Methods for Determining the Working Electrode Interfacial Area for Electroanalytical Measurements of Metal Ions in Molten LiCl-KCl

Rappleye, Devin; Horváth, Dávid; Wang, Zhonghang; Zhang, Chao; Simpson, Michael F.

doi:10.1149/07515.0079ecst

Cited by 8 publications

(12 citation statements)

References 6 publications

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“…This method has been demonstrated to be accurate within 0.5 mm for molten salts. 41 In our experiments the working electrode was typically immersed 2-3 cm, resulting in a calculated surface area error of less than 2%. Visual observation of the experiments confirmed no salt wicking up the electrodes.…”

Section: Methodsmentioning

confidence: 97%

Continuous Purification of Molten Chloride Salt: Electrochemical Behavior of MgOHCl Reduction

Witteman

Rippy

2023

J. Electrochem. Soc.

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We present a study on the electrochemical behavior of magnesium hydroxide (MgOH+) reduction on a tungsten (W) cathode in molten chloride salt (MgCl2-KCl-NaCl) across the temperature range of 475-525℃. MgOH+, which forms within the salt upon exposure to moisture, is a leading cause of corrosion. Corrosion is a major barrier to deployment of chloride salts across a number of applications, including concentrating solar power plants and nuclear power plants. While pre-purification protocols have been developed to ensure MgOH+ is removed from molten chloride salts prior to deployment, MgOH+ forms in-situ during operation of chloride-salt based plants. Thus, methods for continuous purification during plant operation are needed. Continuous electrochemical purification via electrolysis using a Mg anode and W cathode has been proposed, but little has been done to assess scalability. Here, we assess fundamental properties of electrochemical removal of MgOH+ to enable future scale up of this method.

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Section: Methodsmentioning

confidence: 97%

Continuous Purification of Molten Chloride Salt: Electrochemical Behavior of MgOHCl Reduction

Witteman

Rippy

2023

J. Electrochem. Soc.

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“…Three general approaches have been taken in the literature for measuring the surface area: physical measurement, differential height and fixed area. [92][93][94][95] The physical measurement method uses observed salt lengths adhering to the WE and known dimensions of the WE (i.e., diameter) to determine the WE surface area. It is important to account for the effects of surface tension when using this method.…”

Section: Other Methods and Considerationsmentioning

confidence: 99%

“…It is important to account for the effects of surface tension when using this method. 92 This is best done by immersing the WE into the salt and allowing enough time for the WE to be wetted by the salt and equilibrate thermally. Simply dipping, then immediately removing the electrode can introduce significant errors (∼20%).…”

Section: Other Methods and Considerationsmentioning

confidence: 99%

“…Simply dipping, then immediately removing the electrode can introduce significant errors (∼20%). 92 The differential height method measures the current at various WE immersion depths or with an array of WEs of different lengths. The change in current with the change in surface area (i.e., depth of WE) is then used with electrochemical relations.…”

Section: Other Methods and Considerationsmentioning

confidence: 99%

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Review—Concentration Measurements In Molten Chloride Salts Using Electrochemical Methods

Williams

Shum

Rappleye

2021

J. Electrochem. Soc.

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The electrochemical measurement of concentration in molten chloride salts is a valuable tool for the control of existing and potential industrial processes, recycling of precious materials and energy production. The electrochemical techniques commonly used to measure concentration and each techniques’ associated theory are discussed. Practices which improve measurement accuracy and precision are set forth. Exceptionally accurate and precise measurements published in the literature are evaluated based on their performance in specified concentration ranges. The strengths and weaknesses of the most accurate measurements are briefly explored. Chronopotentiometry (CP) and square wave voltammetry (SWV) are accurate and precise with low concentration measurements. SWV was accurate at low concentrations, even in multi-analyte mixtures. CP was accurate for only single analyte mixtures. Open-circuit potentiometry (OCP) is accurate and precise in single-analyte mixtures but yields large errors in multianalyte mixtures. Cyclic voltammetry (CV), chronoamperometry (CA) and normal pulse voltammetry (NPV) are accurate and precise across all concentration ranges. NPV is exceptionally well suited for measurements in melts with multiple electroactive species.

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“…Solution resistance between the working electrode (WE) and reference electrode (RE) was measured via an electrical impedance spectroscopy (EIS) method using a Gamry Reference 600+ potentiostat, and all CV was performed with an Autolab PGSTAT302N potentiostat. A vertical translator featuring a Velmex X-slide was used to precisely control the depth of the working electrode for an accurate estimate of surface area, as described elsewhere [15]. The WE surface area for the measurements varied from 0.5 to 1 cm 2 .…”

Section: Equipmentmentioning

confidence: 99%

Effect and measurement of residual water in CaCl2 intended for use as electrolyte in molten salt electrochemical processing

Faulkner

Monreal

Jackson

et al. 2020

J Radioanal Nucl Chem

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CaCl 2 has applications for electrochemical processing of nuclear materials. Thermal dehydration leads to formation of oxide ions, which are shown to react and cause precipitation of dissolved CeCl 3 that was selected as a surrogate for actinide chlorides. Thus, measurement of residual water in CaCl 2 is an essential capability. Thermogravimetric analysis (TGA) was shown to underestimate starting water concentration. Subsequent analysis of solid samples via acid-base titration and cyclic voltammetry (CV) of the molten salt yielded consistent values within 5% for residual water. Hydroxides were shown to be unstable, thus oxygen is retained as oxide ions. Thus, total water in a sample of CaCl 2 can be quantified by combining TGA with with either CV of molten salt or titration of salt samples. The importance of quantifying residual water in the salt was demonstrated by showing that cerium chloride (surrogate for actinide chlorides) will react with oxide ions in CaCl 2 to form insoluble oxides and oxychlorides.

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Methods for Determining the Working Electrode Interfacial Area for Electroanalytical Measurements of Metal Ions in Molten LiCl-KCl

Cited by 8 publications

References 6 publications

Continuous Purification of Molten Chloride Salt: Electrochemical Behavior of MgOHCl Reduction

Continuous Purification of Molten Chloride Salt: Electrochemical Behavior of MgOHCl Reduction

Review—Concentration Measurements In Molten Chloride Salts Using Electrochemical Methods

Effect and measurement of residual water in CaCl2 intended for use as electrolyte in molten salt electrochemical processing

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