Studies on Cerium Electrochemistry in High Temperature Ionic Liquids

2018 ◽  
Vol 69 (1) ◽  
pp. 112-115
Author(s):  
Ana Maria Popescu ◽  
Virgil Constantin
Keyword(s):  
Molten Salts ◽  
Electrochemical Techniques ◽  
Active Species ◽  
Single Step ◽  
Cathodic Process ◽  
Molybdenum Electrode ◽  
Solute Interaction ◽  
Ohmic Drop ◽  
State Potential ◽  
Direct Discharge

The cathodic behavior of Ce3+ ions in LiF-NaF-BaF2, LiF-NaF-NaCl and NaCl-KCl molten salts at 730� C has been studied using different electrochemical techniques. The decomposition potential (Ed) and the cathodic overvoltage were determined by introducing NaCeF4 as electrochemical active species using steady-state potential-current curves recorded under galvanostatic conditions. The values of |Ed| were 1.85 V in LiF-NaF-BaF2, 2.114 V in LiF-NaF-NaCl and 2.538 V in NaCl-KCl, respectively. It was also found that the ohmic drop potential in melt is not dependent on NaCeF4 concentration and it rises as the current intensity increases. The Tafel slopes and other kinetic parameters were calculated on the assumption that the cathodic process consisted of direct discharge of Ce3+, with no solvent-solute interaction. In order to elucidate the mechanisn of cathodic process the cyclic voltammetry technique was finally used. From the evolution of the voltammograms we conclude that the electrochemical reduction of Ce3+ ion is actually a reversible process on the molybdenum electrode and cathodic reduction of Ce3+ takes place in one single step involving three electron exchange. Our study adds to the accumulating data and confirms available results of electrodeposition of metalic cerium from molten salts using NaCeF4 as solute.

scholarly journals Corrosion Performance of AISI-309 Exposed to Molten Salts V2O5-Na2SO4at 700°C Applying EIS andRpElectrochemical Techniques

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
E. F. Diaz ◽  
C. Cuevas-Arteaga ◽  
N. Flores-García ◽  
S. Mejía Sintillo ◽  
O. Sotelo-Mazón
Keyword(s):  
Molten Salts ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Metallic Surface ◽  
Corrosion Performance ◽  
Potentiodynamic Polarization Curve ◽  
Linear Polarization Resistance ◽  
Second Stage ◽  
Tafel Slopes ◽  
Bode Plots

The corrosion performance of AISI-309 exposed 5 days to molten salts 50 mol% V2O5-50 mol% Na2SO4at 700°C is reported in this paper. Such evaluation was made using three electrochemical techniques: potentiodynamic polarization curve (PC), electrochemical impedance spectroscopy (EIS), and linear polarization resistance (Rp). FromPC, the Tafel slopes,Icorr, andEcorrwere obtained. From Nyquist and Bode plots, it was possible to determine two different stages; the first one showed just one loop, which indicated the initial formation of Cr2O3layer over the metallic surface; after that, the dissolution of Cr2O3formed a porous layer, which became part of the corrosion products; at the same time a NiO layer combined with sulfur was forming, which was suggested as the second stage, represented by two capacitive loops. EIS plots were in agreement with the physical characterization made from SEM and EDS analyses. Fitting of EIS experimental data allowed us to propose two electrical circuits, being in concordance with the corrosion stages. Parameters obtained from the simulation of EIS data are also reported. From the results, it was stated that AISI-309 suffered intergranular corrosion due to the presence of sulfur, which diffused to the metallic surface through a porous Cr2O3layer.

Nitrogen-Doped Carbon Spheres-Decorated Graphite Felt as a High-Performance Electrode for Fe Based Redox Flow Batteries

2021 ◽  
Author(s):  
Anarghya Dinesh ◽  
Anantha Mylarapattana Shankaranarayana ◽  
Santosh Mysore Srid ◽  
Narendra Kumar Muniswamy ◽  
Krishna Venkatesh ◽  
...  
Keyword(s):  
High Performance ◽  
Coulombic Efficiency ◽  
Electrochemical Techniques ◽  
Single Step ◽  
Carbon Spheres ◽  
Active Nitrogen ◽  
Graphite Felt ◽  
Redox Flow Batteries ◽  
Flow Batteries ◽  
Carbon Catalysts

Abstract In this paper, the performance of Fe based redox flow batteries (IRFBs) was dramatically improved by coating N-doped carbon spheres (NDCS) on the graphite felt electrodes. NDCS was synthesized by the single-step hydrothermal method using dextrose and ammonia as a precursor and coated over a graphite felt electrode by electrostatic spraying. The weight of NDCS required for the modification of the electrode to achieve the effective performance of the battery was studied using electrochemical techniques. Cyclic voltammetry (CV) and potentiodynamic polarization study was used to evaluate the kinetic reversibility and linear polarization resistance offered by the electrode towards electrolyte. The characterizing features of the NDCS, untreated graphite felt (UGF) electrode, and optimized modified graphite felt (MGF) electrode were analyzed using SEM, EDAX, XRD, and Raman spectroscopy. The charge-discharge studies were performed for the 132 cm2 IRFB using a 2 mg/cm2 MGF electrode as a positive electrode by varying the current densities from 20 to 60 mA/cm2. The cell resulted in an average coulombic efficiency (CE) of 93%, voltaic efficiency (VE) of 72%, and energy efficiency (EE) of 68% for 15 cycles at the current density of 30 mA/cm2. The improvement in the performance of the IRFB is due to the presence of electrochemically active nitrogen-bearing carbon catalysts. In this paper, the pioneering effort has been made to improve the efficiency of the IRFB with an active area of 132 cm2 using glycine as the ligand.

scholarly journals Effect of Minor Alloying Elements on the Corrosion Behavior of Fe40Al in NaCl-KCl Molten Salts

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
G. Salinas ◽  
J. G. Gonzalez-Rodriguez ◽  
J. Porcayo-Calderon ◽  
V. M. Salinas-Bravo ◽  
M. A. Espinoza-Medina
Keyword(s):  
Weight Loss ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Corrosion Rate ◽  
Corrosion Behavior ◽  
Molten Salts ◽  
Electrochemical Techniques ◽  
The Other ◽  
Type Stainless Steel ◽  
Waste Gasification

The hot corrosion behavior of Fe40Al intermetallic alloyed with Ag, Cu, Li, and Ni (1–5 at.%) in NaCl-KCl (1 : 1 M) at 670°C, typical of waste gasification environments, has been evaluated by using polarization curves and weight loss techniques and compared with a 304-type stainless steel. Both gravimetric and electrochemical techniques showed that all different Fe40Al-base alloys have a much higher corrosion resistance than that for stainless steel. Among the different Fe40Al-based alloys, the corrosion rate was very similar among each other, but it was evident that the addition of Li decreased their corrosion rate whereas all the other elements increased it. Results have been explained in terms of the formation and stability of an external, protective Al2O3layer.

A Study on Voltametric Electro-kinetic Mechanism of Catechol at l-glutamic Acid-Carbon Paste Sensor

2017 ◽  
Vol 33 (1-2) ◽  
pp. 1
Author(s):  
Tadesse Abrha ◽  
Rishi Pal ◽  
R. C. Saini
Keyword(s):  
Electron Transfer ◽  
Glutamic Acid ◽  
Rate Constant ◽  
Living Organism ◽  
Active Species ◽  
Electrochemical Process ◽  
Single Step ◽  
Body Parts ◽  
Carbon Paste ◽  
Electronic Chemical

Quinones and quinoles, the pervasive components of living organism, perform different biochemical and physiological activities. These compounds have found their widespread applications as life saving drugs in cancer chemotherapy, antioxidant, anti bacterial and antifungal agents. These contribute as components of biological electron transfer chains located indifferent body parts. Electrochemical redox behavior of catechol using cyclic and differential pulse voltammetry at the surface of ℓ-glutamic acid modified carbon paste sensor was observed quite sensitive. There was a remarkable increase in the magnitude of both peak currents of catechol at the surface of modified electrode as compared to that of bare carbon paste electrode. Optimizations of working parameters for both techniques have been performed to perk up the working efficiency during experimentation. The electrochemical process occurs under both the diffusion and adsorption controlled conditions. The kinetic parameters such as heterogeneous electron transfer rate constant for electrode process (K<sub>h</sub>), diffusion coefficient (D), standard rate constant of surface reaction (k°), electron transfer coefficient (α) and the average surface concentrations of electro-active species (χ<sub>1</sub>&amp;χ<sub>2</sub>) at the electro-chemical barriers catechol/o-quinone radical and o-quinone radical/o-quinone were calculated. The calculated value of K<sub>h</sub> lie in close vicinity to limiting value of a complete irreversible process and in far range of quasi-reversible process. In the higher range of applied scan rates at lower potentials of the used potential window, the forward scan revealed the formation of well stable reaction intermediate, at relatively slower rate. This is the rate determining step of the oxidation process but in case of reduction pulse of the same scan rate, there is no indication of any reduction intermediate moieties. The chemical process during electrochemical oxidation of catechol follows pseudo first order kinetics. Furthermore, a two step oxidation, Electronic-Chemical-Electronic-Chemical reactions (ECEC) mechanism has been proposed and single step reduction has been observed for the coupled redox process at the sensor/analyte interface.

scholarly journals Formation of Gd-Al Alloy Films by a Molten Salt Electrochemical Process

2008 ◽  
Vol 63 (1-2) ◽  
pp. 98-106
Author(s):  
Concha Caravaca ◽  
Guadalupe De Córdoba
Keyword(s):  
Cyclic Voltammetry ◽  
Intermetallic Compounds ◽  
Surface Characterization ◽  
Electrochemical Techniques ◽  
Open Circuit ◽  
Electrochemical Process ◽  
Single Step ◽  
Al Alloy ◽  
Cathodic Potential

The electrochemistry of molten LiCl-KCl-GdCl3 at a reactive Al electrode has been studied at 723 to 823 K. Electrochemical techniques such as cyclic voltammetry and chronopotentiometry have been used in order to identify the intermetallic compounds formed. Cyclic voltammetry showed that, while at an inert W electrode GdCl3 is reduced to Gd metal in a single step at a potential close to the reduction of the solvent, at an Al electrode a shift towards more positive values occurs. This shift of the cathodic potential indicated a reduction of the activity of Gd in Al with respect to that ofW, due to the formation of alloys. The surface characterization of samples formed by both galvanostatic and potentiostatic electrolysis has shown the presence of two intermetallic compounds: GdAl3 and GdAl2. Using open-circuit chronopotentiometry it has been possible to measure the potentials at which these compounds are transformed into each other. The values of these potential plateaus, once transformed into e. f. m. values, allowed to determine the thermodynamic properties of the GdAl3 intermetallic compound.

Evaluation of corrosion resistance of two engineering alloys in molten salts by electrochemical techniques

2003 ◽  
Vol 54 (1) ◽  
pp. 32-36 ◽  
Author(s):  
A. Martínez-Villafañe ◽  
F. Almeraya-Calderón ◽  
C. Gaona-Tiburcio ◽  
J. Chacón-Nava ◽  
G. González-Rodríguez
Keyword(s):  
Corrosion Resistance ◽  
Molten Salts ◽  
Electrochemical Techniques ◽  
Engineering Alloys

Reprocessing of spent hydrogen absorbing alloys by using electrochemical techniques in molten salts

2005 ◽  
Vol 66 (2-4) ◽  
pp. 439-442 ◽  
Author(s):  
H. Matsuura ◽  
H. Numata ◽  
R. Fujita ◽  
H. Akatsuka
Keyword(s):  
Molten Salts ◽  
Electrochemical Techniques

scholarly journals Electrochemical behavior of lanthanum and yttrium ions in two molten chlorides with different oxoacidic properties: The eutectic LiCl-KCl and the equimolar mixture CaCl2-NaCl

2003 ◽  
Vol 39 (1-2) ◽  
pp. 109-135 ◽  
Author(s):  
Y. Castrillejo ◽  
M.R. Bermejo ◽  
A.M. Martínez ◽  
Arocas Díaz
Keyword(s):  
Electrochemical Behavior ◽  
Electrochemical Techniques ◽  
Three Dimensional ◽  
Earth Metal ◽  
Active Species ◽  
Chloride Ions ◽  
Equimolar Mixture ◽  
Transport Parameters ◽  
Tungsten Electrode ◽  
Simple Diffusion

The electrochemical behavior of LaCl3 and YCl3 was studied in two molten chloride mixtures with different oxoacidic properties, the eutectic LiCl-KCl and the equimolar CaCl2-NaCl melt at different temperatures. The stable oxidation states of both elements have been found to be (III) and (0) in both melts, and it was found that both La(III) and Y(III) cations were less solvated by the chloride ions in the calcium-based melt, which was explained by the stability of CaCl4 2- ions in that melt. Transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry and chronoamperometry were used in order to study the reaction mechanism and the transport parameters of electro active species at a tungsten electrode. The results showed that in the eutectic LiCl-KCl, the electro crystallization of lanthanum and yttrium seems to be the controlling electrochemical step while in CaCl2-NaCl this phenomenon has not been observed. That was explained in terms of the differences in the physicochemical properties of the systems, especially interfacial tensions. In the eutectic LiCl-KCl chronoamperometric studies indicated instantaneous and three dimensional nucleation and crystal growth of lanthanum and yttrium whatever the applied over potential of the rare earth metal is, whereas in the equimolar mixture CaCl2-NaCl, the corresponding electrochemical exchanges were found to be quasi-reversible, and the values of the kinetic parameters, K0 and ?,were obtained for both reactions. Mass transport towards the electrode is a simple diffusion process, and the diffusion coefficients have been calculated. The validity of the Arrhenius law was also verified by plotting the variation of the logarithm of the diffusion coefficient versus 1/T.

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