Rapid synthesis of Ni(OH)₂/graphene nanosheets and NiO@Ni(OH)₂/graphene nanosheets for supercapacitor applications

Hexagonal β-Ni(OH)₂ nanoplates grown on commercial graphene nanosheets (GNSs) were successfully prepared through a fast and facile microwave hydrothermal method. The GNSs/NiO@Ni(OH)₂ composite was obtained via an additional treatment, due to which NiO separated out from the hexagonal nanoplates. A possible formation mechanism of these composites was put forward based on their morphology and microstructure. The GNSs/Ni(OH)₂ composite exhibited high specific capacitance of 1172 F g⁻¹ at a scan rate of 5 mV s⁻¹ and showed specific capacitance of 1042 F g⁻¹ at a discharge current density of 3 A g⁻¹, whereas the GNSs/NiO@Ni(OH)₂ composite showed higher rate capability (684 F g⁻¹ at a discharge current density of 24 A g⁻¹, ∼92% capacitance retention at 3 A g⁻¹). GNSs/Ni(OH)₂ anodes after the first charge-discharge cycle were characterized by TEM. Besides, both the composites delivered high energy density and high power density, due to which they are promising materials for high-performance supercapacitors.