Electrochemical behaviour of gadolinium ion in molten LiCl-KCl eutectic

This work presents the electrochemical study of GdCl3 in the molten LiCl-KCl eutectic in the temperature range 723823 K. Transient electrochemical techniques such as cyclic voltammetry and chronopotentiometry, on an inert metallic tungsten working electrode, have been used in order to investigate the reduction mechanism and transport parameters. This study shows that Gd3+ ions are reduced to Gd metal by a single step mechanism with exchange of three electrons. Diffusion coefficient of GdCl3 ions was determined at various temperatures, at 723 K the value is D = 0.88 10(-5) cm(2) s(-1). Apparent standard reduction potential of the redox couple Gd3+/Gd has been determined by the open-circuit chronopotentiometry technique at several temperatures. Also the Gibbs free energy of GdCl3 formation was determined and compared with thermodynamic data for pure compounds in the supercooled state in order to estimate the activity coefficient of Gd3+ in the molten LiCl-KCl eutectic. (c) 2006 Elsevier B.V. All rights reserved.