LiNO₃-Supported Electrodeposition of Metallic Nd from Nd-Containing Solvate Ionic Liquid

Abstract

Inexpensive electrolyte systems and readily available rare-earth (RE) precursors are necessary for the facile recovery of RE metals at the lowest temperature, which will allow the sustainable development of RE metal-based industries. Inspired by previous reports on Nd electrodeposition in various expensive and specialized ionic liquids (ILs), herein, we developed a practical, green, and cost-effective Nd-containing solvate IL composed of an organic solvent [(1,3-dimethyl-2-imidazolidinone)] and Nd (CF3SO3)3; the IL is well suited for Nd electrodeposition using LiNO3. The electrolyte structure and electrochemical mechanism of the IL were elucidated through physicochemical analyses and cyclic voltammetry. The role of nitrate was investigated in detail. Nd was successfully electrodeposited using the proposed method, as confirmed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses. Thus, this work provides a firm theoretical basis and a practical strategy for the cost-effective bulk electrochemical extraction of RE metals at relatively low temperatures.

Facile Room-Temperature Electrodeposition of Rare Earth Metals in a Fluorine-Free Task-Specific Electrolyte

“…The high reversibility of the observed redox peaks suggests that the peaks are due to Li/Li + as all other reported instances of low-temperature REE electrodeposition show irreversibility for REE electrodeposition. [11][12][13][14][15][16][17]20,36 However, the position of these peaks deviates significantly from the literature value for Li/Li + vs Fc/Fc + , which is typically between 3.3 and 3.7 V. 45,46 It is possible that the positive shift of Li/Li + vs Fc/Fc + could arise from the effect of the solvation energy; however, such a shift is only ∼0.3 V based on previous literature reports. 46 In order to gain more understanding of this peak, control experiments were performed by studying the CV curve of a lithium-free Nd(BH 4 ) 3 -EE solution (denoted as pure-Nd(BH 4 ) 3 -EE) and a neodymium-free LiBH 4 -EE solution.…”

“…Due to the high electropositivity of REE metals, a nonaqueous electrolyte with a wide electrochemical window is required for electrodeposition. , Previous efforts have been focused on Fluorine (F)-containing systems, in particular, ionic liquids (ILs) and organic electrolytes containing bis­(trifluoromethane)­sulfonimide (TFSI) or trifluoromethanesulfonate anions. − While the electrodeposition of various REE metals has been reported in these systems, the application of F-containing ILs has been greatly hindered by various obstacles. Among them is the so-called passivation effect which can significantly impede stable deposition. ,, This effect likely originates from an electrically insulating layer formed by either coreduction of anions alongside the REE metal ions or decomposition of the organic solvent.…”

Fluorine-free organic electrolytes for the stable electrodeposition of neodymium metal

“…Similarly, Zhang and co-workers have recently proposed two different systems, NdCl 3 -AlCl 3 and Nd(SO 3 CF 3 ) 3 -LiNO 3 dissolved in the green aprotic organic solvent 1,3-dimethyl-2-imidazolidinone, for the electrodeposition of neodymium at ambient temperature. 26,27 Evidence for the presence of metallic neodymium in the deposits was provided by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis.…”

Electrochemical Solvometallurgy Pathway for the Sustainable Recovery of Bulk Metallic Lithium

“…That is, molecular liquids serve as the raw materials of ILs. 19 Therefore, identifying aprotic functional molecular liquids without the conventional shortcomings, including high volatility, toxicity, flammability, and low electrochemical stability, is important to the field of electrochemical solvometallurgy. 20 As opposed to ILs, many aprotic molecular liquids have rich categories, controllable quality, and capacity for large-scale industrial synthesis.…”

“…Preparation of traditional ILs requires substantial quantities of chemical compounds and organic solvents. That is, molecular liquids serve as the raw materials of ILs . Therefore, identifying aprotic functional molecular liquids without the conventional shortcomings, including high volatility, toxicity, flammability, and low electrochemical stability, is important to the field of electrochemical solvometallurgy .…”