One-step synthesis of NiCo2O4 nanorods and firework-shaped microspheres formed with necklace-like structure for supercapacitor materials

Abstract NiCo 2 O 4 nanorods and firework-shaped microspheres formed with necklace-like structures were prepared through a facile hydrothermal method by using cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) aggregates as soft templates. The morphologies of NiCo 2 O 4 were manipulated by adjusting the amount of β -cyclodextrin ( β -CD) added to the mixture of CTAB and SDS. Necklace-like NiCo 2 O 4 nanorods composed of numerous nanospheres were obtained under low β -CD content. Under high β -CD content, NiCo 2 O 4 transformed into firework-shaped microspheres through the self-assembly of necklace-like NiCo 2 O 4 nanorods. NiCo 2 O 4 reverted to nanorods as β -CD content further increased. The two morphologies of NiCo 2 O 4 were characterized in 2 M KOH electrolyte solution with a three-electrode system. At the current density of 1 A g −1 , the specific capacitance of firework-shaped NiCo 2 O 4 microspheres reach the high value of 697.5 F g −1 and is higher than that of NiCo 2 O 4 nanorods (525 F g −1 ). In addition, the firework-shaped NiCo 2 O 4 microspheres demonstrate excellent long-term cycle stability with 85.77% capacitance retention after 10,000 cycles at the current density of 1 A g −1 . These findings imply that the firework-shaped NiCo 2 O 4 microspheres obtained by adjusting the β -CD content of CTAB and SDS aggregates have considerable application potential as electrode materials for supercapacitors.