Zhang et al. synthesized the g-C3N4 nanosheets by chemical oxidation method and thermal oxidation methods . The electrochemical measurements were performed using a three-electrode cell with a 2M KOH aqueous solution. The study reported that, the g-C3N4, the g-C3N4 nanosheets after oxidation, and the g-C3N4 nanosheets after thermal oxidation exhibited different electrochemical properties. The g-C3N4 nanosheets after thermal oxidation of 580 ˚C demonstrated the higher specific capacitance of 170.1 F g -1 than g-C3N4 (127.7 F g - 1 ), and g-C3N4 after oxidized with 12M sulfuric acid (133.6 F g -1 ) at 0.5 A g -1 . The g-C3N4 nanosheets showed a cyclic stability with a capacity retention of about 95.9% after 1000 cycles in a 2M KOH solution. Moreover, the g-C3N4 nanosheets after thermal oxidation of 580 ˚C showed the energy density of 3.740 Wh Kg -1 and the power density of 99.46 W K g -1 exhibited