Electrochemical Reduction of Tungsten Oxide in LiCl-KCl Molten Salt Eutectic using the Fluidised Cathode Process

The electrochemical reduction of WO3 to W metal using a fluidised cathode process has been investigated. Voltammetry was compared with thermodynamic predictions using a predominance diagram for the system to help explain the reaction mechanism. The main reduction potential was located to be −2.14 V vs. Ag/Ag+. By performing near-exhaustive electroreduction at constant potential, the Faradaic current efficiency was estimated to be >82%. The metal is produced in the form of homogeneous particles bound to the substrate electrode, which can periodically spall off. The effects of metal oxide-to-salt ratio and of fluidisation conditions on the process were investigated. Higher loading of metal oxide particles resulted in an increase in the rate of metallic deposit growth and less current 'noise', while the rate of reduction was relatively insensitive to flow rate of the Ar agitation gas feed, up to a limit where transition to a different flow regime is expected to be the cause of increased reaction rate.