Exchange current density of Th4+|Th couple in LiCl-KCl eutectic

Exchange current density (i∘) of thorium in LiCl-KCl eutectic at tungsten(inert) and liquid cadmium electrodes is reported in the present work. A cadmium electrode was designed in our laboratory for estimating i∘ of thorium in liquid cadmium. Cyclic voltammetry of thorium at tungsten electrode was associated with a cathodic peak at −1.59 V at 773 K attributed to Th4+|Th redox couple. Cathodic peaks corresponding to Th4+|ThCd11 and Th4+|ThCd5 couples at −1.31 V and −1.38 V, respectively (at 773 K) were observed in the cyclic voltammograms of thorium at liquid cadmium electrode. i∘ of thorium in LiCl-KCl eutectic at tungsten electrode (cathodic polarization) estimated by Tafel and Allen-Hickling methods were compared with those estimated from the cyclic voltammograms of LiCl-KCl-ThCl4. i∘ at tungsten electrode was found to be higher than that at liquid cadmium electrode. The temperature dependence of i∘ was studied to estimate the activation energy associated with Th4+|Th couple at tungsten, liquid cadmium (cathodic polarization) and dissolution of thorium (anodic polarization). The compositional dependence of i∘ of thorium at tungsten electrode was also addressed. This is the first report on the i∘ of thorium in LiCl-KCl eutectic.

134 Figure 1: Tafel plots of anodic and cathodic polarization of thorium and inert and liquid cadmium cathode in LiCl-KCl eutectic.