Capacitance studies of cobalt compound nanowires prepared via electrodeposition

The capacitor properties of cobalt compound nanowire (CCNW) electrodes, prepared by the one-step electroreduction of [Co(NH3)6]3+ in water, have been investigated. The CCNW electrode changes its various properties during its growth. During the initial growth stage, the CCNW electrodes consist of nanowires with smooth surfaces and have a specific capacitance (Cm) of 310 F g−1. During the middle stage, prickles grow on the CCNW surface, leading to a reduction in its real surface area and its Cm value to 230 F g−1. During the final stage, further growth of the prickles is accompanied by the fusion of the CCNWs, and hence, a drastic decrease in the real surface area. However, a maximum capacitance of Cm = 420 F g−1 was obtained during this stage. This unexpected capacitance change was discussed in terms of the effects of rapid ion transfer and the electroactive material/electrolyte interface area. In addition, the aging effect and the cycle life of the CCNW electrode were also investigated.

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► Cobalt compound nanowire electrodes are prepared for application in supercapacitors.
► The nanowire electrodes exhibit good electrochemical capacitor behaviors.
► The nanowires change their morphology and capacitance properties during their growth.
► Ion transfer in nanospaces and nanowire real surface area can explain the change.