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

Abstract

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.