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2016

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том 14 / 

выпуск 2

 



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Б. П. Бахматюк, І. Я. Дупляк
«Електрохемічна ефективність і механізм процесу електросорбції йоду активованим вуглецевим матеріялом в системі гібридного суперконденсатора»
271–283 (2016)

PACS numbers: 81.05.U-, 82.45.Fk, 82.45.Yz, 82.47.Uv, 82.47.Wx, 82.80.Fk, 84.32.Tt

In this work, using standard methods of galvanostatic charge–discharge and electrochemical impedance spectroscopy, the study of the influence of the current density (i) in the range from 0.86 A?g?1 to 6.86 A?g?1 on specific energy capacity and power, and the influence of number of cycles on specific capacity and Coulomb efficiency of the microporous activated carbon material in the system of hybrid supercapacitor in 25% ZnI2 aqueous solution is carried out for the first time. Using data of galvanostatic discharge, the dependence of the specific pseudocapacity (Сп) on the fractional surface coverage (?) of activated carbon material with iodine atoms and desorption isotherms of iodine are obtained. Comparisons of experimental and theoretical dependences of ? on Сп and iodine desorption isotherms with the theoretical iodine adsorption isotherms show that the process of iodine electrosorption on the surface of the nanoporous activated carbon material corresponds to the Frumkin model. This process has a high ? of iodine atoms (from 0.8 to 0.97) and relatively small values of parameter of interatomic interaction g in the adsorption layer (from 0.25 to 1.6). The comparison of the experimental dependences with relevant theoretical is made. The high yields of the specific discharge capacity (Cp???1020 C?g?1) and energy (W???1072 J?g?1), i.e. 86% and 81%, respectively, of the corresponding theoretical values with the changing of power density from 1.1 W?g?1 to 7.3 W?g?1 and Ср???1064 C?g?1 during 1000 investigated galvanostatic cycles are obtained. The data of electrochemical impedance spectroscopy show that galvanostatic charge–discharge for 1000 cycles leads to improvements of the nanoporous-structure ability to the higher pseudocapacitive charge of activated carbon material. Specific polarization resistance decreases from 8.8 Ohm after the first cycle to 7.1 Ohm after 500th cycle and 3.5 Ohm after 1000th cycle. The charged electrode is characterized by the 43 times greater pseudocapacity 7.2 F?m2 (10?3 Hz), which almost coincides with a theoretical maximum of iodine pseudocapacity (7.4 F?m2). The connection of high electrochemical efficiency of the electrode with the mechanism of the iodine electrosorption process on the surface of the nanoporous activated carbon material.

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