Sulfide-enhanced electrochemical capacitance of cobalt hydroxide on nanofibered parent substrate |
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Authors: | Svetlana Lichušina Ala Chodosovskaja Konstantinas Leinartas Algirdas Selskis Eimutis Juzeliūnas |
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Institution: | (1) Institute of Chemistry, A. Goštauto 9, 01108 Vilnius, Lithuania; |
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Abstract: | Two approaches—substrate nanostructuring and incorporation of sulfide—were studied with the aim to increase electrochemical
capacitance of cobalt (hydro)oxide. A fiber structure of cobalt was deposited electrochemically with the fibers in the order
of tens of nanometers in thickness and hundreds of nanometers in length. Cobalt hydroxide film was formed on the nanostructured
substrate by anodic polarization in an alkaline solution. The hydroxide formation and its electrochemical capacitance have
been studied by cyclic voltammetry in conjunction with the electrochemical quartz crystal microbalance (EQCM). An irreversible
behavior was typical of the first anodic polarization cycle; it turned gradually to a reversible one during subsequent cycling.
EQCM measurements indicated exponential electrode mass growth during the first cycle, with subsequent transition to a quasipassive
state. The redox transitions Co(II) → Co(III) → Co(IV), which determine pseudocapacitance, did not cause remarkable electrode
mass change. The electrochemical capacitance of the nanofiber sample was found up to five times higher when compared to that
formed on conventional cobalt (abraded surface). Specifics of “per 1 g” evaluation of capacitance performance is discussed.
Measurements showed that about 10% of the entire hydroxide structure took part in the capacitive process. The capacitance
value determined per 1 g of active Co(OH)2 was in agreement with the limiting value predicted by the Faraday’s law (2,421 F g−1) sulfide-enhanced system with 18% CoS exhibited up to three times higher capacitance when compared to that of the sulfide-free
counterpart. The system shows promise for practical applications due to its low cost and technical simplicity. |
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