In the paper, charging-discharging processes in symmetric electrochemical supercapacitors with activated carbon electrodes were studied. Mathematical modeling and experimental verification of these processes were performed. Such factors as the charging of the electric double layer, diffusion-migration transport of species in pores of the electrodes and separator, quasi-reversible Faraday redox reactions of surface groups, kinetics of which is related to the ButlerVolmer type, and porous structure of the electrodes with hydrophobic-hydrophilic characteristics were taken into consideration. The dependencies of energy efficiency on time of charging and discharging, current, and thickness of the electrodes have been calculated. These relations are very important when supercapacitors are applied to smoothing of peak load of electrical networks. The dependence of the efficiency on current is characterized by a maximum and a minimum. The optimal operating modes for the supercapacitors have been found to depend on device parameters. It is important to note that the efficiency value is close to 100 % for supercapacitors under certain conditions, but this magnitude is unattainable for batteries.
Based on a MK 40 sulfocation exchange membrane, a hybride electrode material containing nanodispersed copper is prepared. The methods of scanning electron microscopy and X ray diffraction (XRD) analysis reveal the formation of copper agglomerates measuring 250-470 nm and consisting of indi vidual particles of 20-30 nm. The procedure of multistage chemical deposition of copper into the ion exchange carrier makes it possible to obtain a continuous cluster of metal particles which determines the elec tron conducting properties of the resulting hybrid material. The electrochemical activity of the nanocompos ite electrode is studied in the reaction of nitrate ion electroreduction. Nanodispersed copper deposited into the membrane is shown to intensify the electroreduction of nitrate ions by a factor of 1.5-2 as compared with a compact copper electrode. The electroreduction of nitrate ions on compact copper is shown to involve 6 electrons, whereas the electroreduction on the nanocomposite involves 8 electrons. The electroreduction products of nitrate ions are identified by the IR spectroscopy method.
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