Volume 60, Nº 4 (2024)

The kinetic features of the process of electrodeposition of a wear- and corrosion-resistant composite electrochemical coating (CEC) nickel-cobalt-aluminum oxide from a colloidal chloride electrolyte are studied. The use of potentiodynamic, chronopotentiometric and temperature-kinetic methods, as well as the use of the calculated values of the temperature coefficient of the reaction rate and the diffusion coefficients of nickel ions, made it possible to establish the mechanism of CEC electrodeposition. An analysis of the research data on the kinetic features of CEC electrodeposition showed that the nature of the slow stage of the studied process is due to the electrophoretic transfer of electroactive particles to the cathode and the stage of overgrowth of dispersed particles adsorbed on the cathode surface with electrodeposited metals, proceeding at comparable rates.

A set of computational and experimental methods was used to study side chemical interactions in the lithium-ion cathode half-cell based on LiMn₂O₄ (LMO) in the temperature range of 25–60°C. It was shown that the degradation of LMO electrode starts upon contact of LiMn₂O₄ particles with a standard (basic) electrolyte solution (1 m LiPF₆ in a mixture of ethylene carbonate and dimethyl carbonate (1:1, wt.)). Significant increase in the resistance of the interface layer with time accompanies this process. It has been established that the cause of the degradation without current applying is the relative thermodynamic instability of LiMn₂O₄ and the lithium salt LiPF₆. The equilibrium interaction products were determined, and the mechanism of the critical influence of temperature on the degradation of LIB with lithium-manganese spinel was refined. A model was proposed for the formation of a primary surface layer at the LiMn₂O₄/electrolyte interface, which explains the distinctive features of the degradation processes in this system.

A comparative study of the electrochemical behavior of various forms of the antitumor antibiotic doxorubicin (DOX) - free and encapsulated in micelle-like nanoparticles of the biocompatible amphiphilic copolymer N-vinylpyrrolidone (VP) — methacrylic acid — triethylene glycol dimethacrylate (TEGDM) — in aqueous neutral buffer solutions on a glassy carbon electrode was carried out. The hydrodynamic radii of the R_h copolymer and DOX polymer nanostructures were determined using the dynamic light scattering method. It was demonstrated using cyclic and square wave voltammetry the presence of two main redox transitions for both forms of DOX at pH 7.24: irreversible oxidation/reduction in the potential range from 0.2 to 0.6 V and reversible reduction/reoxidation — from −0.4 to −0.7 V (saturated Ag/AgCl reference electrode), and their redox potentials were determined. The difference in the potentials of the corresponding peaks of both redox transitions does not exceed several tens (20–30) mV, while the oxidation of the encapsulated form is easier than the free one, and reduction is somewhat more difficult. Analysis of the dependence of the reduction current of both forms of DOX on the rate of potential sweep shows that electron transfer to a molecule of free DOX is largely determined by the rate of accumulation of the reagent in the adsorption layer, and the encapsulated form is characterized by mixed adsorption-diffusion control. Based on voltammetric data and the results of quantum chemical modeling, it was concluded that a hydrogen bond is formed between the oxygen-containing groups of the monomer units of the copolymer and the H-atoms OH and NH₂ groups of DOX. The bond energies in the structures considered are calculated and it is shown that their values are close to classical ones if the carbonyl group of the lactam ring of VP in the encapsulating polymer is an electron donor, and the hydrogens OH and NH₂ groups of DOX are acceptors. At the same time, the bonds formed with the participation of the oxygen atom of the ester group of the TEGDM unit are extremely weak.