Electrochemical behavior of tantalum ion in LiF-NaF-K2TaF7 molten salt system

Abstract

It is of great significance to clarify the electrochemical behavior of Ta⁵⁺ in LiF-NaF-K₂TaF₇ molten salt systems for the preparation of tantalum metal by molten salt electrodeposition. The aim of this work was to explore the reaction steps and behavior of the reduction of metal Ta from Ta⁵⁺ in fluorine molten salt by electrochemical method. The cyclic voltammetry, square wave voltammetry, chronopotentiometry were used to determine the reduction steps of Ta⁵⁺. The results showed that there were two reduction steps which the first reduction step R₁ was ${\text{TaF}}_7^{2-}+2e^{-}\rightleftharpoons \text{Ta}{F}_3+4F^{-}$ and the second reduction step R₂ was $\text{Ta}{F}_3+3e^{-}\to \text{Ta}+3F^{-}$. SEM, XRD and EDS results showed that the reduction product of Ta⁵⁺ in molten salt is Ta and the tantalum atom was selectively deposited and grew on the (200) crystal plane in priority.