Synthesis of a rGO/NiO composite with a hierarchical porous structure by self-assemblyand its electrochemical performance as a supercapacitor electrode

A GO/Ni(HCO3)2 composite was synthesized by the self-assembly of layered Ni(HCO3)2 and GO in their suspension mixture under sonication, followed by heat treatment to obtain rGO/NiO for the use as the electrode material of supercapacitors. The structural change from the GO/Ni(HCO3)2 to the rGO/NiO was investigated by XRD, SEM, and nitrogen adsorption. Results indicate that the rGO/NiOhas a specific surface area of 121.3 m2 g-1 and pore volume of 0.26 cm3 g-1. The rGO/NiO possesses a hierarchical porous structure with a pore size range of 2-100 nm. The high specific surface area and the hierarchical porous structure endow the rGO/NiO composite with a high specific capacitance of 919 F g-1 (0.5 A g-1) and improved rate capability of 71% when the current density increases from 0.5A g-1 to 5A g-1. The specific capacitance retains 91% of its original value after the composite is cycled at the current densityof 2 A g-1for 3000 cycles, indicating a good rate capability.