Synthesis of Ni-MOF derived NiO/rGO composites as novel electrode materials for high performance supercapacitors

Ni-MOF derived NiO nanosheets growing on rGO have been successfully synthesized by a hydrothermal method following by a series of calcination procedures (300 °C, 400 °C, and 450 °C). The influence of the introduction of rGO and the calcination temperature on electrochemical performance of Ni-MOF derived NiO nanosheets as the electrode material were highlighted in detail. For the three-electrode test system, Ni-MOF derived NiO/rGO composites subjected to calcination at 300 °C demonstrated the highest specific capacitance (435.25 F·g−1 at 1 A·g−1), and maintained 68.00% of its initial value at 8 A·g−1. Its specific capacitance was increased by 49.34% when compared with the initial value after 25,000 cycles at 50 mV·s−1. With the increase in calcination temperature, the specific capacitance presented the downward tendency (400 °C: 171.50 F·g−1 at 1 A·g−1, 450 °C: 116.00 F·g−1 at 1 A·g−1) due to the reduction in specific surface area originating from the agglomeration of NiO nanosheets. The introduction of rGO greatly enhanced the electrochemical performance of the composites treated at 300 °C (increased by 40.40% at 1 A·g−1 and 47.30% in specific capacitance at 8 A·g−1). The assembled hybrid supercapacitors (HSC) with Ni-MOF derived NiO/rGO composites (300 °C) and active carbon as the cathode and anode also displayed the outstanding electrochemical performance. The value of energy density reached to 76.96 Wh·kg−1 at the power density of 400 W·kg−1. All these results confirm that the MOF-derived NiO/ rGO composite should be a potential electrode material for supercapacitors.