Origin of high storage capacity in N-doped graphene quantum dots

Study of high performance supercapacitor using doping and edge states in graphene is an interesting area of research, however, the storage capacity and understanding of the origin of enhancement are still in its infant stage. In the present work, nitrogen doped graphene quantum dot (N_GQD) is synthesized to enhance the storage capacity exploiting both the doping level as well as edge states. The results are compared with undoped graphene quantum dot and doped large graphene sheet. It is seen that the highest value of average specific capacitance (509 F g(-1)) is achieved in case of N_GQD. The origin of this high performance is explained on the basis of trap states created by both dopants and edge states which can adsorb charge carriers to enhance the storage capacity. The charge transport in N_GQD sample is also studied on the basis of trap induced electron transport. (C) 2016 Elsevier Ltd. All rights reserved.