Russian Journal of Electrochemistry最新文献

The electrocatalysts based on platinized TiO₂(Ru) oxides with different ruthenium content are studied as the working electrode in solid-state potentiometric sensors for H₂ and CO. Increasing the ruthenium content does not affect the size of platinum particles, but reduces its content in the metallic state. The results of X-ray diffraction, X-ray fluorescence, and scanning electron microscopic studies are presented. The synthesized electrocatalysts are tested as the working-electrode materials in hydrogen and carbon monoxide sensors for the gas concentration in the air flow from 1 to 50 000 ppm. The characteristics of the sensors are shown to depend on the oxide support composition and structure. The electrocatalysts with the rutile structure are recommended for the practical use; the ruthenium content is determined by the range of analyzed CO concentrations.

Hybrid flow chemical power source (Pt–C)H₂|Nafion|VO₂⁺(C) in which the membrane–electrode assembly combines gas-diffusion anode of hydrogen–air fuel cell and cathode of vanadium redox flow battery is studied. Concept of such a hydrogen–vanadium flow battery had been proposed earlier (2013) as an alternative to the vanadium redox flow battery, also designed for large-scale electrical energy storage but its practical implementation has so far been limited to single cells having the active area within several tens of cm². The goal of this work is the establishing of the factors limiting the discharge power density of such hybrid. hydrogen–vanadium flow battery cells which is inferior to both hydrogen–air fuel cell and vanadium redox flow batteries, even though the hydrogen–vanadium flow battery cell represents a combination of their more reversible half-cells. The object of the study is a cell with a 2 × 2 cm membrane–electrode assembly equipped with Luggin capillary on the vanadium electrolyte side. Measurements of the current–voltage characteristics of the entire cell, as well as the polarization characteristics of its half-cells, are performed using a six-electrode scheme of the cell connection with varied vanadium electrolyte circulation rate and different cathode materials (carbon felts, 4.6 or 2.5 mm thick, as well as carbon paper). The contribution of the hydrogen gas diffusion electrode to the total dc resistance of the hydrogen–vanadium flow battery cell is shown being twice that of the flow-through vanadium cathode. A record high discharge power density has been achieved: 0.75 W cm^–2, for the cell based on the commercially available material, Sigracell GFD 2.5 EA-TA carbon felt as the cathode material, without its special surface modification.

Co-NTA nanowires were used as a precursor in synthesizing Co@NC, CoPd@NC-1, and CoPd@NC-2 via active participation of 3-aminopropyltrimethoxysilane (3-APTMS). To regulate the existence of nanostructured silica after calcination at 700°C beneficial in OER, porous CoPd@NC was created using a variable amount of nanostructured silica in an N-doped carbon matrix. XRD, TEM, SEM, and EDX investigated coPd@NC-1 with high silica content and CoPd@NC-2 with relatively less silica content. Nanostructured silica enabled the formation of stabilized bimetallic Nano geometry of cobalt and palladium components, followed by improvement in OER compared to that made without nanostructured silica. The nanostructured silica-derived thin film made from CoPd@NC-1 generated a very high current density at a low potential of 0.79 V vs. RHE with current density of 10 mA cm^–2 together small Tafel slope of 28 mV/decade for (CoPd@NC-1), 44 mV/decade for (CoPd@NC-2) at a catalyst loading of 3.5 mg cm^–2 on the carbon cloth.

A novel electrochemical sensor was designed by using a synthesized anthraquinone azo dye-based glassy carbon electrode was fabricated and used for enhanced selective determination of Dopamine (DA) and serotonin (5-HT) simultaneously at an optimum working potential (0.11 V for DA and 0.27 V for 5-HT). Utilizing spectroscopic techniques like FT-IR, HR-MS, and ¹H-NMR, a synthesized azo dye molecule structure was characterized. Different electrochemical techniques, including cyclic voltammetry (CV) and differential pulse voltammetry (DPV), were employed to study the electrochemical sensing abilities of the modified working electrode. The DA and 5-HT linear response ranges between current intensities and concentration were found to be 0.001–0.055 and 0.01–1.15 µM and the lower limit of detection (LOD) was 1.9 and 4.16 nM respectively. Further demonstrating the constructed electrochemical sensor’s practical application were tests of reproducibility, stability, and real sample analysis with excellent recovery.

This work focuses on optimizing the structure of CZTS/ZnO thin film heterostructure to increase the photocatalytic property in visible region. The CZTS thin films were fabricated on glass substrates by dip coating method. Then ZnO thin films were grown on the CZTS layer by chemical bath deposition method at low temperature. Secondary phase formation in CZTS thin films with four different molar ratios of Cu : Zn : Sn : S of 1.4 : 1 : 1 : 8, 1.6 :1 : 1 : 8, 1.8 : 1 : 1 : 8 and 2 : 1 : 1 : 8 were investigated. In order to improve the crystallinity, CZTS thin films were annealed at 450°C in N₂ atmosphere without sulfurization. The results showed that the CZTS thin film exhibited phase pure kesterite structure and good crystallinity at the ratio of 1.8 : 1 : 1 : 8 (Cu : Zn : Sn : S), absence of secondary phase formation in CZTS thin film was important to reduce charge recombination. For ZnO/CZTS thin film heterostructure, in order to reduce the lattice mismatch of ZnO and CZTS, some seed layers were coated onto the surface of CZTS thin film to support the growth of ZnO thin film in these heterostructures. Raman spectra, XRD patterns and SEM images data confirm that the ZnO/CZTS thin film heterostructures with two seed layers achieved optimal crystal structure and film morphology. UV-Vis spectra of heterostructures suggested that photocatalytic activity is extended toward visible-light region from 380 to 800 nm. Finally, the photocatalytic performance was examined through degradation of methylene blue (MB) and apparent rate constant (k_app), namely: the highest degradation of MB was obtained with ZC2 labelled heterostructure samples up to 92.8% in 150 min; k_app of this sample is much larger (as high as 6.5 and 29.2 times respectively) than that of pristine CZTS and ZnO films.

Electrochemical study of the mechanism of dimethylsulfoxide electrooxidation on a platinum electrode in acidic and alkaline solutions is carried out. On the stationary anodic polarization curves taken in acidic and alkaline dimethylsulfoxide solutions, the oxidation currents preceded those measured in the supporting electrolyte. By the analyzing of linear segments of anodic voltammograms, the coefficients of the Tafel equation are determined. This allowed choosing the current density range and conditions for the dimethylsulfoxide electrooxidation on the platinum electrode. The electrolysis was carried out at controlled current density in electrolyzers both with unseparated compartments and the anodic and cathodic compartments separated with MK-40, MA-40 membranes and a MF-4SK fluoropolymer sulfocationite membrane. The high electrical conductivity and selectivity of the membranes provided good performance of the electrolysis process and obtaining of high-purity final product. Raman spectroscopy and gas chromatography–mass spectrometry confirmed that the products of dimethylsulfoxide electrooxidation in the acidic solution are dimethylsulfone and dimethylsulfoxide; in alkaline solution, the dimethyl sulfone and sodium methanesulfonate. The method of quantum-chemical calculations showed good adsorption of dimethylsulfoxide molecules at platinum within the frames of the cluster model. It is shown that the dimethylsulfoxide formation at the platinum electrode surface at high current densities occurs by the radical-ion mechanism, involving breaking of the C–S bond. Based on the experimental results obtained, a scheme for the dimethylsulfoxide electrochemical oxidation at platinum is proposed.

The possibility of targeted electrodeposition of metal coatings in the lead–bismuth binary system is considered. The analysis of metal content in the deposits is performed using square-wave stripping voltammetry of solutions containing both lead and bismuth. The results are supported by the data of scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analysis. The conditions for the formation of Pb₇Bi₃ (ε-phase), which is promising for the application in superconducting microelectronics, are found.

In pulsed electrochemical machining (PECM), it is difficult to control machining stability and surface quality numerous due to the interrelated variables with highly nonlinear and complex characteristics. Thus, how to determine the optimal process parameters to ensure optimal machining performance became a hot research. In this paper, we investigate the recurrence behavior of Ti–48Al–2Cr–2Nb alloy in PECM by recurrence plots and the quantitative analysis. Besides, the Technique for Order Preference by Similarity to Ideal Solution with Criteria Importance through Intercriteria Correlation (CRITIC-TOPSIS) is employed to determine the optimal process parameters for PECM. The results demonstrate that the recurrence plots exhibit periodic characteristics at the macro level, and effectively identify current density changes in different dissolution stages of the alloy at the micro level. Each pulse stage exhibits an inherent oscillation frequency, and the recurrence plots display a similar block structure with evident fractal features. The optimal result show that the optimal process parameters for the potential, the duty cycle, electrolyte pressure and the feed velocity is 16 V, 40%, 0.4 MPa and 0.9 mm/min, respectively. After optimization, the machining stability and the surface morphology uniformity improves by 29.82 and 72.78%, respectively, and the surface roughness decreases by 24.09%, providing a basis for establishing the quantitative relationship between the machining stability and the surface roughness.

The charge-transfer resistance R₁ as a function of the electrode potential Е for the hydrogen evolution reaction passing by the Volmer–Heyrovsky mechanism involving atomic hydrogen adsorbed according to Temkin isotherm is studied. For a quasiequilibrium Volmer reaction, logR₁,E-curves have a minimum and a maximum. With the increasing of the surface nonuniformity factor f the minimum has been shifted toward lower electrode potentials, the minimum region in the voltammogram is widened. The half-width of the minimum region allowed determining the f value. At the lowest and highest values of the surface coverage, the logR₁,E-dependence demonstrated the same regularities as the Langmuir isotherm.

La_{1 – x}Sr_xCoO₃ (x = 0.1, 0.2, 0.3, 0.4, and 0.5) were prepared by the alginic acid sol–gel route and characterized by thermo gravimetric analysis (TGA), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM) techniques. The electrocatalytic activity of fabricated oxide electrodes (Ni/oxide) was studied for oxygen evolution reaction (OER) in an alkaline medium. The cyclic voltammetry of oxide electrodes shows a pair of redox couple at anodic peak potential (E_pa) = 400 ± 6 mV and cathodic peak potential (E_pc) = 296 ± 8 mV. The observed values of electrode kinetic parameters such as the Tafel slope (b) lie between 91 and 126 mV dec^–1 and current density (j) lie between 17.0–73.1 mA cm^–2 at 0.85 V. The Sr-substitution in lanthanum cobaltate matrix improve electrocatalytic activity for OER in an alkaline medium and maximum improvement was observed in the case of 0.4 mol Sr-substituted oxide. The order of reaction (p) with respect to the concentration of [OH^–] is found unity and the highly negative value of entropy of the reaction indicated the oxygen evolution follows the same mechanism and involves the adsorption of the reaction intermediate.