Electrochemical Study of Eu(III)/Eu(II) in LiF-BeF2 Molten Salt

Abstract

The electrochemical behavior of Eu(III)/Eu(II) (C Eu total = 2.34 × 10−5 mol g−1) in LiF-BeF2 (FLiBe) molten salt is studied by cyclic voltammetry (CV), square wave voltammetry (SWV), chrono potentiometry (CP) and linear polarization (LP) in the temperature range of 773 to 973 K. The coexistence of Eu(III) and Eu(II) and the ratio of Eu(III)/Eu(II) are determined by SWV test. The redox reaction of Eu(III)/Eu(II) couple on an inert tungsten electrode is demonstrated to be a quasi-reversible process with diffusion controlled mass transfer. The diffusion coefficient and diffusion activation energy of Eu(III) and Eu(II) are obtained by CP method at different temperature. The thermodynamic and kinetic characteristics of the redox reaction of Eu(III)/Eu(II) couple are investigated by various electrochemical methods. With the obtained data, the thermodynamic data ΔG 0 (−1046.1 KJ mol−1), ΔH 0 (−1218.2 KJ mol−1), ΔS 0 (−0.197 KJ mol−1), and E 0 EuF2/Eu (−0.799 V vs E 0 BeF2/Be ) for EuF2 are calculated at 873 K and the possibility of the application of the Eu(III)/Eu(II) couple as redox buffering species or salt potential indicator is evaluated.