Russian Journal of Electrochemistry最新文献

Zinc–nickel coatings based on the zinc-enriched gamma phase exhibit the maximum corrosion resistance and form the basis of the production of highly electrocatalytically active nanoporous nickel by selective dissolution. The electrodeposition of Zn–Ni alloys is the most widely used method of their preparation which proceeds by the mechanism of anomalous codeposition, where the deposition rate of the electropositive component (nickel) is lower as compared with the electronegative component (zinc). To obtain coatings of the particular morphology, chemical and phase composition, it is necessary to know the kinetics of the cathodic deposition of Zn–Ni alloys in the stage of heterogeneous nucleation, which is the goal of this study. The kinetics of this process is studied in non-stirred ammonium chloride electrolytes using the methods of cyclic voltammetry and chronoamperometry. The mechanism of heterogeneous nucleation at the electrodeposition of zinc and nickel is determined using the approach proposed by Palomar-Pardavé et. al which takes into account the contributions to the total cathodic current made by the parallel reaction of hydrogen reduction and the electric double layer charging. The nucleation mechanism for zinc–nickel coatings is described using the model of Scharifker–Hills for the electrodeposition of binary alloys additionally modified by taking into account the experimentally determined dependence of the composition of zinc–nickel coatings on the time in the stage of cathodic nucleation of the deposit. Using the method of energy-dispersive X-ray spectroscopy, the anomalous character of the deposition of Zn–Ni coatings is confirmed, where the ratio of atomic fractions Ni/Zn turns out to be lower than the ratio of concentrations of ions Ni²⁺/Zn²⁺ in the electrolyte. It is found that both during the electrodeposition of zinc and nickel from their individual solutions and during their anomalous codeposition, the nucleation rate constant increases with an increase in the cathodic potential but in average does not exceed 3 s^–1, which points to the predominantly progressive nucleation. The growth of the new phase, regardless of its chemical composition, is limited by the 3D-diffusion of zinc and nickel ions to the electrode surface. The nucleation site density depends weakly on the deposition potential, decreasing with the transition from zinc to nickel and zinc–nickel alloys. As expected, the contribution of the side reaction of hydrogen reduction is the maximum for nickel electrocrystallization and decreases with the transition to Zn–Ni alloys and zinc, increasing with an increase in the cathodic potential, in agreement with the values of current efficiency.

It is studied how the treatment of a metal lithium surface with a 1 M LiN(CF₃SO₂)₂ solution in the 1,3-dioxolane/1,2-dimethoxyethane (2 : 1) mixture affects the resistance of the interphases formed by lithium with the polymer and nanocomposite electrolytes based on the 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid. The liquid-phase therapy is shown to reduce the resistance at the Li/electrolyte interphase by a factor of 2.5 at room temperature and extend the working temperature range to –30°C. The introduction of TiO₂ nanoparticles into the polymer electrolyte, along with the liquid-phase therapy of both the cathode and the Li-anode, provides a high and stable discharge capacity of the Li//LiFePO₄ battery for 100 charge–discharge cycles.

Earlier, we developed (Russ. J. Electrochem., 2018, vol. 54, p. 879) a new nonlocal electrostatic method for calculating an electric field distributions in systems containing spatially constrained regions filled with polar media with nonlocal dielectric properties. This method is used for nonlocal electrostatic analysis of the stabilization of a monovalent cation in a spherical cavity filled with water and surrounded by a local dielectric. For one- and three-mode models of the dielectric function, nonlocal electrostatic formulas are obtained for the field distribution inside such a cavity, if the ion is located at its center. The nonlocal electrostatic relations are derived for the change in the cation solvation energy ΔW during its transfer from solution to the center of such a cavity. It is shown that when the correlation length of water in the cavity decreased as compared with the solution (at the same values of the dielectric constant of water in the cavity and in the solution bulk), the amount of work required for the ion transfer from the solution into the cavity (−ΔW) decreased significantly as compared to that calculated by using the local theory used in the work of Roux, B. and MacKinnon, R. (Science, 1999, vol. 285, p. 100).

Here we illustrate the use of dimethylglyoximate (DMG) as shape directing agent for the synthesis of nickel oxide nanowires (NiONWs) via hydrothermal process followed by calcination at elevated temperature. As-prepared NiONWs were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) techniques and Fourier Transform Infra-red (FTIR) spectroscopy. The surface area of 27 m² g^–1 and pore diameter of 22 nm was true for the product. The prepared NiONWs were drop casted over the active surface of glassy carbon electrode (GCE) to apply it for the electrochemical sensing of hydroquinone based on cyclic voltammetry (CV) and amperometry techniques. The phosphate buffer solution (PBS) of pH 5.8 was used for the measurement of hydroquinone during electrochemical investigation. The developed sensor displayed a wide linear range of 0.5 to 11 µM for hydroquinone detection with sensitivity of 200 µA mM^–1 cm^–2 and limit of detection (LOD) equal to 0.01 µM. The sensor was further examined and found to be highly stable and extremely selective for the oxidation of hydroquinone. The sensor was successfully applied for amperometric detection of hydroquinone from water samples.

The electrochemical polymerization of 3,4-ethylenedioxythiophene in the presence of a water-soluble Na⁺-containing fullerene with hydroxyl groups is studied. The monitoring of the electrosynthesis process by spectroscopic methods shows that during the polymerization of 3,4-ethylenedioxythiophene, fullerenol incorporates into the film composition, regardless of the fullerenol concentration used. The electronic structure, morphology, spectroelectrochemical and electrochemical properties, and near-IR photoconductivity of the poly-3,4-ethylenedioxythiophene–fullerenol composite films are studied for the first time. A mechanism of photoconductivity is proposed, related to the fact that during the photoexcitation of the composite, the electron transfer from the polaron (bipolaron) state of poly-3,4-ethylenedioxythiophene to the LUMO level of fullerenol increases the concentration of photogenerated charge carriers.

A review of modern scientific literature on the electric double layer capacitors based on the recharging of the electric double layer is presented. The electric double layer capacitors are used in pulse technology devices, as electric energy storage devices, for starter firing, for the recuperating of the braking energy of internal combustion engines, for smoothing peak loads in electric networks, and in various portable devices. The electric double layer capacitors are subdivided into the power electric double layer capacitors and the energy ones. The power (pulse) electric double layer capacitors have a high specific power (up to hundreds of kW/kg), whereas the energy electric double layer capacitors have a high specific energy (~25 W h/kg and higher). Compared to batteries, the power electric double layer capacitors have a much higher power density and better cyclability—up to hundreds of thousands and millions of cycles. Publications on the electric double layer capacitors’ self-discharge are reviewed.

Sodium-ion batteries (SIBs) are important new energy storage devices. Due to the abundance of sodium and the similar operating principles of SIBs to lithium-ion batteries (LIBs), SIBs are considered as an important complementary technology to LIBs that will dominate the next generation of energy storage. However, large-scale application of SIBs is hindered by severe capacity decay and low rate capability. The actual capacity of batteries is closely related to the specific capacity of anode materials. Therefore, the development of high-capacity anode materials has become a key area of research for SIBs. Transition metal compounds can improve these problems due to their unique electronic band structure, good chemical adsorption ability, and excellent catalytic ability. Cobalt-based phosphide anode materials have the characteristics of high theoretical capacity, abundant reserves, and low prices, making them become promising anode materials for SIBs. Furthermore, adjusting the size and structure and combining with carbon-based or non-carbon-based materials can effectively alleviate the defects of cobalt-based phosphide electrodes, thereby improving the specific capacity, cyclic stability, and rate capability of SIBs. This review summarizes the recent research progress on cobalt-based phosphide anode materials for SIBs, including the current research status and future development prospects.

The solid oxide direct carbon fuel cell (SO–DCFC) is a vital future technology for producing high-efficiency and environmentally friendly electricity. To improve the performance of SO–DCFC, it is required to examine the optimal operation condition selection and anode reaction process optimization. The DCFC reaction model is derived from the anode Boudouard reaction in this study. Electrochemical reaction dynamics, mass transfer, and electrode processes are incorporated into the model. Higher Boudouard reaction rate, gasification rate, and power density of anode carbon were discovered to impact the performance of fuel cells directly. In addition, simulation provides the CO concentration and current density distribution under different output voltage settings, which can be used to assess the performance and give a basis for the best design of DCFC.

Moxifloxacin evaluation in pharmaceuticals and biological fluids is in high demand. It is important to fabricate a simple, sensitive, selective, miniaturized, and cost-effective chemical sensor to detect moxifloxacin in the environment. In this study, an electrochemical sensor based on molecularly imprinted polymer (MIP) was fabricated for the detection of moxifloxacin in which interdigital electrodes (IDEs) were used as transducers. Thermal free-radical bulk polymerization was used to synthesize MIP, methacrylic acid (MAA) was used as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, azobisisobutyronitrile (AIBN) as a free radical initiator, and dimethyl sulfoxide (DMSO) as a porogenic solvent in a poly (methacrylic acid) system for efficient recognition. The LCR meter was used to measure various electrical properties such as inductance and resistance. A concentration-dependent linear response was observed by the fabricated sensor having a lower limit of detection of 240 and 63 ppb for series and parallel resistance, respectively. Meanwhile, series and parallel inductance had lower detection limits of 48 and 8 ppb, respectively. Furthermore, in the presence of competing agents such as uric acid, ascorbic acid, and paracetamol, the fabricated sensor showed a selective response for moxifloxacin. The fabricated sensor also showed reversible and reproducible response.

Nanocomposites of few-layer graphene structures with PdNi-alloy nanoparticles are synthesized using the electrochemical dispersion method. The composites’ chemical modification is shown to lead to a significant increase in their electrocatalytic activity in the methanol oxidation reaction.