Russian Journal of Electrochemistry最新文献

The physical and chemical properties of the (0.76LiClO₄–0.24KClO₄)_eut eutectic system and its heterogeneous composites with nanosized aluminum oxide powder are investigated by Raman spectroscopy, differential scanning calorimetry, and electrochemical impedance spectroscopy at different temperatures, phase states, and Al₂O₃ concentrations. The Al₂O₃ addition increased the ionic conductivity and lowered the activation energy. It is shown by the Raman spectroscopy that the addition of aluminum oxide leads to the formation of an amorphous phase, due to the lithium perchlorate crystalline phase destruction.

We have developed an electrochemical sensor for the rapid detection of nitrofurazone (NFZ) in aquaculture seawater, utilizing a glassy carbon electrode (GCE) modified with Au nanoparticles (AuNPs). Compared to the unmodified electrode, the modified electrode exhibited higher electrocatalytic activity than the GCE and could be used efficiently for the detection of NFZ. It was found that the AuNPs modified electrode exhibited a higher specific surface area, as determined by scanning electron microscopy characterization. The effects of various parameters, including the number of electrodeposition cycles for modified electrode preparation and the pH of the electrolyte for NFZ detection were optimized. Under optimized experimental conditions, the peak current and concentration of NFZ exhibited a linear relationship in the range of 3 to 100 μM when analyzed using square wave voltammetry (SWV), with a limit of detection of 0.24 μM. The proposed sensor was successfully utilized for the detection of NFZ in aquaculture seawater. The spiked recoveries ranged from 96.35 to 107% (RSD < 4.13%), indicating that the method demonstrates satisfactory accuracy and performance for detecting NFZ in real seawater.

Monitoring of heavy metal ions Pb²⁺ is a meaningful topic due to their high toxicity and serious damage on human health and ecological environment. In this paper, iron doped polymeric dopamine micro/nanospheres modified glassy carbon electrodes (Fe@PDA/GCE) were prepared and for the first time applied in heavy metal Pb²⁺ detection. Differential pulse voltammetry (DPV) method was used for the quantitative determination of lead. The results showed that Fe@PDA/GCE exhibited excellent detection performance for Pb²⁺, with a wide concentration response linear range of 0.05–110 μM (10.4–22 792 μg L^–1) and a low detection limit of 2.9 nM (0.6 μg L^–1) (S/N = 3). This performance is comparable to or even superior to the reported electrochemical platforms for Pb²⁺ determination. We attributed the improvement to the enrichment effect and charge transfer ability of Fe@PDA toward Pb²⁺. Fe@PDA/GCE also shared many advantages such as good reproducibility, anti-interference capability and low cost, allowing actual samples detection with recovery 95.9–104.0% and RSD 1.8–2.2%. Therefore, the Fe@PDA/GCE electrochemical sensors have good application prospect in water environment monitoring.

A single-unit of rechargeable power source, the hydrogen–vanadium battery (Pt‒C)H₂|Nafion|({text{VO}}_{2}^{ + })(C), is studied for various sulfuric-acid contents in the vanadium electrolyte (catholyte) over the 3–6 M range of the total amount of sulfuric-acid residues and a total concentration of vanadium compounds of 1 M. For this composition range, the dependences of the cell voltage and the half-cell potentials on the vanadyl-to-vanadate ratio in the electrolyte is determined for the open-circuit regime while the voltage and potentials shifts are measured for the current passing through the cell in both directions. The contributions to the cell voltage from both half-cell potentials as well as their polarizations are found separately by means of an external reference electrode branched to the vanadium flow electrode via a film-shaped Luggin capillary. The vanadium electrolyte conductivity is measured in the course of charge–discharge cycling and its dependence on the vanadyl-to-vanadate ratio for the series of electrolyte compositions is determined. For the high-current region, the cell maximal specific discharge power is found to decrease from 0.68 to 0.45 W/cm² with increase of the catholyte acidity, as a consequence of the concentration polarizations of both the positive and the negative half-cells, with a much higher relative contribution from the latter one. For the low-current region (±0.25 A/cm²), the current–voltage curves of both half-cells are linear. With growing electrolyte acidity, the slope (i.e., the polarization resistance) increased in the hydrogen half-cell; decreased, in the vanadium one. As a result, their sum (i.e., the total cell resistance) increased from 0.34 to 0.39 Ω cm² over the studied acidity range.

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.