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.

Electrochemical Behavior of Pr(Ⅲ) in the LiCl-KCl Melt on a Ni Electrode†

The electrochemical behavior of Pr(Ⅲ) on a Ni electrode in the LiCl-KCl melt and the alloying mechanism of Pr-Ni alloys were investigated by cyclic voltammetry, square wave voltammetry, chronopoten-tiometry and open-circuit chronopotentiometry. Cyclic voltammetry and square wave voltammetry experiments indicate that the reduction of Pr(Ⅲ) ions into Pr metal occur in a single step with three electrons exchanged. Compared with the cyclic voltammograms on an inert Mo electrode, four reduction peaks are observed, which indicates the under-potential deposition of Pr(Ⅲ) on the reactive Ni electrode due to the formation of Pr-Ni intermetallic compounds. The Pr-Ni alloys obtained by potentiostatic electrolysis were characterized by X-ray diffraction(XRD) and scanning electron micrograph-energy dispersive spectrometry(SEM-EDS). The results show that only one Pr-Ni intermetallic compound, i.e. PrNi₂, PrNi₃, Pr₂Ni₇ or PrNi₅, is obtained at each potential, respectively. This process can also be used for other electrochemical formation of lanthanide-Ni alloys.