Electrochemical studies of molten sulfates in LiCl-KCl-Na2SO4 at 700 °C

Kumar, Kuldeep; Smith, Nathan D.; Lichtenstein, Timothy; Kim, Hojung

doi:10.1016/j.corsci.2017.12.022

Cited by 18 publications

(9 citation statements)

References 18 publications

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“…Because in our simulations ions cannot react, we are not constrained to voltages across the cell that are lower than the electrochemical window of the species and hence we can also investigate what happens at the interface when the drop in voltage across the cell is large. We find that even when the potential across the cell is much larger than the electrochemical window for most salts (typically <4 V), 97 there is no saturation in U(z), the number-or electron-density profiles, or as we will show below, the reflectivity. In fact, the charge per atom at the diamond surface is usually very small compared to that of the ions, and structural changes in the salt density profiles are gradual with an increase of surface charge density at 1100 K. Applied surface charges and hence voltages significantly larger than should be needed to electrolize most salts do cause significant structural rearrangements, but below 4 V only moderate enhancements and depletions in the number density profiles of the ions are observed, as can be gleaned from Figure 3a− , for all our salts and for all applied biases, these mostly decay to zero after two or three oscillations on a distance between 12 to 15 Å; however, particularly in the case of RbCl at very high bias (much larger than the electrochemical window of most salts), we observe some systematic small amplitude oscillations (difficult to see on the scale of Figure 4) all the way to ∼22 Å.…”

Section: Resultsmentioning

confidence: 65%

Structure of Molten Alkali Chlorides at Charged Interfaces and the Prediction and Interpretation of Their X-ray Reflectivity

et al. 2021

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The fundamental properties of molten salts have been the subject of research that spans a century. Yet, in the past few years, there has been an unprecedented surge in interest for these systems in the bulk and under confinement by walls and interfaces including under applied potentials. This is driven by the prospect of exciting and very practical energy technologies, including those in the solar and nuclear fields. This article sets to answer two simple but fundamental questions. How does the liquid structure of alkali chlorides change at a real interface when it is charged? Also, how would such changes on the liquid side of the interface be detected in X-ray reflectivity experiments? We use an interface mimicking conductive diamond, which because of its lattice spacing, is an excellent choice for reflectivity experiments. The reason for our interest in X-ray reflectivity is that, as opposed to electrochemical measurements alone, this is likely the only technique in which atomic level information at the liquid side of the interface can be gained under the extreme temperature environments of molten salts. As it will become apparent, the interpretation of reflectivity results in terms of atomic positions is complex when multiple species with different X-ray contrasts on the liquid side are considered. A theoretical scheme termed “the peaks and antipeaks analysis of reflectivity” originally introduced in our prior work (J. Phys. Chem. C 2019, 123 (8), 4914–4925) is expanded to interpret the structural changes at the interface as a function of applied electrical bias.

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Section: Resultsmentioning

confidence: 65%

Structure of Molten Alkali Chlorides at Charged Interfaces and the Prediction and Interpretation of Their X-ray Reflectivity

et al. 2021

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“…The following conclusions were drawn from the results of the study: (1) The corrosion rate of the coated specimen decreased compared to that of the bare specimen. In the case of 3 wt.% Li 2 O, it decreased by approximately 60% at 72 h and approximately 38% at 168 h. On the other hand, for the 8 wt.% Li 2 O, the corrosion rate decreased by approximately 54% at 72 h and 30% at 168 h.…”

Section: Discussionmentioning

confidence: 87%

“…Molten salts are used in various industries due to their high electrical conductivity, high-density processing, and fluid properties. Recently, they have been attracting increasing attention for applications in jet engines [1][2][3][4][5], fuel cells [6][7][8], energy storage [9][10][11], and metal purifications [12][13][14]. However, molten salts corrode container materials and various components of electrolysis equipment.…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Corrosion Behavior of Al-Coated Ni-Base Alloys in Lithium Molten Salt for Electroreduction

et al. 2021

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The electrolytic reduction of a spent oxide fuel involves the liberation of oxygen in a molten salt LiCl–Li2O electrolyte, which creates a corrosive environment for typical structural materials. In this study, the corrosion behaviors of Al–Y-coated specimens in a Li molten salt kept under an oxidizing atmosphere at 650 °C for 72 and 168 h were investigated. The weight loss fraction of the coated specimen to bare specimen was approximately 60% for 3% Li2O and 54% for 8% Li2O at 72 h, and approximately 38% for 3% Li2O and 30% for 8% Li2O at 168 h. Corrosion was induced in the LiCl–Li2O molten salt by the basic oxide ion O2− via the basic flux mechanism, and the corrosion product was found to be dependent on the activity of the O2− ion. The increase in weight loss may have been caused by the increase in the O2− concentration due to the increase in the Li2O concentration rather than being because of the increased reaction time. The Al–Y coating was found to be beneficial for hot corrosion resistance, which can be useful for handling high-temperature lithium molten salt under an oxidizing atmosphere.

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“…The reduction and oxidation peak potentials shifted to negative and positive directions slightly, respectively, indicating that the charge transfer kinetics of the electrode reaction may be slow. [ 49 ] The molten salt between the reference electrode and the working electrode exhibited resistance during the electrochemical test. Thus, the molten salt resistance needs to be deducted to obtain the more accurate peak potential.…”

Section: Resultsmentioning

confidence: 99%

Electroreduction of Dy(III) assisted by Zn and its co‐deposition with Zn(II) in LiCl–KCl molten salt

Han

et al. 2020

Applied Organom Chemis

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To recover dysprosium (Dy) from LiCl–KCl molten salt, the electrochemical mechanism of Dy(III) on liquid Zn electrode and co‐deposition of Dy(III) and Zn(II) on W electrode were studied using electrochemical methods. Cyclic voltammetry results demonstrated that the redox process of Dy on liquid Zn electrode is reversible and controlled by diffusion. Reverse chronopotentiograms showed that the transition time ratio of reduction and oxidation is ~3:1, revealing the redox of Dy on liquid Zn electrode is a kind of soluble–soluble system: Dy(III) + 3e− = (Dy–Zn)solution. The half‐wave potential of Dy(III) was almost constant with the increase in scanning rate. The electrochemical separation of metallic Dy from the molten salt was performed using constant potential electrolysis, and the product characterized using X‐ray diffraction and scanning electron microscopy–energy‐dispersive X‐ray spectroscopy was the thermodynamic unstable compound DyZn5. Also, the co‐deposition mechanism of Dy(III) and Zn(II) was explored, indicating that Dy(III) could deposit on pre‐deposited Zn and form Dy–Zn compounds: Zn(II) + 2e− = Zn and xDy(III) + yZn + 3xe− = DyxZny. Moreover, the effect of Dy(III) concentration on the formation of Dy–Zn compounds was investigated. The redox peak currents corresponding to different Dy–Zn compounds changed with the increase in Dy(III) concentration. The co‐deposition of Dy(III) and Zn(II) was performed using constant current electrolysis at diverse Dy(III) concentrations. The different Dy–Zn compounds were produced by controlling Dy(III) concentration.

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Electrochemical studies of molten sulfates in LiCl-KCl-Na2SO4 at 700 °C

Cited by 18 publications

References 18 publications

Structure of Molten Alkali Chlorides at Charged Interfaces and the Prediction and Interpretation of Their X-ray Reflectivity

Structure of Molten Alkali Chlorides at Charged Interfaces and the Prediction and Interpretation of Their X-ray Reflectivity

High-Temperature Corrosion Behavior of Al-Coated Ni-Base Alloys in Lithium Molten Salt for Electroreduction

Electroreduction of Dy(III) assisted by Zn and its co‐deposition with Zn(II) in LiCl–KCl molten salt

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Electrochemical studies of molten sulfates in LiCl-KCl-Na2SO4 at 700 °C

Cited by 18 publications

References 18 publications

Structure of Molten Alkali Chlorides at Charged Interfaces and the Prediction and Interpretation of Their X-ray Reflectivity

Structure of Molten Alkali Chlorides at Charged Interfaces and the Prediction and Interpretation of Their X-ray Reflectivity

High-Temperature Corrosion Behavior of Al-Coated Ni-Base Alloys in Lithium Molten Salt for Electroreduction

Electroreduction of Dy(III) assisted by Zn and its co‐deposition with Zn(II) in LiCl–KCl molten salt

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Electrochemical studies of molten sulfates in LiCl-KCl-Na2SO4 at 700 °C