2D/2D nanoarchitecture of Ni/NiCo₂O₄ deposited onto reduced graphene oxide for high-performance hybrid supercapacitor applications

The advanced energy storage electrode materials should mainly be focused on nanoarchitecture, multiple redox states, large surface area, and plenty of surface-active sites. Thereby, designing well-defined nanostructured electrode materials and tailoring them with a suitable supporting material is a prime requirement for supercapacitor application. Herein, we report the facile solvothermal synthesis of Ni/NiCo₂O₄ nanosheets directly decorated onto reduced graphene oxide (rGO) followed by thermal treatment. The porous 2D/2D Ni/NiCo₂O₄@rGO framework could enable easier ion diffusion to the electroactive site with reduced resistance for charge and mass transportation. In addition, a 2D/2D nanoarchitecture with strong face-to-face contacts can provide an extremely coupling interface that exhibits to have tremendous potential for energy storage performance. Interestingly, the resulting Ni/NiCo₂O₄@rGO nanoarchitecture electrode exhibits a higher specific capacitance of 1110 F g⁻¹ at a specific current of 1 A g⁻¹, which is much higher than those of Ni/NiO@rGO (500 F g⁻¹) and CoO/Co₃O₄@rGO (425 F g⁻¹) electrodes under the similar condition. Besides, the Ni/NiCo₂O₄@rGO nanoarchitecture electrode shown considerably high specific capacitance (574 F g⁻¹) even though the specific current increased to 20 A g⁻¹, demonstrating that the nanoarchitecture electrode preserves good rate capability. Further, a hybrid supercapacitor was constructed using the Ni/NiCo₂O₄@rGO nanoarchitecture electrode, and it delivered a high specific capacitance of 127 F g⁻¹, with a high energy density of 40.63 Wh kg⁻¹ for a power density of 854.81 W kg⁻¹. As well as the hybrid supercapacitor exhibited excellent long-term cyclability with 90.1 % retention over 20,000 charge-discharge cycles.