Electrochemical Properties of Europium(III), Samarium(III) and Cerium(III) in Tetrabutylammonium Chloride Ionic Liquid

Tsion Raz-Ohaion tsionohaion@gmail.com ¹ Yeshayahu Ben-Eliyahu ¹ Armand Bettelheim ² Philippe Moisy ³ Laurence Berthon ³

¹Chemistry Department, Nuclear Research Center Negev, Beer-Sheva
²Chemical Engineering Department, Ben-Gurion University of the Negev, Beer-Sheva
³Nuclear Energy Division, RadioChemistry & Processes Department, CEA, Bagnols-Sur-Ce`ze Cedex

The Electrochemical behavior of the trivalent lanthanides europium(III), samarium(III) and cerium(III) in tetrabutylammonium chloride (Bu₄NCl) was investigated by cyclic voltammetry at glassy carbon working electrode in 398 K.

The cyclic voltammograms of Eu(III) and Sm(III) consisted of quasi-reversible waves occurring at -0.15V and -1.23 V (vs. Ag wire) respectively, attributed to the reduction to the divalent states. Cyclic voltammogram of Ce(III) shows oxidation peak potential of 1.14V (vs Ag wire) occurring very close to the potential window limit. The reversed reduction of Ce(IV) consists of two reduction peaks at -0.42V and -0.62V (vs. Ag wire) possibly due to addition of chloride ligand. Since the reference potential of the Ag wire within Bu4NCl is somewhat vague, FeCp₂/FeCp₂⁺ redox potential was measured as an internal reference and was found to be 0.62V vs the Ag wire.

The diffusion coefficients of the trivalent lanthanides in Bu₄NCl were determined to be of the order of ∼10⁻¹⁰ cm²/s by cyclic voltammetry and the electron transfer coefficients (k_s) were determined to be of the order of ∼10⁻⁴ cm/s.