Electrochemical Behavior of Sm(III) and Electrodeposition of Samarium from 1-Butyl-1-Methylpyrrolidinium Dicyanamide Ionic Liquid

Abstract

Electrodeposition of rare-earth metals using ionic liquids is considered as a potential alternative to conventional high-temperature molten salt electrolysis. Herein, the electrochemical reduction of samarium(III) at near ambient conditions is investigated using different samarium precursors, namely, triflate (Sm(OTf)3), nitrate (Sm(NO3)3.6H2O) and chloride (SmCl3), in 1-butyl-1-methylpyrrolidinium dicyanamide ([BMP][DCA]) ionic liquid. FT-infrared and Raman spectroscopy analyses of Sm3+/[BMP][DCA] solutions confirm the coordination of Sm3+ species with [DCA]^- ion through nitrogen atom. Cyclic voltammetry of Sm3+ at glassy carbon electrode provides evidence of a two-step reduction process in all the systems via Sm3+ to Sm2+ and Sm2+ to Sm0 with peaks observed at similar reduction potentials owing to indifference in samarium(III) chemistries in each medium which is supported by a plausible mechanism. The diffusion coefficient of Sm3+ in [BMP][DCA] was determined to be 3.00x10-7, 3.64 x 10-8 and 1.90x10-7 cm2.s-1 for Sm(OTf)3, Sm(NO3)3.6H2O and SmCl3 systems, respectively. The electrodeposition of samarium was achieved on nickel and glassy carbon substrates under two different potentials and temperatures. X-ray photoelectron spectroscopy confirms that the samarium electrodeposits are a mixture of metallic and oxide forms.

Voltammetric Behaviour and Electrodeposition of Samarium in 1-Butyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquid

“…5a) occurred at a less positive values when compared to the reported reduction potentials of -1.35 V, -1.9 V, and -1.70 V for the reduction of Sm(III) to Sm(II) and -2.40 V, -2.57 V and -2.50 V (vs Ag/Ag + ) for the reduction of Sm(II) to Sm(0), respectively, during the electrochemical behaviour of samarium nitrate, samarium triflate and samarium chloride, respectively in a dicyanamide based ionic liquid. 20 Similarly, the observed samarium(III) reduction potentials in [BMP][Tf 2 N] in the present study occurs at more positive values when compared to neutral ligand-based ionic liquid (Sm(III) → Sm (II) reduction occuring at -2.22 V and Sm(II) → Sm(0) at -3.30 V vs Pt quasi-reference). 21 The difference observed in the reduction potentials of samarium species can likely be attributed to the nature of the electrolyte, presence of moisture in the electrolyte, different reference electrodes used and the speciation of Sm(III) complex formed in the respective systems.…”

“…Silver wire immersed in 10 mM AgOTf in [BMP][Tf 2 N] was used as the reference electrode and detailed fabrication process can be found in our previous study. 20 All the potentials reported in this study are referenced with respect to Ag/Ag + . Owing to the relatively high viscosity of the ionic liquid and to minimize the effect of electrolyte resistance, all voltammetric studies were carried out with iR drop compensation by measuring the solution resistance (R u ) using impedance spectroscopy and the value was compensated by 85% while performing voltammetric studies using an inbuilt protocol in the potentiostat.…”

“…17,18 Dicyanamide based ionic liquid has been utilized to investigate the voltammetric behaviour of Sm(III) and no electrodeposition of samarium was performed in this ionic liquid electrolyte. 19 Our group recently investigated the electrochemical behaviour and electrodeposition of samarium from a dicyanamide based ionic liquid 20 and in neutral ligand-based ionic liquid 21 at near ambient conditions. Fundamental insights on the electrochemical redox behaviour and properties of lanthanide ions in ionic liquid electrolytes is a crucial prelude for successfully translating laboratory findings to practical technologies related to their electrochemical separation, recovery and electrowinning from primary and secondary sources.…”

Study of the anticorrosive behavior of samarium as a corrosion inhibitor in multilayer systems for aluminum alloy

“…All the other elements originated in the propelled solution interacting with the air plasma, basically nitrogen/oxygen. The EDS spectrum for the samarium coating obtained by APPJ shows the same peaks as similar systems obtained by other methods 67,68 . Therefore, the APPJ method could be an option for the deposition of samarium species.…”

Electrochemical Deposition with Redox Replacement of Lanthanum with Uranium in Molten LiCl-KCl

“…One notable aspect of both designs is that the porous frit is conductive, so there is electronic conductivity between the inner melt inside the reference electrode and the outer melt, in addition to the ionic conductivity due to the porosity of graphite. Walker and Dick 45 reported an electrode for aqueous media, and Andrew et al 46 another for ionic liquids, that used a solid platinum wire instead of a porous frit as a conductive element that connected the inner reference electrode solution with the outer solution. The implication for all of these reference electrodes is that there can be redox reactions across this conductive interface to maintain the charge balance, without the need for mass transfer across a frit.…”