Electrochemical formation of Pr aided by additive (KF) in LiCl–KCl molten salt.

In order to investigate the influences of the additive (KF) on electrochemistry and deposit morphology of Pr, various electrochemical techniques were used to comparative investigate the electroreduction potential and diffusion coefficient of Pr3+ and kinetic properties of Pr3+/Pr in LiCl–KCl-PrCl3 before and after the addition of KF at different molar concentration ratios of F− to Pr3+ (k). Cyclic voltammetry, square wave voltammetry, and reverse chronopotentiometry results showed that the value of k (k = 0, 1, 2, 3, and 4) had no effect on reduction mechanism of Pr3+. With the increase of k, the reduction peak potential moved in the negative direction, the diffusion coefficient decreased, and diffusion activate energy increased. Meanwhile, the exchanged current densities (j0), charge transfer resistances (Rct), and activate energies (Ea) were measured at different k by linear polarization technique, which illustrated that with the increase of k, j0 gradually decreased, and Ea and Rct increased. Furthermore, the electrochemical preparation of Pr aided by KF was explored by potentiostatic electrolysis at different k, and the products were characterized by XRD, SEM, and EDS, which indicated that with the increase of k, the morphology of metallic Pr changed from slender needles to granular.Graphical abstract: In order to investigate the influences of the additive (KF) on electrochemistry and deposit morphology of Pr, various electrochemical techniques were used to comparative investigate the electroreduction potential and diffusion coefficient of Pr3+ and kinetic properties of Pr3+/Pr in LiCl–KCl-PrCl3 before and after the addition of KF at different molar concentration ratios of F− to Pr3+ (k). Cyclic voltammetry, square wave voltammetry, and reverse chronopotentiometry results showed that the value of k (k = 0, 1, 2, 3, and 4) had no effect on reduction mechanism of Pr3+. With the increase of k, the reduction peak potential moved in the negative direction, the diffusion coefficient decreased, and diffusion activate energy increased. Meanwhile, the exchanged current densities (j0), charge transfer resistances (Rct), and activate energies (Ea) were measured at different k by linear polarization technique, which illustrated that with the increase of k, j0 gradually decreased, and Ea and Rct increased. Furthermore, the electrochemical preparation of Pr aided by KF was explored by potentiostatic electrolysis at different k, and the products were characterized by XRD, SEM, and EDS, which indicated that with the increase of k, the morphology of metallic Pr changed from slender needles to granular. [ABSTRACT FROM AUTHOR]

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