Vol 55, No 11 (2019)

The data on polymeric complexes of nickel with salen-type Schiff bases containing electron-withdrawing nitro groups in ligand’s aromatic fragments are acquired by an in situ technique based on collecting electron paramagnetic resonance spectra simultaneously with absorption spectra in the UV, visible, and near IR regions in the course of oxidation-reduction of a polymer film on the surface of an optically transparent electrode under conditions of cyclic voltammetry. Based on the combined analysis of spectroscopic and electrochemical data, it is shown that as the potential of the polymer-modified electrode shifts in the positive region, the different types of charge carriers successively appear in the system (phenoxyl radical cations, radical pairs, and dications). The results obtained suggest that the positive charge can be delocalized either between aromatic rings in monomer fragments or between fragments of neighboring polymer chains.

The changes in indicator-electrode potential and (quasi)equilibrium solution composition in the anodic compartment of a model electrolyzer initially filled with aqueous electrolyte containing 0.5 M concentration of bromide anions are calculated under the condition that pH 2 is maintained constant in this compartment. The theoretical analysis is carried out for three different hypotheses concerning the possible depth of electrolysis and the nature of processes involved: (1) no bromine compounds with positive degree of oxidation are formed; (2) bromine compounds with the degree of oxidation not higher than +1 are formed; (3) the process can involve the formation of both bromate ions and bromine compounds with the lower degrees of oxidation (\({\text{Br}}_{{\text{3}}}^{ - },\)\({\text{Br}}_{{\text{5}}}^{ - },\) Br₂, BrO^–, HBrO) in solution as well as the liquid phase of bromine \(\left( {{\text{Br}}_{{\text{2}}}^{{{\text{liq}}}}} \right).\) All electrochemical and chemical reactions involving bromine-containing species taken into account within the framework of hypotheses of system evolution 1, 2, and 3 are assumed to be (quasi)equilibrium, and the electric current through the cell separator is assumed to be provided by supporting electrolyte ions. Methods are proposed for experimental determination of the version of evolution of Br-containing anolyte during electrolysis.

Initial stages of aniline galvanostatic polymerization at platinum electrode in aqueous solutions of poly-2-acrylamido-2-methyl-1-propansulfonic acid and polystyrenesulfonic acid are studied by the method of Raman spectroelectrochemistry. A laser with wavelength of 532 nm excited the Raman scattering. The very presence of intermolecular associates able to luminescence in the polyacid solution (in the case of polystyrenesulfonic acid) was shown to result in the Raman-spectrometer photodetector overload if normal incidence of laser beam at the electrode (the angle 0°) was used. The Raman-spectrometer photodetector overload can be avoided by the varying of the incidence angle over the 0°–20° range, even without using other techniques (leading to a decrease in the reliability of the studied Raman band registration, such as the lowering of the integration time, intensity or energy of the excitation). Comparative study of aniline electropolymerization in the presence of poly-2-acrylamido-2-methyl-1-propansulfonic acid, polystyrenesulfonic acid, and HCl revealed some characteristic bands in the Raman spectra of the polyaniline–polyacid complexes in the Raman frequency range from 2000 to 3000 сm^–1; these bands relate to the polyacid’s backbone and are absent in the Raman spectra of the polyaniline–HCl film. The dynamics of changes in the contribution to the integral Raman spectrum of the band of radical-cations (1330–1350 сm^–1) characterizing the highly conductive emeraldine form of polyaniline was compared for the polymerization media. In the course of the electrosynthesis it was found, that the accumulation rate of these species in the film decreased in the series poly-2-acrylamido-2-methyl-1-propansulfonic acid > HCl > polystyrenesulfonic acid.

A mixed catalyst based on platinum and nickel oxide was obtained as a result of the synthesis and subsequent alkaline hydrolysis of thin polymer films of poly[Ni(Salen)] with platinum nanoparticles previously electrodeposited in its pores. The efficiency of catalyst operation was tested in oxygen electroreduction in an alkaline medium. A distinction of the catalyst is its high activity and tolerance to methanol impurities compared with commercial analogs.

The pyrrole electrochemical polymerization in the presence of salt and acid forms of flexible-chain sulfoacid polyelectrolytes is studied comparatively. Electrochemical and spectral methods of the synthesis control showed the polypyrrole electrosynthesis in the presence of polyelectrolytes to occur more rapidly and with lesser monomer concentration than in inorganic-anion-containing aqueous solutions. With the using of the polyelectrolytes’ Н⁺-form, the pyrrole polymerization rate was shown to exceed that in the Na⁺-salt solutions. Electrochemical, spectroelectrochemical properties in visible and near-IR spectral regions, and morphology of the obtained hybrid polypyrrole films were also studied.

Experimental results are presented on the electrochemical behavior of BPA at a gold | 0.1 M sodium perchlorate electrode. During the cycling of the electrode potential an adherent thin polymer layer was formed on the electrode. The film buildup process was followed in situ with an electrochemical quartz crystal microbalance (EQCM) and ex situ by electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) was used for the study of the structure/morphology of the deposited polymer coating. The results imply that polymerization and degradation of the BPA monomer may occur simultaneously during its electrochemical oxidation.

Fe₂O₃ short nanorods, nanorods and nanowires were prepared by a facile hydrothermal method by using different flexible ligands (oxalic acid, succinic acid, adipic acid) as templates to adjust the L/D (length/diameter) ratios of the one-dimensional (1D) Fe₂O₃–nanostructures for the first time. The growth mechanism of Fe₂O₃ nanorods and nanowires were proposed. Their potential applications as anodes for lithium ion batteries were investigated by electrochemical analysis. This novel straightforward strategy to fabricate 1D metal oxide with different L/D ratios may provide a promising method to make advanced Fe₂O₃-based nanostructures for Li-ion battery applications.