In this study, polyaniline (PANI)/graphene nanosheet (GNS) composites were synthesized through chemical oxidation polymerization by changing the weight ratio of aniline mono-mers. To examine the morphological structure of the composites, scanning electron micros-copy and transmission electron microscopy (TEM) were conducted. TEM results revealed that fibril-likePANI with a diameter of 50 nm was homogeneously coated on the surface of the GNS. The electrochemical properties of the composites were studied by cyclic voltam-metry in 1 M H2SO4 electrolyte. Among the prepared samples, the PANI/GNS (having 40 wt% aniline content) showed the highest specificcapacitance, 528 Fg-1, at 10 mVs-1. The im-proved performance was attributed to the GNS, which provides a large number of active sites and good electrical conductivity. The resulting composites are promising electrode materials for high capacitative supercapacitors.

In this study, cobalt oxide (Co3O4)/graphene composites were synthesized through a simple chemical method at various calcination temperatures. We controlled the crystallinity, particle size and morphology of cobalt oxide on graphene materials by changing the annealing temperatures (200, 300, 400℃). The nanostructured Co3O4/graphene hybrid materials were studied to measure the electrochemical performance through cyclic voltammetry. The Co3O4/graphene sample obtained at 200℃ showed the highest capacitance of 396 Fg-1 at 5 mVs-1. The morphological structures of composites were also examined by scanning electron microscopy and transmission electron microscopy (TEM). Annealing Co3O4/graphene samples in air at different temperatures significantly changed the morphology of the composites. The flower-like cobalt oxides with higher crystallinity and larger particle size were generated on graphene according to the increase of calcination temperature. A TEM analysis of the composites at 200℃ revealed that nanoscale Co3O4 (~7 nm) particles were deposited on the surface of the graphene. The improved electrochemical performance was attributed to a combination effect of graphene and pseudocapacitive effect of Co3O4.