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

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.