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 O^2- 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 O^2-. The square wave voltammetry results confirmed that O^2- is oxidized to O₂, with the electrode reaction controlled by ion diffusion. chronopotentiometry confirmed that the electrochemical behavior of O^2- obeyed the Sand law. The diffusion coefficient of O^2- in FLiBe by chronopotentiometry followed Arrhenius' law. Then, a well-fitted linear relationship between O^2- 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 O^2- was achieved. This study presents an in situ electrochemical quantitative analysis method to monitor the O^2- 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.