Density Functional Theory Calculations for the Quantum Capacitance Performance of Graphene-Based Electrode Material

With first-principles density functional theory calculations, we demonstrate that quantum capacitance of graphene-based electrodes can be improved by the N-doping, vacancy defects, and adsorbed transition-metal atoms. The enhancement of the quantum capacitance can be contributed to the formation of localized states near Dirac point and/or shift of Fermi level induced by the defects and doping. In addition, the quantum capacitance is found to increase monotonically following the increase of defect concentrations. It is also found that the localized states near Fermi level results in the spin-polarization effect.