A cyclic voltammetry study of the electrochemical behavior of platinum in oxide-ion rich LiCl melts

Joseph, Teena; Sanil, N K; Shakila, L.; Mohandas, K.S.; Nagarajan, K.

doi:10.1016/j.electacta.2014.07.025

Cited by 23 publications

(19 citation statements)

References 10 publications

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“…Similar kind of anodic behavior noticed on platinum anode has been reported in our previous article. 17 The potential window of the LiCl-1 wt%. Li 2 O melt for CO 2 formation was found to be 1.0 V (+ 0.75 to + 1.7 V) beyond which the chlorine evolution took place on the graphite electrode.…”

Section: Cyclic Voltammetry Of Tantalum and Graphite In Licl-li 2 O Mmentioning

confidence: 99%

A Study of Graphite as Anode in the Electro-Deoxidation of Solid UO₂in LiCl-Li₂O Melt

Joseph

Sanil

Mohandas

et al. 2015

J. Electrochem. Soc.

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Electrochemical behavior of graphite in LiCl and LiCl melts containing up to 1 wt% Li 2 O was studied by using cyclic voltammetry and electrolysis, in the context of its probable use as anode in the electrochemical reduction of solid UO 2 in the molten salt at 650 • C. The lithium deposition and chlorine evolution potentials of LiCl melt were determined by CV of tantalum (cathodic polarization) and graphite (anodic polarization) working electrodes as −2.19 V and +1.21 V vs Ni/NiO reference electrode respectively. In LiCl-Li 2 O melts, carbon dioxide was formed on the graphite WE from > +0.75 V onwards and its current and potential range of formation increased with increase in the Li 2 O content of the melt. Cathodic polarization of a UO 2 disc WE in LiCl-1 wt% Li 2 O melt showed that the reduction of UO 2 to U occurs at −2.18 V and the lithium metal deposition on it at −2.36 V. Electro-reduction experiments carried out with a dense UO 2 pellet cathode and graphite anode in both LiCl and LiCl-Li 2 O melts proved that the surface of the pellet was reduced to U metal at ≥ −2. Nuclear energy is considered as a major source of electricity for the present and future demands of the modern world. Sodium cooled fast reactor with metal fuel is proposed as one of the future reactor systems in the Generation IV concept and such reactors are considered to be inherently safe, economically viable and resistant to nuclear proliferation.1 U-Pu-Zr alloy is used as the metal fuel and hence production of these metals is of importance in the context of nuclear electricity. These metals have been produced from their oxides by the conventional chemical processes for the past several decades and there has been a great deal of interest to develop more efficient methods of production of the metals directly from the oxides.Spent metal fuels are reprocessed by pyrometallurgical process, in which the major and minor actinides are recovered by an electrorefining process carried out in a molten bath of LiCl-KCl at 500• C. 2Most of the nuclear reactors use uranium oxide and mixed oxide of uranium and plutonium (MOX) as the fuel and the spent fuel containing UO 2 and PuO 2 along with other oxides and fission products can be processed to obtain U and Pu for preparation of metal fuel. Reprocessing of spent oxide fuels by the molten salt electrorefining process is difficult as the oxides do not dissolve in the molten chlorides.Hence an intermediate process is required to convert the spent-oxide fuel to a metal form, which can be subsequently electrorefined to separate the actinides of interest. Chemical reduction of the spent oxide fuel by lithium metal in molten LiCl at 650• C was reported in this context. 3 The process required handling of large quantities of highly reactive lithium metal. The process also demanded frequent change of the molten bath due to build up of Li 2 O and hence the use of large quantities of the molten salt. Obviously these factors raise issues of safety of handling and storage of hygroscopic salt and highly irradiated fu...

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Section: Cyclic Voltammetry Of Tantalum and Graphite In Licl-li 2 O Mmentioning

confidence: 99%

A Study of Graphite as Anode in the Electro-Deoxidation of Solid UO₂in LiCl-Li₂O Melt

Joseph

Sanil

Mohandas

et al. 2015

J. Electrochem. Soc.

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“…In consideration the close combination of U with Fe for the synthesis of uranium‐iron alloy, the working electrode (WE) is molybdenum wire (A.R, Φ=1 mm×300 mm, ρ=10.20 g/cm 3 ) for electrochemical testing because of its chemical inertness or stainless steel (304 stainless steel, S.P, Φ=1 mm×300 mm, ρ Fe =7.93 g/cm 3 ), and the working electrodes (WE) were polished by SiC paper. We selected graphite rod (S.P, Φ=4 mm×300 mm, ρ=2.25 g/cm 3 ) as anode rather than Pt, because the Pt counter electrode (CE) will dissolve, according to Faradays law, and the anodic effect increases the wear and tear, and Li 2 PtO 3 is deposited in the electrolytes affecting electrochemical signals, and corrosion also occurred on the platinum electrode in Li 2 O containing LiCl melts . As such, Carbon materials like 3‐D graphite doped materials and reduced graphene oxide are promising anodes ,.…”

Section: Methodsmentioning

confidence: 99%

“…The reference electrode (RE) is a Ag/AgCl electrode composed of a high purity alumina tube containing AgCl (1 wt%) in LiCl−KCl (41 : 59 mol %) melts whose total weight is 7 g. The potential of the reference electrode was standardized against Ag + /Ag, and all of the potentials texted in the experiment were referred to this Ag/AgCl electrode couple. The reference electrode was used in a similar manner ,. Before carrying out the experiment, all electrodes were pretreated.…”

Section: Methodsmentioning

confidence: 99%

Electrochemical Mix‐Reduction Process of U and U‐Fe Alloys on the Surface of Cathode in LiCl‐KCl‐U₃O₈ at 773 K

Jiang

Liu

et al. 2018

ChemElectroChem

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“…7,50 Research into the anodic behavior of platinum under these conditions has demonstrated that platinum can operate as a nearly inert anode if the concentration of Li 2 O is maintained above 0.5 wt% and the anode potential is less than +2.6 V vs Li/Pb. 51 If the activity of the O 2− ion decreases significantly, the dissolution of platinum occurs via Reaction 3.…”

Section: Experience With the Reduction Processmentioning

confidence: 99%

Review—Metallic Lithium and the Reduction of Actinide Oxides

Merwin

Williamson

Willit

et al. 2017

J. Electrochem. Soc.

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Extensive research and process development has been conducted on the electrolytic reduction of actinide oxides in molten LiCl-Li 2 O. It is now accepted that the reduction of these metal oxides occurs via two separate reduction mechanisms: direct electro-chemical reduction and mediated chemical reduction by metallic lithium. The deposition of metallic lithium at the cathode (mediated chemical reduction mechanism) during the process is known to be essential in order to achieve high process throughputs and reduction yields, and yet a knowledge gap exists regarding the nature of metallic lithium in this system. This review summarizes the formation of lithium during the process and its dispersion into the molten salt electrolyte. Previously reported aspects of the physical chemistry of the LiCl-Li 2 O-Li system are presented with a specific focus on the dispersion of Li in the solution. Finally, issues regarding the effect of the presence of lithium on the electrolytic reduction process are discussed. Evidence shows that electrochemically generated metallic lithium is likely a significant source of experimental uncertainty, low current efficiency and Li 2 O consumption in the oxide reduction process. The reduction of uranium, plutonium and minor actinide oxides to a metallic form is an important nuclear fuel cycle process.2-9 The ability of metallic lithium to reduce various uranium oxides, importantly UO 2 and U 3 O 8 , has been known for many years.10 A molten salt metalothermic reduction process employing metallic lithium (Li) as a reductant dissolved in molten LiCl was first developed by Argonne National Laboratory (ANL) to consolidate a variety of forms of actinide oxides for integration into a single electrometallurgical reprocessing system. 11-13 An electrolytic process, often referred to as electro-deoxidation or simply oxide reduction, was subsequently developed as a more controllable method of reducing metal oxides. A feasibility study conducted by Poa et al. demonstrated that oxides of uranium and plutonium could be reduced electrochemically in molten salts as long as the reduction potential of the metal oxide in question was more noble than the cation of the electrolyte.14,15 This approach was further developed by Gourishankar et al. to better understand processes chemistry and develop the electrolytic cell technology. 13,[16][17][18][19][20] Independent research conducted by Fray, Farthing, and Chen (FFC) applied the principles of electrochemical reduction in molten salt electrolytes to a variety of metal oxide reduction processes. 21,22 The FFC process has been the subject of several literature reviews.23-25 While these review articles address the processes associated with the reduction of nuclear fuel in LiCl, they focus on the electro-deoxidation phenomena and the CaCl 2 -CaO system. Additionally, the process engineering of the electrolytic reduction of nuclear fuel, and experience in incorporating oxide fuel into pyroprocessing, has been the focus of a recent review article. 26 The current review wi...

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A cyclic voltammetry study of the electrochemical behavior of platinum in oxide-ion rich LiCl melts

Cited by 23 publications

References 10 publications

A Study of Graphite as Anode in the Electro-Deoxidation of Solid UO₂in LiCl-Li₂O Melt

A Study of Graphite as Anode in the Electro-Deoxidation of Solid UO₂in LiCl-Li₂O Melt

Electrochemical Mix‐Reduction Process of U and U‐Fe Alloys on the Surface of Cathode in LiCl‐KCl‐U₃O₈ at 773 K

Review—Metallic Lithium and the Reduction of Actinide Oxides

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A cyclic voltammetry study of the electrochemical behavior of platinum in oxide-ion rich LiCl melts

Cited by 23 publications

References 10 publications

A Study of Graphite as Anode in the Electro-Deoxidation of Solid UO2in LiCl-Li2O Melt

A Study of Graphite as Anode in the Electro-Deoxidation of Solid UO2in LiCl-Li2O Melt

Electrochemical Mix‐Reduction Process of U and U‐Fe Alloys on the Surface of Cathode in LiCl‐KCl‐U3O8 at 773 K

Review—Metallic Lithium and the Reduction of Actinide Oxides

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A Study of Graphite as Anode in the Electro-Deoxidation of Solid UO₂in LiCl-Li₂O Melt

A Study of Graphite as Anode in the Electro-Deoxidation of Solid UO₂in LiCl-Li₂O Melt

Electrochemical Mix‐Reduction Process of U and U‐Fe Alloys on the Surface of Cathode in LiCl‐KCl‐U₃O₈ at 773 K