Russian Journal of Electrochemistry最新文献

Sodium-ion polymer electrolytes based on polyvinyl alcohol (PVA) and sodium thiocyanate (NaSCN) are studied as the promising energy storage materials. Attention is focused on the effect of the NaSCN concentration on the ionic conductivity, phase transitions, and structural changes in this system in the temperature interval from 293 to 373 K. The results of differential thermal analysis, spectroscopy, and electrochemical impedance spectroscopy show that the system with 20 wt % NaSCN has the considerably higher ionic conductivity. The ion transport is considerably improved due to the break of hydrogen bonds in the polymer matrix and an increase in the amorphous phase fraction in the polymer. Quantum chemical calculations reveal the effect of solvation and hydration on the properties of ions in the system, in particular, the preferential interaction of sodium cations with OH groups in PVA.

To gain a more thorough understanding of the conductive mechanism of Sc-doped CaZrO₃ electrolyte, solid electrolyte specimens of CaZr_{1 − x}Sc_xO_{3 − δ} (with x values of 0.06, 0.12, 0.18, and 0.24, hereinafter referred to as CZS) were meticulously prepared using a high-temperature solid-state method. The phase structure of the electrolyte was thoroughly analyzed using X-ray diffraction (XRD). The electrical conductivity of the CZS electrolyte was rigorously tested within a temperature range of 573 to 1473 K, both in oxygen-rich and hydrogen-rich atmospheres, employing the two-terminal AC impedance spectroscopy method. Additionally, the H/D isotope effect of the electrolyte at various temperatures in both H₂ and D₂ atmospheres was meticulously examined through AC impedance spectroscopy. The electromotive force (EMF) of the electrolyte was precisely measured by a high-impedance ohmmeter at temperatures ranging from 573 to 1273 K. Furthermore, based on crystal defect chemistry theory, estimates were made for the partial conductivities of the conducting species, the active doping concentration of Sc, and the standard Gibbs free energy changes associated with the production of interstitial protons through the dissolution of water and hydrogen within the CZS electrolyte. The results clearly indicated that protons serve as the primary charge carrier in both oxygen-rich and hydrogen-rich atmospheres at temperatures below 1073 K. However, as temperatures rise above 1073 K, the situation changes: in hydrogen-rich atmospheres, oxygen ion vacancies emerge as the dominant charge carrier, whereas in oxygen-rich atmospheres, electron holes take precedence. Notably, CZY stands out as a promising candidate for a proton-conducting electrolyte material, suitable for high-temperature hydrogen sensors.

In this work, we demonstrated the use of nano-porous glassy carbon electrode (NPGCE) decorated with nickel oxide nanoparticles (NiO_x/NPGCE) as a highly sensitive and straightforward platform for the non-enzymatic electrochemical detection of ethanol. The glassy carbon electrode (GCE) was pretreated by applying constant oxidizing and reducing potentials, respectively, to create a porous carbon nanostructure with an increased surface area. This pretreatment enhanced the loading of NiO_x and its activity towards ethanol electrooxidation. The modified electrode showed a wide ethanol concentration range (0.5–5 mM) with excellent linearity (r = 0.987), a very low detection limit of 75 μM, and a sensitivity of 924.3 µAcm^–2µM^–1 using controlled potential amperometry. The surface coverage of NiO_x/NPGCE was estimated to be 4.86 × 10^–11 mol cm^–2. Furthermore, the specificity of the designed sensor was evaluated, and no cross-reactivity was observed. This developed sensitive platform offers a practical strategy for rapid, simple and cost-effective determination of ethanol in clinical and food samples.

The paper examines the potential of using of commercially available thin perfluorinated sulfocationic CTPEM membranes, produced through solution-casting, as a polymer matrix for the manufacture of the electrolytes with lithium and sodium ion conductivity. The study demonstrates that the membranes under examination share similar molecular and supramolecular structure and thermal stability with the known Nafion™ membrane, exhibiting a comparable dependence of physicochemical properties on the cation nature. The main differences between the membrane brands under study and Nafion are in the thermal decomposition processes of the polymer matrix. In terms of the ionic conductivity for sodium cations, thinner CTPEM membranes plasticised with propylene carbonate (5 × 10^–5 S cm^–1 at 70°C) are comparable to the Nafion membrane obtained by extrusion.

The effect of concentration of acetic acid ranged from 0 to 5000 ppm on the processes of initiation and propagation of pitting corrosion in martensitic class stainless steel containing 13% chromium was studied. The research was conducted in CO₂-saturated 5 wt % sodium chloride solutions at various temperatures using electrochemical methods, including cyclic potentiodynamic polarization and pulse potentiostatic technique. The results show that the presence of acetic acid stimulates the formation and development of localized corrosion, increases the metal dissolution rate within the pits, promotes the initiation of a greater number of pits, and facilitates their spread on surface, leading to the expansion due to smaller pits adjacent to the main ones.

The gas permeability of perfluorinated proton-exchange MF-4SK membranes modified with an inert fluoropolymer and zirconium hydrophosphate is studied under operating conditions of a low-temperature hydrogen–air fuel cell; electrochemical methods of cyclic and staircase voltammetry are used. The adequacy of the methods used for the estimating of the hydrogen crossover current is demonstrated using different-thickness membranes. The relationship between the membrane hydrogen permeability and the diffusion permeability for the electrolyte solution is studied for membranes modified with zirconium hydrophosphate. The optimal content of the inert fluoropolymer and zirconium hydrophosphate in the proton-exchange perfluorinated MF-4SK membrane is found; it provided an improvement in the power characteristics of the fuel cell and reduced the hydrogen permeability.

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.