Preparation and electrochemical behaviors of petal-like nickel cobaltite/reduced graphene oxide composites for supercapacitor electrodes

Petal-like nickel cobaltite (NiCo₂O₄)/reduced graphene oxide (rGO) composites with different rGO-to-NiCo₂O₄ weight ratios were synthesized using a simple hydrothermal method and subsequent thermal treatment. In the NiCo₂O₄/rGO composite, the NiCo₂O₄ 3-dimensional nanomaterials contributed to the improvement of electrochemical properties of the final composite material by preventing the restacking of the rGO sheet and securing ion movement passages. The composite structure was examined by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and Fourier-transform infrared (FT-IR) spectroscopy. The FE-SEM and TEM images showed that petal-like NiCo2O4 was supported on the rGO surface. Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) were used for the electrochemical analysis of composites. Among the prepared composites, 0.075 g rGO/NiCo₂O₄ composite showed the highest specific capacitance of 1,755 Fg^-1 at a current density of 2 Ag^-1. The cycle performance and rate capability of the composite material were higher than those of using the single NiCo₂O₄ material. These nano-structured composites could be regarded as valuable electrode materials for supercapacitors that require superior performance.