Electrochemical and thermodynamic properties of europium(III), samarium(III) and cerium(III) in 1-butyl-3-methylimidazolium chloride ionic liquid

Electrochemical behavior of trivalent lanthanides such as europium(III), samarium(III) and cerium(III) in 1-butyl-3-methylimidazolium chloride (bmimCl) was investigated by cyclic voltammetry and chronopotentiometry at platinum working electrode in the temperature range of 343–373 K. The cyclic voltammograms of these metal ions in bmimCl at Pt electrode consisted of quasi-reversible waves occurring at a cathodic peak potential of −0.769 V, −0.547 V and −0.558 V (vs. Pd, 373 K) were attributed to the reduction of Eu(III), Sm(III) and Ce(III) to their respective divalent states. A prewave observed in the cyclic voltammogram of Eu(III) represents the reduction of Eu(III) to Eu(II) adsorbed on Pt electrode. The diffusion coefficients of these trivalents in bmimCl were determined to be of the order of ∼10 −8 cm 2 s −1 by cyclic voltammetry and chronopotentiometry and the charge transfer rate constants ( k s ) were determined to be of the order of ∼10 −5 cm s −1 by Nicholson method. The apparent standard potentials, E 0 * (vs. Cl 2/Cl −), and some thermodynamic properties of reaction of LnCl 3 from LnCl 2 were determined and the results are reported in this paper.