Effect of coexistence of defect and dopant on the quantum capacitance of graphene-based supercapacitors electrodes

The influence of doping (B, N, Al, Si, P, S), vacancy, and Stone-Wales defect on stability, electronic structures, quantum capacitance, and surface charge storage of graphene is explored by density functional theory calculations. The results indicate that the quantum capacitance and surface charge storage can be significantly improved by the introducing of defect and doping. Furthermore, the enhancement of doped vacancy-defected graphene is more obvious than that of doped Stone-Wales defected graphene. By analyzing the density of states, it can be obtained that the improvement of quantum capacitance is resulted from the presence of localized states around Fermi level by doping or defect. Moreover, the effect of concentration of doping and defect on the graphene is also explored, and the results suggest that the quantum capacitance increases with the increasing of concentration for most modified graphene-based substrates. The findings can provide effective approach for improving the performance of graphene-based surpercapacitors.