ⅲ)离子的电化学还原过程为三电子转移的一步反应. 与惰性Mo电极上的循环伏安曲线相比, Pr(Ⅲ) 离子在活性Ni电极的循环伏安曲线上还出现了4对氧化还原峰, 表明Pr(Ⅲ)离子在Ni电极上发生欠电位沉积, 是由于生成不同的Pr-Ni金属间化合物. 采用X射线衍射仪和扫描电子显微镜-能谱仪等对恒电位电解的产物进行了表征. 结果表明, 在不同电位下进行恒电位电解时, 每个电位上只得到一种Pr-Ni金属间化合物, 分别为PrNi₂, PrNi₃, Pr₂Ni₇和PrNi₅.     

在LiCl-KCl-ZnCl2熔盐体系中电化学共还原提取钕

针对镧系元素钕,本文通过循环伏安、开路计时电位、方波伏安等方法研究了773 K时Nd（Ⅲ）在钼电极上在LiCl-KCl-ZnCl₂熔盐体系中的电化学行为及Zn-Nd合金的形成过程. 结果表明：在LiCl-KCl-ZnCl₂熔盐中,Nd（Ⅲ）在预先沉积的Zn 阴极上欠电位沉积形成三种Zn-Nd金属间化合物. 基于电化学行为研究,采用恒电位电解提取Nd并用方波伏安曲线测量来检测Nd（Ⅲ）离子浓度的变化,然后通过电解前后Nd（Ⅲ）离子浓度变化评估了Nd的电解提取效率. 实验结果表明：-1.84 V恒电位电解进行50 h后,Nd（Ⅲ）离子浓度接近于零,提取效率为99.67%. 在973 K时通过恒电流电解提取Nd并获得了Zn-Nd合金,通过X射线衍射（XRD）和扫描电子显微镜（SEM）附带能量散射谱（EDS）对合金的相组成和微观形貌进行了分析. XRD分析表明在Zn-Nd合金中存在Nd₂Zn₁₇,LiZn 和Zn相,EDS能谱分析表明Nd在合金中的原子分数高达14.99%.     

AlCl3(ZnCl2,MgCl2)对Sm2O3的氯化效果及电化学行为

研究了AlCl₃(ZnCl₂、MgCl₂)对Sm₂O₃的氯化效果以及Sm₂O₃在LiCl-KCl-AlCl₃(ZnCl₂、MgCl₂)熔盐体系中的电化学行为。在LiCl-KCl-Sm₂O₃熔盐中加入AlCl₃(ZnCl₂、MgCl₂)后,ICP测量结果表明,AlCl₃体系中Sm(Ⅲ)离子的浓度最高,并且在923 K时达到最大值;固相反应表明,AlCl₃氯化Sm₂O₃生成SmCl₃,而Sm₂O₃和ZnCl₂(MgCl₂)反应生成SmOCl。电化学行为表明,AlCl₃体系中观察到了两种Al-Sm的合金峰,而ZnCl₂体系中只观察到Zn-Sm金属间化合物的形成峰,MgCl₂体系中没有形成合金。在-6.25 A·cm^-2下,W电极上恒电流电解2 h获得了Al-Li-Sm合金,经XRD分析,合金为Al₂Sm相。     

苯硫酚盐基溶液的可充镁电池电解液

将4-甲基苯硫酚、4-异丙基苯硫酚和4-甲氧基苯硫酚(RSH)分别与格氏试剂C₂H₅MgCl/THF(四氢呋喃)反应制得的苯硫酚氯化镁(RSMgCl)(分别标记为MBMC、IPBMC和MOBMC)/THF和进一步与Lewis 酸AlCl₃反应制得的(RSMgCl)_n-AlCl₃/THF(n=1,1.5,2)苯硫酚盐基溶液用作可充镁电池电解液,采用循环伏安和恒电流充放电测试研究了电解液的镁沉积-溶出性能和氧化分解电位. 结果表明,苯硫酚上的基团种类和RSMgCl与AlCl₃的比例对其电化学性能有影响. 其中,0.5 mol·L^-1(IPBMC)_1.5-AlCl₃/THF 溶液具有最佳的电化学性能,其氧化分解电位适宜(2.4 V(vs Mg/Mg²⁺)),镁沉积-溶出循环效率稳定,过电位低,电导率较高(2.48 mS·cm^-1),与正极材料Mo₆S₈兼容性良好,且具有一定的空气稳定性,配制方便,有希望应用于实际的可充镁电池体系中.     

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.     

Crystal chemistry of M[PO2(OH)2]2·2H2O compounds (M=Mg, Mn, Fe, Co, Ni, Zn, Cd): Structural investigation of the Ni, Zn and Cd salts

The compounds M[PO₂(OH)₂]₂·2H₂O (M=Mg, Mn, Fe, Co, Ni, Zn, Cd) were prepared from super-saturated aqueous solutions at room temperature. Single-crystal X-ray structure investigations of members with M=Ni, Zn, Cd were performed at 295 and 120 K. The space-group symmetry is P2₁/n, Z=2. The unit-cell parameters are at 295/120 K for M=Ni: a=7.240(2)/7.202(2), b=9.794(2)/9.799(2), c=5.313(1)/5.285(1) Å, β=94.81(1)/94.38(1)°, V=375.4/371.9 Å³; M=Zn: a=7.263(2)/7.221(2), b=9.893(2)/9.899(3), c=5.328(1)/5.296(2) Å, β=94.79(1)/94.31(2)°, V=381.5/377.5 Å³; M=Cd: a=7.356(2)/7.319(2), b=10.416(2)/10.423(3), c=5.407(1)/5.371(2) Å, β=93.85(1)/93.30(2)°, V=413.4/409.1 Å³. Layers of corner-shared MO₆ octahedra and phosphate tetrahedra are linked by three of the four crystallographically different hydrogen bonds. The fourth hydrogen bond (located within the layer) is worth mentioning because of the short O_h?O bond distance of 2.57-2.61 Å at room temperature (2.56-2.57 Å at 120 K); only for M=Mg it is increased to 2.65 Å. Any marked temperature-dependent variation of the unit-cell dimension is observed only vertical to the layers. The analysis of the infrared (IR) spectroscopy data evidences that the internal PO₄ vibrations are insensitive to the size and the electronic configuration of the M²⁺ ions. The slight strengthening of the intra-molecular P-O bonds in the Mg salt is caused by the more ionic character of the Mg-O bonds. All IR spectra exhibit the characteristic “ABC trio” for acidic salts: 2900-3180 cm⁻¹ (A band), 2000-2450 cm⁻¹ (B band) and 1550-1750 cm⁻¹ (C band). Both the frequency and the intensity of the A band provide an evidence that the PO₂(OH)₂ groups in M[PO₂(OH)₂]₂·2H₂O compounds form weaker hydrogen bonds as compared with other acidic salts with comparable O?O bond distances of about 2.60 Å. The observed shift of the O-H stretching vibrations of the water molecule in the order M=Mg>Mn≈Fe≈Co>Ni>Zn≈Cd has been discussed with respect to the influence of both the character and the strength of M↔H₂O interactions.     

Electrochemical co-reduction of Y(III) and Zn(II) and extraction of yttrium on Zn electrode in LiCl-KCl eutectic melts

This work presents an electrochemical study of Y(III) ions on W electrode and liquid Zn electrode and co-reduction mechanism of Y(III) and Zn(II) on W electrode in LiCl-KCl eutectic melts. Cyclic voltammogram and current reversal chronopotentiogram revealed that the electrochemical reaction of Y(III) on W electrode proceeds a single step mechanism of Y(III) to Y(0). On liquid Zn electrode, the deposition potential of Y(III) is more positive than that on W electrode due to the formation of Y-Zn solution and the reduction process was found to be a diffusion controlled and quasi-reversible at lower scan rate of 0.1 V/s. Based on the results of cyclic voltammometry, square wave voltammetry, and chronopoteniometry, the Y-Zn intermetallics could be formed by co-reduction process of Y(III) and Zn(II) on W electrode in LiCl-KCl-ZnCl₂-YCl₃ molten salts. Moreover, the electrochemical extracting metallic Y was conducted by galvanostatic and potentiostatic electrolysis on liquid Zn electrode. Electrolysis products consisted of Zn and YZn₁₂ phases characterized by scanning electron microscopy with energy dispersive spectrometry and X-ray diffraction. Meanwhile, the change of Y(III) concentration in LiCl-KCl eutectic melts was detected by inductive coupled plasma atomic emission spectrometer and the extraction efficiency could be estimated.     

Hemoglobin Modified Carbon Paste Electrode: Direct Electrochemistry and Electrocatalysis

Abstract

A new hemoglobin (Hb) modified carbon paste (CP) electrode was fabricated by simply mixing the hemoglobin with carbon powder and paraffin homogeneously. To prevent the leakage of Hb from the electrode surface, a Nafion film was further applied on the surface of Hb-carbon composite paste electrode. Direct electrochemistry of hemoglobin in the paste electrode was easily achieved, and a pair of well-defined quasi-reversible redox peak of heme Fe(III)/Fe(II) couple appeared with the formal potential (E^0′) as ?0.335 V (vs. Saturated calomel electrode; CE) in pH 7.0 phosphate buffer solution (PBS). The fabricated Hb modified electrode showed good electrocatalytic ability to the reduction of trichloroacetic acid (TCA) and H₂O₂.     

High-pressure transitions in MgAl2O4 and a new high-pressure phase of Mg2Al2O5

Phase transitions in MgAl₂O₄ were examined at 21-27 GPa and 1400-2500 °C using a multianvil apparatus. A mixture of MgO and Al₂O₃ corundum that are high-pressure dissociation products of MgAl₂O₄ spinel combines into calcium-ferrite type MgAl₂O₄ at 26-27 GPa and 1400-2000 °C. At temperature above 2000 °C at pressure below 25.5 GPa, a mixture of Al₂O₃ corundum and a new phase with Mg₂Al₂O₅ composition is stable. The transition boundary between the two fields has a strongly negative pressure-temperature slope. Structure analysis and Rietveld refinement on the basis of the powder X-ray diffraction profile of the Mg₂Al₂O₅ phase indicated that the phase represented a new structure type with orthorhombic symmetry (Pbam), and the lattice parameters were determined as a=9.3710(6) Å, b=12.1952(6) Å, c=2.7916(2) Å, V=319.03(3) Å³, Z=4. The structure consists of edge-sharing and corner-sharing (Mg, Al)O₆ octahedra, and contains chains of edge-sharing octahedra running along the c-axis. A part of Mg atoms are accommodated in six-coordinated trigonal prism sites in tunnels surrounded by the chains of edge-sharing (Mg, Al)O₆ octahedra. The structure is related with that of ludwigite (Mg, Fe²⁺)₂(Fe³⁺, Al)(BO₃)O₂. The molar volume of the Mg₂Al₂O₅ phase is smaller by 0.18% than sum of molar volumes of 2MgO and Al₂O₃ corundum. High-pressure dissociation to the mixture of corundum-type phase and the phase with ludwigite-related structure has been found only in MgAl₂O₄ among various A²⁺B³⁺₂O₄ compounds.     

CO2 to CO Electroreduction,Electrocatalytic H2 Evolution,and Catalytic Degradation of Organic Dyes Using a Co(II) meso-Tetraarylporphyrin

The meso-tetrakis(4-(trifluoromethyl)phenyl)porphyrinato cobalt(II) complex [Co(TMFPP)] was synthesised in 93% yield. The compound was studied by ¹H NMR, UV-visible absorption, and photoluminescence spectroscopy. The optical band gap Eg was calculated to 2.15 eV using the Tauc plot method and a semiconducting character is suggested. Cyclic voltammetry showed two fully reversible reduction waves at E_1/2 = −0.91 V and E_1/2 = −2.05 V vs. SCE and reversible oxidations at 0.30 V and 0.98 V representing both metal-centred (Co(0)/Co(I)/Co(II)/Co(III)) and porphyrin-centred (Por²⁻/Por⁻) processes. [Co(TMFPP)] is a very active catalyst for the electrochemical formation of H₂ from DMF/acetic acid, with a Faradaic Efficiency (FE) of 85%, and also catalysed the reduction of CO₂ to CO with a FE of 90%. Moreover, the two triarylmethane dyes crystal violet and malachite green were decomposed using H₂O₂ and [Co(TMFPP)] as catalyst with an efficiency of more than 85% in one batch.     

MnO_2/NiCo_2O_4的静电自组装合成及其电化学性能

通过带负电荷的MnO2纳米片与带正电荷的Co-Ni层状双氢氧化物(LDHs)纳米片的静电自组装外加后续热处理合成了异质层状结构的MnO2/NiCo2O4复合物.采用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、拉曼光谱、原子吸收光谱(AAS)、场发射扫描电镜(FESEM)和透射电子显微镜(TEM)对其结构和形貌进行了表征.用循环伏安(CV)、恒流充放电和电化学交流阻抗技术对其电化学性能进行了测试.研究结果表明,该方法制得的异质复合物具有多孔层状堆垛结构,这种特殊的结构不仅增大了电解液离子的接触面积,而且还为其嵌入-脱出提供了有效途径.该复合物在1 A·g-1电流密度时,-0.6-0.45 V电位窗口内的比电容达482 F·g-1,优于纯组分MnO2和NiCo2O4的电容性能.     

Direct electrochemistry and electrocatalysis of hemoglobin immobilized in a magnetic nanoparticles-chitosan film

Magnetic nanoparticles (Fe₃O₄) were synthesized by a chemical coprecipitation method. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to confirm the crystallite structure and the particle's radius. The Fe₃O₄ nanoparticles and chitosan (CS) were mixed to form a matrix in which haemoglobin (Hb) can be immobilized for the fabrication of H₂O₂ biosensor. The Fe₃O₄-CS-Hb film exhibited a pair of well-defined and quasi-reversible cyclic voltammetric peaks due to the redox of Hb-heme Fe (III)/Fe (II) in a pH 7.0 phosphate buffer. The formal potential of Hb-heme Fe(III)/Fe(II) couple varied linearly with the increase of pH in the range of 4.0-10.0 with a slope of 46.5 mV pH⁻¹, indicating that electron transfer was accompanied with single proton transportation in the electrochemical reaction. The surface coverage of Hb immobilized on Fe₃O₄-CS film glassy carbon electrode was about 1.13 × 10⁻¹⁰ mol cm⁻². The heterogeneous electron transfer rate constant (k_s) was 1.04 s⁻¹, indicating great facilitation of the electron transfer between Hb and magnetic nanoparticles-chitosan modified electrode. The modified electrode showed excellent electrocatalytic activity toward oxygen and hydrogen peroxide reduction. The apparent Michaelis-Menten constant for H₂O₂ was estimated to be 38.1 μmol L⁻¹.     

Advantages and effects of nitrogen doping into the central channel of plasma in axially viewed-inductively coupled plasma optical emission spectrometry

The effects and benefits of N₂ addition to the central channel of the ICP through the nebulizer gas used in ICP OES with axial view configuration were investigated in the present study. The N₂ flow rate, nebulizer gas flow rate, RF power and sample uptake rate were evaluated and compared for two sample introduction systems (pneumatic nebulization/aerosol desolvation and conventional pneumatic nebulization). It was observed that N₂ did not affect solution nebulization and aerosol transport but affects the ICP characteristics. The higher thermal conductivity of N₂ (in comparison with Ar) changes energy distribution in the ICP, observed by monitoring the signals of Ar emission lines and sodium emission. The ratio Mg(II)-280.270 nm/Mg(I)-285.213 nm was utilized as a diagnostic tool for plasma robustness. The addition of N₂ (20 mL min⁻¹) increased plasma robustness significantly and mitigated effects caused by Na, K and Ca. For 40 spectral lines evaluated, it was observed that the emission signals of ionic spectral lines were in general more affected by N₂ than those of atomic spectral lines. Detection limits, precision, sensitivity and linearity of calibration curves obtained using N₂-Ar-ICP were almost similar to those obtained using Ar-ICP. The analysis of 5 different reference materials revealed that accuracy was not degraded by adding N₂ to the Ar-ICP.     

Use of Nb(2)O(5)-SiO(2) in an automated on-line preconcentration system for determination of copper and cadmium by FAAS

A procedure for the determination of trace level of copper(II) and cadmium(II) by FAAS using an on-line preconcentration system has been proposed. In this system, copper and cadmium ions were adsorbed onto a minicolumn packed with silica gel modified with niobium(V) oxide (Nb₂O₅-SiO₂), followed by nitric acid elution in reverse mode and determination on-line by flame atomic absorption spectrometry (AAS) without interference of the matrix. Chemical and flow variables as well as concomitant ions were studied in the developed procedure. The enrichment factor for copper(II) and cadmium(II) was 34.2 and 33.0, respectively, using a preconcentration time of 2 min. The limit of detection for copper(II) and cadmium(II) was 0.4, and 0.1 μg l⁻¹, respectively. The precision of the method, evaluated as the relative standard deviation in solutions containing 15 μg l⁻¹ of copper and 10 μg l⁻¹ of cadmium, by analyzing a series of seven replicates, was 1.8 and 1.6%, respectively. The accuracy was assessed through recovery experiments of certified material and water samples.     

单分子水对H_2O_2+Cl气相反应影响的理论研究

在aug-cc-pVTZ基组下采用CCSD(T)和B3LYP方法,研究了H2O2+Cl反应,并考虑在大气中单个水分子对该反应的影响.结果表明,H2O2+Cl反应只存在一条生成产物为HO2+HCl的通道,其表观活化能为10.21kJ·mol-1.加入一分子水后,H2O2+Cl反应的产物并没有发生改变,但是所得势能面却比裸反应复杂得多,经历了RW1、RW2和RW3三条通道.水分子在通道RW1和RW2中对产物生成能垒的降低起显著的负催化作用,而在通道RW3中则起明显的正催化作用.利用经典过渡态理论(TST)并结合Wigner矫正模型计算了216.7-298.2 K温度范围内标题反应的速率常数.结果显示,298.2 K时通道R1的速率常数为1.60×10-13cm3·molecule-1·s-1,与所测实验值非常接近.此外,尽管通道RW3的速率常数kRW3比对应裸反应的速率常数kR1大了46.6-131倍,但该通道的有效速率常数k'RW3却比kR1小了10-14个数量级,表明在实际大气环境中水分子对H2O2+Cl反应几乎没有影响.