物理化学学报 >> 2016, Vol. 32 >> Issue (10): 2531-2537.doi: 10.3866/PKU.WHXB201606223

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LiCl-KCl-LaCl3熔盐体系中La(III)的电化学行为

姜涛1,田杰1,王宁1,彭述明1,*(),李梅2,韩伟2,张密林2   

  1. 1 中国工程物理研究院核物理与化学研究所,四川绵阳621999
    2 哈尔滨工程大学材料科学与化学工程学院,教育部超轻材料与表面技术重点实验室,哈尔滨150001
  • 收稿日期:2016-03-18 发布日期:2016-09-30
  • 通讯作者: 彭述明 E-mail:pengshuming@caep.cn
  • 基金资助:
    国家自然科学基金重大研究计划-集成项目(91426302);和国家自然科学基金资助(21301163)

Electrochemical Behavior of La(III) in Molten LiCl-KCl-LaCl3

Tao JIANG1,Jie TIAN1,Ning WANG1,Shu-Ming PENG1,*(),Mei LI2,Wei HAN2,Mi-Lin ZHANG2   

  1. 1 Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999, Sichuan Province, P. R. China
    2 Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, P. R. China
  • Received:2016-03-18 Published:2016-09-30
  • Contact: Shu-Ming PENG E-mail:pengshuming@caep.cn
  • Supported by:
    The project was supported by the Major Research Plan of the National Natural Science Foundation of China(91426302);and National Natural Science Foundation of China(21301163)

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摘要：

在773 K条件下，研究了La（III）在LiCl-KCl熔盐中W和Ni电极上的电化学行为。La（III）还原反应是一步三电子转移的准可逆反应；通过在Ni电极上直接电沉积La的方法可以获得La-Ni金属间化合物；恒电位电解可以获得含三种金属间化合物（LaNi5、La7Ni16和La2Ni3）的La-Ni合金层，并且通过X射线衍射仪（XRD）和扫描电镜-能谱分析仪（SEM-EDS）确定物相并表征结构。采用开路计时电位法估算了LaNi5金属间化合物的标准生成吉布斯自由能。揭示了恒电位电解方法是制备La-Ni镀层合金以及提取熔盐中La的有效方法。

关键词: LiCl-KCl-LaCl3, La-Ni, 镀层合金, 吉布斯自由能

Abstract:

Electrochemical and thermodynamic studies on the formation of La-Ni intermetallic compounds in molten LiCl-KCl-(3.5%(w))LaCl3 at 773 K were performed. The electrochemical reduction of La(III) ions was investigated on inert W and reactive Ni electrodes by cyclic voltammetry. The reduction potential of La(III)/La on a Ni electrode was observed at more positive potential than that on a W electrode because of the formation of La-Ni intermetallic compounds when La ions reacted with the Ni substrate. Square-wave voltammetry, chronopotentiometry, and open-circuit chronopotentiometry provided further evidence for the formation of La-Ni intermetallic compounds. Potentiostatic electrolysis on a Ni electrode led to the formation of three La-Ni intermetallic compounds, LaNi5, La7Ni16 and La2Ni3, according to X-ray diffraction (XRD) and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) analyses. The standard Gibbs free energies of formation for LaNi5 were estimated from open-circuit chronopotentiometric measurements using the Gibbs-Helmholtz equation and Hess law. The formation of the La-Ni alloy layer could be controlled by the applied potential and time. Potentiostatic electrolysis was an effective method for electrochemical extraction of La.

Key words: LiCl-KCl-LaCl3, La-Ni, Alloy layer, Gibbs free energy