Electrochemical studies on uranyl (VI) chloride complexes in ionic liquid, 1-Butyl-3-methylimidazolium chloride

Abstract

UV-visible absorption spectra of solutions prepared by dissolving Cs 2 UO2 Cl4 or UO2 Cl2 · nH2O into 1-butyl-3-methylimidazolium chloride (BMIC1) have been measured. As a result, it was clarified that uranyl species in BMIC1 exist as [UO2Cl4]2-. Cyclic voltammograms of [UO2Cl4]2-in BMIC1 were measured at 80 ± 1°C using a glassy-carbon working electrode, a platinum wire counterelectrode, and a Ag/AgCl reference electrode with a liquid junction filled with BMIBF4 in a glove box under Ar atmosphere. Peaks corresponding to one redox couple were observed around -0.73 (Epc) and -0.65 V (Epa). The potential differences between two peaks (ΔEp) at scan rates in the range from 10 to 50mV s-1 are 70-80 mV, and are almost consistent with the theoretical ΔEp value (67 mV) for the reversible one-electron-transfer reaction at 80°C. Furthermore, the (Epc + Epa)/2 value is constant, -0.690 V, regardless of the scan rate. From these results, it is concluded that [UO2Cl4] 2-in BMICl is reduced to [UO2Cl4] 3-quasi-reversibly. © Atomic Energy Society of Japan.