LiCl-KCl-LaCl3熔盐体系中La(III)的电化学行为

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。

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

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.