Charge Transfer Rate Constant Research Articles

Designing and Screening High‐Performance Non‐Fullerene Acceptors: A Theoretical Exploration of Modified Y6

Recently, the application of the non‐fullerene acceptor (NFA) Y6 and its derivatives has increased the power conversion efficiencies (PCEs) of organic solar cells (OSCs) up to 18.22%. It has opened up a new revolutionary direction of the molecular design of high‐performance NFAs. Despite the recent exciting experimental progress of Y6‐based OSCs, studies of molecular modifications of Y6, which may be the most effective way to improve the PCE of OSCs, are still few. Herein, a series of modified Y6 molecules is systematically designed and modeled. Their physical and optical properties are predicted with reliable density functional theory (DFT) and time‐dependent DFT calculations. The dipole moments, frontier molecular orbital energies, UV–vis absorption spectra, singlet–triplet energy gaps, exciton binding energies, charge transfer rate constants at the donor–acceptor interface, and electron mobility are computed to comprehensively analyze the potential of these Y6 derivatives. The results show that proper extension of the backbone by inserting thiophene rings with a single‐bond connection is conducive to designing highly efficient NFAs. The most striking finding here is that one (named BTPTT‐4F‐2T) of the screened Y6 derivatives is superior to prototype Y6 in all aspects and may be the next star high‐performance NFA.

Electrochemical Behavior of Titanium Complexes in the KCl-KF Melt with Additions of Alkaline Earth Metal Cations

The charge transfer kinetics for the Ti(IV)/Ti(III) redox couple in the KCl-KF(10 wt.%)-K2TiF6 melt was studied. The standard rate constants of charge transfer (k s ) for the redox couple Ti(IV)/Ti(III) in the KCl-KF(10 wt.%)-K2TiF6 melt were calculated. The temperature dependence of the standard rate constants of charge transfer was described by the empirical equation: logk s = (2.01 ± 0.40) – (4178 ± 810)/Т. The activation energy of charge transfer was equal to (80 ± 15) kJ mol–1. Influence of strongly polarizing cations (Mg2+, Ca2+, Sr2+ and Ва2+) on the charge transfer kinetics was studied. It was determined the linear dependence of k s on the ionic potential of alkaline earth metal cations. Values of activation energy of charge transfer for systems with strongly polarizing cations were considerably less than activation energy of the initial system and decrease in case of ionic potential increasing.

Kinetic and Thermodynamic Properties of Samarium Chlorides Dissolved in Alkali Chloride Melts Obtained by Electrochemical Transient Techniques

The electrochemical behavour of samarium in NaCl-KCl, KCl and CsCl melts have been studied in the temperature range 973–1173 K by different electrochemical methods. The diffusion coefficients (D) of Sm(III) and Sm(II) have been determined by linear sweep voltammetry, chronopotentiometry and chronoamperometry methods. The standard rate constants of charge transfer (k s) for the Sm(III)/Sm(II) redox couple have been calculated on the basis of cyclic voltammetry data using Nicholson’s equation. The nature of working electrode on the standard rate constants of charge transfer for the Sm(III)/Sm(II) redox couple has been studied. The formal redox potentials E * Sm(III)/Sm(II) have been obtained in alkali chloride melts from the cyclic voltammetry data.

Electrochemical oxidation of salicylic acid on the nanostructured electrodes based on nickel with additionally precipitated platinum

We studied the electrochemical process of salicylic acid oxidation in acidic solutions on the nanostructured anodes prepared on the basis of nickel with additionally precipitated platinum. The investigation was carried out by means of linear and cyclic voltammetry methods in combination with quantum chemical calculations. The results of voltammetry study showed that clearly expressed current maxima were observed in the range of 0.43 V to 1.15 V in the anode sections of the voltammograms, in contrast to the background electrolyte. The oxidation potentials of the depolarizer almost coincided with those typical of a smooth platinum electrode, but the current density was 1.8 times higher on the electrode under study. Based on the analysis of voltammetric curves, the effective rate constants of heterogeneous charge transfer, activation energy and diffusion coefficient were calculated. The calculation of the thermodynamic parameters of the intermediates of salicylic acid electrooxidation showed that the heat of formation of 2,3-dihydroxybenzoic acid is higher than that of 2,5-dihydroxybenzoic acid, which indicates a higher stability of the latter. Analysis of the calculated thermodynamic characteristics of each stage of salicylic acid electrochemical oxidation showed that the process is endothermic, occurs with an increase in entropy and the Gibbs energy decreases. The rate of the overall process is determined by the rate of the first stage.

Charge Transfer Kinetics at Ag(111) Single Crystal Electrode/Ionic Liquid Interfaces: Dependence on the Cation Alkyl Side Chain Length

AbstractThe influences of the electrode/ionic liquids interfaces on the charge transfer kinetics are addressed with the example of the oxidation of chromocene at a single crystal Ag(111) electrode. We considered three different imidazolium‐based room temperature ionic liquids (RTILs) with alkyl chains of different lengths but with a common anion. The standard charge transfer rate constants k° are extracted from cyclic voltammograms (CVs) by analyzing the peak potential variations with the scan rate and/or performing semi‐integral electroanalysis with a careful treatment of the ohmic drop. Linear variations between the logarithms of k° and the longitudinal relaxation times τL or the dynamic viscosity η of the ionic liquids are obtained. However, the amplitude of the decrease is much larger than it could be expected from the sole bulk properties of the ionic liquid indicating a strong effect of the interface on the kinetics. These observations agree with a well‐organized electrode/RTIL interface that behaves as a sort of self‐assembled monolayer that controls the charge transfer kinetics with an exponential tunneling coefficient β of 5.51 nm−1.

Indium electrowinning kinetics on titanium, aluminum and copper supports from sulfate solution

Abstract Indium electrowinning process from sulfate solution on copper, titanium and aluminum cathodes (Cu, Ti and Al) were studied using the methods of cyclic voltammetry (CV) and chronoamperometry (CA). Voltammogram features indicated the irreversible behavior of indium discharge on each cathode. The heterogeneous charge transfer rate constant (k0) has been evaluated on Cu, Ti and Al cathodes and their values were 7.1·10−5 cm/s, 6.2·10−5 cm/s and 5.4·10−5 cm/s, respectively. The indium ions electro-reduction seems to be quite different on these diverse cathodic supports: a nucleation process appears on Cu and Al cathodes, while is absent on Ti cathode due to the hydrogen evolution overlapping at high cathodic overpotentials. CV and CA techniques allowed to calculate the diffusion coefficient (D0) of indium ion in sulfate solution. Furthermore, calculating the roughness coefficient (φ) by CV technique on each metal surface, it was possible to establish the real surface area of Cu, Ti and Al cathodic supports. The charge transfer coefficient values (α) calculated by Tafel curves agreed those obtained by CV results, while the k0 value and the exchange current density (i0) showed a similar trend for each cathode. By these results, the exchange current density was equal to 1.20 mA/cm2, 0.30 mA/cm2 and 0.075 mA/cm2 for Cu cathode Ti and Al cathodes, respectively. The findings of this investigation can provide an understanding of the indium electrowinning process on three different support electrodes (Cu, Ti and Al) from sulfate solution.

Evaluation of charge-transfer rates in fullerene-based donor-acceptor dyads with different density functional approximations.

The shift towards renewable energy is one of the main challenges of this generation. Dye-sensitized solar cells (DSSCs), based on donor-acceptor architectures, can help in this transition as they present excellent photovoltaic efficiencies yet cheap and simple manufacturing. For molecular heterojunction DSSCs, donor-acceptor pairs are linked in a covalent manner, which facilitates their tailoring and rational design. Nevertheless, reliable computational characterization of charge transfer rate constants (kCT) is needed to speed this development process up. In this context, the performance of time-dependent density functional theory for the calculation of kCT values in donor-acceptor fullerene-based dyads has not been benchmarked yet. Herein, we present a detailed analysis on the performance of seven well-known density functional approximations (DFAs) for this type of system, focusing on several parameters such as the reorganization energies (λ), electronic couplings (VDA), and Gibbs energies (ΔG0CT), as well as the final rate constants. The amount of exact exchange at short range (SR) and long range (LR) electron-electron distances (and the transition from the SR to LR) turned out to be key for the success of the prediction. The tuning of these parameters improves significantly the performance of current DFAs.

Charge Transfer and Recombination Processes at p-CuBi2O4 Photoelectrodes

Photoelectrochemical water splitting is an attractive method to convert solar energy to storable chemical energy in the form of hydrogen, however, the materials requirements to achieve this efficiently are challenging: the semiconducting material needs to absorb sunlight efficiently, must to be capable of reducing and/or oxidizing water, and has to be stable under illumination under current flow in an aqueous electrolyte solution. In particular, for small bandgap semiconductors, stability is often an issue, and it is difficult to fully avoid degradation of the material. In addition, the water reduction and oxidation processes need to occur fast, in order to favorably compete with recombination or surface degradation processes; hence, the kinetic rate constants for charge transfer and surface recombination are very important parameters. Intensity-modulated photocurrent spectroscopy (IMPS) is a powerful technique to study the carrier dynamics in a photoelectrochemical cell. The photocurrent admittance corresponds to the frequency-dependent external quantum efficiency, and time constants for charge transfer and surface recombination can be determined, provided a simple model can be applied.1 In this presentation, we focus on the dynamic properties of p-CuBi2O4 in order to elucidate the rate determining steps that determine the efficiency of photocathodic reactions. In inert aqueous solutions at pH 5, an unfavorable balance exists between the rate constants for charge transfer and surface recombination, which limits the conversion efficiency.2 On the other hand, upon adding H2O2 as an electron acceptor, the photoelectron transfer efficiency is improved related to faster electron transfer to the solution or slower surface recombination due to passivation effects. Strategies to improve the applicability of CuBi2O4 in solar water splitting systems are discussed.The authors gratefully acknowledge CONACYT, SENER and CICY for funding through the Renewable Energy Laboratory of South East Mexico (LENERSE; Project 254667; SP-4), and CONACYT under the Basic Sciences (CB) project A1-S-28734. References “Photoelectrochemical Water Splitting at Semiconductor Electrodes: Fundamental Problems and New Perspectives”. L. M. Peter and K. G. Upul Wijayantha, ChemPhysChem, 15, 1983–1995 (2014). “Charge Transfer and Recombination Dynamics at Inkjet-Printed CuBi2O4 Electrodes for Photoelectrochemical Water Splitting”. Ingrid Rodríguez-Gutiérrez, Rodrigo García-Rodríguez, Manuel Rodríguez-Pérez, Alberto Vega-Poot, Geonel Rodríguez Gattorno, Bruce A. Parkinson, and Gerko Oskam. J. Phys. Chem. C, 122, 27169−27179 (2018).

Mechanistic analysis of the cathodic stripping square-wave voltammetric response of the copper‑arsenic system at a mercury electrode

Despite arsenite can be reduced to As(0) and deposited at the surface of solid electrodes such as gold, platinum, or copper, it cannot form amalgams with mercury, and so the addition of other metal ions is required for its deposition. In this manuscript, mechanistic analysis of the cathodic stripping square-wave voltammetric response of the system copper‑arsenic is presented. For the analysis of experimental responses, a mathematical model is used to consider that a surface-active reagent undergoes a charge transfer step followed by a chemical reaction. The dependences of the differential peak current, and the respective peak potential and half-peak width on the square-wave frequency were used to estimate the apparent stability constant of arsenide formation and that the electrode reaction would involve the direct transfer of 2 electrons, while the simulation and fit of forward and backward voltammetric responses have been useful for inferring other parameters such as the formal charge transfer rate constant of the global electron transfer reaction, a pseudo-first order homogeneous rate constant associated with arsenide formation, and the charge transfer coefficient of the global electron transfer reaction. Besides the values estimated for each of those parameters, all simulations indicate that the reduction of copper instead of arsenic would be taking place during the cathodic stripping scan. Accordingly, the trace-analysis reaction of arsenic in the presence of copper would be based on the surface accumulation of a metal complex, where Cu 2+ would be the metal cation and an arsenide species the ligand. The stability of that complex at the surface of a mercury electrode would depend not only on the applied potential, but also on the ratio between copper, arsenic, and protons. • Mechanistic analysis of the CS-SWV response of the system copper-arsenic is presented. • This is the first time that a mathematical model of such complexity is used for simulating experimental voltammograms. • The simulation and fit of the experimental curves are step-by-step described. • Simulations indicate that the reduction of Cu(II) instead of As(0) takes place during the cathodic stripping scan. • A surface analysis is required when the scan-rate affect the apparent reversibility of more than one kinetic constant.

Electroreduction of Hafnium and Electrodeposition of its Protective Coatings on a Molybdenum Substrate in Chloride-Fluoride Melt

The electroreduction of HfF62− complexes to Hf on a molybdenum electrode in the NaCl-KCl-K2HfF6-NaF (5 wt%) melt in the temperature range 973–1123 K was studied by cyclic voltammetry and impedance spectroscopy. It was found that discharge of Hf(IV) complexes to Hf occurs in one step and is irreversible. The diffusion coefficients of Hf(IV) fluoride complexes were determined by cyclic voltammetry. The impedance spectroscopy was used for the determination of the standard rate constants of charge transfer. Electrodeposition of hafnium coatings on a molybdenum substrate was performed in the NaCl-KCl-K2HfF6 (10 wt%)-NaF (5 wt%) melt at the cathodic current density 5–100 mA cm−2 and temperatures 973, 1023 and 1073 K. The influence of the current density and temperature on the roughness of hafnium coatings was studied. It was determined that hafnium coatings with significantly higher purity than that of the hafnium anode were obtained confirming that metal impurities were removed during electrodeposition. The oxidation kinetics data were obtained on a sample with hafnium and a sample of pure molybdenum, which were tested in a water/oxygen mixture at 773 K. The hafnium coating improves the corrosion resistance of coated plates in comparison with that of pure molybdenum.

Electrochemical behaviors of neodymium ions on a solid iron electrode in molten lithium fluoride and reaction kinetics of forming Nd2Fe17 intermetallic compound

Nd2Fe17 intermetallic compound exhibits excellent magnetic and microwave absorption properties due to its high saturation magnetization. This work investigated the electrochemical behaviors of neodymium ions on a solid iron electrode in molten LiF, focusing on the reaction kinetics of forming Nd2Fe17 intermetallic compound. The results showed that Nd2Fe17 firstly and then Nd5Fe17 intermetallic compounds formed on the iron electrode. The equilibrium electrode potentials for forming the two intermetallic compounds were measured by open circuit chronopotentiometry. The reaction kinetics of forming Nd2Fe17 intermetallic compound was investigated by cyclic voltammetry and chronopotentiometry. The electrode reaction of forming Nd2Fe17 intermetallic compound was an irreversible process that was diffusion-controlled. The diffusion activation energy and heterogeneous charge transfer rate constant were obtained. The research on the reaction kinetics indicated that the charge transfer rate could be improved by increasing overpotential. The Nd2Fe17 intermetallic compound was successfully prepared on a solid iron electrode by potentiostatic electrolysis.

Choline Oxidase Based Composite ZrO2@AuNPs with Cu2O@MnO2 Platform for Signal Enhancing the Choline Biosensors

AbstractA novel metal composite material based on zirconium dioxide decorated gold nanoparticles (ZrO2@AuNPs), copper (I) oxide at manganese (IV) oxide (Cu2O@MnO2) and immobilized choline oxidase (ChOx) onto a glassy carbon electrode (GCE) (ChOx/Cu2O@MnO2‐ZrO2@AuNPs/GCE) has been developed for enhancing the electro‐catalytic property, sensitivity and stability of the amperometric choline biosensor. The ChOx/Cu2O@MnO2‐ZrO2@AuNPs/GCE displayed an excellent electrocatalytic response to the oxidation of the byproduct H2O2 from the choline catalyzed reaction, which exhibited a charge transfer rate constant (Ks) of 0.97 s−1, a diffusion coefficient value (D) of 4.50×10−6 cm2 s−1, an electroactive surface area (Ae) of 0.97 cm2 and a surface concentration (γ) of 0.54×10−8 mol cm−2. The modified electrode also provided a wide linear range of choline concentration from 0.5 to 1,000.0 μM with good sensitivity (97.4 μA cm−2 mM−1) and low detection limit (0.3 μM). The apparent Michaelis‐Menten constant was found to be 0.08 mM with Imax of 0.67 μA. This choline biosensor presented high repeatability (%RSD=2.9, n=5), excellent reproducibility (%RSD=2.9, n=5), long time of use (n=28 with %I>50.0 %) and good selectivity without interfering effects from possible electroactive species such as ascorbic acid, aspirin, amoxicillin, caffeine, dopamine, glucose, sucrose and uric acid. This optimal method was successfully applied for choline measurement in prepared human blood samples which demonstrated accurate and excellent reliability in the recovery range from 96.7 to 102.0 %.

On the Interplay between Electronic Structure and Polarizable Force Fields When Calculating Solution-Phase Charge-Transfer Rates.

We present a comprehensive analysis of the interplay between the choice of an electronic structure method and the effect of using polarizable force fields vs. nonpolarizable force fields when calculating solution-phase charge-transfer (CT) rates. The analysis is based on an integrative approach that combines inputs from electronic structure calculations and molecular dynamics simulations and is performed in the context of the carotenoid-porphyrin-C60 molecular triad dissolved in an explicit tetrahydrofuran (THF) liquid solvent. Marcus theory rate constants are calculated for the multiple CT processes that occur in this system based on either polarizable or nonpolarizable force fields, parameterized using density functional theory (DFT) with either the B3LYP or the Baer-Neuhauser-Livshits (BNL) density functionals. We find that the effect of switching from nonpolarizable to polarizable force fields on the CT rates is strongly dependent on the choice of the density functional. More specifically, the rate constants obtained using polarizable and nonpolarizable force fields differ significantly when B3LYP is used, while much smaller changes are observed when BNL is used. It is shown that this behavior can be traced back to the tendency of B3LYP to overstabilize CT states, thereby pushing the underlying electronic transitions to the deep inverted region, where even small changes in the force fields can lead to significant changes in the CT rate constants. Our results demonstrate the importance of combining polarizable force fields with an electronic structure method that can accurately capture the energies of excited CT states when calculating charge-transfer rates.

Electrocatalytic Properties of 3D Hierarchical Graphitic Carbon-Cobalt Nanoparticles for Urea Oxidation.

A 3D hierarchical graphitic carbon nanostructure encapsulating cobalt(0)/cobalt oxide nanoparticles (CoGC) has been prepared by solid-state pyrolysis of a mixture of anthracene and cobalt 2,2′-bipyridine terephthalate complex at 850 °C. Based on the Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods, the prepared material has high surface area (186.8 m2 g–1) with an average pore width of 205.5 Å. XPS reveals the functionalization of carbon with different oxygen-containing groups, such as carboxylic acid groups. The presence of metallic cobalt nanoparticles with cubic and hexagonal crystalline structures encapsulated in graphitized carbon is confirmed using XRD and TEM. Raman spectroscopy indicates a graphitization degree of ID/IG = 1.02. CoGC was cast onto a glassy carbon electrode and used for urea electrooxidation in an alkaline solution. The electrochemical investigation shows that the newly prepared CoGC has a promising electrocatalytic activity toward urea. The specific activity is 128 mA cm–1 mg–1 for the electrooxidation of 0.3 M urea in 1 M KOH at a relatively low onset potential (0.31 V vs Ag/AgCl). It can be mainly attributed to the morphological structure of carbon and the high reactivity of cobalt nanoparticles. The calculated charge-transfer resistance, Rct, of the modified electrode in the presence of urea (10.95 Ω) is significantly lower than that in the absence of urea (113.5 Ω), which indicates electrocatalytic activity. The value of charge-transfer rate constant, ks, for the anodic reaction is 0.0058 s–1. Electrocatalytic durability in 1000 s chronoamperometry of the modified electrode suggests high structure stability. The modified electrode retained about 60% of its activity after 100 cycles as indicated by linear sweep voltammetry.

Kinetic and Thermodynamic Properties of Samarium Chlorides Dissolved in Alkali Chloride Melts Obtained by Electrochemical Transient Techniques

Lanthanide elements, which are present in spent fuel from fast nuclear reactors can be converted into molten salts by anodic dissolution. The lanthanide elements are the most difficult fission products to separate from actinides due to their similar chemical properties. 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 SmCl3 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 Sm(III) and Sm(II) were determined by linear sweep voltammetry, chronopotentiometry and chronoamperometry methods showing that D decreases with increase of samarium oxidation state, while the activation energy for diffusion increases. Decreasing values of D were also 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 Sm(III)/Sm(II) redox couple were calculated on the basis of cyclic voltammetry data using Nicholson’s equation. 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 nature of working electrode on the rate of charge transfer for the Sm(III)/Sm(II) redox couple was studied. It was found that the values of k s determined at a molybdenum electrode were higher than those at a glassy carbon electrode.The formal redox potentials E* Sm(III)/Sm(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:SmCl2(sol.) +1/2 Cl2(g.) « SmCl3(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.

Synthesis of Refractory Metal Carbides on Carbon Fibers in Molten Salts and Their Electrochemical and Electrocatalytic Properties

Method of currentless transfer in molten salts was used for synthesis of tantalum and niobium carbides coatings and crystals of molybdenum carbide on carbon fibers. Temperature of process was varied from 800 up to 900 °C, and time of process from 0.5 up to 24 hours.Figure 1. Micrographs of carbon fiber with TaC and NbC coatings and Mo2C crystals (from left to right), obtained in molten salts melts by currentless transfer.The splicing of fibers with each other was not observed; coatings were uniform in a cross section as well as along the fiber. Thickness of TaC and NbC coatings on carbon fiber was 50 – 250 nm. Size of crystals of Mo2C was approximately several micrometers.Investigation of refractory metal (Ta, Nb, Mo) carbides on carbon fiber of the Carbopon-B-22 brand was carried out by impedance spectroscopy method. The values of the standard rate constants of charge transfer and capacities of the double electric layer were determined for synthesized materials in water solution with hydrogen peroxide.Coatings and crystals of refractory metal carbides on carbon fibers can be used as catalysts and electrocatalysts. The kinetics of the electrocatalytic decomposition of hydrogen peroxide on the surface of TaC/C, NbC/C and Mo2C/C composite materials was studied. This reaction was investigated on measuring the volume of released oxygen. The initial carbon fiber of the Carbopon-B-22 brand was used as the cathode. The composite materials made of carbon fiber coated with tantalum carbide TaC (NbC) or modified by molybdenum carbide Mo2C served as the anode. The reaction order was established, the rate constants and activation energies of the hydrogen peroxide decomposition were calculated. The composition with the highest electrocatalytic activity was determined. Figure 1

Electrochemical Behavior of Titanium Complexes in the KCl-KF Melt with Additions of Alkaline Earth Metal Cations

The goal of the present investigation was to study of Mg2+, Ca2+, Sr2+ and Ва2+ strongly polarizing cations influence on the standard rate constants of charge transfer (ks ) for the redox couple Ti(IV)/Ti(III) in the KCl-KF(10 wt.%)-K2TiF6 melt.Electrochemical studies were carried out in the temperature range of 1073-1173 K by cyclic voltammetry. Voltammetric curves were recorded at a glassy carbon electrode vs. a glassy carbon quasi-reference electrode. The sweep rate (v) varied from 0.1 up to 2.0 V s-1. The electrochemical redox process Ti(IV)+e-↔Ti(III) was classified as quasi-reversible at a sweep rate 1.0 V s-1≤ν≤2.0 V s-1.The values of k s were calculated by using the Nicholson’s method [1]. It was shown that k s increase with increasing the temperature. It is due to the number of particles capable of overcoming the potential barrier increases [2].Addition of alkaline earth metal cations resulted in increasing of ks up to the certain ratio of Me2+/Ti(IV) for all alkaline earth metal cations. It was determined the linear dependence of ks on ionic potential of alkaline earth metal cations.The activation energies of the charge transfer in the case of strongly polarizing cations addition were calculated. It was shown that values of the activation energy for molten systems with strongly polarizing cations are considerably less than activation energy of the initial melt and decrease with increasing of ionic potential.It was determined that the k s for the redox couple Ti(IV)/Ti(III) in the KCl-KF(10 wt.%)-K2TiF6 melt (for all systems) are less than k s in the NaCl-KCl based melt [3].

Erratum: "Charge transfer rate constants for the carotenoid-porphyrin-C60 molecular triad dissolved in tetrahydrofuran: The spin-boson model vs the linearized semiclassical approximation" [J. Chem. Phys. 153, 044105 (2020)

Erratum: "Charge transfer rate constants for the carotenoid-porphyrin-C60 molecular triad dissolved in tetrahydrofuran: The spin-boson model vs the linearized semiclassical approximation" [J. Chem. Phys. 153, 044105 (2020)

Kinetic and Thermodynamic Properties of Samarium Chlorides Dissolved in Alkali Chloride Melts Obtained by Electrochemical Transient Techniques

The electrochemical behavior of samarium 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 Sm(III) and Sm(II) were determined by linear sweep voltammetry, chronopotentiometry, and chronoamperometry methods. The standard rate constants of charge transfer (k s) for the Sm(III)/Sm(II) redox couple were calculated on the basis of cyclic voltammetry data using Nicholson’s equation. The nature of working electrode on the standard rate constants of charge transfer for the Sm(III)/Sm(II) redox couple was studied. The formal redox potentials E* Sm(III)/Sm(II) were obtained in alkali chlorides melts from the cyclic voltammetry data.

Electrochemical Behavior of the SmF3 in Alkali Chloride Melts

Electrochemical studies of the redox couple Sm(III)/Sm(II) were carried out in NaCl-KCl, KCl, and CsCl melts in a temperature range of 973-1173 K by cyclic voltammetry. Diffusion coefficients (D) of Sm(III) in these melts were determined using Randels–Shevchik equation. The diffusion coefficients decrease with a change in the composition of the second coordination sphere from sodium to cesium. It is associated with a decrease in the counter-polarizing effect during the transition from Na to Cs, which in turn causes a decrease the metal–ligand bond length in the complexes. The standard rate constants of charge transfer (k s) of the redox couple Sm(III)/Sm(II) were determined by cyclic voltammetry in the all studied melts using the Nicholson’s equation, which is valid for quasi-reversible processes. The following series of the standard charge transfer constants was found k s(CsCl)<k s(KCl)<k s(NaCl–KCl).