In Situ Electrochemical Monitoring and Removal of Oxide Ions in FLiBe Molten Salts

In this work, cyclic voltammetry, square wave voltammetry, and chronopotentiometry were employed to systematically investigate the electrochemical behavior of O2− in LiF–BeF2 (66.7: 33.3 mol%) (FLiBe) molten salt on a gold electrode. Comparative analysis demonstrated that square wave voltammetry is more suitable than cyclic voltammetry for studying the electrochemical behavior of O2−. The square wave voltammetry results confirmed that O2− is oxidized to O2, with the electrode reaction controlled by ion diffusion. chronopotentiometry confirmed that the electrochemical behavior of O2− obeyed the Sand law. The diffusion coefficient of O2− in FLiBe by chronopotentiometry followed Arrhenius’ law. Then, a well-fitted linear relationship between O2− concentration and square wave voltammetry peak current density was established, enabling rapid determination and real-time monitoring of oxide content in an unknown FLiBe molten salt. Furthermore, the electrochemical deoxygenation of FLiBe was performed using the potentiostatic electrolysis technique, and a satisfactory removal efficiency of O2− was achieved. This study presents an in situ electrochemical quantitative analysis method to monitor the O2− concentration in FLiBe, overcoming the drawback of the long testing cycle in conventional chemical analysis. Meanwhile, this study provides new technical support for the deoxygenation and purification of the fuel salt in molten salt reactors.