Preparation and electrochemical properties of multiwalled carbon nanotubes-nickel oxide porous composite for supercapacitors

Porous nickel oxide/multiwalled carbon nanotubes (NiO/MWNTs) composite material was synthesized using sodium dodecyl phenyl sulfate as a soft template and urea as hydrolysis-controlling agent. Scanning electron microscopy (SEM) results show that the as-prepared nickel oxide nanoflakes aggregate to form a submicron ball shape with a porous structure, and the MWNTs with entangled and cross-linked morphology are well dispersed in the porous nickel oxide. The composite shows an excellent cycle performance at a high current of 2 A g(-1) and keeps a capacitance retention of about 89% over 200 charge/discharge cycles. A specific capacitance approximate to 206 F g(-1) has been achieved with NiO/MWNTs (10 wt.%) in 2 M KOH electrolyte. The electrical conductivity and the active sites for redox reaction of nickel oxide are significantly improved due to the connection of nickel nanotlakes by the long entangled MWNTs. (C) 2006 Elsevier Ltd. All rights reserved.