Russian Journal of Electrochemistry最新文献

Zinc oxide (ZnO) remains a promising candidate in the field of photo(electro)catalytic hydrogen/electricity production from water/biomass and wastewater treatment. However, there has been a need for the development of sustainable, versatile tools for achieving controlled and economically viable production of nano ZnO. This research is aimed at assessing the electrochemical approaches to tune ZnO morphology through electrosynthesis using pulse alternating current (PAC) by varying the average anodic/cathodic current densities ratio (j_a : j_c) and NaCl electrolyte as one of the most naturally abundant compounds. The composition, morphology, and specific surface area (SSA) of the ZnO synthesized at different j_a : j_c were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and low-temperature nitrogen adsorption-desorption (BET) methods. The synthesized ZnO nanopowders were applied as photoelectrocatalytic (PEC) and photocatalytic (PC) materials. PEC performance of ZnO/FTO was investigated using Na₂SO₃, ethanol, glycerol, ethylene glycol, formic acid, and glucose as inorganic and organic oxygenates. The PC activity of nano ZnO was evaluated using 2,4-dinitrophenol (DNP) as an organic pollutant. The variation in PEC and PC performance depending on the ZnO electrosynthesis conditions was shown.

A modified glassy carbon electrode (GCE) with immobilized nickel manganese oxide nanoparticles (Ni₆MnO₈ NPs) was developed for the sensitive and selective detection of dopamine (DA) in the presence of serotonin (5-HT). The Ni₆MnO₈ NPs were synthesized and characterized by using techniques such as powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), elemental mapping, energy dispersive X-ray analysis (EDAX), and High-resolution transmission electron microscopy (HR-TEM). Electrochemical studies of the Ni₆MnO₈ NPs for detecting DA and 5-HT were conducted using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimal conditions, DPV was used for the simultaneous detection of DA and 5-HT at Ni₆MnO₈ NPs modified surfaces, achieving low detection limits of 0.021 µM for DA and 0.11 µM for 5-HT. The fabricated sensor demonstrated excellent reproducibility and stability, making it suitable for the analysis DA and 5-HT simultaneously. Additionally, the sensor showed satisfactory recovery rates in real sample analyses.

Platinum-free cathodic electrocatalysts of the hydrogen evolution reaction are developed based on iron complexes of sodium pectate. These catalysts are promising for water electrolysis. The catalyst with 25% substitution of iron ions for sodium ions demonstrates the highest efficiency in the hydrogen evolution reaction and can replace platinum with 93% efficiency when used as the cathodic catalyst in water electrolyzers with proton-exchanging membrane at 80°С.

This review is devoted to the examination of modern literature on aluminum batteries developed in recent years, which have already reached the stage of industrial production. Currently, lithium-ion batteries dominate the market. However, they have serious drawbacks: they are explosive and fire hazardous and also contain rare/expensive components (lithium, cobalt, nickel, electrolyte). Aluminum-ion batteries have advantages over lithium-ion batteries, namely: aluminum is cheap because it is the most widespread metal in the Earth’s crust; aluminum batteries are fire- and explosion-proof. As a result of comparing the “specific energy–specific power” combination for different types of aluminum-ion batteries, it is found that the most favorable combination of specific energy (247 W h/kg) and specific power (44.5 kW/kg) is shown by aluminum-ion batteries consisting of a graphite cathode etched with alkali, an aluminum anode, and an aluminum-chloride-based electrolyte. The highest combinations of specific capacity and current density are demonstrated by aluminum-ion batteries with CoSe cathode: 427 mA h/g at 1 A/g, and those based on MoSe₂: 753 mA h/g at 0.3 A/g. The highest specific energy (685 W h/kg) is achieved by aluminum-ion batteries with CoMnO-cathode. Aluminum-ion batteries are characterized by a very high charging rate: up to 10 000 C (the discharge time 0.35 s) and also very high cyclability—up to 30 000 cycles.

Comparative investigation of potentiometric characteristics for coatings electropolymerized from phosphate buffer and the 4-(2-hydroxyethyl)-1-piperazineethanesulfonic-acid-based buffer solutions or deep eutectic solvents, such as reline and mixture of citric acid, glucose and water is carried out. Both the effect of media acidity on the sensor potential and the potentiometric response reversibility are evaluated for all the coatings synthesized. The solid-contact potentiometric sensor array is developed for the determination of easily oxidizable organic compounds: hydroquinone, dopamine, quercetin, and ascorbic acid. Analytical characteristics of such easily oxidizable organic compounds are established. According to the media pH, the analytes can perform either as single-charged ions demonstrating the slopes approaching the Nernstian values or as reducing agents affecting polymer redox forms’ ratio in the modifying coatings. The coatings synthesized from deep eutectic solvents showed wider linear ranges of determined concentrations. Also, they had better sensitivity as compared with those electrodeposited from aqueous media. The solid contact potentiometric sensors were tested for analytes’ determination in real samples of cosmetics, pharmaceuticals, and biologically active additives with 92–107% recovery.

The composition of brass metallurgical waste is determined using X-ray fluorescence analysis. The copper content in the slag is shown to reach 15 wt %; the zinc content, 83 wt %. Sulfuric-acid leaching was performed to separate zinc from the metallurgical dust. Optimal process parameters are selected as: leaching duration 60 min, sulfuric acid concentration 0.1 M. After the sulfuric-acid leaching, the acid solution is subjected to electrochemical treatment, in order to recover copper and zinc; the copper cake (copper in unoxidized form), to copper–ammonia leaching for 40 min. The concentration of copper in the copper–ammonia solution reached 35 g/L. At the final stage, solvent extraction of copper from the copper–ammonia leach solution is carried out, for which the most effective extracting agent has been selected. Extracting agents of different nature and classes are studied: D2EHPA (a strong acidic organophosphorus extractant), DХ510А and LIX54 (classified as β-diketones). The concentration of extracting agentnts ranged from 50 to 100%, the diluent is kerosene. Copper stripping from the copper–ammonia extract was performed using 2 M sulfuric acid. The best extractant is found to be LIX54 (50% concentration in kerosene). The final stage is copper electrowinning from the stripping solutions at a current density of 3 A/dm², with a current efficiency of 65%. Based on the conducted research, a process flow-sheet is developed for the recovery of copper and zinc from the brass metallurgical dust.

A new composite material based on poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) and a network of oriented nickel fibers (NiSFs) distributed throughout the polymer matrix is considered as a possible electrode in devices of alternative energetics. The relationship between the electrochemical and electrooptical characteristics of GC/PEDOT:PSS and GC/NiSFs/PEDOT:PSS electrodes is investigated using several electrochemical methods (cyclic voltammetry, electrochemical impedance spectroscopy). By measuring cyclic voltammograms with different potential scanning rates, the mechanism of electrochemical reactions in systems GC/PEDOT:PSS and GC/NiSFs/PEDOT:PSS is studied, and their limiting stages are determined. Based on the redox potentials, the band gap is calculated for these electrodes. F, or GC/PEDOT:PSS the band gap E_g is 1.34 eV. The incorporation of a network of oriented nickel fibers into the PEDOT:PSS matrix only insignificantly narrows the band gap in the system GC/NiSFs/PEDOT:PS to 1.31 eV, which confirms that the optical properties of these materials remain almost unchanged. The GC/PEDOT:PSS and GC/NiSFs/PEDOT:PSS electrodes are studied by impedance spectroscopy. The incorporation of the network of nickel fibers into the polymer film is shown to slow down the charge transfer in the GC/NiSFs/PEDOT:PSS system, as follows from the increase in the charge-transfer resistance R_et to 171 Ω as compared with 131 Ω for unmodified GC/PEDOT:PSS. The analysis of these data makes it possible to conclude that the composite materials based on PEDOT:PSS and a network of oriented nickel fibers can be used in electrooptical devices and power generating systems.

It was discovered earlier that the calix[n]arene sulfonic acids have a record high proton conductivity, so that it was suggested that lithium salts of calix[n]arene sulfonic acids plasticized with aprotic solvents should also have ionic conductivity. It was found that the medium salt of calix[n]arene sulfonic acid in combination with propylene carbonate as a plasticizer has an ionic conductivity of 10^–1–10^–2 mS/cm, which makes it a promising material for further study and use as an electrolyte for lithium-ion batteries.

Bismuth manganese oxide (BMO) nanoparticles (NPs) modified glassy carbon electrode (GCE) It was developed to detect dopamine (DA) with sensitivity and selectivity in the existence of uric acid (UA). The BMO nanoparticles were synthesized by simple combustion method. Characterisation and structural morphology of prepared BMO NPs were investigated by FT-IR, powder XRD, FE-SEM and EDAX, HR-TEM and elemental mapping.The electrochemical detection of DA at BMO NPs modified GCE was performed by cyclic voltammetry technique (CV) and differential pulse voltammetry (DPV) under optimum conditions, DPV had been employed for the contemporaneous estimation of DA and UA at BMO NPs modified glassy carbon electrode surface and thus prepared biosensor showed low limit of detection 0.091 µM and 0.023 µM for DA by CV and DPV technique respectively. The fabricated sensor could serve as a medium for the simultaneous investigation of DA due to its excellent reproducibility, and stability. Additionally, the created sensor displayed satisfactory recoveries for real sample analysis.

In this work, the electrochemical behavior of dysprosium, neodymium, and lanthanum ions and their co-reduction with nickel ions on tungsten and nickel electrodes in a KCl–NaCl–CsCl eutectic melt at a temperature of 823 K is studied. The electroreduction of Ln³⁺ ions is found to proceed reversibly in one three-electron stage up to the polarization rates of 0.1 V/s. At the compresence of lanthanide and nickel ions, the voltammograms show reduction waves of nickel ions at potentials of –0.12…–0.3 V; those and of lanthanide ions, at –2.13…–2.18 V vs. silver/silver chloride reference electrode. In addition to these waves, the voltammograms have three more recovery waves in the potential regions: –1.68…–1.77 V; –1.95…–2.0 V; ‒2.13…–2.18 V. The appearance of these waves is connected with the joint electroreduction of lanthanide and nickel ions on the metallic nickel pre-deposited onto the tungsten electrode with a certain depolarization and formation of intermetallic phases of lanthanides and nickel of different compositions (Ln_xNi_y). The open-circuit chronopotentiograms revealed plateaus of potential delay corresponding to the dissolution of separate phases of intermetallides. Electrolysis under potentiostatic condition at potentials –1.7…–2.1 V and at certain concentrations ratio of lanthanide and nickel chlorides produced intermetallic phases LnNi₅, Ln₂Ni₇, Ln₂Ni₃, LnNi₃, and LnNi₂. The synthesized samples of lanthanide and nickel intermetallides were characterized by X-ray diffraction analysis and scanning electron microscopy. The e.m.f. for Ln_xNi_y intermetallic compounds in two-phase coexisting states at 823 K is measured. The relative partial molar Gibbs free energy and activity values for lanthanide in the Ln_xNi_y intermetallic compounds were calculated from the measured e.m.f. s.