Vol 59, No 11 (2023)

The electrochemical oxidation-reduction of polymeric nickel(II) complex of N,N′-bis(3-methoxysalicylidene)ethylenediamine was investigated in acetonitrile and 1,2-dichloroethane-based solutions by a combination of in situ conductance measurements, quartz crystal microbalance, and cyclic voltammetry. The type of electrolyte solution is shown to have a pronounced effect on the variations in the electrical conductance and ion and solvent transfer at the polymer/solution interface when the polymer is electrochemically switched between various oxidation states. 

It was investigated the preparation in an undivided cell of Pd-Cu and Pd-Au bimetallic nanoparticles (NPs) by methylviologen (MV2+) -mediated electrochemical reduction of equimolar amounts of Cu(II), Pd(II) and Au(I) in the presence of poly(N-vinylpyrrolidone) (PVP) and nanocellulose (NC) at controlled potential of generating MV  cation radical in aqueous medium at room temperature. Electrosyntheses were performed by sequential or joint reduction of metal ions by passing a theoretical amount of electricity. When Pd(II) ions are added to CuNPs, as well as Au(I) ions are added to PdNPs, a galvanic replacement process is observed, namely oxidation of Cu0 by Pd(II) and Pd0 Au(I) ions. The results of complete reduction are nanocomposites of mainly spherical MNPs, dispersed in the solution bulk, and stabilized by PVP on the surface of the NC. In the sequential synthesis of CuNPs and then PdNPs, the nanocomposite is presented as Cu2O nanoroses coated with fine PdNPs. Nanocomposites of Pd NPs with Cu2O or Au shows the mainly formation of spherical particles with the size of 4 to 50 nm depending on the production method. X-ray powder diffraction (XRD) data of nanocomposites confirm the formation of a mixture of PdNPs (0.8 - 10 nm) with large gold crystallites (until 24 nm), as well as the oxidation of CuNPs to cuprite (Cu2O). The size of metal crystallites and copper oxide varies in the range from 0.8 to 24 nm. In the test reaction of p-nitrophenol reduction with sodium borohydride in aqueous medium, all tested nanocomposites showed time-increasing catalytic activity. When Cu is added to Pd, the catalytic reduction reaction is maintained, while the addition of Au to Pd decreases the catalytic activity of PdNPs by an order of magnitude. 

Electrocatalytic phosphorylation of terminal acetylenes with diarylphosphine oxides in the presence of a bpyCo(BF4)2 catalyst was first implemented under electro-reducing conditions with yields up to 75%. The nature of the solvent and the background electrolyte, the presence of oxygen and water determine the formation of certain products of phosphorylation of acetylenes. The variation of the above factors was carried out in order to select optimal conditions for electrosynthesis to achieve stereo and chemoselectivity. Voltammetric studies were used to establish the redox properties of participants to optimize processes involving a cobalt catalyst. 

The article is devoted to the creation of a new generation element base for aqueous alkaline electrolyzers with anion-exchange membranes. As a result of the research, two new membranes and various types of electrodes have been proposed, which significantly increase the purity of the generated electrolysis gases and the operating outlet pressure directly at the outlet of the electrolysis module while maintaining low values of specific energy consumption. In this case, the electrolysis module consists entirely of electrode-membrane blocks. Their composition includes components tested in industrial alkaline electrolysis, which distinguishes them from known analogues in chemical resistance. Various types of catalysts that can be used as part of membrane-electrode blocks are considered separately. The results of express tests of electrodes made of stainless steel 12X18H10T are presented, the oxidation process of chromium, which is part of the alloy, is shown, which leads to a decrease in its corrosion resistance. When testing electrodes based on a steel mesh coated with a protective layer of nickel, extensive pitting corrosion was detected on the anode during its operation at high current densities. As an alternative, electrodes made of nickel mesh are proposed. These samples showed excellent corrosion resistance and high adhesion to electrodeposited catalysts. Catalytic coatings consisting of nickel or nickel-cobalt powder with additionally chemically precipitated phosphorus were investigated as catalysts.