Electrochemical behavior of [UO_2Cl_4]~(2-) in 1-ethyl-3-methylimidazolium based ionic liquids

In order to examine the chemical form of uranyl species in 1-ethyl-3-methylimidazolium(EMI) based ionic liquids,UV-visible absorption spectra of solutions prepared by dissolving EMI] 2 UO2Cl4] into a mixture of EMICl and EMIBF 4(50:50 mol%) were measured.As a result,it was confirmed that uranyl species in the mixture of EMICl and EMIBF 4 existed as UO2Cl4]2-.Cyclic voltammograms(CVs) of UO2Cl4]2-in the mixture were measured at 25 ℃ using a Pt working electrode,a Pt wire counter electrode,and an Ag/Ag + reference electrode(0.01 M AgNO 3,0.1 M tetrabutylammonium perchlorate in acetonitrile) in a glove box under an Ar atmosphere.Peaks corresponding to one redox couple were observed around-1.05 V(Epc) and-0.92 V(Epa) vs.ferrocene/ferrocenium ion(Fc/Fc +).The potential differences between two peaks(Ep) increased from 101 to 152 mV with an increase in the scan rate from 50 to 300 mV s-1,while the(Epc+Epa)/2 value was constant,-0.989 V vs.Fc/Fc + regardless of the scan rate.Furthermore,the diffusion coefficient of UO2Cl4]2-and the standard rate constant were estimated to be 3.7 × 10-8 cm 2 s-1 and(2.7-2.8) × 10-4 cm s-1 at 25 oC.By using the diffusion coefficient and the standard rate constant,the simulation of CVs was performed based on the reaction,UO2Cl4]2-+ e = UO2Cl4]3-.The simulated CVs were found to be consistent with the experimental ones.From these results,it is concluded that UO2Cl4]2-in the mixture of EMICl and EMIBF 4 is reduced to UO2Cl4]3-quasi-reversibly at-0.989 V vs.Fc/Fc +.

Electrochemical behavior of [UO2Cl4]2? in 1-ethyl-3-methylimidazolium based ionic liquids

In order to examine the chemical form of uranyl species in 1-ethyl-3-methylimidazolium (EMI) based ionic liquids, UV-visible absorption spectra of solutions prepared by dissolving EMI]₂UO₂Cl₄] into a mixture of EMICl and EMIBF₄ (50:50 mol%) were measured. As a result, it was confirmed that uranyl species in the mixture of EMICl and EMIBF₄ existed as UO₂Cl₄]^2?. Cyclic voltammograms (CVs) of UO₂Cl₄]^2? in the mixture were measured at 25 °C using a Pt working electrode, a Pt wire counter electrode, and an Ag/Ag⁺ reference electrode (0.01 M AgNO₃, 0.1 M tetrabutylammonium perchlorate in acetonitrile) in a glove box under an Ar atmosphere. Peaks corresponding to one redox couple were observed around ?1.05 V (E _pc) and ?0.92 V (E _pa) vs. ferrocene/ferrocenium ion (Fc/Fc⁺). The potential differences between two peaks (??E _p) increased from 101 to 152 mV with an increase in the scan rate from 50 to 300 mV s^?1, while the (E _pc + E _pa)/2 value was constant, ?0.989 V vs. Fc/Fc⁺ regardless of the scan rate. Furthermore, the diffusion coefficient of UO₂Cl₄]^2? and the standard rate constant were estimated to be 3.7 × 10^?8 cm² s^?1 and (2.7?C2.8) × 10^?4 cm s^?1 at 25 °C. By using the diffusion coefficient and the standard rate constant, the simulation of CVs was performed based on the reaction, UO₂Cl₄]^2? + e^? = UO₂Cl₄]^3?. The simulated CVs were found to be consistent with the experimental ones. From these results, it is concluded that UO₂Cl₄]^2? in the mixture of EMICl and EMIBF₄ is reduced to UO₂Cl₄]^3? quasi-reversibly at ?0.989 V vs. Fc/Fc⁺.