Vol 60, No 10 (2024): Спецвыпуск “Электрохимия-2023”, часть 1

Zinc-nickel coatings based on the zinc-enriched gamma phase are characterized by maximum corrosion resistance and are the basis for the production of electrocatalytically highly active nanoporous nickel by selective dissolution. Electrodeposition of Zn–Ni alloys is the most common method of their preparation and proceeds by the mechanism of anomalous co-deposition, in which the rate of an electropositive component (nickel) deposition is lower than of an electronegative component (zinc). To obtain coatings with certain morphology, chemical and phase composition, it is necessary to know the kinetic regularities of cathodic deposition of Zn–Ni alloy at the stage of heterogeneous nucleation, the determination of which is the purpose of this work. The kinetics of the process was studied in non-stirred ammonium chloride electrolytes using the methods of cyclic voltammetry and chronoamperometry. The mechanism of heterogeneous nucleation during electrodeposition of zinc and nickel was determined within the framework of the approach by Palomar-Pardave et al., taking into account the contributions of the hydrogen reduction reaction and charging of the double electric layer to the total cathodic current, and for zinc-nickel coatings using the model by Scharifker et al. for electrodeposition of a binary alloy, additionally modified taking into account the experimentally determined dependence the composition of zinc-nickel coatings on time at the nucleation stage of the cathodic deposit formation. Using the method of X-ray spectral analysis, the anomalous nature of deposition of Zn–Ni coatings was confirmed, the ratio of atomic fractions of Ni/Zn in which turned out to be lower than the ratio of concentrations of Ni²⁺/Zn²⁺ ions in the electrolyte. It was found that both during electrodeposition of zinc and nickel from their individual solutions and during their anomalous co-deposition, the nucleation rate constant increases with the cathodic potential, but on average does not exceed 3 s^–1, which indicates predominantly progressive nucleation. The growth of a new phase, regardless of the chemical composition of the resulting deposit, is limited by the 3D-diffusion of zinc and nickel ions to the electrode surface. The density of nucleation active sites is weakly dependent on the deposition potential, decreasing during the transition from zinc to nickel and zinc-nickel alloys. The contribution of the side reaction of hydrogen reduction as expected is maximum in the case of nickel electrocrystallization. It decreases during the transition to alloys and zinc, increasing with the cathodic potential, which is consistent with the current efficiency of the electrodeposition process.

The electrochemical polymerization of 3,4-ethylenedioxythiophene in the presence of a water-soluble Na⁺-containing fullerene with hydroxyl groups was studied. Spectral methods for monitoring the progress of electrosynthesis have shown that during the polymerization of 3,4-ethylenedioxythiophene, fullerenol is included in the film composition, regardless of the fullerenol concentrations used in the synthesis. The electronic structure, morphology, spectroelectrochemical, electrochemical properties and near-IR photoconductivity of composite films of poly-3,4-ethylenedioxythiophene with fullerenol were studied for the first time. A mechanism of photoconductivity has been proposed, related to the fact that during photoexcitation of the composite, electron transfer from the polaron (bipolaron) state of poly-3,4-ethylenedioxythiophene to the LUMO level of fullerenol increases the concentration of photogenerated charge carriers.