Hybrid two-dimensional nickel oxide-reduced graphene oxide nanosheets for supercapacitor electrodes

The graphene oxide (GO) nanosheets as well as the two-dimensional Ni(OH)₂ with excellent uniformity were prepared with a hydrothermal and Hummers method, respectively. Ni(OH)₂ nanosheets treated by cationic surfactants and graphene oxide with negative charges were mixed by electrostatic self-assembly. After annealing, hybrid two-dimensional NiO-reduced graphene oxide nanosheets (NiO-rGO) were obtained. Attributing to the synergistic effects, the NiO-rGO electrode exhibits an optimized electrochemical performance, in contrast to pure NiO or rGO supercapacitor. The results show the NiO nanosheets are homogeneously dispersed on the surface of rGO nanosheets and the hybrid NiO-rGO nanosheets electrode can deliver an excellent capacity of 343 C·g⁻¹ (1 A·g⁻¹). Furthermore, the electrodes made up of NiO-rGO nanosheets are employed to assemble symmetric supercapacitor. The energy density of as-prepared supercapacitor device can reach up to 5.4 Wh·kg⁻¹ at a power density of 0.43 kW·kg⁻¹ operated in the voltage range of 0–1.4 V. In addition, the symmetric supercapacitor also exhibits an excellent capacitance retention of 90% after 10,000 cycles (10 A·g⁻¹).