Èlektrohimiâ

The role of iodine, pyridine bases and nitroxyl radical (NR) – 4-AcNH-TEMPO in the electro oxidative transformation of alcohols to carbonyl compounds in a two-phase environment CH₂Cl₂/NaHCO₃ (aq.) has been studied. Using the CV method, it was established that the iodide ion in a weakly alkaline medium (pH 8.6) is oxidized to active forms of iodine (I₂ and I⁺), which are terminal oxidizers for NR capable of being converted into oxoammonium cations (OС), necessary for the oxidation of alcohol. Spectrophotometrically it has been established that pyridine bases are capable of stabilizing I₂ and/or I⁺ in the form of [PyI₂], [PyI]⁺ complexes, the formation of which occurs predominantly in the organic phase. Stabilized forms of iodine effectively convert NR into OC at the interface. The formation of a catalytic complex between OС and a pyridine base occurs in the aqueous phase. CV studies have shown that the rate of NR-mediated alcohol oxidation increases up to 4 times in the presence of a pyridine base, in contrast to the oxidative transformation without a pyridine base. This proves the advantages of the NR/pyridine base catalytic system and the role of the pyridine base as a promoter in the inderect electrooxidation of alcohols.

Ruddlesden–Popper phases are known materials for electrochemical devices such as solid oxide fuel cells/electrolyzers, oxygen separation membranes. Doping A-site with lanthanides with less radii can allow to increase the oxygen mobility, however, this problem is still not studied well. This work aims at studying phase composition and transport properties of Sm doped Nd nickelates sintered by radiation-thermal technique using e-beams. Nd_2–xSm_xNiO_4+δ (x = 0.2, 0.4) were synthesized by modified Pechini technique and sintered by e-beams at 1150–1250°C. The materials obtained were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed isotope exchange of oxygen with C¹⁸O₂ in a flow reactor. The surface oxygen presents in two forms differing in binding energy. According to the temperature-programmed isotope exchange data, the samples possess nonuniformity in the oxygen mobility, and slow diffusion channel is present for the sample with x = 0.4. Such an oxygen diffusion features are probably related to the effect of doping with and radiation-thermal sintering on the structure with formation of admixed phases, hampering the cooperative migration due to emergence of local defects and variation of the surface and grain boundary composition.

Magnetic films for creating magnetic field amplifiers must have a high magnetic permeability. The magnetization characteristics of electrochemically deposited Co–Ni–Fe films of variable composition are investigated using a magnetic force microscope at the nanometer scale. The difference in the magnetization of the samples is explained from the standpoint of the peculiarities of the local domain and crystallographic structure. We suppose that high magnetic permeability in weak magnetic fields is determined by the crystal lattice of the tremag Co₆₀Ni₂₀Fe₂₀, in which the cells fcc and bcc are adjacent to each other.