Russian Journal of Electrochemistry最新文献

The distance between ions and molecules in a solution of an ionic liquid is estimated. It is found that in the concentration range of 1–2 mol/L, the concentration dependence of the electrical conductivity should have a maximum associated with the formation of contact ion pairs in solution. The conductivity of concentrated solutions of 1-butyl-4-methylpyridinium tetrafluoroborate in dimethylformamide is measured in the temperature interval of 10–70°C and the density of these solutions is measured in the temperature interval of 10–60°C. The conductivity and the density are analyzed as a function of the temperature and the concentration. The density of solutions decreases linearly with increasing temperature, and the conductivity passes through a maximum as the concentration increases. As the temperature rises from 10 to 70°C, the concentration c_max that corresponds to the maximum conductivity κ_max increases from 1.258 to 1.825 mol/L. The general form of the conductivity dependences on the temperature and the concentration is obtained using the normalized values of conductivity (κ/κ_max) and concentration (c/c_max). In the κ/κ_max vs. c/c_max coordinates, all the values of normalized conductivity κ/κ_max fit a single curve. It is shown that for the concentration not exceeding ~1.0 mol/L, as the temperature rises, the conductivity κ increases in proportion to the limiting high-frequency conductivity of the solvent κ_∞. Based on the analysis of the κ vs. κ_∞ dependencies, the solvation numbers of ionic-liquid ions in dimethylformamide are shown to decrease from 2.89 to 1.09 as the concentration increases from ~0.1 to ~1.0 mol/L.

Cr and Cr–10Ta coatings were prepared on CrNi3MoVA using electrospark deposition technology and evaluated for their corrosion resistance. The findings indicated that the Cr–10Ta coating demonstrated a 76% decrease in corrosion current density (I_corr) and a 13% increase in corrosion potential (E_corr) compared to the CrNi3MoVA. The Cr coating exhibited a 46% reduction in I_corr and an 8% elevation in E_corr. The charge transfer resistances of the Cr and Cr–10Ta coatings were 1.5 and 6.4 times higher than that of the CrNi3MoVA. The Cr–10Ta coating demonstrated better corrosion resistance than the Cr coating for the latter had a localized corrosion.

A high-entropy compound (Mg_0.2Zn_0.2Ni_0.2Co_0.2Mn_0.2)Nb₂O₆ with the columbite structure and its Ti-substituted (5%) composition were synthesized for the first time. The synthesis was carried out using a modified method of solution combustion followed by high-temperature sintering. The samples were examined using the methods of X-ray diffraction analysis and scanning electron microscopy. The band gap of direct electronic transition ((E_{{text{g}}}^{{{text{dir}}}}) ≈ 2.98–3.05 eV) was calculated using the diffuse reflectance spectra. The solid solutions are characterized by predominantly electronic conductivity. The substitution of titanium cations for niobium cations leads to an increase in the conductivity by 1.2 orders of magnitude in the temperature range of 160 to 750°C.

Operation of a single cell of redox-flow hydrogen–halogenate power source converting the energy of the oxidation reaction of gaseous hydrogen by sodium chlorate in aqueous sulfuric-acid solution into electric energy with the use of a following membrane–electrode assembly: (–) H₂, Pt–C//PEM//NaClO₃, C (+) is studied. A load combined operation regime (which includes stages of potentiostatic and galvanostatic control) is applied, in order to take into account specific features of the chlorate electroreduction half-reaction, i.e., its redox-mediator autocatalytic mechanism (EC-autocat). For aqueous electrolytes containing various sulfuric acid contents, the system parameters determining the power and efficiency of the hydrogen–chlorate power source are found: the Faradaic and energy efficiencies, the average discharge power, and the time necessary for the reaching of the steady-state mode. The hydrogen–chlorate cell under study is found to function most efficiently with 5 M sulfuric-acid electrolyte: it reached the current density 0.25 A/cm² within 1.5 min; it can convert chemical energy into electric one with the 55%-efficiency at the average specific discharge power of 0.23 W/cm².

Capacitive deionization (CDI) is a promising water treatment technology for removing ions from wastewater. The performance of the CDI System mainly depends on the electrode materials. Foam is also one of the significant materials used as a substrate in the preparation of electrodes for CDI. This mini-review covers the fundamentals of CDI, the importance of foam materials for electrode development, foam-based electrode preparation, characterization of methodologies used in foam electrode material, and a comparative tabulation of foam-based electrode performance. This review also discusses the future extent of the research scope of foam materials-based electrodes for CDI.

The polytungstates of rare earth elements M₁₀W₂₂O₈₁ (M = La, Nd, Ce) were synthesized by a solid-phase method; their thermal and electrical-transport properties were studied. The electrical conductivity depending on the temperature and oxygen pressure in the gas phase was measured by the electrochemical impedance method. A combination of three methods (the measurements of electrical conductivity as a function of oxygen pressure, the transport number measurements by the EMF method, and the Tubandt method) showed the studied polytungstates to be oxygen-ion conductors.

In this work, we report a hybrid nanocomposite material composed of reduced graphene oxide/zinc oxide (RGO/ZnO), which has gained attention for photocatalytic wastewater treatment and photoelectrochemical applications. We synthesized RGO/ZnO thin films using modified Hummer’s method and electrochemical deposition. Initially, RGO was coated onto indium tin oxide (ITO) via drop-casting, followed by ZnO electrodeposition. The surface morphology of ZnO was adjusted using additives to enhance porosity and surface area. This RGO/ZnO composite was employed for photodegradation of methylene blue (MB) dye under visible light. The combination of RGO and ZnO improved catalytic properties due to ZnO electronic, optical, and catalytic characteristics, with RGO serving as an excellent electron conductor with high mobility. Characterization of the nanocomposite was conducted using X-ray diffraction, scanning electron microscopy, and UV–Visible diffuse reflectance spectroscopy. The UV–visible spectrum showed significant MB absorption over time, and photocatalytic activity was evaluated by degradation kinetics of MB dye under solar illumination. The RGO/ZnO composite demonstrated 95.4% photodegradation of MB compared to 63.4% by pure ZnO. Additionally, the RGO/ZnO showed an enhanced photocurrent response of 5.5 mA/cm² with lower overpotential. Our work suggests a pathway for the fast synthesis of RGO-semiconductor nanocomposites with superior photocatalytic properties for modern applications.

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 increasing 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 – x}Sm_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 is present in two forms differing in binding energy. According to the temperature-programmed isotope exchange data, the samples exhibit 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 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.

The role of iodine, pyridine bases, and the nitroxyl radical 4-AcNH-TEMPO in the electrooxidative conversion of alcohols into carbonyl compounds in a two-phase medium CH₂Cl₂/NaHCO₃(aq) is studied. Using cyclic voltammetry, it was established that in a weakly alkaline medium (pH 8.6) the iodide ion is oxidized to active forms of iodine (I₂ and I⁺), which are terminal oxidizing agents converting the nitroxyl radical into oxoammonium cations necessary for the oxidation of alcohol. It has been established spectrophotometrically that the pyridine bases are capable of stabilizing I₂ and I⁺ as [PyI₂], [PyI]⁺ complexes whose formation occurs predominantly in the organic phase. The stabilized forms of iodine effectively convert the nitroxyl radical into oxoammonium cations at the electrode interface. The formation of a catalytic complex between the oxoammonium cations and the pyridine base occurs in the aqueous phase. The cyclic-voltammetry studies showed that the rate of nitroxyl-radical-mediated alcohol oxidation increased up to fourfold in the presence of the pyridine base, as compared to the oxidative transformation in the absence of the pyridine base. This proves the advantages of the nitroxyl radical/pyridine base catalytic system and specifies the role of the pyridine base as a promoter in the alcohol indirect electrooxidation.

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