Cadmium Electrode Research Articles

Еlectrochemical behavior of cadmium by alternating current polarization in hydrocloric acid solution

This paper presents the results of a study of the electrochemical behavior of a cadmium electrode in aqueous solutions of hydrochloric acid under polarization by stationary and non-stationary currents and shows the possibility of synthesis of its chloride. The purpose is to develop the electrochemical behavior of cadmium under alternating current polarization in a solution of perchloric acid. Methods. During the study, it was found that when two cadmium electrodes are polarized with an alternating current of 50 Hz, their dissolution does not occur, however, when one electrode is replaced with a titanium one, cadmium is intensively dissolved. Results and discussion. The influence of the main parameters, such as the duration of electrolysis, current density, concentration and nature of the electrolyte on the electrochemical process has been studied. A schematic diagram of an installation for dissolving cadmium by polarization with a non-stationary current is proposed. It is shown that on the titanium electrode in the range of 20-80 kA/m2, the current yield of the dissolution of the cadmium electrode gradually increases, and with a current density equal to 80 kA/m2, the current yield reaches 135%. Conclusion. It is shown that with alternating current polarization, the rate of chemical dissolution of cadmium, increases with the release of hydrogen. During the experiment, with the polarization of the cadmium electrode by alternating current, the possibility of obtaining cadmium chloride was shown. Based on chemical and X-ray phase analyses, it was proved that cadmium forms compounds CdCl2∙H2O.

ELECTROCHEMICAL SYNTHESIS OF INTERMETALLIC U–Ga AND U–Cd COMPOUNDS IN MOLTEN LiCl–KCl–CsCl EUTECTIC

The processes of cathodic reduction of U(III) ions to metal in a low–melting LiCl–KCl–CsCl eutectic at the temperature range 650–850 K on tungsten, gallium and cadmium electrodes in an inert gas atmosphere have been studied by non-stationary and stationary electrochemical methods. Reagents without contain impurities of moisture, oxygen and their compounds were used in the experiments. All major operations were performed in a dry glove box. The following methods were used to analyze the electrochemical processes: cyclic voltammetry, square-wave voltammetry and potentiometry at zero current. On cyclic voltammogram of the molten LiCl–KCl–CsCl–UCl3 solution on an inert tungsten electrode, one cathode current peak corresponding to the deposition of metallic uranium and one anode current peak associated with its dissolution were recorded. It was found that the potential of the cathode peak was shifted to a region of more negative values with an increase of the scan rate. The value of the cathode peak current was directly proportional vs. the square root of the polarization rate, but this dependence does not pass through the origin. Consequently, the system of U(III)/U(0) couple was irreversible and proceeds in one stage. It was found that on square-wave voltammograms in the studied “electrochemical window” the deposition of uranium on liquid reactive gallium and cadmium electrodes was carried out at more positive values than on inert tungsten electrode. It was established that this potential shift was associated with the formation of intermetallic compounds of uranium with the material of reactive electrodes. The values of the alloy formation potentials were determined. For identification of the composition of cathode deposits, potentiostatic electrolysis was performed. By X–ray diffraction analysis, it was found that the formation of the intermetallic compounds Ga3U and Ga2U occurs on the gallium reactive electrode, and Cd11U occurs on the cadmium one. The conditions of their formation during the electrolysis of molten LiCl–KCl–CsCl–UCl3 solutions were established. The reaction of the electrochemical extraction of uranium from molten LiCl–KCl–CsCl–UCl3 electrolyte was investigated on liquid reactive electrodes at different duration of electrolysis. It was found that the electrochemical extraction of uranium exceeds 97% on both Ga and Cd electrodes.

Electrochemical CO2/CO Reduction and C–C Coupling Path for Mimicking Fischer–Tropsch Synthesis over Cadmium Electrodes

Converting CO2 into Cn>2 hydrocarbons has been a significant challenge, but recent research has shown that cadmium (Cd) can be used to produce C2–7 hydrocarbons (CnH2n and CnH2n+2) directly through electrochemical CO2 reduction in a K2HPO4/KH2PO4 buffer. The production of hydrocarbons was found to be enhanced by engineering the interface of the Cd surface with other transition metals. This process imitates the Fischer–Tropsch (F–T) synthesis, which involves surface polymerization reactions that couple carbon atoms together, resulting in the formation of long-chain hydrocarbons via the insertion of CO and CHx molecules. While the formate path was almost completely suppressed, the CO path remained. While the current Faradaic efficiency may be low, this study highlights the potential of electrochemical CO reduction for Cd. The study demonstrates that CO and H can directly participate in F–T synthesis through electrochemistry. Furthermore, Cd was observed to recrystallize into stacked wall structures resembling flowers after the electrochemical process. As a result, this research provides crucial insights that can aid in a better understanding of C–C coupling paths via electrochemistry.

Mechanism of Metallic Uranium and Bimetallic U-Ga, U-Cd Alloys Electrodeposition in Molten LiCl–KCl–CsCl Eutectic

Speciation and behavior of uranium (III) chloride in the ternary low melting LiCl–KCl–CsCl eutectic was studied by electrochemistry and spectroscopy techniques. Cathodic reduction of U(III) ions on inert (tungsten) and reactive (gallium, cadmium) electrodes was investigated at 623–923 K using cyclic and square wave voltammetry. The potential scan rate was changed from 0.075 to 0.5 V s−1 in all experiments. It was established that the electrochemical reduction process on the inert electrode was irreversible, proceeded in one stage, and was controlled by the charge transfer. Formation of uranium alloys with gallium and cadmium was studied using active liquid Ga and Cd electrodes. Reduction of uranium ions of the reactive electrodes proceeded with considerable depolarization. The effect of current density on the composition of the cathodic product was considered. Conditions for the electrochemical production of alloys of a given composition were determined.

Исследование кинетики цементации кадмия в присутствии ПАВ

The aim of the paper is to study the kinetics of cadmium cementation with zinc powder in aqueous media in a continuous mode using an ion-selective cadmium electrode. Reduction of cadmium from aqueous solutions was carried out with zinc powder, with particle sizes from 63 to 200 μm. In a number of experiments, the influence of the cationic flocculant Besfloc K6645 on the cadmium cementation process was tested. The process was carried out in the temperature range from 30 to 50 °C with continuous stirring at 200 rpm with an overhead stirrer. Kinetic curves were recorded using a cadmium-selective electrode. The kinetic curves were conditionally divided into linear segments. Tangents were drawn to each section, which made it possible to determine the apparent rate constants using the first-order equation, as well as the mode coefficients using the Erofeev–Kolmogorov equation. An increase in temperature had a positive effect on cementation. The introduction of a flocculant into the electrolyte in the amount of 70 mg/L reduced the degree of cementation from two to three times over a period of 600 s. The data obtained made it possible to calculate the activation energies of the process rates on the linear sections of the kinetic curves, which amounted to approximately 46, 32 and 11–13 kJ/mol in the first, second, and third sections, respectively, for reduction without the addition of a flocculant, as well as 117–130 and 82–85 kJ/mol in the presence of Besfloc K6645 flocculant. It has been shown that in the presence of a flocculant, the activation energy increases, especially in the first section, which is characterized by a slow cementation rate. The study demonstrates the effect of the Besfloc K6645 additive on the duration of the initial section of the cementation kinetic curves.

Estimation of Discharge Capacities Using Generalized Peukert’s Equation for Saft Industrial Standby Batteries

Saft Industrial Standby (ISD) battery utilizes robust nickel-cadmium alkaline electrochemistry that delivers reliable performance and long life of at least 15 years over a wide range of temperature (-20 °C to 50 °C). The battery is designed with nickel based positive electrode and plastic bonded cadmium electrode in a vented prismatic cell. Typically, telecom applications used to require long duration backup power sources. With the advent of 4G/5G, the duration for backup power has been reduced to 1 hour or less. Therefore, new ISD battery was designed for power applications like 174 W/cell discharge for 1 hour and at the same time it can deliver high energy density up to 100 Wh/l. Additionally, low water consumption due to the high charge efficiency makes this battery ideal for the maintenance free remote installations. All these features render the battery aptly suitable for providing back-up power in telecom networks (4G and 5G) including remote cabinets at the lowest total cost of ownership.The ISD battery (Tel.X-Plus) is compliant to the Telecordia GR (Generic Requirement)-3020 CORE standard, which is recommended for the secondary alkaline batteries used in the telecom back-up application. This standard requires declaration of minimum 28 discharge currents entailing different durations and end voltages for a specific battery capacity. Hence, correct estimation of deliverable capacities for any definite duration and end voltage can reduce significant number of test trials. In addition, it helps sizing the battery for different power and energy installations. There are a few analytical techniques, such as Peukert’s and Shepherd’s equations that can be used to model the discharge characteristics of batteries. There are three different forms of generalized Peukert’s equations: algebraic, hyperbolic tangent and complementary error functions. In this study, to evaluate the discharge capacities we investigated the complementary error function of the generalized Peukert’s equations described in the equation 1: C= (Cm/erfc(-1/n)) * efrc(((i/ik)-1)/n) ... (1)where, C is the capacity of the battery during discharge, Cm is the highest discharge capacity, i is the discharge current, ik and n are statistical parameters. We know that phase transition is key to the discharge of a battery. Therefore, we selected the equation which also defines the phase transition process. The discharge capacities were calculated between 24-hour and 0.20-hour discharge durations for 1 V/cell, 1.05 V/cell, 1.10 V/cell and 1.14 V/cell end points using the equation 1. Here, the discharge capacity that was experimentally determined at the nominal C/24 rate was used as the maximum discharge capacity, Cm. The value of the statistical parameter n is within 0 and 1 to satisfy the capacity limits when discharge current tends to infinite and zero. For example, n equals to 0.6 is used for the calculations pertaining to the 180 Ah rated battery. The other statistical parameter ik was empirically selected for each end point voltage e.g., 250 A for 1.1 V/cell. Figure 1 shows the results for the calculated discharge capacities along with the experimental values at the 1.1 V/cell cut-off. The calculated numbers closely match with the experimentally obtained values with the r2 of 0.998 (Figure 1)Results for the other cut-off voltages (1.0 V/cell, 1.05 V/cell and 1.14 V/cell) were also obtained using the equation 1 and closely match the experimental values. Thus, the phase transition form of generalized Peukert’s equation (complementary error function) can be used for evaluating the capacities between 24-hour and 0.20-hour of discharge durations. Consequently, it enhances the test efficiency remarkably and sets the stage for battery sizing. Future studies include but not limited to the significance of n and ik, algebraic form of Peukert’s equation and Shepherd’s equation to understand the effectivity of each model with a focus on the discharge durations below 0.20-hour. Figure 1

Research of Nanomaterials as Electrodes for Electrochemical Energy Storage.

This paper has experimentally proved that hydrogen accumulates in large quantities in metal-ceramic and pocket electrodes of alkaline batteries during their operation. Hydrogen accumulates in the electrodes in an atomic form. After the release of hydrogen from the electrodes, a powerful exothermic reaction of atomic hydrogen recombination with a large energy release occurs. This exothermic reaction is the cause of thermal runaway in alkaline batteries. For the KSL-15 battery, the gravimetric capacity of sintered nickel matrix of the oxide-nickel electrode, as hydrogen storage, is 20.2 wt%, and cadmium electrode is 11.5 wt%. The stored energy density in the metal-ceramic matrix of the oxide-nickel electrode of the battery KSL-15 is 44 kJ/g, and in the cadmium electrode it is 25 kJ/g. The similar values for the KPL-14 battery are as follows. The gravimetric capacity of the active substance of the pocket oxide-nickel electrode, as a hydrogen storage, is 22 wt%, and the cadmium electrode is 16.9 wt%. The density of the stored energy in the active substance oxide-nickel electrode is 48 kJ/g, and in the active substance of the cadmium electrode it is 36.8 kJ/g. The obtained results of the accumulation of hydrogen energy in the electrodes by the electrochemical method are three times higher than any previously obtained results using the traditional thermochemical method.

Fouling and corrosion of electrode plates in nickel cadmium batteries

The aim of this study is investigation of fouling propensity in nickel cadmium electrodes after degradation of alkaline-electrolyte from rich-hydroxide to rich-carbonate along with time. Gradually, CO2 absorption from the air into the alkaline electrolyte leads to the destruction of electrodes and the formation of precipitated layers resulting in reduction of electrical capacity and life time of batteries. Based on the microscopic observations (SEM), spectroscopic evidences (FTIR and XRD) and thermal experiments (TG-DTA) significant damages and fouling phenomena were categorized as: salt islands, graphite films, etched graphite, cadmium dendrites, cadmium oxide/sulfide and cathodic corrosion. The experimental results revealed that nickel cathodes have experienced more surface damages with respect to cadmium anodes. Although the anode is the source of cadmium species, however the fouling layers of cadmium oxide and cadmium sulfide were assigned to be the main causes of cathode damage, leading to the decreasing of electrode current and the increasing of internal resistance of the cells. On the other hand, the main damage on the surface of anode electrode was attributed to graphite coatings and cadmium hydroxide stripped from the cathode. The microscopic observations showed that almost 2% of cathode surface was corroded, while the anode surface had experienced no corrosion.

Nickel-cadmium batteries with pocket electrodes as hydrogen energy storage units of high-capacity

In this paper, the hydrogen accumulation was studied in the pocket electrodes of the Ni-Cd batteries during their operation. The gravimetric capacity of the active substance of the oxide-nickel electrode was found to be equal to 22 wt% and its volumetric capacity to 444.2 kg m−3. The results obtained are 4 times higher than previously obtained results in the world for any reversible metal hydrides and nanostructure carbon materials, as well as the requirements of the US Department of Energy for mobile hydrogen storage systems. The total energy density of the hydrogen stored in the active substance of the oxide-nickel electrode was equal to 79.40 kJ g−1 and 160.24 kJ cm−3. Note that the relevant parameters for the gasoline are 46 kJ g−1 and 32.7 kJ cm−3. The relevant specific capacities of the active substance of the cadmium electrode were found to be equal to 16.9 wt%, 404.4 kg m−3, while the total energy density of the hydrogen stored in the active substance of the cadmium electrode was equal to 60.99 kJ g−1 and 145.80 kJ cm−3. In this paper also, the reasons for such a large hydrogen storage capacity were established experimentally. The effect of a number of factors on the hydrogen accumulation was analyzed in the case of active substance with graphite use for the electrodes.

Digital Simulation of Discharge of Nickel–Cadmium Batteries

A computer analysis of the mathematical model for the nickel–cadmium battery discharge with different types of electrodes is presented. The model includes the analysis of processes in the positive nickel-oxide and negative cadmium electrodes; it allows estimating the dependence of the electrode polarization and the battery voltage on the electrolyte concentration, the discharge current density, and the design features of the electrodes. The calculations take into account the mechanisms of processes in the positive and negative electrodes, diffusion, migration and convective transfer of electrolyte components both in the electrodes and in the interelectrode space. The calculated data showed the applicability of the developed model to the studying of the influence of various factors on the discharge characteristics of the nickel–cadmium batteries.

Investigating the effects of copper cadmium electrode on Inconel 718 during EDM drilling

One of the effective unconventional machining processes used in industries is Electrical Discharge Drilling. High quality material removal, good surface finish, high tolerance but with minimal tool wear are the key features expected in a drilling operation. These can be accomplished by adding of powder particles with dielectric fluid by proportionately varying process parameters. This project focus on the Tool Wear Rate (TWR) of Tungsten Powder Mixed for Electrical Discharge Drilling (W-PMEDD) of Inconel 718 superalloy using single channel hollow Copper Cadmium as electrode. Response Surface Methodology (RSM) is used as an experimental analysis tool in order to compare the input variable such as peak current (Ip), pulse on time (Ton), pulse off time (Toff). ANOVA table was used to determine the capability of varying parameter in the drilling operation and finally came to a conclusion that Ip, Ton and, Toff is the most significant parameters.

Synthesis of Ag and Cd nanoparticles by nanosecond-pulsed discharge in liquid nitrogen

The synthesis of CdO, Ag2O (5 nm) and Ag (∼20–30 nm) nano-objects is achieved simultaneously by nanosecond-pulsed discharges in liquid nitrogen between one cadmium electrode and one silver electrode. Oxidation occurs when liquid nitrogen is fully evaporated and nanoparticles are in contact with the air. No alloy is formed, whatever the conditions, even though both elements are present simultaneously, as showed by time-resolved optical emission spectroscopy. This lack of reactivity between elements is attributed to the high pressure within the discharge that keeps each metallic vapor around the electrode it comes from. Each element exhibits a specific behavior. Cubic Cd particles, formed at 4 kV, get elongated with filamentary tips when the applied voltage reaches 7 and 10 kV. Cd wires are formed by assembly in liquid nitrogen of Cd nanoparticles driven by dipole assembly, and not by dielectrophoresis. On the contrary, silver spherical particles get assembled into 2D dendritic structures. The anisotropic growth of these structures is assumed to be due to the existence of pressure gradients.

Thermodynamic properties of praseodymium on the liquid cadmium electrode and evaluation of anodic dissolution behavior in LiCl-KCl eutectic

The electrochemical and thermodynamic properties of Pr on a liquid Cd electrode and the formation of Cd-Pr intermetallic compounds were systematically studied by a series of electrochemical techniques in LiCl-KCl eutectic. The activity coefficient of Pr in the liquid Cd was determined by galvanostatic intermittent titration and in-situ open circuit chronopotentiometry at various temperatures. The measurement of electromotive force was conducted to calculate the partial molar Gibbs free energies of Pr in two phase coexisting states. In addition, the thermodynamic parameters of seven Cd-Pr intermetallic compounds such as the Gibbs free energy, enthalpy and entropy of formation were also determined. The deposited Cd-Pr alloy sample was prepared by galvanostatic electrolysis and further characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS). The dissolution behavior of Cd-Pr alloy as an anode material was also evaluated by monitoring the variation of anodic potential.

Effect of Surfactants on the Reduction of Cadmium(II) Ions on Cadmium Electrode

The effect high molecular weight water-soluble surfactants with different functional groups have on the electroreduction of cadmium(II) ions on a cadmium electrode in various electrolytes is studied. A copolymer of methacryloylaminophenol with acrylic acid, a leather waste hydrolyzate, and a copolymer of monoethanolamine with vinyl ether acetate are used as surfactants. The electrolytes that are used are 1 M KCl, KBr, KNO3, HCOONa, NH2SO3H, 0.5 M Na2SO4, and 0.35 M Na3C6H5O7 · 2H2O. It is shown that in 1.0 M KCl or KBr solutions, there is no inhibition of the electroreduction of cadmium(II) ions by the adsorption layers of surfactants. It is found that the inhibitory effect of polymers on the electroreduction of cadmium(II) ions in different background electrolytes increases in the order KCl > KBr > KNO3 > NH2SO3H > Na2SO4 > Na3C6H5O7 · 2H2O > HCOONa.

Formula omitted] couple in LiCl-KCl eutectic: Anodic polarization of thorium and electrochemical impedance spectroscopy study at tungsten, cadmium and thorium electrodes

Cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate electrochemical behaviour of thorium at inert tungsten, liquid cadmium and thorium electrodes in LiCl-KCl eutectic. Equilibrium potentials of Th4+|Th couple were measured from the cyclic voltammograms at thorium electrode in LiCl-KCl-ThCl4 electrolyte and compared with theoretically estimated equilibrium potential using ΔfGThCl4,LiCl−KCl∘, ΔfGThCl4,liq.∘ and γThCl4 from literature sources as input. It was observed that deviation of estimated values from measured data of −1.437 V at 773 K could be ascribed not only to different experimental conditions employed but also to difference in ΔfGThCl4,liq.∘ values taken from various thermochemical data compilations. Considering all experimental uncertainties and errors in linear fitting of electromotive force data from literature sources, theoretical equilibrium potential of thorium dissolution was estimated at −1.462 ± 0.065 V (vs.Ag+|Ag as ref.) for xThCl4 = 3.86 × 10−3 at 773 K. Complex impedance plots were recorded for inert tungsten, liquid cadmium and thorium electrodes at various applied potentials in the frequency and temperature range of 10 Hz-10 kHz and 698–798 K, respectively. They were further validated using Kramers-Kronig transforms and interpreted using equivalent circuit model consisting of melt resistance (Rs), charge transfer resistance (Rct) and constant phase elements (Q) as circuit components. Mechanism of anodic dissolution of thorium in LiCl-KCl eutectic melt was proposed, which was based on semi-infinite Warburg diffusion at lower frequencies having slope greater than unity and double layer capacitance at higher frequencies due to partial accumulation of Th4+ ions at the electrode-electrolyte interface. Heterogeneous rate constant estimated from Rct was used to address reversibility of Th4+|Th couple using Matsuda-Ayabe criteria for anodic (thorium electrode) and cathodic polarization (inert tungsten) cases, which was found to be quasi-reversible in the scan rate range 10–100 mV/s and temperature range 698–798 K.

Controlling Selectivity in the Electrochemical Reduction of Acrylonitrile: Towards a Solar-Driven Nylon 6,6 Production Process

Fossil fuel derived carbon dioxide (CO2) emissions have continuously increased over the past century and their impact in climate change is self-evident. The chemical industry is a large contributor to this increase, accounting for more than 5.5% of the global CO2 emissions. Implementing electrochemical routes for the production of large volume chemicals can allow for the direct integration of renewable energy sources into chemical manufacturing. In this way, solar- or wind-powered electrochemical processes could greatly contribute to the reduction of the carbon footprint of the chemical industry. Although inorganic electrosynthetic processes have been successfully implemented in industry at scale (i.e. chloro-alkali and Aluminum production), the implementation of electrochemical methods for the production of organic chemicals has been limited. Adiponitrile (ADN) is the largest-volume organic chemical product currently produced electrochemically (>1.5 million tons/year). ADN is a precursor used in Nylon 6,6 manufacturing and it can be obtained via the electrohydrodimerization of acrylonitrile (AN). Although the electrosynthesis of ADN is considered the most successful organic electrochemical process in industry, it still faces many challenges owing to its energy conversion efficiency and selectivity. Optimizing the composition of the electrolyte can result in significant performance improvements. The implementation of tetraalkylammonium (TAA) ions has been shown to increase the reaction selectivity towards adiponitrile, but there is limited understanding on their role in the mass transport and kinetic aspects of the transformation. In this study, we provide experimental insights into the effects of TAA ions in the selectivity and efficiency of the AN electrohydrodimerization reaction. TAA ions can limit the hydrogen evolution reaction by sterically hindering water molecules from approaching the electrode surface and locally increasing the concentration of organic reactants. These effects are believed to be responsible for the increase in selectivity towards the reduction of AN. In our study, we explored electrolytes containing TAA ions with varying lengths of the alkyl substituents (i.e., methyl, ethyl, butyl and hexyl) and assessed the effects of their molecular size, affinity towards AN, and concentration on the electrolyte conductivity and selectivity. Using a combination of cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry at a cadmium electrode, we showed that optimal performance is achieved for electrolytes containing tetrabutylammonium (TBA) ions. A maximum selectivity towards ADN of 80% was demonstrated for TBA concentrations ranging between 0.04 to 0.5 mM. Furthermore, we studied the effects of TAA ions on the ohmic and mass transport limitations under varying current densities. Our results suggest that (i) the local concentration of AN in the electrical double layer strongly depends on the nature of the TAA and the applied current density and (ii) that this concentration is important in determining the predominant reaction pathways and thus the product distribution between ADN and other electrochemical side products (e.g., propionitrile and 1,3,6 tricyanohexane). The results obtained in this study can be used to derive electrolyte design guidelines which will improve the efficiency of the electrochemical adiponitrile production process. Furthermore, understanding the effects of current density in the selectivity of the reaction allows for the design of operating protocols to directly drive electrochemical transformations with intermittent sources of energy such as solar power. These design guidelines can lead to highly efficient solar-ADN reactors and enable the clean manufacture of precursors for the polymer industry. The performance of proof-of-concept prototypes solar-AND devices will be discussed. Figure 1

Highly selective and efficient reduction of CO2 to CO on cadmium electrodes derived from cadmium hydroxide.

A non-noble cadmium electrode was synthesized via an electrolysis strategy, which can electroreduce carbon dioxide into carbon monoxide with high selectivity and efficiency. The partial current density for CO can reach up to 59.0 mA cm-2 at a Faradaic efficiency of 99.2% using 1-butyl-3-methylimidazolium hexafluorophosphate/acetonitrile as the electrolyte.

The Cadmium Electrode Revisited: Kinetic Data

The kinetics of a cadmium electrode in contact with a cadmium-ion containing electrolyte solution have been studied with impedance and potentiodynamic polarization measurements. Results of both methods agree, they are found to be within the range of previously reported data.

Exchange current density of Th4+|Th couple in LiCl-KCl eutectic

Exchange current density (i∘) of thorium in LiCl-KCl eutectic at tungsten(inert) and liquid cadmium electrodes is reported in the present work. A cadmium electrode was designed in our laboratory for estimating i∘ of thorium in liquid cadmium. Cyclic voltammetry of thorium at tungsten electrode was associated with a cathodic peak at −1.59V at 773K attributed to Th4+|Th redox couple. Cathodic peaks corresponding to Th4+|ThCd11 and Th4+|ThCd5 couples at −1.31V and −1.38V, respectively (at 773K) were observed in the cyclic voltammograms of thorium at liquid cadmium electrode. i∘ of thorium in LiCl-KCl eutectic at tungsten electrode (cathodic polarization) estimated by Tafel and Allen-Hickling methods were compared with those estimated from the cyclic voltammograms of LiCl-KCl-ThCl4. i∘ at tungsten electrode was found to be higher than that at liquid cadmium electrode. The temperature dependence of i∘ was studied to estimate the activation energy associated with Th4+|Th couple at tungsten, liquid cadmium (cathodic polarization) and dissolution of thorium (anodic polarization). The compositional dependence of i∘ of thorium at tungsten electrode was also addressed. This is the first report on the i∘ of thorium in LiCl-KCl eutectic.

Exchange Current Density and Diffusion Layer Thickness in Molten LiCl-KCl Eutectic: A Modeling Perspective for Pyroprocessing of Metal Fuels

The DIFAC (DIFfusion of Actinides in EleCtrorefiner) computer code for pyroprocessing, developed earlier by the authors, is modified in the present work to model electrorefining at the liquid cadmium electrode. The modeling of electrorefining of metal fuels requires accurate knowledge of two important kinetic parameters: exchange current density io and diffusion layer thickness δ. These are estimated in the present work by polarization methods and employing Tafel and Allen-Hickling analysis for Gd3+/Gd, U3+/U, and Zr2+/Zr couples in LiCl-KCl eutectic at 773 K for an inert cathode and compared with literature data, wherever possible. The equilibrium potentials for these couples at an inert electrode are found to be –1.94, –1.52, and –1.22 V, respectively, at 773 K. Electrochemical studies are also carried out in LiCl-KCl eutectic to estimate io and δ for the anodic dissolution of Na-bonded U-Zr and Gd-U-Zr alloy and are compared with the anodic dissolution of U-Pu-Zr alloy. The equilibrium potential of Na-bonded U-Zr alloy in LiCl-KCl-UCl3 was found to be –1.46 V, and those for Gd-U-Zr alloy in blank LiCl-KCl and LiCl-KCl-UCl3 were –1.56 and –1.34 V, respectively, at 773 K. The exchange current densities of Na-bonded U-Zr and Gd-U-Zr alloy were found to be in the range of 40.1 to 46.5 mA · cm−2 and 16.8 to 27.3 mA · cm−2 at 773 K, respectively.A preliminary design of the liquid cadmium electrode suitable for laboratory-scale experiments on uranium- and plutonium-based systems is also reported in the present work. The io and δ of gadolinium, uranium, and zirconium are subsequently estimated at the liquid cadmium electrode at 773 K. The equilibrium potentials for Gd3+/Cd6Gd, U3+/[U]Cd, and Zr2+/Cd3Zr couples in LiCl-KCl eutectic at 773 K for the liquid cadmium electrode are found to be –1.35, –1.13, and −1.12 V, respectively. Finally, a few algorithms are proposed for modeling electrorefining data at the liquid cadmium electrode for multicomponent systems.