Electrochemical Formation and Characterization of Ni-Sc Intermetallic Compounds in Lif-Caf2 Eutectic Melt

Abstract

This study investigates the cathodic behavior of Sc(III) on an reactive Ni electrode using a fluoride molten salt system for the first time. Various electrochemical methods are employed to elucidate the electrochemical formation process of the Ni-Sc alloy in the LiF-CaF2 eutectic melt. The generation of Ni-Sc intermetallic compounds results in a depolarizing effect, which facilitates the underpotential deposition of scandium onto the Ni electrode. The thermodynamic data of Ni-Sc intermetallic compounds (Ni5Sc, Ni7Sc2, Ni2Sc, NiSc, and NiSc2) are estimated using open-circuit chronopotentiometry measurements. Furthermore, Ni-Sc alloy are fabricated via potentiostatic and galvanostatic electrolysis methods and subsequently characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The findings indicate a sequential emergence of Ni5Sc, Ni2Sc, and combined NiSc+NiSc2 intermetallic compounds as the cathodic polarization potential escalates. By controlling the electrolysis conditions, different Ni-Sc intermetallic compounds can be synthesized, providing new insights for the preparation of Ni-Sc alloy and establishing a theoretical foundation for the synthesis of Ni-Sc intermediate alloy for solid-state reactive cathodes.

Keywords: LiF-CaF2 eutectic melt, Cathodic behavior, Ni-Sc intermetallic compounds, Thermodynamic data