▎ 摘　　要

In this research, the electrochemical exfoliation of pencil rods was carried out for the synthesis of graphene sheets in different mixtures of H2SO4 and HNO3 solution. Influence of different volume ratios of H2SO4: HNO3 at a low concentration (0.6 M) on the morphology and structure of prepared graphene sheets was investigated by field emission electron microscopy (FESEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Raman spectroscopy and atomic force microscopy (AFM) analyses. Results indicated that the mixtures of fewlayered graphene, multi-layered graphene, and graphene oxide were achieved by applying an anodic voltage of + 10 V. However, the number of layers, degree of oxidation and defect density of the synthesized powders were different. By increasing the volume ratio of HNO3 in electrolytes, the degree of exfoliation of graphite decreased. On the other hand, the highest degree of oxidation was achieved for the prepared graphene by electrochemical method in the mixture of H2SO4: HNO3 with 1:1 ratio. EDS results of the prepared powders demonstrated the occurrence of nitrogen and sulfur co-doping of graphene sheets.