Electrochemical Behavior of Cr(III) in LiCl-KCl Molten Salt on MoC-Mo 2 C Heterojunction Electrode

To suppress dendrite formation, MoC-Mo 2 C electrode was selected as the working electrode for extracting Cr from LiCl-KCl molten salt. The MoC-Mo 2 C electrode was prepared by anodization at 0.005 A cm −2 for 2 h in Li 2 CO 3 -K 2 CO 3 molten salt, which displayed a porous structure. Then, the electrochemical mechanism of Cr(III) on this electrode was studied by cyclic voltammetry, square wave voltammetry, and current reversal chronopotentiometry, confirming that reduction of Cr(III)/Cr(II) and Cr(II)/Cr(0) was reversible and diffusion-controlled. The diffusion coefficient of Cr(III) was determined to be on the order of 10 –5 cm 2 s −1 in the temperature range of 713–833 K, and the diffusion activation energy of Cr(III) was also estimated. Meanwhile, the electrode kinetics of Cr(II)/Cr(0) was measured by Tafel and LP techniques. The exchange current density( j 0 ) measured by the two methods were very close, and j 0 increased with increasing the temperature. Moreover, the nucleation mechanism of Cr measured by CA conformed to instantaneous nucleation on MoC-Mo 2 C electrode. Potentiostatic electrodeposition was performed on Mo and MoC-Mo 2 C electrodes, respectively. The obtained products characterized by scanning electron microscopy-energy-dispersive microscopy and X-ray diffraction indicated that the formed Cr exhibited a sparse dendritic morphology on Mo electrode, while a dense spherical morphology on MoC-Mo 2 C electrode.