NaCl-KCl-MgCl2熔盐Mg2+在钨电极上的 电化学还原机理

采用三电极在NaCl-KCl熔盐电解质体系,以MgCl₂为原料应用AUTOLAB电化学工作站分别通过循环伏安法、计时电流法、计时电位法研究了1 073 K时NaCl-KCl-MgCl₂熔盐体系中Mg2+在钨电极上的电化学还原过程.循环伏安测试结果表明:1 073 K时NaCl-KCl-MgCl₂熔盐体系中Mg2+在钨电极上的电化学还原是1步反应转移2个电子过程,电极反应受扩散控制,扩散系数为3.81×10-6 cm2/s,电极反应为Mg2++2e-→Mg.计时电位测试结果验证了循环伏安测试结果的正确性.计时电流测试数据拟合结果表明:1 073 K时NaCl-KCl-MgCl₂熔盐中Mg2+在钨电极上的电结晶是瞬时成核方式.      

氢化物对Mg2Ni基合金储氢性能的影响

采用机械球磨法制备了纯Mg₂Ni合金和加入添加剂的Mg₂Ni+10%(质量比,下同)TiH₂、Mg₂Ni+10%NbH储氢合金,研究了添加剂TiH₂或NbH对Mg₂Ni储氢合金物相组成、显微形貌和储氢性能的影响。结果表明,相较于纯Mg₂Ni储氢合金,充分吸氢/放氢后,添加了10%TiH₂或10%NbH的储氢合金的Mg₂Ni H₄/Mg₂Ni相晶胞体积均不同程度地减小;机械球磨后,TiH₂在储氢合金中均匀分布,NbH存在一定程度团聚。添加10%TiH₂或10%NbH的Mg₂Ni储氢合金的吸氢平台和放氢平台都高于纯Mg₂Ni合金,放氢反应过程中的焓变和熵变都小于纯Mg₂Ni合金。在相同时间内,储氢合金的放氢容量从大到小的顺序为：Mg_2...     

LiCl-KCl-MgCl2熔盐体系中Li-Mg共沉积机理研究

Li-Mg合金作为锂电池负极材料在新能源领域中具有广阔的应用前景,熔盐电解法制备Li-Mg合金极具优势。本文采用三电极体系研究了Mg²⁺在LiCl-KCl-MgCl₂熔体中钨电极上的电化学行为及Li-Mg共沉积机理,探究了MgCl₂浓度对电解共沉积Li-Mg的影响。方波伏安法与计时电流法实验结果表明：Mg²⁺在钨电极上一步两电子还原为金属Mg,属于瞬时成核过程,不受温度的影响。计时电位法实验结果表明：随着MgCl₂浓度的增加,LiCl-KCl-MgCl₂熔体电解共沉积Li-Mg所需的阴极电流密度逐渐增大。当LiCl-KCl-MgCl₂熔体中MgCl₂浓度为5%时,实现Li-Mg共沉积的最小阴极电流密度为0.287 A/cm²。恒电流电解结果表明：当MgCl₂浓度≤5%时,Li-Mg产品中金属Mg含量随着熔体中MgCl₂浓度的增加而增大,当MgCl<...     

Mg-Y-Ni储氢合金吸放氢动力学性能的研究

针对镁基储氢合金吸放氢动力学缓慢的问题,构建 Mg-Y-Ni储氢合金体系,预通过 Y元素和 Ni元素引入催化基团,以获得改善其动力学性能的途径。通过真空感应熔炼制备了 Mg_95-xY₅Ni_x(x=5,10,15)合金,并采用 X射线衍射(XRD)对其不同状态下的相组成进行分析,并采用扫描电镜(SEM)和透射电镜(TEM)分析合金微观结构和晶体状态。同时,采用 Sievert 等体积方法测试了试样在不同温度下的等温吸放氢动力学性能。结果表明,氢化后的试样是由 MgH₂,Mg₂NiH₄和 YH₃相组成的纳米晶结构,然而在放氢后,仅有 MgH₂和 Mg₂NiH₄相发生分解反应,生成相应的 Mg 和 Mg₂Ni相并放出氢气。原位生成的 YH₃相没有发生分解,并弥散分布在母合金中,且扮演积极的催化效应。此外,随着Ni含量的增加,合金吸放...     

电化学原位拉曼光谱技术在高温熔盐中的应用

综述了熔盐电化学原位拉曼光谱用样品池结构及特点、熔盐电化学原位拉曼光谱的研究进展。所用样品池主要以配合90°拉曼散射模式研究为主,且样品池通常都通入惰性气体。研究中主要采用恒电流/恒电位电解的电化学方法,研究内容涉及到在氯化物熔盐中电解还原金属铝、汞、镉和钽的阴极行为,(Li-K)CO₃和Li₂CO₃燃料电池中氧的还原,在以金属铝为阳极的高能熔盐电池中I₂在AlCl₃-NaCl熔盐中的电化学过程,钠-硫电池放电过程中S元素在AlCl₃-NaCl熔盐中的行为,Y₂O₃稳定的ZrO₂(YSZ)氧离子导体在Na₂SO₄熔盐中的电化学腐蚀,以及不同电位条件下熔融KNO₃、NaNO₃与铂电极界面的熔盐结构变化。最后,展望了熔盐电化学原位拉曼光谱的研究发展方向。     

LiF-CaF_2-SmF_3体系熔盐电解制备SmFe合金的电化学机制研究

研究了1173 K时在Li F-CaF_2-5SmF_3(%,质量分数)体系中,Sm(III)在Mo电极和Fe电极上的电化学行为。当研究电极为惰性Mo电极时,通过循环伏安法(CV)和方波伏安法(SWV)的研究结果表明:Sm(III)在-1.58 V左右发生了一步单电子转移还原反应,生成了Sm(II),通过不同扫速(扫速不高于0.25 V·s-1)的CV曲线证实,Sm(III)/Sm(II)转换的氧化还原反应为可溶-可逆反应,该反应的存在将使电解电流效率降低;在Mo电极上未观察到Sm(II)→Sm(0)的信号,说明在该体系中无法在惰性电极上通过熔盐电解直接得到金属Sm;当研究电极为Fe电极时,CV和开路计时电位(OCP)检测均发现了Sm Fex合金生成的电化学信号,证实Sm(II)可以在活性铁电极上发生欠电位沉积从而生成Sm Fex合金;对合金进行了电感耦合等离子体发射光谱(ICP)、X射线衍射(XRD)和扫描电子显微镜(SEM)分析,确认了合金中的相成分为Sm Fe2,Fe和Sm。     

超声振动原位Al2O(3(p))/7075汽车零件合金组织与耐腐蚀性能研究

通过超声振动在7075合金中添加SiO₂,原位生成Al₂O₃颗粒,利用X射线衍射仪(XRD)、自带能谱分析仪(EDS)的扫描电子显微镜(SEM)、透射电镜(TEM)、浸泡腐蚀实验和电化学测试实验对合金的微观组织、物相组成和耐腐蚀性能进行分析。结果显示,超声振动和Al₂O₃颗粒的原位生成可以细化合金的微观组织,将团聚的Al₂O₃颗粒分散均匀,且Al₂O₃颗粒可作为异质形核的核心,提高形核率。超声态Al₂O₍3(p))/7075合金主要由Al、Al₂O₃、Al₇Cu₂Fe、Al₂CuMg、Mg₂Zn相组成。相比于7075合金,超声态Al₂O₍3(p))/7075合金的失重腐蚀速率...     

AB3.3～3.7型La-Y-Ni稀土储氢合金微观结构和电化学性能研究

采用磁悬浮感应熔炼的方法制备了(LaSmY)(NiMnAl)_x(x=3.3,3.4,3.5,3.6,3.7)系列稀土储氢合金,并在氩气气氛、1273 K下热处理24 h。通过X射线衍射(XRD)和电化学测试分析了合金的相结构以及在常温和低温下的电化学性能。结果表明,合金为多相结构,含有Ce₂Ni₇相、PuNi₃相、Gd₂Co₇相、LaNi₅相以及Ce₅Co₁₉相。主相Ce₂Ni₇相的含量随化学计量比x值的增加先增加后降低,当x=3.5时最高,为74.67%。Gd₂Co₇相和PuNi₃相含量随x值的增加逐渐降低,Ce₅Co₁₉相逐渐增加。电化学测试结果表明,在常温下,随化学计量比x值的增加,合金的最大放电容量从317.7 mAh·g^...     

退火温度对汽车镍氢电池用储氢合金电化学性能的影响

采用真空电弧熔炼和退火的方法制备了电池负极用La_0.35Y_0.65Ni_3.5Mn_0.2Al_0.1储氢合金,研究了退火温度对储氢合金微观结构与电化学性能的影响。结果表明,随着退火温度从1173 K增加至1373 K,储氢合金中Ce₅Co₁₉相丰度先增大后减小,Ce₂Ni₇相和LaNi₅相逐渐转变成LaNi₃相,Ce₂Ni₇相在退火温度大于等于1273 K时消失;储氢合金在退火温度为1273 K时具有最正的腐蚀电位和最小的腐蚀电流密度,此时储氢合金的容量保持率S₁₀₀为89.95%、最大放电容量C_max为385.5 mAh/g,储氢合金电极的循环稳定性与电极表面耐腐蚀性能有关;随着退火温度从1173 K增加至1373 K,储氢合金的HRD₉₀₀...     

聚L-天冬氨酸/多壁碳纳米管复合膜修饰玻碳电极测定亚硝酸根

采用滴涂法和电聚合法制备了聚L-天冬氨酸/多壁碳纳米管复合膜修饰玻碳电极,利用循环伏安(CV)法研究了亚硝酸根 ( NO^-₂) 在该修饰电极上的电化学行为,建立了一种电化学测定NO^-₂的新方法。实验结果表明,该修饰电极对于 NO^-₂的氧化具有良好的电催化性能,并且显著促进 NO^-₂在电极表面的电化学过程。利用差分脉冲伏安法测定,在2.0 × 10^-6~2.0 × 10^-4 mol/L浓度范围内,NO^-₂的氧化峰电流与浓度呈现良好的线性关系,相关系数为 0.998 9。信噪比为 3 时,NO^-₂的检出限为 2.0 × 10^-7 mol/L。方法成功地用于环境水样中NO^-₂测定。     

Electrochemical formation of Mg–La–Mn alloys by coreduction of Mg(II), La(III) and Mn(II) in LiCl+KCl molten salts

In the present work, cyclic voltammetry (CV), square wave voltammetry (SWV) and chronopotentiometry (CP) were used to investigate the electrochemical coreduction behaviors of La(III) and Mg(II) as well as La(III), Mg(II) and Mn(II) on Mo electrode in LiCl + KCl molten salts. CV and SWV results exhibit that the coreduction mechanism of La (III) and Mg(II) on Mo electrode is that La(III) is reduced and Mg–La intermetallic compound is formed, leading to the deposition potential of La(III) shifting to more positive one. The electrochemical signals pertaining to the formation of metallic La, Mg and Mn as well as Mg–La intermetallic compound are also observed by coreduction of La(III), Mg(II), and Mn(II) in LiCl + KCl molten salt on the inert Mo electrode. However, the electrochemical signals associated with the formation of La–Mn and Mg–Mn alloys are not observed, which means that the depolarization effect of La(III) and Mg(II) does not occur on pre-deposited Mn electrode. The Mg–La–Mn alloys were formed by co-deposition of La(III), Mg(II), and Mn(II) on Mo electrode at various concentration ratios of La(III) and Mg(II). The results of scanning electron microscopy equipped with energy dispersive spectroscopy and X-ray diffraction displays that the Mg–La–Mn alloys are comprised of La–Mg compound Mg₁₇La₂, Mg and Mn phases. The concentration ratio of La(III) and Mn(II) has few effects on the alloy composition.     

Electrochemical formation process and phase control of Mg-Li-Ce alloys in molten chlorides

An electrochemical approach for the preparation of Mg-Li-Ce alloys by co-reduction of Mg,Li and Ce on a molybdenum electrode in KCl-LiCl-MgCl2-CeCl3 melts at 873 K was investigated.Cyclic voltammograms (CVs) and square wave voltammograms indicated that the underpotential deposition (UPD) of cerium on pre-deposited magnesium led to the formation of Mg-Ce alloys at electrode potentials around-1.87 V.The order of electrode reactions was as follows:discharge of Mg(Ⅱ) to Mg-metal,UPD of Ce on the surface of pre-deposited Mg with formation of Mg-Ce alloys,discharge of Ce(Ⅲ) to Ce-metal and after that the discharge of Li+ with the deposition of Mg-Li-Ce alloys,which was investigated by CVs,chronoamperometry,chronopotentiometry and open circuit chronopotentiometry.X-ray diffraction (XRD) illuminated that Mg-Li-Ce alloys with different phases were obtained via galvanostatic electrolysis by different current densities.The microstructures of Mg-Li-Ce alloys were characterized by optical microscopy (OM) and scanning electron microscopy (SEM),respectively.The analysis of energy dispersive spectrometry (EDS) showed that Ce existed at grain boundaries to restrain the grain growth.The compositions and the average grain sizes of Mg-Li-Ce alloys could be obtained controllably corresponding with the phase structures of the XRD patterns.     

Electrodeposition of magnesium-yttrium alloys by molten salt electrolysis

Electrodeposition of magnesium-yttrium alloys from molten salts was studied by electrochemical techniques.LiF-YF3 was electrolyte system with magnesium oxide and Yttrium oxide as raw materials.It was proved that Mg2+ and Y3+was deposited more prior than other ions during cyclic voltammetry and potential step measurement at 1050 °C.Voltammograms showed Mg2+ could be deposited at-0.5 V,and Y3+ could be deposited at-0.7 V on tungsten electrode compared with platinum electrode.The sedimentation of Mg2+ was more positive about 230 mV than that of other ions in electrolyte.The electrolytic codeposition of yttrium and magnesium was 0.58 V on condition that the weight ratio of Y2O3/MgO was 4:1.Chronopotentiogram indicated that the process of electrodeposition of magnesium-yttrium alloys on tungsten electrode was controlled by diffusion of ions from electrolyte to electrode interface.It was feasible to prepare Magnesium-Yttrium alloys by controlling content of ions in molten salt electrolyte.     

Nd(III)在NaF-KF熔盐钨电极上电化学行为

钕铁硼磁体中稀土元素钕占据较大比重,从钕铁硼废料回收稀土有重大意义。为进一步了解钕在高温下氟化物熔盐的行为,本文在1 063 K采用NaF-KF(摩尔比2:3)电解质体系,加入质量分数为1%的NdF₃,以Pt为参比电极,钨棒为对电极,用循环伏安法等电化学暂态测试研究了Nd(III)在惰性钨电极上的电化学过程,探究Nd(III)的还原机理。结果显示:Nd(III)于NaF-KF-NdF₃熔盐中在惰性钨电极上的电化学还原过程是受扩散控制的不可逆的一步反应:Nd(III)+3e-=Nd,1 063 K时循环伏安法得到Nd(III)的扩散系数为2.107×10-5 cm2/s,钕的成核机制为瞬时成核。      

The Electrochemical Formation of Ni-Tb Intermetallic Compounds on a Nickel Electrode in the LiCl-KCl Eutectic Melts

The work presents an electrochemical study on the formation of Ni-Tb intermetallic compounds in the LiCl-KCl-TbCl₃ melts on tungsten and nickel electrodes at 773 K (500 °C) by electrochemical techniques. For a tungsten electrode, cyclic voltammetry and square-wave voltammetry showed that the electrochemical reduction of Tb(III) proceeded in a one-step process involving three electrons at ?2.06 V (vs Ag/AgCl). For a nickel electrode, the reduction potential of Tb(III)/Tb was observed at more positive values than those on W electrode by cyclic voltammetry, due to the formation of Ni-Tb intermetallic compounds. Square-wave voltammetry and open-circuit chronopotentiometry put into evidence the formation of intermetallic compounds at around ?1.27, ?1.63, and ?1.88 V, respectively. Three alloy samples were obtained by potentiostatic electrolysis on a Ni electrode at various potentials and analyzed by X-ray diffraction, scanning electron micrograph, and energy-dispersive spectrometry. The analysis results confirmed the formation of Ni₁₇Tb₂, Ni₅Tb, and Ni₂Tb alloy compounds.     

Structure and electrochemical hydrogen storage characteristics of the as-cast and annealed La0.8-xSmxMg0.2Ni3.15Co0.2Al0.1Si0.05 （x=0-0.4） alloys

In order to ameliorate the electrochemical cycle stability of the RE-Mg-Ni based A2B7-type electrode alloys, the Mg content in the alloy was reduced and La in the alloy was partially substituted by Sm. The La0.8-xSmxMg0.2Ni3.15Co0.2Al0.1Si0.05 (x=0, 0.1, 0.2, 0.3, 0.4) elec-trode alloys were fabricated by casting and annealing. The microstructures of the as-cast and annealed alloys were characterized by XRD and SEM. The electrochemical hydrogen storage characteristics of the as-cast and annealed alloys were measured. The results revealed that all of the experimental alloys mainly consisted of two phases: (La,Mg)2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure. As Sm content grew from 0 to 0.4, the discharge capacity and the high rate discharge ability (HRD) first in-creased and then decreased for the as-cast and annealed alloys, whereas the capacity retaining rate (S100) after 100 cycles increased continuously.     

Electrochemical behavior of cerium ion in molten LiCI-KCI

The electrode process of cerium(Ⅲ) on the Mo electrode in eutectic LiCl-KCl melt was investigated by electrochemical transient techniques in the temperature range of 673-783 K,respectively.These results unanimously indicated that the reduction process of cerium(Ⅲ) to cerium metal was a single step exchanging three electrons which was controlled by diffusion of cerium(Ⅲ).Diffusion coefficients(D Ce(Ⅲ)) in eutectic LiCl-KCl melt were determined by cyclic voltammetry,chronopotentiometry and square wave voltammetry.An empirical diffusion coefficient function depending on temperature was proposed:lnD Ce(Ⅲ) =-2.129-5704/T.The formal potentials(Eθ’ Ce(Ⅲ)/Ce(0) versus Ag/AgCl reference electrode) at different temperatures were obtained from chronopotentiometry,which were-2.10 V(673 K) and-2.07 V(733 K),respectively.     

Electrochemical formation of Mg-Li-Y alloys by co-deposition of magnesium, lithium and yttrium ions in molten chlorides

An electrochemical approach for the preparation of Mg-Li-Y alloys via co-reduction of Mg, Li, and Y on a molybdenum electrode in LiCl-KCl-MgCl2-YCl3 melts at 943 K was investigated. Cyclic voltammograms (CVs) illuminated that the underpotential deposition (UPD) of yttrium on pre-deposited magnesium led to the formation of a liquid Mg-Y alloy, and the succeeding underpotential deposition of lithium on pre-deposited Mg-Y led to the formation of a liquid Mg-Li-Y alloy. Chronopotentiometry measurements indicated that the order of electrode reactions was as follows: discharge of Mg(II) to Mg-metal, electroreduction of Y on the surface of Mg with formation of ε-Mg24+xY5 and after that the discharge of Li+ with the deposition of Mg-Li-Y alloys. X-ray diffraction (XRD) indicated that Mg-Li-Y alloys with different phases were formed via galvanostatic electrolysis. The microstructure of different phases of Mg-Li-Y alloys was characterized by optical microscope (OM) and scanning electron microscopy (SEM). The analysis results of inductively coupled plasma atomic emission spectrometer (ICP-AES) showed that the chemical compositions of Mg-Li-Y alloys corresponded with the phase structures of the XRD patterns, and the lithium and yttrium contents of Mg-Li-Y alloys depended on the concentrations of MgCl2 and YCl3 .     

Cathodic behavior of scandium(III) on reactive copper electrodes in LiF–CaF2 eutectic molten salt

The electrochemical formation of Sc–Cu alloy was investigated in LiF–CaF₂ eutectic molten salt employing various electrochemical methods. Cyclic voltammetry and square wave voltammetry indicate that the reduction of scandium(III) on the tungsten electrode is a one-step reduction process with three electrons transfer. And underpotential deposition of scandium on the copper electrode occurs owing to the depolarization effect, i.e., forming Sc–Cu intermetallic compounds. The thermodynamic properties of the Sc–Cu intermetallic compounds ScCu₄, ScCu₂, and ScCu in the temperature range of 1153–1223 K were estimated by open-circuit chronopotentiometry. Moreover, the Sc–Cu alloys were prepared by potentiostatic electrolysis and characterized by optical microscope, X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results reveal that only Sc–Cu alloy composed of Cu-ScCu₄ can be synthesized at low cathodic current density and above eutectic temperature.