Electrochemical behavior and cathodic nucleation mechanism of molybdenum ions in NaCl-KCl.

• The electrochemical behavior of molybdenum ions and their electrodeposition mechanism in molten salts were systematically investigated. • The variation of Mo element concentration and the valence state of the molten salt bottom product was tested by in situ salt extraction during electrolysis. • The causes of current fluctuation during constant voltage electrolysis were revealed, culminating in the successful electrolysis of molybdenum. The electrochemical behaviors of molybdenum ions in NaCl-KCl molten salt at 750 °C were studied in detail, and pure metallic molybdenum was collected on the cathode. The reduction and diffusion processes of molybdenum ions in NaCl-KCl molten salt were also identified using cyclic voltammetry and square wave voltammetry. The diffusion coefficient and nucleation mode of molybdenum ions were analyzed. Electrodeposition was performed at a constant voltage and the variation of current with time was recorded. The variation of Mo element concentration and the valence state of the molten salt bottom product was tested by in situ salt extraction during electrolysis. The result demonstrated that the electrode reduction process of molybdenum ion in NaCl-KCl molten salt at 750 °C was a two-step reaction, Mo(V) → Mo(III) → Mo, all of which was reversible and controlled by diffusion. Meanwhile, the nucleation mode of molybdenum ions was found to be progressive nucleation. It was determined by XRD, SEM and EDS that the primary component of the cathode deposition product was molybdenum. [ABSTRACT FROM AUTHOR]