Russian Journal of Electrochemistry最新文献

Developing highly efficient and robust catalysts as anode materials is crucial for improving the electrocatalytic degradation of dye wastewater, yet it remains a significant challenge. Here, a reduced graphene oxide-tin (rGO–Sn) nanocomposite was synthesised as an advanced anode material and applied to a low-cost electrode (graphite felt) through a dip-coating method. The physico-chemical and electrochemical analyses were performed to elucidate the properties and validate the successful synthesis of nanomaterials and modified electrodes. Benefitting from the incorporation of highly conductive rGO together with high oxygen evolution potential (OEP) of Sn, the rGO–Sn modified GF exhibits improved electrocatalytic properties by demonstrating lower charge transfer resistance, R_ct (4.601 Ω), higher specific capacitance (0.056 mF cm^–2) and OEP at 1.490 V when compared with unmodified graphite felt (38.664 Ω, 0.033 mF cm^–2 and 1.253 V). The improvement of electrochemical properties results in enhanced efficiency in electro-degradation performance, achieving a 92.44 ± 0.94% removal of the dye Congo red after 2 h of reaction in contrast to the 60.14 ± 0.71% removal by unmodified GF. Moreover, the enhanced mechanical strength contributed by rGO and the elevated oxidation resistance provided by Sn, which safeguards the underlying substrate, significantly prolongs the service lifetime of the modified GF to 6.8 h, as compared to the unmodified GF’s 1.2 h. This study opens up new avenues for improving the performance of low-cost electrodes through an easy coating method of rGO–Sn since cost is a major concern for the EO process.

So-called anode-free sodium batteries represent a very promising version of post-lithium era devices. The present brief review considers their principal features (both advantages and disadvantages). The main problems connected with their development are phenomena of dendrite formation and encapsulation. These problems could be solved via improvement of negative electrode current collectors (enhancing of their sodiophilicity), as well as the electrolytes’ optimization, in particular, for the development of high-quality solid electrolyte interphases (SEI).

The anodic formation of silver oxide in 0.1 M KOH deaerated alkaline solution at the alloys of the Ag–Pd system, including those with increased structural surface disorder due to its preliminary anodic modification in 0.01 M HNO₃ + 0.09 M KNO₃ deaerated solution is studied. The anodic modification includes silver selective dissolution at potentials below the critical value, hence, not causing destruction of the alloy structure. As a result of the anodic modification, the alloy surface is depleted in silver, but enriched with structural defects, primarily vacancies, which leads to an increase in surface roughness and in the free energy of the system as a whole. The oxide formed anodically on such a surface is expected to change a number of parameters, primarily related to its structure and electronic structure. In this paper, the electronic parameters of Ag(I) oxide are considered, namely, the type and concentration of its structural defects, as well as the flat-band potential. The work is aimed at the determining of the electronic parameters of Ag(I) oxide anodically formed in 0.1 M KOH on the Ag–Pd system alloys with an atomic fraction of palladium from 0.05 to 0.30 and different levels of structural ordering of the surface. The surface roughness was found to increase by a factor of 3–17 in the process of anodic modification, depending on the alloy initial bulk composition. With the increasing of palladium concentration, the particle sizes of the anodically formed Ag(I) oxide increased slightly, and the particle number decreased. The concentration of donor defects in the structure of the Ag(I) oxide and its flat-band potential increased with increasing both palladium bulk content in the alloy and its structural surface disorder.

The thermodynamic properties of a high-temperature (HT) modification of Ag₈SiSe₆ and solid solutions Ag₈Si_{1 – x}Sn_xSe₆ are studied using the EMF method with the solid Ag⁺-conducting electrolyte Ag₄RbI₅. Based on the EMF measurements of concentration cells such as

(left( {-} right){text{Ag}}left( {text{s}} right)left| {{text{A}}{{{text{g}}}_{{text{4}}}}{text{Rb}}{{{text{I}}}_{{text{5}}}}left( {text{s}} right)} right|left( {{text{Ag}{-}text{in alloy}}} right)left( + right),,,,,,,,,(1))

the linear equations for the temperature dependence of EMF are obtained in the temperature interval of 300–450 К and the partial thermodynamic functions of silver in alloys are calculated. Based on the data on solid-state equilibria in the system Ag–Si–Sn–Se, the equations for the potential-generating reactions responsible for these partial molar functions are obtained and the integral thermodynamic functions of formation and entropy are calculated for the HT-Ag₈SiSe₆ and solid solutions with a composition x = 0.2, 0.4, 0.6, and 0.8.

The effect of the electrolysis mode on internal stresses in zinc, tin–zinc, and nickel electroplates is studied experimentally. The stationary, unipolar galvanostatic pulse, reverse galvanostatic pulse, and potentiostatic pulse electrolysis modes are compared. It was found that the reverse pulse mode provides the maximum stress reduction, viz., by 71% (from 350 to 100 MPa) for nickel electroplates deposited from the Watts electrolyte and the transition from tensile (+25 MPa) to compressive stresses (–5 MPa) for the tin–zinc alloy. The possibility of minimizing the use of organic additives through application of pulse methods is demonstrated. The results highlight the potential of pulse electroplating technologies for improving coating quality under environmental requirements.

Al³⁺-doped vanadium oxide is synthesized by hydrothermal method. The Al : V atomic ratio determined by inductively coupled plasma optical emission spectroscopy is 0.036 : 1, which corresponds to the formula Al_0.072V₂O₅. The layered structure of Al³⁺-doped vanadium oxide is determined by the powder X-ray diffraction analysis. The electrochemical properties of Al³⁺-doped-vanadium-oxide-cathodes are studied in magnesium-containing propylene carbonate electrolyte 1 M Mg(ClO₄)₂ using cyclic voltammetry and galvanostatic charge–discharge. Due to the large interlayer distance of 12.11 Å, the Al³⁺-doped vanadium oxide can reversibly intercalate magnesium ions into its crystal lattice. In addition to the electrochemical characterization of the cathodes, their structural changes after charge–discharge cycling are investigated by X-ray diffraction analysis, and the magnesium content of the cathode in the discharged state is estimated.

The recently proposed express-method for experimental determination of transport characteristics of ion-exchange membranes (Russ. J. Electrochem., 2022, vol. 58, p. 1103) is based on the comparison of measurements of the current transients in an electrode/membrane/electrolyte solution system after applying a large-amplitude potential step with theoretical predictions for this dependence. In previous studies, this approach was used in the study of the transport of bromide anions through a membrane under conditions of its pure diffusional mechanism owing to the electric-field suppression by background ions, for which analytical solutions are available. In this paper, both the solution and the membrane contain only two mobile single-charge ionic species: background cation (counterion) M and electroactive anion (co-ion) X which is subject to the redox-transformation into a neutral product at the electrode/membrane boundary. Then, the non-stationary electrodiffusion transport of these ions inside the membrane as a result of applying a potential step from the equilibrium state of the whole system to the transport-limited current regime is considered. Equilibrium with respect to the exchange of each ion across the membrane/solution boundary is assumed to be retained. It is established that within a short-time interval after the potential step, when the non-stationary diffusion layer thickness is significantly shorter than that of the membrane, the distributions of ion concentrations and electric field strength can be represented as functions of a self-similar variable, х/t^1/2, where x is the spatial coordinate, t is the time. Dependence of these functions on the system parameters are found by numerical integration. The limiting current varies over time according to the Cottrell formula: I ~ t^–1/2. The dependence of the dimensionless current amplitude on the system characteristics is found by numerical calculation. Explicit analytical formulas are derived for the cases of high and low cation concentrations in the membrane as compared with the concentration of immobile charged groups. If the counterion mobility strongly exceeds that of the electroactive component, an approximate analytical formula is proposed that is applicable within a wide range of system parameters. Estimates of the limits of applicability of the expressions obtained are given.

Samples of palladium foil with thickness of 1000 and 40 μm obtained at the initial and final stages of cold rolling, respectively, are studied. The influence of the deformation degree in the formation of the substructure and structure was revealed by the studying of hydrogen permeability processes. Electrochemical studies were carried out by cyclic voltammetry and cathodic–anodic chronoamperometry in 0.1 M H₂SO₄ deaerated solution. Different deformation degrees are found not to affect the substructure of the obtained samples, but manifested themselves in surface processes. At the same time, the rate constants of the atomic hydrogen injection and extraction increased. The values of the hydrogen-permeability diffusion parameters for the studied samples confirm that the movement of atomic hydrogen in the solid phase mainly occurs through the crystallite bodies, while the grain boundaries act as trapping defects.

The performance and durability of proton exchange membrane fuel cells (PEMFCs) are closely related to their operating temperature. Although existing studies have revealed the macroscopic relationship between temperature and performance, the degradation mechanisms of the membrane electrode assembly (MEA) are complex and involve mesoscale structures. These mechanisms are difficult to analyze in detail using conventional experimental methods. In this study, a multiscale numerical model was developed to couple the common degradation mechanisms of PEMFC MEAs, including carbon corrosion, platinum (Pt) oxidation, dissolution, redeposition, and changes in structural characteristics. The model was used to investigate the effects of different operating temperatures on MEA degradation. The results show that operating temperature significantly affects the relative humidity distribution, carbon corrosion rate, Pt dissolution rate, and degradation of the proton exchange membrane (PEM) in PEMFCs. Specifically, at low temperatures (45°C), higher relative humidity leads to more severe carbon corrosion, while at high temperatures (85°C), the dissolution rate of Pt and the degradation rate of PEM increase. For every 1°C increase in temperature, the average Pt dissolution rate increases by 5.8 × 10⁻⁸ g/m². Moreover, the membrane degradation exhibits a higher degradation rate as the temperature decreases at temperatures below 90°C, with the degradation rate at 45°C being faster than at 85°C.This study provides a theoretical basis for optimizing the operating temperature of PEMFCs to enhance their performance and durability and offers new insights into the relationship between temperature and degradation mechanisms.

Using COMSOL Multiphysics and a modified 3D model of a PEM fuel cell, a computational optimization of a hydrogen-air proton exchange membrane fuel cell is carried out. The influence of the bipolar plate profile (widths of gas channels and current-carrying ribs) on the fuel cell’s polarization curve is investigated. The model is validated using the authors’ own experimental data and shows good agreement between the simulation and experimental results. The fuel cell operational conditions and the parameters of its components are recommended, enabling the achievement of the high specific performance of the power system at current densities above 1 A/cm².