Abstract:

The electrochemical behavior of Pr(Ⅲ) ions was studied on a Bi-coatedWelectrode in LiCl-KCl melts by a series of techniques, such as cyclic voltammetry, square wave voltammetry, and open circuit chronopotentiometry. From the cyclic voltammogram and square wave voltammogram, the underpotential deposition of Pr(Ⅲ) on pre-deposited Bi (i.e., a Bi-coated W electrode) occurs, owing to the formation of Pr-Bi intermetallic compounds, resulting in the electrochemical reduction of Pr(Ⅲ) at less cathodic potentials than that on an inert W electrode. Using the open circuit chronopotentiometry technique, two plateaus, corresponding to the co-existence of two phases of Pr-Bi intermetallic compound, were observed. Thermodynamic properties, such as the activities and relative partial molar Gibbs energies of Pr in the Pr-Bi alloys as well as Gibbs energies of the formation for the Pr-Bi intermetallic compounds, were estimated from the open circuit potential measurement in the temperature range of 723-873 K. Pr-Bi alloys were produced on the liquid Bi pool electrode by potentiostatic electrolysis, and were characterized by X-ray diffraction (XRD) and scanning electronic microscopy with energy-dispersive spectrometry (SEM-EDS). The results indicated that the intermetallic LiClcompounds, PrBi₂ and PrBi, were obtained.