Effects of F– on the Electrochemical Behavior of Zr(IV) and the Nucleation Mechanism of Zr in the LiCl–KCl–K2ZrF6 System

• Published in: Inorganic chemistry 2023-07, Vol.62 (26), p.10221-10231
• Main Authors: Wang, Wei, Su, Zijin, Han, Wei, Chen, Jiayi, Li, Mei, Zhang, Meng, Liu, Rugeng
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.3c00921

To determine the effect of F– on the electrochemical formation of Zr, the reduction mechanism, kinetic properties, and nucleation mechanism of Zr­(IV) were compared in the LiCl–KCl–K2ZrF6 system before and after the addition of F– at different concentration ratios of F–/Zr­(IV). As indicated by the results, when the ratio of F–/Zr­(IV) ranged from 7 to 10, the intermediate state Zr­(III) was detected, and the reduction mechanism of Zr­(IV) was converted into Zr­(IV) → Zr­(III) → Zr. The diffusion coefficients of Zr­(IV), Zr­(III), and Zr­(II) decreased with an increase in the value of F–/Zr­(IV). The exchange current density (j 0) of Zr­(II)/Zr exceeded that of Zr­(III)/Zr, and the j 0 and α values of Zr­(III)/Zr decreased with the increase of F–/Zr­(IV). The nucleation mechanism at different ratios of F–/Zr­(IV) was investigated through chronoamperometry. The result suggested that the nucleation mechanism of Zr varied with the overpotential at F–/Zr­(IV) = 6. The addition amount of F– led to the variation of the nucleation mechanism of Zr, i.e., progressive nucleation when F–/Zr­(IV) = 7 and instantaneous nucleation when F–/Zr­(IV) = 10. Zr was prepared through constant current electrolysis at different concentrations of F– and then analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM), suggesting that the concentration of F– can exert a certain effect on the surface morphology of products.