Vol 59, No 9 (2023)

The formation of metal microstructures on metal substrates is theoretically analyzed by the example of local silver electrodeposition using the numerical simulation of interrelated electrochemical and homogeneous chemical reactions.
The distributions of the concentrations of the participants in the reactions and the current density of silver ion reduction are calculated for various concentrations of solution components and interelectrode distances. The degree of localization of metal deposition depends on the distribution of the concentrations of electroactive silver cations and the nonelectroactive complex of this metal near the anode. The conditions for reaching the maximum rate of local silver electrodeposition are determined.

Metal electrodeposition into the nanopores of template of porous anodic alumina type under the conditions of mixed kinetics is studied theoretically using analytical and numerical methods. Two main stages of the process are studied: the non-steady-state formation of diffusion layer in the template pores and much longer process of pore filling with metal. The effect of nonlinearity of the concentration dependence of exchange current density of metal electrodeposition on the current density of the diffusion layer formation and pore filling with metal is studied.

The nanocomposite of resorcinol-formaldehyde xerogel (RF-xerogel) and carbon nanotubes after carbonation at 800 °С was obtained in the form of composite carbon nanopaper (CCNP) with a thickness of 100-300 microns, a density from 0.1 g/cm2 to 0.5 g/cm2 and an electronic conductivity of more than 10 S/cm. According to the low temperature nitrogen adsorption data, the microporous structure of the nanopaper is formed by carbonized RF-xerogel, and the mesoporous structure is formed by the nanotube framework. The specific surface area of the nanopaper calculated by the method of nonlocal density function theory (NLDFT) exceeds 600 m2/g. The main contribution to the specific surface area of CCNP is made by pores with a width of ~ 0.7 nm, therefore, electrodes for a supercapacitor made of such paper are quite effective only in aqueous solutions of H2SO4 and KOH with small sizes of solvated ions. A technique for nanopaper activation with potassium hydroxide has been developed for the use of CCNP with organic electrolytes. The maximum specific surface area (NLDFT method) of activated CCNP reaches 1182 m2/g  with a loss of carbon xerogel mass of ~ 25%. At the same time, the pore surface area of more than 1 nm width increases from 350 m2/g in CCNP to 685 m2/g in activated CCNP. Nanopaper has mechanical strength, pretty cheap and convenient for use in supercapacitors. 

Electrodeposition of silver(I) selenide possessing pronounced thermoelectric properties was carried out from aqueous solutions containing thiocyanate complexes of silver(I) and Se (IV) compounds at pH 4.7. Ag2Se is formed at cathode potentials more negative than –0.9 V (s.h.e.). The obtained coatings were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray phase analysis (XPA), and atomic force microscopy (AFM). The stoichiometry of the cathode deposit is close to Ag2Se. Diffraction studies have shown that an orthorhombic modification of silver(I) selenide is formed under electrodeposition conditions. Cathode deposits have a columnar nanostructure.