Study on improved electrochemical properties of graphene nanosheet/nickel oxide composite as electrode materials

Graphene nanosheets (GNS)/nickel oxide (NiO) composites were synthesized by a chemical method with a various amount of nickel precursor. For all composites, NiO nanoparticles were well decorated on the surface of graphene nanoplatelets. The structure and morphology analysis was performed by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). We confirmed that pure NiO particles are aggregated with each other and NiO particles dispersed on GNS prevent graphene from restacking in the composite. Electrochemical properties were also examined by cyclic voltammetry (CV). The optimum ratio of GNS to NiO was 1:20 (2 g of NiCl₂ ·6H₂O), showing the highest specific capacitance of 1034.7 Fg^-1 at 2 mV s^-1. This value was much higher than that of pure NiO and GNS, respectively. However, as the amount of nickel precursor increased, the specific capacitance displayed a decreasing tendency. It was probably due to the large agglomeration of NiO particles in high content of NiCl₂·6H₂O.