This was ascribed to the fact that the SBET, total pore volume and GHTC-a are appreciably larger than those of HTC-a. which might be due to the decrement in the level of nitrogen from 4.5 to 0.9 at. %. Further increment towards the capacitance was obtained when the quantity of ammonium hydroxide enhanced from 5 to 7 mL due to the increased content of nitrogen from 0.9 to 1.7 at. %. TEM investigations revealed that the structure of graphene is destabilized by using the higher quantity of N-precursor. Thus, the optimization in the quantity of the heteroatom precursor played a significant role in the performance of heteroatom doped graphene towards energy storage applications. In another report, Chen et al. developed the functionalized N-doped graphene via hydrothermal at 180 °C for 12 h using ethylene diamine and hydroquinone .