Russian Journal of Electrochemistry最新文献

This study aimed to develop an electrochemical sensor based on a derivative of graphene oxide (GO) and a molecularly imprinted polymer (MIP) on a pencil graphite electrode (PGE) for the detection of ascorbic acid (AA). MIP was fabricated onto the surface of the electrode by electropolymerization technique using cyclic voltammetry with a scan rate of 10 mV/s consisting of template molecule (ascorbic acid), functional monomer (polypyrrole), cross-linker (LiClO₄) and citrate buffer at pH 4. Then, the template removal process was conducted to create the imprinted cavities for detecting the analyte. Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) methods were used to perform quantitative analyses of the modified electrodes. CV analysis was performed at the optimum scan rate of 10 mV/s, and the electrolyte concentration at 1.0 mM K₃[Fe(CN)₆] in 0.1 M KCl. MIP-PGE (2) produced the best performance by having the highest redox peak current response when scanning with the CV compared to other modified electrodes. The optimum parameters for DPV measurement are 100 mV pulse amplitude, 200 ms pulse period, and 10 mV/s scan rate. The straightforward instrumentation and easy preparation of the proposed sensor make it a valuable system for constructing simple devices for determining ascorbic acid.

The effect of pluronics L61 and F68 containing hydrophobic poly(propylene oxide) blocks of the same length and hydrophilic poly(ethylene oxide) blocks of different lengths on the conductance of planar bilayer lipid membranes made of azolectine is investigated. The conductance of these membranes increases as the concentration of both pluronics increases. For the same concentration of pluronics in solution, the conductance is higher for L61. Based on the literature data, the concentration of pluronics bound with the bilayer is calculated. For the close concentration of membrane-bound pluronics, the conductance of membranes is also close. It is concluded that in the first approximation, the appearance of the same hydrophobic parts of pluronics L61 and F68 in a membrane is accompanied by the same increase in its conductance. The conductance vs. concentration curves are superlinear for L61 and sublinear for F68. In the presence of either of these pluronics, the conduction spikes with the amplitude from 10 to 300 pSm and higher are observed for approximately 40% of membranes. These surges of conductance are associated with the appearance of conductive pores or defects in the membrane. The number of pores observed in the membrane is a random variable with a large scatter and does not correlate with the pluronic concentration. The difference between the average pore conductivities for membranes containing L61 and F68 is statistically insignificant.

The goal of this work is to confirm our earlier conclusion that the regularities observed during the electrodeposition of metallic lithium on copper and lithium electrodes can be associated with differences in the properties of the so-called solid electrolyte interphase formed at these electrodes in contact with the electrolyte. To do this, we analyzed the electrochemical impedance spectra measured during the above processes by using the method of the distribution of relaxation times. The electrolyte addition with surfactants (the cetyltrimethylammonium bromide and hexadecylpyridinium bromide) was shown to lead to a significant change in the properties of the solid electrolyte interphase layers and a noticeable increase in the values of the impedance components associated with the Faradaic processes at these electrodes. This indicates an inhibition of the lithium electrodeposition processes and the related process of dendrite formation under these conditions. At the same time, no such impedance components were observed at the fresh-formed deposit, which confirms our earlier conclusion that the effects of surfactants on the dendrite formation are associated with the changes in the properties of the solid electrolyte interphase layers in the presence of the surfactants, rather than the surfactants’ adsorption at lithium and blocking of the dendrite growth.

The processes at platinum electrodes during the cathode polarization in an alcohol solution of erbium nitrate are discussed. The current density maxima on the cathode branch of voltammograms were found to correspond to the potentials of the hydrogen reduction reactions. The gel-like deposit Er(OH)_x(NO₃)_y(С₂Н₅О)_z·nH₂O, x + y + z = 3, formed during the cathode treatment was shown to be not a product of the electron exchange between the cathode and the solution components. The following formation mechanism of the erbium-containing deposit has been suggested. First, the electrochemical process of the hydrogen cathode reduction is implemented. This process leads to the ionic unbalance and causes the alkalinization of the cathode space. This creates conditions for the chemical process of the gel-like erbium hydroxide formation, which is physically adsorbed on the cathode surface as a precipitate.

The aim of this work is to study the possibility of suppressing the metallic lithium dendrite formation during the operation of lithium secondary batteries, including those with a metallic lithium anode. The electrochemical deposition of lithium on copper and lithium substrates in the presence or absence of two surfactants, cetyltrimethylammonium bromide and hexadecylpyridinium bromide, is studied by the current transient and electrochemical impedance measurements. A typical lithium-ion battery electrolyte based on lithium hexafluorophosphate in the mixture of ethylene carbonate and diethyl carbonate is used. The presence of the so-called SEI (solid electrolyte interphase) layer on the electrode surface is shown to have a significant effect on the electrodeposition process. It is also shown that the mechanism of lithium electrodeposition on copper and lithium substrates is different. It can be assumed that the observed effect of surfactants on the dendrite formation is associated not with the adsorption of surfactants on lithium and blocking the growth of deposits, but with the surfactant effect on the properties of the SEI layer formed at these substrates.

We developeda facile method to construct flexible, freestanding three dimensional hierarchical electrodes that consist of graphene encapsulated one-dimensional conducting polyaniline (PANi)@MnO₂ coaxial nanowires grown on electrospun carbon nanofibers (denoted as G-PANi@MnO₂/ECNFs). A combination of XRD, SEM, and TEM techniques were used to characterize the structures of G‑PANi@MnO₂/ECNFs. Electrochemical measurements confirmed that such nanostructured composites possessed higher electrochemical capacitance than that of each individual component due to synergistic effects. The G-PANi@MnO₂/ECNFs electrode exhibited extremely high specific capacitance (1364.3 F/g at 0.3 A/g) and superior cycling stability (89.2% retention rate after 2000 cycles) in a 1 M Na₂SO₄ aqueous solution. The excellent electrochemical performance of such nanoscale architectured electrodes provides a new route to develop flexible, freestanding, and high-performance supercapacitors.

The electrochemical behavior of the biologically active redox chemicals is essential in point of view antibacterial activity. In some cases, the electronic exchanges are coupled to chemical reactions that produce new oxidative or reductive species, which might form electrodeposits. This contribution presents a comparative study of the antibacterial activities and the anodic oxidation of S-triazino-benzimidazole derivatives substituted at the triazine ring with phenyl, 4-fluorophenyl and pentafluorophenyl groups. By combining bactericidal screening against E. coli, P. aeruginosa, S. aureus, and S. typhimurium, to a cyclic voltammetry investigation, it was revealed that the fluorine phenyl substituents in the S-triazine benzimidazole derivatives enhance the electrons ejection to the platinum disk and the subsequent chemical reactions. Additionally, by cycling of potential the non-fluorinated chemical produces a rather passive film on the electrode surface, whereas the fluorinated ones generate electroactive and electrocatalytic coatings. Comparing the results obtained with S-triazino-benzimidazole derivatives to those with 2-aminobenzimidazole, plausible mechanisms of their bactericidal action are suggested.

The kinetic features of electrodeposition of wear- and corrosion-resistant composite electrochemical coating (CEC) of nickel–cobalt–alumina from a chloride colloidal electrolyte are studied. The application of potentiodynamic, chronopotentiometric and temperature–kinetic methods, as well as the use of the calculated temperature coefficient of reaction rate and the diffusion coefficients of nickel ions, enabled us to determine the mechanism of CEC electrodeposition. The analysis of the data on the kinetic features of CEC electrodeposition showed that the nature of the slow stage of the process is associated with the electrophoretic transfer of electroactive particles to the cathode and the stage of the overgrowth of dispersed particles adsorbed on the cathode surface with the electrodeposited metals, which proceed at comparable rates.

A set of computational and experimental methods is used in the study of chemical side interactions in the LiMn₂O₄-based lithium-ion cathodic half-cell over the 25–60°C temperature range. The degradation of LiMn₂O₄-spinel-based electrodes is shown to start upon the LiMn₂O₄ granules contacting the standard (basic) electrolyte solution (1 m LiPF₆ in a mixture of ethylene carbonate and dimethyl carbonate (1 : 1, by wt)). It is established that under current-less conditions, the degradation of the LiMn₂O₄-based electrode is caused by the mutual thermodynamic instability between LiMn₂O₄ and the LiPF₆ lithium salt. The equilibrium interaction products are determined, and the mechanism of the critical temperature influence on the degradation of lithium-ion batteries with lithium–manganese spinel is refined. A model is proposed for the primary surface layer at the LiMn₂O₄/electrolyte interface formation and evolution, which explains the distinctive features of the degradation processes in this system.

The aim of the present study is to evaluate the potential of both the use of zinc oxide (ZnO) nanoparticles as primary filler and graphene as secondary filler in carboxy methyl cellulose based polymer electrolyte. The films were characterized structurally and morphologically by X-ray diffraction (XRD), Fourier-transform infra red spectroscopy (FT-IR), scanning electron microscopy (XRD). XRD results showed that ZnO nanoparticles inclusion reduced the crystallinity of the prepared biopolymer electrolyte. Addition of graphene as secondary filler further reduced the crystallinity of the prepared biopolymer electrolyte film. The FTIR technique and SEM images confirmed the complexation of salts with the polymer matrix. Due to graphene’s ability to create conductive layers, the inclusion of a little amount of it as a supplementary filler increased the A.C. conductivity from 1.63 × 10^–5 to 2.6 × 10^–4 S cm^–1. The synergistic effects of both fillers contributed to raising the polymer electrolyte film’s electrical conductivity. Utilizing this polymer electrolyte layer enabled the creation of a solid state DSSC with an efficiency of 2.6%.