Redox electrochemistry of europium fluoride complexes in an equimolar NaCl-KCl melt

The electrochemical behavior of europium fluoride complexes was studied by different electrochemical methods at a glassy carbon electrode in the temperature range 973-1100 K in the NaCl-KCl melt. The diffusion coefficients of Eu(III) and Eu(II) were determined by linear sweep voltammetry. The standard rate constants of charge transfer for the Eu(III)/Eu(II) redox couple were found on the base cyclic voltammetry, impedance spectroscopy and chronoamperometry data. The formal standard redox potentials EEu(III/Eu(II)∗ were obtained by linear sweep and cyclic voltammetry. The electrochemical behavior of europium fluoride and europium chloride complexes in NaCl-KCl melt was compared and discussed in connection with the strength and stability of these complexes. It was shown that the formation of stronger fluoride complexes reduced values of diffusion coefficients, standard rate constants for charge transfer of the Eu(III)/Eu(II) redox couple and shifted the formal standard redox potentials to the more electronegative values.