Rhenium Electrodeposition and Its Electrochemical Behavior in Molten KF-KBF4-B2O3-KReO4

The electrochemical behavior of rhenium ions in the molten KF-KBF4-B2O3 salt was systematically studied, and pure metallic rhenium was obtained at the cathode. The processes of rhenium ions reduction and diffusion in molten KF-KBF4-B2O3 were determined using cyclic voltammetry, stationary galvanostatic and polarization curves analyses. The values of diffusion coefficients were 3.15 x 10(-5) cm(2)/s and 4.61 x 10(-5) cm(2)/s for R-1 and R-2,R- respectively. Rhenium electrodeposition was carried out at a constant potential. The process of rhenium cathode reduction in KF-KBF4-B2O3 at 773 K was found to be a one-step reaction Re(VII) -> Re, and rhenium electrodeposition presumably occurred from two types of complex rhenium ions (KReO4 and K3ReO5). Both processes are quasi-reversible and controlled by diffusion. The obtained cathode deposit was analyzed by SEM, EDX, ICP-OES and XRD methods. The obtained deposit had a thread structure and rhenium was the main component.