Controllable synthesis of ZnCo2O4@NiCo2O4 hierarchical nanosheets for high performance supercapacitors

The ZnCo2O4@NiCo2O4 hierarchical nanosheets on nickel foam were successfully synthesized via hydrothermal and annealing approaches. The structure, morphology and composition of the prepared ZnCo2O4@NiCo2O4 hierarchical nanosheets were systematically characterized by XRD, SEM, TEM and EDS. Then the electrochemical properties of the ZnCo2O4@NiCo2O4 hierarchical nanosheets were measured in three-electrode system. It is shown that the ZnCo2O4@NiCo2O4 hierarchical nanosheets exhibited higher specific capacitance and better cycling stability as electrode materials than ZnCo2O4 nanosheets. The specific capacitance of the ZnCo2O4@- NiCo2O4 hierarchical nanosheets could reach to a high value of 3021 F g-1 (377 mAh g-1) at current density of 1 A g-1. Moreover, the specific capacitance of the ZnCo2O4@NiCo2O4 hierarchical nanosheets could remain 96.4% of the initial value after 5000 cycles. The excellent electrochemical properties show that the prepared ZnCo2O4@NiCo2O4 hierarchical nanosheets can be a promising electrode material for supercapacitor.