Study on the molybdenum electro-extraction from MoS2 in the molten salt

Abstract In this study, the electrochemical behavior of MoS2 in NaCl-KCl eutectic system was revealed by transient electrochemical techniques, using a homemade Mo metallic cavity electrode (MCE). In order to investigate the difference of molybdenum ions in MoS2 and molybdenum free ions in the molten salt, a metallic molybdenum was electro-dissolved into the electrolyte in the form of molybdenum ions. The valence of molybdenum free ions was estimated to be in form of Mo6+ through the XPS analysis. The results of the electrochemical tests show that the reduction steps for MoS2 in NaCl-KCl salt was two and the corresponding reduction potentials were -0.37 V and -0.65 V (vs. Pt), respectively. A three-step reduction was found while investigating molybdenum free ions and the corresponding reduction potentials were 0.15 V, -0.40 V and -0.54 V (vs. Pt), respectively. The results of electrochemical impedance spectroscopy (EIS) analysis on the MoS2 pellet show a decreasing resistance with the increasing of potential. Moreover, potentiostatic electrolysis processes under different potentials were also carried out. Na2Mo3S4 was found to be the intermediate product during the reduction of MoS2 and Mo powder with residual sulfur content of 372 ppm was obtained as the cathode product after the electrolysis under 2.60 V for 20 h. At the same time, elemental sulfur was collected as the anodic product with a self-design condense apparatus.