Èlektrohimiâ

A series of ZnO/ZnWO4 nanocomposites with different ZnWO4 content based on ZnO and WO3 nanopowders electrochemically synthesized under pulse alternating current was obtained. A complex of physicochemical methods (X-ray diffraction, Raman spectroscopy, transmission electron microscopy, energy dispersive X-ray microanalysis) was used to study the composition and structural characteristics of the obtained materials. The nanocomposite with optimal composition (ZnO 90%, ZnWO4 ~6%) was used as a photoanode material for a flow photocatalytic fuel cell with sulfate electrolyte with the addition of organic and inorganic fuel. The maximum values of Eoc and Pmax, which were 850 mV and 85.8 μW/cm2, respectively, were achieved using Na2SO4 with the addition of glucose as a fuel.

The electrochemical behavior of tungsten in chloride electrolytes with various cationic compositions (Na+, K+, Li+, NH4+) under pulse alternating current has been studied. The decisive influence of the nature of the electrolyte on the phase composition of the resulting dispersed products is shown. The use of NH4Cl ensures the formation of pure crystalline WO3 with a particle size of 30–35 nm. The photoelectrochemical activity of the synthesized WO3 in a sulfuric acid medium under simulated solar radiation has been studied. The addition of glycerol to H2SO4 causes a cathodic shift in the oxidation onset potential by 0.25 V and a threefold increase in the maximum photocurrent density. The possibility of using a WO3/FTO photoanode as part of a flow-through photocatalytic fuel cell (fuel - glycerol, air-breathing Pt/C cathode), characterized by excellent stability in an acidic environment and the maximum power density of 64.0 μW cm-2 is shown.

The influence of the positive electrode properties on the activation time of the reserve chemical power sources of the system lead – perchloric acid – lead dioxide has been studied. Coatings of cathodes with lead dioxide obtained under various conditions are characterized by scanning electron spectroscopy, X-ray spectral microanalysis, X-ray photoelectron spectroscopy, standard contact porosimetry. The improvement of the performance characteristics of power sources including the ensuring of a short time of their activation at a low temperature has been shown to be possible with the use of a nanoporous coating of lead dioxide. To estimate the applicability of cathodes for the manufacture of power sources having minimal activation time a diagnostic principle has been used that it based on testing of cathodes by the method of chronopotentiometric measurements during galvanostatic discharge. Pilot industrial samples of small-sized reserve power sources of the mentioned electrochemical system with unprecedented short activation time (less than 30 ms at temperarure –50°С) were manufactured and tested.

The influence of the method of organising the cathode microstructure based on Pr2CuO4 (PCO) on the electrochemical characteristics of a model electrolyte-supported solid oxide fuel cell (SOFC) has been investigated. It is shown that an increase in the thickness of the PCO cathode layer and the introduction of a pore-forming agent contribute to an increase in the power density of the SOFC test cell compared to a sample with an initial unmodified cathode structure, whose power density at 850°C was 34 mW/cm2. It was found that the optimum thickness of the cathode layer to achieve maximum electrochemical performance was in the range of 40-50 μm, while the power density achieved was 116 mW/cm2 at 850°C. At the same time, the transition from a single-phase PCO cathode to a composite of PCO-Ce0.9Gd0.1O1.95 (60/40 wt. %) provides an increase in power density up to 130 mW/cm2 at 850°C, while the dynamics of its decrease with reducing temperature is slower compared to the single-phase cathode. The analysis of the changes in the values of the total electrode polarisation resistance of the model SOFC, determined by impedance spectroscopy, as a function of the method of cathode formation, showed that during the transition from the initial sample to the samples with increased thickness of the cathode layer and the composite cathode, a twofold (in the first case) and threefold (in the second case) decrease in the level of polarisation losses is observed, which correlates with an increase in the power density. The proposed methods of modifying the initial cathode microstructure based on PCO show a positive dynamic of increasing the electrochemical activity of the cathode/electrolyte interface and the power density characteristics of the fuel cell as a whole.

The effect of Ga and  In compounds on the process of anodic dissolution of Al in KOH solutions in a mixed ethanol/acetonitrile solvent has been studied. The influence of the water content in the electrolyte on the electrochemical behavior of the Al electrode is considered. A change in the water content in the electrolyte containing additions of Ga and  In compounds from 2 to 4% leads to a twofold increase in the current of anodic dissolution of Al. The galvanostatic  discharge curves in an electrolyte containing Ga3+ and In3+ additives exhibit a flat discharge plateau up to a discharge current density of 8 mA/cm2.   

The features of electrochemical deposition of copper layer on titanium and tantalum flexible substrates, as well as modes of sequential electrochemical deposition of tin layer on Cu/Ti and Cu/Ta and nickel layer on Sn/Cu/Ti and Sn/Cu/Ta from corresponding electrolyte solutions were studied by cyclic voltammetry. Deposition potentials for each metal layer were determined taking into account the type of substrate, and a wide set of the Cu-Sn-Ni/Ti and Cu-Sn-Ni/Ta stable precursor films were synthesized. The stage of annealing in an active sulfur atmosphere (sulfurization) has been optimized in order to obtain the Cu2NiSnS4 stable compounds. Based on the obtained XRD and Raman spectroscopy data, it was found that annealing in active sulfur atmosphere at 550 °C for 60 minutes is necessary to synthesize the Cu2NiSnS4 stable single-phase compounds with polycrystalline structure on Ta and Ti substrates