Russian Journal of Electrochemistry最新文献

Here, we study processes of Li insertion into Ni₃Si₂O₅(OH)₄ phyllosilicate nanoscrolls in the 0.01–4.5 V voltage range aiming to establish electrochemical reactions and reveal the reasons of electrode degradation. The first cathodic polarization initiates the phyllosilicate crystal structure destruction with formation of NiO, and probably SiO₂ and Si, capable of reversible interaction with lithium. As cycling proceeds, the electrode capacity decreases, and the cathodic/anodic processes voltages change. The main cause of the degradation of nickel phyllosilicate-based electrodes is a decrease in the electrochemical activity of nickel oxide and its gradual transition first to cubic Li_xNi_2–xO₂ and then to hexagonal LiNiO₂.

Anthropogenic activities are the major cause of emerging contaminants in the environment. The endocrine-disrupting compounds (EDCs), as part of the micropollutants in the aquatic environment, are compromising the quality of water, impairing the development of humans and animals. Most of EDCs are responsive to bioaccumulation and bioconcentration in the environment. Wastewater treatment plants are reported as the prime source of these compounds in aquatic environments, as they are not designed to specifically remove these steroid compounds. Common methods such as chromatography, mass spectroscopy, and others are employed to quantify the level of different kinds of EDCs, although they suffer from a few drawbacks. In this work, we appraise alternative methods of sensing systems for EDC detection. The advantages of these techniques are lost cost, they use low sample volume, high sensitivity, and selectivity. This review summarizes each of some of the methods used to detect EDCs and their respective limits of detection (LOD). The sensitivity of each technique towards the EDC of interest varied according to the type of EDCs measured, the type of electrochemical probe and electrode, substrates, and the type of nanomaterial.

The composites based on the few-layer graphene structures decorated with Pt nanoparticles are synthesized by the low-voltage and plasma-assisted electrochemical dispersion of platinum electrodes. A comparison study of their catalytic activity toward oxygen reduction reaction is performed. It is shown that the synthesis of electrocatalysts for the oxygen reduction reaction by the electrochemical sputtering of platinum under the action of anodic-cathodic electrolytic plasma has potential.

The need for effective treatment techniques stems from growing environmental concerns over refinery wastewater discharge. In order to improve the treatment of refinery wastewater (RWW), this study investigates the construction of hybrid electrocoagulation–electro-oxidation (EC–EO) systems that combine the advantages of both processes with new design of Electro oxidation reactor. The suggested approach uses electro-oxidation to target refractory substances that are generally intractable by conventional means, while electrocoagulation was utilized to efficiently eliminate organic contaminants and suspended particles. The EC–EO hybrid approach offers a promising solution for sustainable refinery wastewater management, offering a balance between operational efficiency and environmental compliance. Analyses using modeling and simulation techniques with response surface method (RSM) by Minitab software were used to optimize working parameters, such as, Fenton reagent, pH and electrolysis time. Experimental validation was carried out using real refinery wastewater samples; demonstrating significant reductions in organic pollutants with high efficiency 99.5% under ideal conditions of 50-ppm hydrogen peroxide, 6 ppm iron Sulphate, 3 pH, and 30 min of electrolysis time.

Protective coatings based on cobalt-manganese spinel for solid-oxide fuel cell (SOFC) interconnects made of stainless steel are synthesized by nonstationary electrolysis. According to X-ray diffraction data, the main phase of these coatings is Co₂MnO₄. The evolution of the microstructure of coatings is studied in operando in a SOFC cathode chamber. It is found that during the oxidation process, chromium and iron diffuse from the substrate into the coating, are oxidized, so that, after the service-life tests, the coating itself becomes a mixture of Co₂MnO₄, Fe₃O₄, and Cr₂O₃ oxides. Studying the dependence of the specific contact resistance of the interconnect/cathode junction on the time spent under a current load of 0.5 A cm^–2 in the model conditions of a SOFC cathode chamber in a measuring assembly for 1000 h at 850°C has shown that the resistance is about 35 mΩ cm^–2.

This study is directed to the electrochemical synthesis, characterization, and non-enzymatic cholesterol sensor application of Cr₂O₃/reduced graphene oxide (rGO) nanostructures (Cr₂O₃/rGO) on pencil graphite electrodes (PGE). For this purpose, Cr₂O₃/rGO nanostructures were synthesized using a one-pot electrochemical deposition technique from the electrolyte medium containing Cr³⁺ ions and graphene oxide (GO). Different methods, such as XPS, Raman, SEM, and EDS, were used to characterize the prepared nanostructures. The electrode material, whose structural and morphological characterization was completed, was used for the non-enzymatic determination of cholesterol. The detection limit was determined as 0.0048 mM in the linear concentration range of 0.05–5 mM. Both voltammetric and amperometric studies showed that the synthesized Cr₂O₃/reduced graphene oxide nanostructures can be used as cholesterol sensors.

A simple synthesis using Allium schoenoprasum plant extract as a reducing agent has been done for the preparation of copper oxide nanoparticles (CuO NPs). Firstly, copper ions are reduced to copper atoms by plant extract, and then, they could be changed to CuO during calcination. Some techniques such as X-ray diffraction (XRD), UV–visible (UV–Vis), Fourier-transform infrared (FT-IR), scanning electron microscopy (SEM), and electrochemical methods have been applied to the evaluation of the CuO NPs formation. These results showed that CuO NPs were synthesized with uniform spherical morphology and crystallite size was about 41 nm. The electrochemical studies have been performed using a modified carbon paste electrode with CuO (CPE/CuO). This modified electrode depicted electrocatalytic activity to oxidation of glucose without enzyme. The linear dynamic range of this modified electrode and the limit of detection (LOD) were 1–120 and 0.8 μmol L^–1 (3δ), respectively. Simplicity, low cost, and ease of preparation are the prominent features of this sensor. Also, the stability, reproducibility, and repeatability of this modified electrode are acceptable.

In order to expand the range of electrolytes for low-temperature double-layer supercapacitors, the possibility of using a 2.5 M PCl₅ solution in anhydrous hydrogen fluoride as an electrolyte combined with electrodes made of activated carbon cloth CH-900-20 was investigated. Upon the temperature decrease from +20 to –65°C, the specific capacitance of the activated carbon cloth in this electrolyte was shown to decrease linearly from 225 to 200 F/g. The replacing of PCl₅ with P₂O₅ resulted in the appearance of water in the electrolyte, due to the latter’s interaction with HF, the appearance of a noticeable pseudocapacitance at positive temperatures, and a decrease in the capacitance at the temperature of ‒65°C.

This article presents results of a study of titanium bipolar plates of fuel cells with proton-exchange membrane with functional coatings based on chromium nitride, carbide and carbonitride, obtained by magnetron sputtering of a chromium target in argon plasma with different nitrogen and propane contents. The microstructure and morphology of pure CrN and CrС films on titanium and composite coatings of chromium carbonitride Cr_хN_yС_z were studied. The protective chromium carbide films obtained by adding propane to argon plasma were shown to exhibit increased contact surface resistance at the gas diffusion electrode/bipolar plate interface (CrС: ICR = 119.4 mΩ cm²). However, for chromium carbonitride coatings this quantity is only 1.9 mΩ cm², which is lower than for pure CrС films and significantly lower than for uncoated titanium (Ti: ICR = 38.9 mΩ cm²). This is an important indicator for using such bipolar plates in fuel cell power plants with high specific characteristics. Corrosion measurements performed using conventional techniques showed that the corrosion current for chromium carbonitride was less than 1 μA/cm², which is better than for uncoated titanium and pure CrN and CrC films.

Substitutional solid solutions based on polyantimonic acid H₂Sb_{2 – x}Nb_xO₆·nH₂O (left( {n geqslant 1} right)) and their composites H₂Sb_{2 – x}Nb_xO₆·0.5yNb₂O₅ nH₂O (left( {n geqslant 1} right)) the promising components for low-temperature fuel cell membranes, are synthesized by coprecipitation. The Nb⁵⁺ ions which have the similar radius and electronegativity as the Sb⁵⁺ ions are used as the dopant. The elemental composition of samples (the Nb⁵⁺/Sb⁵⁺ ratio) is refined using X-ray fluorescence analysis. The solid solution composition, limiting as regards the dopant concentration, i.e., H₂Sb_1.6Nb_0.4O₆·nH₂O ions increase the lattice parameter for the samples with 0 < x ≤ 0.4. By analyzing the dielectric properties and the protonic conductivity of samples at a temperature of 25°C and a relative humidity of 58%, it is shown that the sample with x = 0.6 has the best transport properties. Its protonic conductivity is 11.5 × 10^–3 S/m. The protonic conductivity of polyantimonic acid and the solid solution with the limiting dopant concentration (x = 0.4) is 7.2 × 10^–3 and 5.0 × 10^–3 S/m, respectively. A possible mechanism of protonic conduction is proposed, namely, the correlated proton transport along a certain chain of hydrogen bonds through channels in the pyrochlore structure and through the intergranular space that contains adsorbed water and niobic acid.