Homogeneous nickel metal-organic framework microspheres on reduced graphene oxide as novel electrode material for supercapacitors with outstanding performance.

Herein, we designed and prepared nickel metal-organic framework microspheres anchored directly on reduced graphene oxide (Ni-MOF/rGO) by a facile hydrothermal and successive calcining process. The electrode for Ni-MOF/rGO composite annealed at an optimized temperature of 300 °C (Ni-MOF/rGO-300) shows desired conductivity, good cycling stability and high ion-accessible surface area, leading to an ultrahigh specific capacitance of 954 F g-1 at a current density of 1 A g-1 and a remarkable rate capability of 80.25% at 5 A g-1. Meanwhile, the assembled Ni-MOF/rGO-300//activated carbon asymmetric supercapacitor (ASC) shows a favorable energy density up to 17.13 Wh kg-1 at a power density of 750 W kg-1 in the potential window of 0-1.5 V. Moreover, the capacitance retention can still maintain 81.63% after 4000 cycles at a high current density of 5 A g-1. The excellent electrochemical properties can be credited to the synergistic effects between the unique structures of Ni-MOF and rGO, which makes the Ni-MOF/rGO composite a potential electrode material for high performance supercapacitors.