Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

Abstract

The electrochemical reduction of trivalent samarium in a LiCl-KCl eutectic melt produced highly stable divalent samarium, whose electrochemical properties and electronic structure in the molten salt were investigated using cyclic voltammetry, UV-vis absorption spectroscopy, laser-induced emission spectroscopy, and density functional theory (DFT) calculations. Diffusion coefficients of Sm and Sm were electrochemically measured to be 0.92 × 10 and 1.10 × 10 cm/s, respectively, and the standard apparent potential of the Sm couple was estimated to be -0.82 V vs Ag|Ag at 450 °C. The spectroelectrochemical study demonstrated that the redox behavior of the samarium cations obeys the Nernst equation ( E°' = -0.83 V, n = 1) and the trivalent samarium cation was successfully converted to the divalent cation having characteristic absorption bands at 380 and 530 nm with molar absorptivity values of 1470 and 810 M cm, respectively. Density function theory calculations for the divalent samarium complex revealed that the absorption signals originated from the 4f to 4f5d transitions. Additionally, laser-induced emission measurements for the Sm cations in the LiCl-KCl matrix showed that the Sm ion in the LiCl-KCl melt at 450 °C emitted an orange color of fluorescence, whereas a red colored emission was observed from the Sm ion in the solidified LCl-KCl salt at room temperature.

Raman Spectroscopic and Theoretical Study of Scandium Fluoride and Oxyfluoride Anions in Molten FLiNaK

“…As a result, the scandium fluoride anions are responsible for the observed Raman bands, while alkali cations are not involved. This is in agreement with the fact that isolated anions can be employed to understand the speciation in an ionic environment including molten salt and ionic liquid. − …”

Electrochemical and Spectroscopic Study of EuIII and EuII Coordination in the 1‐Ethyl‐3‐methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquid

“…[12][13][14][15] Specifically,E u II can be stabilized in aqueous solutions thanks to cyclic ligands such as cryptands or analogues [16] whereasi nn onaqueousm edia, fully dissolved stablef orms of Ln II can be observed. [17,18] The electrochemical behavior of the Eu III /Eu II redoxc ouple was extensively studiedi nawide range of IL [14,[19][20][21][22][23][24][25][26][27] and its apparent standard potential was found to vary between0and À1.0 Vv ersus ferrocenium/ferrocene (Fc + /Fc) reference, depending on the medium. However,t he stabilization of Eu II in these solvents as compared to aqueous solutionsi sp oorly explained in the literature.…”

“…In contrast, IL were shown to be good solvents for the stabilization and study of the oxidation states +II and +IV for Ln [12–15] . Specifically, Eu II can be stabilized in aqueous solutions thanks to cyclic ligands such as cryptands or analogues [16] whereas in nonaqueous media, fully dissolved stable forms of Ln II can be observed [17, 18] . The electrochemical behavior of the Eu III /Eu II redox couple was extensively studied in a wide range of IL [14, 19–27] and its apparent standard potential was found to vary between 0 and −1.0 V versus ferrocenium/ferrocene (Fc + /Fc) reference, depending on the medium.…”

On the Structures of Thorium Fluoride and Oxyfluoride Anions in Molten FLiBe and FLiNaK

“…To counter the high charge of the anions, a polar continuum model (PCM) was adopted with a dielectric constant of 2.37, which is close to the typical values of molten fluorides (around two). , Some of the studied systems (ThF 7 3– and ThF 8 4– ) show positive highest occupied molecular orbital energies in the gas phase, but they become negative with the PCM. The PCM structures are very close to the gas phase geometries, and the major Raman bands of gas-phase ThF 6 2– and ThF 7 3– possess similar relative intensities as those obtained using the PCM, with the major band positions shifted by about 50 cm –1 or less (Figure S2).…”