Electrodeposition of neodymium and dysprosium from organic electrolytes

Geysens, Pieter; Lin, Pin-Cheng; Fransaer, Jan; Binnemans, Koen

doi:10.1039/d0cp06606k

Cited by 19 publications

(44 citation statements)

References 49 publications

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“…A 2-fold increase in the average current densities to 1 mA/cm 2 could be achieved upon an increase of the Nd loading to 70 mM and application of a potential of −2.5 V. Irrespective of the differences in the employed electrolyte conditions (i.e., Nd 3+ concentration, viscosity, etc. ), comparable current densities of 0.6 mA/cm 2 were reported in the Li-based electrolyte in THF and dimethyl ether solvents . Noticeably, collected current densities in Nd-loaded electrolytes displayed a significant initial decay before leveling off at lower limiting values under longer deposition times.…”

Section: Resultssupporting

confidence: 65%

Efficient Room Temperature Neodymium Electrodeposition in a Calcium-Based Electrolyte

Engmann

Yuan

Diaz

et al. 2023

ACS Appl. Eng. Mater.

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The shift to a clean energy economy has been driving a huge demand for rare-earth (RE) metals. Room temperature RE electrodeposition has been a targeted technology to displace the nonenvironmentally friendly and energy-intensive molten salt process. While the recently reported lithium borohydride electrolyte showed promise for neodymium (Nd) electrodeposition, complete information about the system efficiency and consistent interpretation of the voltammetry and characterization of Nd electrodeposition are still lacking. In this work, the employed calcium borohydride electrolyte features several advantages, including intrinsic solubility, a fluorinated-free environment, and more cost-effective and abundant components. Interestingly, the introduction of Nd led to the emergence of a new concentration-dependent voltammetric wave at more positive potentials, exhibiting less coalescence with the background voltammogram. These features indicated high selectivity for Nd reduction and were suggestive of a unique solvation structure of Nd 3+ ions and a pronounced contribution of calcium (Ca)-mediated reduction. Irrespective of the mechanistic nature (direct vs mediated) of Nd reduction, chronoamperometric assessment revealed promising electrodeposition metrics, including about 90% metal basis purity with a Faradaic efficiency approaching 85% at a deposition rate of 1 mA/cm 2 . X-ray photoelectron spectroscopy analysis qualitatively suggested the presence of mixed oxidized and metallic Nd in the bulk electrodeposit. While these results showed great promise for using the more sustainable Ca-based electrolytes, continuous efforts are being sought to optimize the operating deposition rate and product quality. In light of reported studies at room temperature, the outcomes of this work unravel the potential use of alkaline-earth-metal-based electrolytes to drive the room temperature electrodeposition of RE elements.

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Section: Resultssupporting

confidence: 65%

Efficient Room Temperature Neodymium Electrodeposition in a Calcium-Based Electrolyte

Engmann

Yuan

Diaz

et al. 2023

ACS Appl. Eng. Mater.

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“…In addition, DMI, which is an excellent organic solvent with a high boiling point, is also used for large-scale industrial synthesis processes. Therefore, it is superior to conventional ILs for the electrodeposition of RE metals. − Figure a shows the deposit formed on an Al foil substrate during potentiostatic electrolysis at −2.5 V (versus Ag/Ag + ) for 4 h at 323 K. A black substance was formed, even in the protective Ar atmosphere. An SEM image of the corresponding cross section is shown in Figure b.…”

Section: Resultsmentioning

confidence: 99%

“…Recent studies have shown that the electrodeposition of RE metals can be performed successfully using RE-containing perfluorinated salts obtained from phosphonium-, ammonium-, pyrrolidinium-, and imidazolium-based ILs with a sufficiently large electrochemical window. − However, the electrolyte systems reported to date for use in the electrodeposition of Nd are based on highly specialized second-generation ILs and are poorly suited for practical electrometallurgical applications owing to the complexity and high cost of their synthesis routes. , In view of this, Periyapperuma et al reported a cleaner approach to recover Nd via electrochemical deposition using low cost and non-fluorinated IL, which is an important step toward Nd recovery . Therefore, inexpensive electrolyte systems and readily available RE precursors are necessary for the facile recovery of RE metals at the lowest possible temperature.…”

Section: Introductionmentioning

confidence: 99%

“…15−19 However, the electrolyte systems reported to date for use in the electrodeposition of Nd are based on highly specialized second-generation ILs and are poorly suited for practical electrometallurgical applications owing to the complexity and high cost of their synthesis routes. 20,21 In view of this, Periyapperuma et al ) in an organic molecular solvent, namely, trimethyl phosphate (TMP). 23 The RE formed a complex cation with the neutral TMP ligands.…”

Section: ■ Introductionmentioning

confidence: 99%

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

et al. 2021

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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.

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“…Several strategies have been proposed to overcome the limitations of ionic liquids, with the increase of operating temperature, use of organic solvents and neutral ligand-based ionic liquids having been explored. ,− Of interest to this work, water has been reported as a good promoter for the production of electrochemical REMs in ionic liquids. , Early work on the impact of water was reported by Matsumiya et al, where a slight increase of water content (100–200 ppm) in phosphonium ionic liquids switched the reduction process from a consecutive (1 + 2e – ) reduction into a one-step (3e – ) pathway . In addition to this switch, the peak current decreased and the reduction potential shifted to more negative values.…”

Section: Introductionmentioning

confidence: 99%

Water Interplays during Dysprosium Electrodeposition in Pyrrolidinium Ionic Liquid: Deconvoluting the Pros and Cons for Rare Earth Metallization

Orme

Baek

Fox

et al. 2021

ACS Sustainable Chem. Eng.

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The electrochemical production of rare earth metals (REMs) in ionic liquids (ILs) has received much attention as a promising, sustainable replacement to molten salt electrolysis. Water additives have been suggested as a promoting strategy for the ionic liquid process; however, the fundamental understanding of the interfacial processes required to assess the overall viability for REM production is lacking. In this regard, a full investigation of the impact of water on dysprosium (Dy) electrodeposition in pyrrolidinium triflate (BMPyOTf) ionic liquid was carried out. Water introduction was revealed to involve an interplay of implications on the electrodeposition process, including coordination, speciation, reduction pathways, interfacial dynamics, nucleation, and metal stability and purity. Under highly dry conditions, the reduction occurs at a very negative potential (−3.3 V) in a consecutive pathway, resulting in negligible metal electrodeposition (low rate and efficiency) at the electrode surface. Small water concentrations (<500 ppm) lead to partitioning of the Dy complex between water and IL-coordinated speciation, giving rise to an additional wave at a more positive potential (−2.4 V). Probing the heterogeneous Dy speciation by spectroscopic analyses enabled uncovering of the reduction mechanism and evaluation of the mass transport properties. In addition to lowering the reduction thermodynamics, water introduction also improved the nucleation, deposition rate, and faradic efficiency. Despite these benefits, stripping voltammetric analysis predicts substantial chemical reactivity of the deposited Dy metal with water additives and/or electrolyte components, under long timescales. Surface characterization of the obtained product confirmed the instability of Dy metal as an oxidized/fluorinated material and its limited purity (∼60%). Moreover, high water introduction triggered a fast hydrogen evolution reaction (HER), downgrading the robustness of system efficiency. The overall impact of water additives seems to engender both promoting and mitigating effects on electrochemical REM production in IL, requiring a specific technoeconomic assessment and/or more innovative strategies to be sought.

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Electrodeposition of neodymium and dysprosium from organic electrolytes

Abstract: Nd3+ or Dy3+ salts and borohydride form redox-active [Ln(BH4)4]− complexes that enable room-temperature electrodeposition of neodymium- or dysprosium-containing layers from organic electrolytes.

Cited by 19 publications

References 49 publications

Efficient Room Temperature Neodymium Electrodeposition in a Calcium-Based Electrolyte

Efficient Room Temperature Neodymium Electrodeposition in a Calcium-Based Electrolyte

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

Water Interplays during Dysprosium Electrodeposition in Pyrrolidinium Ionic Liquid: Deconvoluting the Pros and Cons for Rare Earth Metallization

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Electrodeposition of neodymium and dysprosium from organic electrolytes

Abstract: Nd3+ or Dy3+ salts and borohydride form redox-active [Ln(BH4)4]− complexes that enable room-temperature electrodeposition of neodymium- or dysprosium-containing layers from organic electrolytes.

Cited by 19 publications

References 49 publications

Efficient Room Temperature Neodymium Electrodeposition in a Calcium-Based Electrolyte

Efficient Room Temperature Neodymium Electrodeposition in a Calcium-Based Electrolyte

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

Water Interplays during Dysprosium Electrodeposition in Pyrrolidinium Ionic Liquid: Deconvoluting the Pros and Cons for Rare Earth Metallization

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