Linear Sweep Voltammetry Methods Research Articles

Recycling the spent cobalt-based perovskites for the high-active oxygen catalysts in zinc-air batteries

Cobalt (Co) is widely used in energy storage and conversion devices, although its content on our planet is not adequate. Therefore, recycling Co from the spent Co-enriched materials is indispensable. Co-based perovskites, which contain abundant Co, are extensively utilized in solid oxide fuel cells, three-way catalysts, and oxygen-permeable membranes, and the recovery of Co from the spent Co-based perovskites is necessary to meet the long-term requirement of Co. In this work, a facile and universal thermal reduction method (750 °C and N2 atmosphere) is employed to convert the spent cobalt-based perovskites into high-performance bifunctional oxygen catalysts for zinc-air batteries (ZABs), achieving high-efficient Co recovery and re-utilization. At high temperatures, melamine and dopamine hydrochloride are transformed into carbon nanotubes, C3N4 and reducing gases (such as NH3 and H2). Simultaneously, the metal elements in the spent Co-based perovskites (SrNb0.1Co0.7Fe0.2O3,SNCF) are converted into nano-scale alloy particles and metal nitrides. Then, the phase structures, micromorphology, and element valences of the obtained multiphase oxygen catalyst (SNCF–Ni-PM) are characterized by X-ray diffraction, scanning/transmission electron microscopy, and X-ray photoelectron spectroscopy, respectively. The electrochemical properties, including oxygen catalytic activities and stability, of SNCF-Ni-PM are measured by linear sweep voltammetry, chronopotentiometry, chronoamperometry, and cyclic voltammetry methods. Considering the practical applications, the aqueous and solid-state ZABs are assembled and measured. The results demonstrate that the multiphase SNCF-Ni-PM mainly includes carbon nanotubes, C3N4 nanosheets, and FeNiN or CoFe nanoparticles. Moreover, SNCF-Ni-PM exhibits excellent bifunctional oxygen catalytic activity, with an oxygen evolution reaction (OER) potential at 10 mA cm−2 of 1.51 V and an oxygen reduction reaction (ORR) half-wave potential of 0.77 V, outperforming most of the reported oxygen catalysts. Using SNCF-Ni-PM, the aqueous and solid-state ZABs can achieve high power densities of 295.9 and 228.4 mW cm−2, respectively, being superior to most ZABs. In addition, the aqueous ZAB with SNCF-Ni-PM can operate stably for 300 h with a slight degradation. This work provides a feasible method for effectively recycling Co from the spent Co-based perovskites.

Corrosion behavior of high- and low-chromium steel grinding balls in chloride solution

The corrosion behaviour of three types of alloys (two low-alloy carbon steel and one stainless iron with ~15 wt.% Cr), in a solution which simulates seawater (3% NaCl solution, pH 8.1) was tested. Tested samples are used to make steel (iron) balls applied in mils for grinding copper and other ore. The corrosion tests were performed using three electrochemical methods, at room temperature in the presence of atmospheric oxygen. The linear polarization resistance (LPR) method, electrochemical impedance spectroscopy (EIS) method, and linear sweep voltammetry (LSV) method were applied. Based on measurements by LPR and EIS methods (as non-destructive methods), the value of polarization resistance (Rp) was determined and the general corrosion rate (vcorr) of the examined samples was calculated. The obtained values of the general corrosion rate can be used to calculate the service life of steel (iron) balls under exploitation conditions (seawater). The appearance of the surface after linear sweep voltammetry (LSV) measurement showed the presence of localized corrosion (pits were formed) of the tested samples, especially stainless iron, and the LSV method is not suitable for the determination of the general corrosion rate of tested samples in seawater. This form of corrosion occurs at high anodic polarizations, during performing LSV measurements.

Improved Power Production in Reverse Electrodialysis Stacks with Ion‐Permselective Woven Net Spacers

In traditional reverse electrodialysis (RED) stacks, the output power is severely lost due to the shadow effect caused by the nonpermselective spacers. To inhibit the spacer shadow effect, a design on ion‐permselective woven net spacer is proposed. By combining the linear sweep voltammetry and electrochemical impedance spectroscopy methods, the effectiveness of permselective woven net spacer is validated together with the shadow effect and concentration polarization measured quantitatively. Additionally, their influence on stack resistance and power production is investigated under various factors. When contrasted to nonpermselective spacers, the use of permselective woven net spacers reduces the spacer shadow effect by 90% whereas also exacerbating the concentration polarization. This results in a higher power density due to a dramatic reduction in resistance. However, compared with permselective spacers, the permselective woven net spacers increase the power density due to its weaker concentration polarization. The factors including the solution concentration, temperature, and spacer thickness have a considerable influence on the power production of stack. Especially, increasing the concentration of concentrated solution alone is most beneficial to improving the output power while the impact of spacer thickness is the weakest.

Hydrothermally Synthesized MoS2 as Electrochemical Catalyst for the Fabrication of Thiabendazole Electrochemical Sensor and Dye Sensitized Solar Cells

In this work we reported the hydrothermal preparation of molybdenum disulfide (MoS2). The phase purity and crystalline nature of the synthesized MoS2 were examined via the powder X-ray diffraction method. The surface morphological structure of the MoS2 was examined using scanning electron microscopy and transmission electron microscopy. The specific surface area of the MoS2 was calculated using the Brunauer-Emmett-Teller method. The elemental composition and distribution of the Mo and S elements were determined using energy-dispersive X-ray spectroscopy. The oxidation states of the Mo and S elements were studied through employing X-ray photoelectron spectroscopy. In further studies, we modified the active surface area (3 mm) of the glassy carbon (GC) electrode using MoS2 as an electrocatalyst. The MoS2 modified GC electrode (MSGC) was used as an electrochemical sensor for the detection of thiabendazole (TBZ). Linear sweep voltammetry (LSV) was used as the electrochemical sensing technique. The MSGC exhibited good performance in the detection of TBZ. A limit of detection of 0.1 µM with a sensitivity of 7.47 µA/µM.cm2 was obtained for the detection of TBZ using the LSV method. The MSGC also showed good selectivity for the detection of TBZ in the presence of various interfering compounds. The obtained results showed that MoS2 has good electrocatalytic properties. This motivated us to explore the catalytic properties of MoS2 in dye sensitized solar cells (DSSCs). Thus, we have fabricated DSSCs using MoS2 as a platinum-free counter electrode material. The MoS2 counter electrode-based DSSCs showed good power conversion efficiency of more than 5%. We believe that the present work is beneficial for the scientific community, and especially for research surrounding the design and fabrication of catalysts for electrochemical sensing and DSSC applications.

Preparation and characterization of polymer blend electrolyte membranes based on lithium acetate‐complexed carboxymethyl cellulose (CMC) and carboxymethyl chitosan (CMCh) blend

AbstractThis work aimed to prepare solid polymer blend electrolytes based on carboxymethyl cellulose (CMC) and carboxymethyl chitosan (CMCh) complexed with lithium acetate (LiCH3COO) for lithium‐ion batteries application. The solid polymer blend electrolytes of LiCH3COO‐complexed CMC/CMCh (50/50) polymer blend electrolyte were prepared by using the casting solution technique, where various weight percentages of LiCH3COO were mixed into CMC/CMCh (50/50) blend as host polymer. Solid polymer blend electrolytes of CMC/CMCh + 30wt% LiCH3COO had the highest ionic conductivity as much as 2.24 × 10−5 S cm−1 among others. The CMC/CMCh blend (50/50) + 30wt% LiCH3COO degraded at temperature interval 256–473°C. Linear sweep voltammetry method shows that CMC/CMCh (50/50) + 30wt% LiCH3COO reached a decomposition voltage around 2.54 V, while CMC/CMCh (50/50) + 10wt% LiCH3COO was decomposed at a lower voltage around 1.55 V. Based on the transference number measurement appeared that the initial and final current values of 0.84 for the CMC/CMCh (50/50) + 30wt% LiCH3COO is higher than that of the CMC/CMCh (50/50) + 10wt% LiCH3COO (0.8). Based on the results obtained, it can be concluded that the CMC/CMCh blend (50/50) + 30wt% LiCH3COO meets the minimum requirements for the main parameters of ion conductivity and thermal stability as a solid electrolyte polymer membrane but needs improvement and attention to its mechanical properties.Highlights CMC and carboxymethyl chitosan (CMCh) have polar groups for ionic conduction. The CMC/CMCh blend (50/50) + 30wt% LiCH3COO has good ionic conductivity of 2.24 × 10−5 S cm−1. The CMC/CMCh blend (50/50) + 30wt% LiCH3COO has high thermal stability 256–473°C. The CMC/CMCh blend (50/50) + 30wt% LiCH3COO has high decomposition voltage around 2.54 V. The CMC/CMCh blend (50/50) + 30wt% LiCH3COO has higher transference number (0.84).

Synthesis of NiBTC metal-organic framework thin layers on nickel foam by different electrochemical methods: A comparative study for hydrogen evolution reaction

In this study, for the first time two electrochemical synthesis techniques including cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were used for MOF synthesis. The Ni3(BTC)2 electrocatalyst was synthesized and deposited without any binder, for a short time and at ambient temperature on the nickel foam substrate. Morphology studies showed that the LSV method leads to preserving the 3D structure of nickel foam which promotes the catalytic activity. It should be noted that two parameters, such as voltage range and scan rate, were optimized during the LSV method. Moreover, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to confirm the MOF's structural integrity. Furthermore, the Brunauer-Emmett-Teller (BET) method verified the porous structure of NiBTC MOF. Additionally, the performance of bare and modified nickel foams was also examined for the hydrogen evolution reaction (HER) which demonstrated the tremendous potential of NiBTC/Ni foam in HER catalytic activity.

Electrocatalytic hydrogen evolution at carbon paste electrodes doped with a manganese(II) imidazoledicarboxylate complex

Abstract A mononuclear Mn(II) complex [Mn(p-MOPhH2IDC)2(H2O)2]·2(DMF), was synthesized by the reaction of p-MOPhH3IDC (2-(4-methoxyphenyl)-1H-imidazole-4,5-dicarboxylic acid) and Mn(CH3COO)2·4H2O under solvothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV–vis spectroscopy. The structure analysis revealed that the manganese(II) center has a six-coordinated octahedral coordination geometry. The performance of a Mn(II) complex-doped carbon paste electrode (Mn-CPE) in the electrocatalytic hydrogen evolution reaction (HER) was evaluated by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) methods. The polarization curve shows that the η 10 298K (overpotential, 10 mA cm−2) of the Mn-CPE was positively shifted by 341 mV compared with the bare CPE (without complex). The Tafel slope of the Mn-CPE was 161 mV dec−1. These data indicate that the Mn-CPE was effective in the HER electrocatalytic reaction. For EIS experiments, the arc diameter of the high-frequency region of the Mn-CPE was much smaller than that of the bare CPE, which further indicates the effective catalytic capacity of the Mn(II) complex for hydrogen evolution. The information obtained from this study will help to expand the application of Mn(II) complexes in the field of electrochemistry.

Antioxidant Activity and Protective Effects of an Oxovanadium (IV) Complex on Heart and Aorta Injury of STZ-Diabetic Rats.

Diabetic people have a much higher rate of cardiovascular disease than healthy people. Therefore, heart and aortic tissues are target tissues in diabetic research. In recent years, the synthesis of new vanadium complexes and investigation of their antidiabetic/lowering effect on the blood glucose levels and antioxidant properties are increasing day by day. Our study aimed to examine the effects of synthesized oxovanadium (IV) complex of 2-[(2,4-dihydroxybenzylidene]hydrazine-1-[(N-(2-hydroxybenzylidene)](S-methyl)carbothioamide [VOL] on diabetic heart and aortic tissues, as well as in vitro lactate dehydrogenase (LDH) and myeloperoxidase (MPO) inhibition, antioxidant properties, and reducing power. Electrochemical characterization of the VOL was carried out by using Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV) methods. In addition, in silico drug-likeness and ADME prediction were also investigated. For in vivo study, male Swiss albino rats were randomly selected and separated into four groups which are control, control + VOL, diabetic and diabetic + VOL. After the experimental procedure, biochemical parameters were investigated in homogenates of heart and aorta tissues. The results showed that VOL has a protective effect on heart and aortic tissue against oxidative stress. According to electrochemical experiments, one reversible oxidative couple and one irreversible reductive response were observed for the complex. In addition, in vitro LDH and MPO inhibition of VOL was examined. It was found that VOL had a protective effect on heart and aortic tissues of diabetic rats, and caused the inhibition of LDH and MPO in in vitro studies. On the other hand, evaluating the synthesized VOL according to in silico drug-likeness and absorption, distribution, metabolism, and excretion (ADME) prediction, it was found that VOL has drug-like properties and exhibited high gastrointestinal absorption. The VOL had a therapeutic impact on the heart and aortic tissues of diabetic rats, according to the findings.

Anodic Behaviour of Ni42Fe38Cu20 Electrode in Molten Fluoride Salts

The anodic behaviour of Ni42Fe38Cu20 alloy at different sodium-potassium-cryolite-based electrolyte compositions was examined by chronopotentiometry, chronoamperometry, and linear sweep voltammetry at 1098 K for different electrolyte compositions. Steady-state anodic polarisation curves show that the anodic overpotential in electrolytes with molar ratio CR = (NaF+KF)/AlF3 = 1.4 is significantly less than in electrolyte with CR = 1.3. Short-term galvanostatic polarisation curves indicate that the potential difference between the anode and reference electrode (Al) was stable in electrolytes with CR = 1.4 and potassium ratio KR = KF/(KF + NaF) = 0.3 and CR = 1.4 KR = 0.35. The linear sweep voltammetry method indicates the presence of a diffusion-controlled reaction at a potential below the onset of oxygen evolution, which can be attributed to oxide formation. Tafel curves indicate the presence of the reactions below the potential of oxygen evolution but show a similar overpotential level for the oxygen-evolving reaction as for carbon anodes. Furthermore, the effect of pre-oxidation and influence of consistent polarisation on the anode performance was explored. Pre-oxidised anodes have better stability and lower exchange current density in similar experimental conditions compared to untreated anodes. It was also observed that leaving anodes unpolarised could lead to their instability and fluoridation of both types of anodes, with less severe effect on the pre-oxidised anode.

Template-assisted electroplating of Sm-Co composite nanowires: Issue of boric acid additive via R-D process

A considerable number of Sm-Co nanowires were synthesized in anodic aluminum oxide (AAO) by electroplating in aqueous solutions. To ensure a uniform Sm composition ratio, the electroplating was conducted using linear sweep voltammetry method. Dispersed Sm-Co nanowires were synthesized via a combination of annealing for densification and template etching. Subsequently, a low-temperature reduction and diffusion process was performed at 700 ℃ in a facile way using NaCl, KCl, and Ca granules. The one-dimensional structure morphology was maintained; however, contrary to expectations, the hysteresis loop in the VSM did not exhibit the excellent magnetic properties of the Sm2Co17 hard ferromagnet. Analysis by XPS, XRD, and TEM revealed that the addition of boric acid during electroplating suppressed the transformation of Sm-Co nanowires into the Sm2Co17 phase. The use of boric acid as an additive when synthesizing nanowires by electroplating using an AAO template has been found to be beneficial for a highly ordered morphology; however, this may lead to undesirable issues in the reduction and diffusion process, and thus should be carefully considered.

Green biopolymer and plasticizer for solid electrolyte preparation: FTIR, electrochemical properties and EDLC characteristics

In this study a green electrolyte was developed by incorporating methylcellulose (MC) polymer with potassium thiocyanate as ion provider and plasticized with glycerol to enhance salt dissociation. The purpose of glycerol addition was to improve DC conductivity and to enhance the performance of an electric double-layer capacitor (EDLC) device. The electrochemical and structural characteristics of the green electrolyte were examined. The broadening of the FTIR bands and a decrease in intensity indicated the interaction between the electrolyte components. The suitability of the electrolyte films for device applications was confirmed by measuring ionic conductivity using electrochemical impedance spectroscopy (EIS) skills. A significant amount of charge was concentrated at the electrode–electrolyte interface because of the high dielectric constant of the electrolyte. The loss tangent (tan δ) and modulus (M“) spectra obtained from electrical impedance spectroscopy showed distinct peaks associated with ion relaxation processes. The results of the transference number measurement (TNM) experiment indicated that ions were more influential than electrons. The stability of the film under different voltage conditions was evaluated using the linear sweep voltammetry (LSV) method. The performance of the EDLC was determined through cyclic voltammetry (CV) and charge–discharge evaluations. The CV pattern of the device at low scan rates showed a non-Faradaic mode of charge storage with a nearly rectangular shape. The newly constructed EDLC exhibited an initial capacitance per unit mass of 79F/g, a utilization efficiency of 87%, a power density of 1950 W/kg, and an energy storage density of 12.1 Wh/kg.

Kinetic and Thermodynamic Properties of Ytterbium Chloride and Fluoride Complexes in Chloride Melts

The electrochemical behavior of trichloride ytterbium in NaCl-KCl, KCl, and CsCl melts was studied in the temperature range 973–1173 K by different electrochemical methods. The diffusion coefficients (D) of Yb(III) and Yb(II) were determined by linear sweep voltammetry, chronopotentiometry and chronoamperometry methods. The standard rate constants of charge transfer (k s) for the Yb(III)/Yb(II) redox couple were calculated on the basis of cyclic voltammetry data using Nicholson’s equation. The formal redox potentials E * Yb(III)/Yb(II) in alkali chloride melts were obtained by the cyclic voltammetry and the Gibbs free energy for the reaction: YbCl2(sol.) + 1/2 Cl2(g.) ↔YbCl3(sol.) in alkali chloride melts was calculated. The electrochemical behavior of the Yb(III)/Yb(II) redox couple in the NaCl-KCl- NaF (5 wt%) melt was studied. A comparative analysis of electrochemical behavior of ytterbium chloride complexes in the NaCl-KCl melt and ytterbium fluoride complexes in the NaCl-KCl- NaF (5 wt%) melt was performed. It was shown that the formation of the stronger fluoride complexes reduced diffusion coefficients, standard rate constants of charge transfer for the Yb(III)/Yb(II) redox couple, and shifted the formal standard redox potentials to more electronegative values.

Environmentally friendly plasticized electrolyte based on chitosan (CS): Potato starch (PS) polymers for EDLC application: Steps toward the greener energy storage devices derived from biopolymers

Biopolymer membranes derived from natural resources are environmentally friendly materials and their use for electrochemical energy storage devices has attracted a great deal of attention. Here, chitosan (CS) and potato starch (PS) doped with ammonium thiocyanate (NH4SCN) were used as host electrolyte. Various weight percent of glycerol (Gly) as a non-toxic plasticizer are used to prepare novel plasticized solid biopolymer electrolytes (PSBEs) through solution casting method, which is subsequently used as a mediator in electric double-layer capacitor (EDLC) application. Inclusion of Gly participated significantly in minimizing the crystallinity nature of the membranes as revealed by the X-ray diffraction (XRD) patterns. Fourier transform infrared (FTIR) spectroscopy revealed the complexation among the constituents of the electrolyte. Ion transport parameters determined by FTIR and electrochemical impedance spectroscopy (EIS) techniques have shown comparable results. The optimum composition of PSBE is achieved when 24 wt% of Gly is added (CPNHG3), which has shown the best ion conductivity (1.62×10−3Scm−1) from the EIS study. This film has exhibited also an excellent ion transference number (tion) of (0.989) and a large electrochemical potential stability (2.1 V) measured by transfer number measurement (TNM) and linear sweep voltammetry (LSV) methods. The restriction to ion movement was observed for the samples overloaded with Gly (32 and 40 wt%) due to the blockage effect, which reflected on ion conductivity and transport parameters. The assembled EDLC device provided a specific capacitance (Cspc) of 16.1 F/g at 10 mV/s scan rate with no sign of redox reaction, which was proven by either cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques. Further, the cyclic stability and high performance of the EDLC regarding energy density, power density, and coulombic efficiency were confirmed throughout the 2500 cycles.

Remediation of ciprofloxacin in soil using peroxymonosulfate activated by ball-milled seaweed kelp biochar: Performance, mechanism, and phytotoxicity

This study explores the catalytic performance of simple physically modified ball-milled kelp-seaweed (Laminaria japonica) biochar (KBCBM) for organic degradation in the soil. The present study is the first attempt at CIP-contaminated soil (CIPsoil) remediation using KBCBM with peroxymonosulfate (PMS) and exploring the phytotoxicity of the intermediates in the treated soil. The surface characterization of the KBCBM catalyst was investigated using different instrumental analyses. The CIPsoil/KBCBM/PMS system showed excellent performance in CIP degradation (96.06%, C0 = 126.15 ± 0.7 mg kg−1) under the conditions of 1.0 mM PMS, 1.5 mg g−1 of KBCBM and unadjusted pH (6.3) condition. The co-existing anions: such as Cl−, HCO3−, and HPO42− enhanced the CIP degradation in the CIPsoil/KBCBM-800/PMS system. However, SO42−, NO3−, and organic matter (HA) showed negligible impacts on pollutant degradation in the KBCBM/PMS system. Reactive oxygen species (ROS) formation was confirmed by chemical scavengers and electron spin resonance spectroscopy (ESR) analysis. The non-radical reaction pathway was verified by electrochemical analysis of linear sweep voltammetry (LSV) and potentiodynamic testing (i-t curve) methods in the KBCBM/PMS. In addition, the phytotoxicity analysis was evaluated by the germination percentage of cucumber seeds with and without remediated soil. The possible CIP degradation mechanisms were proposed using UPLC-MS/MS analysis. The KBCBM/PMS system demonstrated encouraging capabilities in the treatment of CIP-contaminated soil.

Synthesis of perovskite-type potassium niobate using deep eutectic solvents: A promising electrode material for detection of bisphenol A

This study demonstrates a hydrothermal method to prepare perovskite-type potassium niobate (KNbO3) through deep eutectic solvent (DES), which is further used as an electrode material for the determination of bisphenol A (BPA). The as-synthesized KNbO3 was systematically characterized by different microscopic and spectroscopic techniques. The KNbO3-modified electrode demonstrates excellent electrocatalytic activity for BPA compared to the pristine electrode. The enhanced performance of the proposed sensor is attributed to the numerous active sites, large electrochemical surface area, high electrical conductivity, and rapid electron transfer. The fabricated sensor shows a wide detection range (0.01–84.3 μM), a low limit of detection (0.003 μM), a high sensitivity (0.51 μA μM−1 cm−2), and good anti-interference abilities towards the BPA detection by linear sweep voltammetry method. Besides, it was successfully applied to determining BPA in food samples, demonstrating good practicability. This design paves a new way to fabricate efficient electrode material for various electrochemical applications using a DES medium.

Electrochemistry, DFT Calculations, and Antioxidant Capability of Cobalt Cefazolin Complex

The synthesis, characterization, electrochemistry, theoretical investigation and antioxidant capability of cobalt cefazolin [Co(Cefaz)Cl] complex are reported here. Electrochemical characterization of the complex was carried out by using cyclic voltammetry (CV) and Linear Sweep Voltammetry (LSV) methods. Two irreversible oxidative responses and one quasi-reversible reduction couple were observed for the complex on the voltammograms. The ground state energies of the molecules have been estimated using B3LYP functional with LanL2DZ basis set based on time dependent density functional theory (TD-DFT). According to the theoretical calculation, [Co(Cefaz)Cl] complex can be expected to exhibit greater reactivity from Cefazolin (Cefaz) ligand, and the higher antioxidant properties were observed for the complex. The experimental results are in good agreement with the theoretical calculations.

Toward Escherichia coli bacteria-machine for water-oxidation reaction at neutral conditions: Using Ruthenium Red

Water splitting into hydrogen and oxygen is a promising method for storing sustainable but intermittent energies. Ruthenium compounds are promising for the water-oxidation reaction. Herein, an easy method is employed to load a water-oxidation catalyst (Ruthenium Red; ([(NH3)5RuORu(NH3)4ORu(NH3)5]Cl6)) on the surface of the Escherichia coli bacterial template. After the synthetic procedure, the catalyst is characterized by field emission-scanning electron microscopes, high-resolution transmission electron microscopy, visible spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy. Some of the employed methods show that the bacterial template is intact after the synthetic procedure. In the next step, the catalyst is investigated by linear sweep, cyclic, and square wave voltammetry methods. The water-oxidation reaction of the compounds is examined under electrochemical conditions in LiClO4 (0.25 M) at pH = 6.3. Linear sweep voltammetry shows that the onset overpotential of the water-oxidation reaction of the catalyst is 720 mV (based on extrapolation of the Tafel plot) with a Tafel slope of 226.4 mV per decade. Thus, the presence of Ruthenium Red in the material remarkably increases the activity of the water-oxidation reaction.

Kinetic and Thermodynamic Properties of Ytterbium Chloride and Fluoride Complexes in Chloride Melts

An important problem concerning rare earth metals and molten salts is the reprocessing of nuclear fuel, since lanthanides are always present in spent nuclear fuel. According to the technology being developed for pyroelectrochemical processing of nuclear waste spent fuel is converted into molten salts by anodic dissolution, followed by electrochemical extraction of actinides from lanthanides.Thus a knowledge of the electrochemistry and thermodynamics of lanthanide compounds in molten salt systems is very useful for the understanding the recycling of spent nuclear fuel.The electroreduction of YbCl3 in alkali chloride melts (NaCl-KCl, KCl, CsCl) was studied in the temperature range 973-1173 K by different electrochemical methods. The diffusion coefficients (D) for Yb(III) and Yb(II) were determined by linear sweep voltammetry, chronopotentiometry and chronoamperometry methods. Decreasing values of D were obtained when the cation in the second coordination sphere changed from Na to Cs. It was shown that such changes are due to the decreasing of counter polarizing effect of cations with increasing cationic radius.The standard rate constants of charge transfer (k s) for the Yb(III)/Yb(II) redox couple were calculated on the basis of cyclic voltammetry data using Nicholson’s approach. The following row of the standard rate constants of charge transfer has been experimentally determined: k s (KCl) < k s (CsCl) < k s (NaCl-KCl).The formal redox potentials E* Yb(III)/Yb(II were obtained in alkali chlorides melts from the linear sweep voltammetry data. From the values of the formal redox potentials were calculated the Gibbs energies and equilibrium constants for the reaction:YbCl2(sol.) +1/2 Cl2(g.) « YbCl3(sol.) (1)It was determined the increasing of the formal entropy for the reaction (1) in transition from NaCl-KCl to CsCl melt that associated with a greater degree of ordering of the reaction products due to the complex formation.Influence of fluoride ions (NaF) on the electrochemical behavior of the Yb(III)/Yb(II) redox couple in an equimolar NaCl-KCl melt was studied. It was determined а decrease of diffusion coefficients and standard rate constants, as well as a shift of the formal redox potentials to the negative region.

Anodic Behaviour of Ni-Fe-Cu electrode In Molten Fluoride Salts

The anodic behaviour of NixFeyCuz alloy at different sodium- and potassium-cryolite based electrolyte compositions was examined by chronopotentiometry, galvanostatic polarisation, and linear sweep voltammetry at 1098 K. Steady-state anodic polarisation curves show anodic overpotential in electrolyte with molar ratio CR=(NaF+KF)/AlF3=1.4 is significantly less than in electrolyte with CR=1.3. Short-term galvanostatic polarisation curves indicate the potential difference between the anode and reference electrode (Al) was stable in electrolytes with CR=1.4 and potassium ratio KR=KF/(KF+NaF)=0.3 and CR=1.4 KR=0.35. Linear sweep voltammetry method indicates the presence of a diffusion controlled reaction at a potential below onset of oxygen evolution, which can likely be attributed to oxide formation. The diffusion coefficient obtained from linear sweep voltammetry and chronopotentiometry are within a similar range. Tafel curves confirm the presence of a reaction below the potential of oxygen evolution, but indicate a similar overpotential level for the oxygen evolving reaction as for carbon anodes.

Kinetic and Thermodynamic Properties of Ytterbium Chloride and Fluoride Complexes in Chloride Melts

The electrochemical behavior of ytterbium in NaCl-KCl, KCl and CsCl melts was studied in the temperature range 973-1173 K by different electrochemical methods. The diffusion coefficients (D) of Yb(III) and Yb(II) were determined by linear sweep voltammetry, chronopotentiometry and chronoamperometry methods. The standard rate constants of charge transfer (k s) for the Yb(III)/Yb(II) redox couple were calculated on the basis of cyclic voltammetry data using Nicholson’s equation. The formal redox potentials E* Yb(III)/Yb(II) were obtained in alkali chlorides melts from the cyclic voltammetry data. The influence of fluoride ions on the standard rate constants in the NaCl-KCl melt was investigated.