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 nanoflakes by the long entangled MWNTs.