Russian Journal of Electrochemistry最新文献

An electrochemical method is proposed for the forming of contacts to high-temperature thermoelements with barrier layers based on refractory-metal alloys. The contacts are destined for thermoelements with operating temperatures up to 900 K. The barrier layers have specific resistance of no more than 15.3 × 10⁻⁸ Ω m and specific contact resistance of no more than 1.5 × 10⁻⁹ Ω m². The best results were obtained for barrier layers based on Mo–Ni alloy with a Mo content of 36.5 wt %. Ag films obtained by electrochemical deposition were used as a commutation layer in the contacts. The contacts were shown to be thermally stable at the limiting operating temperatures of the thermoelements and have an adhesive strength of at least 10.3 MPa.

The corrosion of low-carbon steel is studied in a flow of H₃PO₄ solutions containing FePO₄ and also with addition of a mixture of corrosion inhibitors, particularly, a 3-substituted derivative of 1,2,4-triazole (IFKhAN-92) and KNCS. In such solutions, the partial reactions of the iron anodic ionization and the cathodic reduction of H⁺ and Fe(III) cations proceed on steel. The former two reactions are controlled by kinetics, whereas the latter reaction is diffusion-controlled. The accelerating effect of FePO₄ on the steel corrosion in H₃PO₄ solutions is mainly due to the reduction of Fe(III). In acid solutions containing inhibitors, Fe(III) cations continue to accelerate all partial reactions on steel. Despite this accelerating effect, the mixtures of IFKhAN-92 and KNCS still exert a strong inhibitory effect on the electrode reactions on steel, which is noteworthy. The data on the corrosion of low-carbon steel in such flows, obtained based on the mass loss of metal samples, adequately agree with the results acquired when studying the partial electrode reactions. The accelerating effect of FePO₄ on steel corrosion in a flow of H₃PO₄ solutions is observed, including the media containing inhibitors. In these media, the steel corrosion is determined by convection, which is typical of diffusion-controlled reactions. The mixed inhibitors IFKhAN-92 + KNCS are shown to considerably inhibit the steel corrosion in a flow of H₃PO₄ solutions containing FePO₄, which is a result of the efficient suppression of all partial electrode reactions on this metal.

The effect of citric acid monohydrate additive on the anodic dissolution and corrosion rate of aluminum in the KOH solutions in 90% ethanol containing additives of gallium and indium compounds is considered. It is shown that an addition of citric acid monohydrate to the solution enables reducing the aluminum corrosion current without decreasing its anodic dissolution rate. When 5 × 10^–4 M citric acid monohydrate is introduced into the solution, its inhibition efficiency is 58%. The discharge galvanostatic curves in this electrolyte contain a discharge plateau up to a current density of 16 mA/cm².

Changes in the electrochemical impedance spectra of lithium–carbon cells during cathodic polarization of a carbon electrode were analyzed using the distribution of relaxation times (DRT) function. The carbon materials included soft carbon and graphite. An analysis of the electrochemical impedance spectra of lithium–carbon cells using the DRT function allows us to establish the number of electrochemical cells and calculate their parameters. The use of DRT functions for modeling electrochemical impedance showed that a lithium–carbon cell contains eight electrochemical elements and allowed quantification of their parameters. The results are in good agreement with theoretical concepts about the structure of carbon materials and electrochemical processes during their polarization. Analysis of the electrochemical impedance spectra of lithium–carbon cells using the DRT function is a more objective method compared to the equivalent electrical circuit (EEC) method.

The operation of biofuel cells (BFC) based on the Micrococcus luteus 1-i strain under the action of the main representatives of various groups of surfactants has been analyzed. The following were tested: cetyltrimethylammonium bromide (cationic surfactant), Tween-80 (non-ionic surfactant), sodium lauryl sulfate (anionic surfactant). It was shown that cetyltrimethylammonium bromide reduced the electrical characteristics of BFC at concentrations of 10 mg/L, Tween-80—from 5 mL/L, sodium lauryl sulfate—from 100 mg/L. A comparison of the electrogenic activity of bacteria in BFCs with their viability and the kinetics of the redox potential of the anolyte allowed us to conclude that the decrease in the efficiency of the studied BFCs under the influence of surfactants in the tested concentration ranges is associated with their toxic effect on microbial cells.

Oxidovanadium 5,10,15,20-tetrakis(3,4,5-trimethoxyphenyl)porphyrin, VO[(3,4,5-(OCH₃)₃TPP)] (complex 1) has been synthesized. The oxidation products of complex 1 were identified and analyzed using Cyclic Voltammetry, UV-Vis, Electron Paramagnetic Resonance, and Nuclear Magnetic Resonance techniques. Cyclic voltammetric data show that complex 1 exhibits a one-electron oxidation process, resulting in the creation of a π-cation radical. This observation is further confirmed by the analysis of the complex using FT-IR. The addition of CF₃COOH (TFA) with complex 1 has resulted in the development of mono-cation with geometrical changes from square pyramidal to octahedral, which has been confirmed by UV-Vis and EPR spectra.The interaction between Complex 1 and TFA, is investigated by Non-covalent Interaction (NCI) analysis, Visual Molecular Dynamics (VMD) visualization, Electron Localization Function (ELF) analysis, and Molecular Electrostatic Potential (MEP) mapping. The vanadium atom in Complex 1 interacts with the oxygen atom in CF₃COOH at a distance of 2.18 Å. NCI and RDG analyses highlight the predominant van der Waals interactions. VMD visualization confirmes these interactions with green patches. ELF analysis shows strong electronic localization around certain atoms and delocalized electron clouds. MEP mapping reveals nucleophilic and electrophilic sites, with prominent acidic strength around the complex and TFA.

A new electrochemical sensor was designed to discriminate and determine Carminic Acid (CA) utilizing a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs). Using this electrode, CA showed an anodic peak at around 0.24 V. The mechanism of the electrochemical process on the surface of the modified electrode was analyzed by obtaining cyclic voltammograms at various potential scan rates. Different electrochemical parameters of present experiments were calculated such as charge transfer coefficient α as 0.46 and diffusion coefficient D as 3.25 × 10^–7 cm² s^–1. After studying the electrocatalytic behavior of the CA, differential-pulse voltammetry (DPV) was subsequently applied as a very sensitive electro-analytical method for the determination of sub-micromolar amounts of CA. Under the optimized conditions, the anodic peak current enhanced with the CA between 0.41 to 5.55 µM. The detection limit was calculated to be 0.24 µM (S/N = 3). The modified electrode was successfully applied for the accurate determination of minor amounts of CA in strawberry milk samples with adequate results.

The electrochemical characteristics of solid-state thin-film lithium-ion batteries with two different structures: Ti/Anode/LiPON/LiCoO₂/Ti (with an anode) and Ti/LiPON/LiCoO₂/Ti (anode-free) are intercompared. Si@O@Al composite anode with thicknesses of 154 and 15 nm, as well as pre-lithiated Li_xSi@O@Al composite with a thickness of 192 nm, were used as anodes. In anode-free batteries, the lithium anode was formed by the in-situ method. Batteries with 154 nm-thick Si@O@Al and Li_xSi@O@Al anodes have good cyclability due to their moderate volume change during lithium-ion insertion/extraction and reliable adhesion to the LiPON solid electrolyte. These batteries are promising in terms of high energy density due to the lithium anode in-situ formation, although they have poor cycling performance due to peeling of the upper current collector. The introducing of a Si@O@Al thin film with a thickness of ~15 nm between the LiPON and the current collector allows maintaining the high energy density that is inherent in batteries with lithium anodes, while also improving their cyclability.

A large number of various organic and inorganic pollutants are produced each day around the globe to lead to the problem of environmental pollution. Excess nitrite remains in the agricultural fields and foods to enter the environment, rendering it one type of typical environmental pollutant. Therefore, a simple, accurate, quick and low-cost sensor to detect nitrite is highly necessary and meaningful for public health and environmental security. In this study, bimetallic transition metal oxide nanoarray materials have been directly grown on nickel foam (NF) to afford a binder-free electrochemical sensor of Co₁Ni₁O/NF to determine nitrite in an amperometric mode. Unique radial needle-like nanoarray morphology was observed for the as-prepared Co₁Ni₁O, which was believed to offer a sufficient conductive pathway for facile electron transfer to enable quick nitrite electro-oxidation. The synergistic effect of the bimetallic Co–Ni oxide nanoarray materials of the binder-free electrochemical sensor rendered a wide linear range of 10 μM to 3.5 mM for nitrite detection, with excellent anti-interference, reproducibility and stability. The Co₁Ni₁O/NF also exhibited good recovery in actual lake water samples, which would be promising for its potential application under the real scenarios.

Catalysts for oxygen reduction (OR) based on cobalt complexes of sodium pectate have been developed, which are interesting from the viewpoint of application in proton-exchange membrane fuel cells. The catalysts were studied by electrochemistry and electron microscopy. The catalyst with 15% Co²⁺ cations substituted for sodium ions was found to be most efficient.