Controlled synthesis of NiCo₂O₄ nanowires and nanosheets on reduced graphene oxide nanosheets for supercapacitors

Abstract

Two types of homogeneous NiCo₂O₄-NW/rGO composite and NiCo₂O₄-NS/rGO composite are synthesized via a facile and effective low-solution approach coupled with a simple post-annealing treatment. Importantly, the morphologies of NiCo₂O₄ can be easily controlled to be nanowires or nanosheets by using different hydrolyzing agents without using of templates, surfactant and stabilizer. These two different morphologies of composite are evaluated as electrodes for supercapacitors, and the NiCo₂O₄-NS/rGO exhibits good electrochemical performance. Compared with NiCo₂O₄-NW/rGO (i.e., 1,137.8 F g⁻¹ at 1 A g⁻¹ and 683.3 F g⁻¹ at 15 A g⁻¹), NiCo₂O₄-NS/rGO achieves much higher capacitance (i.e., 1,217.4 F g⁻¹ at 1 A g⁻¹ and 760 F g⁻¹ at 15 A g⁻¹) with excellent cycling stability of 94 % retention of specific capacitance after 1,000 cycles. The results show that these NiCo₂O₄/rGO composites are promising for high-performance supercapacitors.