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

Abstract NiCo2O4 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 NiCo2O4 were manipulated by adjusting the amount of β-cyclodextrin (β-CD) added to the mixture of CTAB and SDS. Necklace-like NiCo2O4 nanorods composed of numerous nanospheres were obtained under low β-CD content. Under high β-CD content, NiCo2O4 transformed into firework-shaped microspheres through the self-assembly of necklace-like NiCo2O4 nanorods. NiCo2O4 reverted to nanorods as β-CD content further increased. The two morphologies of NiCo2O4 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 NiCo2O4 microspheres reach the high value of 697.5 F g−1 and is higher than that of NiCo2O4 nanorods (525 F g−1). In addition, the firework-shaped NiCo2O4 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 NiCo2O4 microspheres obtained by adjusting the β-CD content of CTAB and SDS aggregates have considerable application potential as electrode materials for supercapacitors.