Enhancement of quantum capacitance by chemical modification of graphene supercapacitor electrodes: a first principle calculation

Graphene-based materials have been proposed as promising electrodes for super capacitors. Recently, it has been found that the main limitation of these electrodes is their low quantum capacitance, which is a direct result of the shortage states near the Fermi level. Using first principle density functional theory calculations, this work explored the variation in electronic structure and the quantum capacitance of chemically modified graphene. Chemical modifications of graphene with different adatom concentration at different positions were tried to enhance the quantum capacitance and compared with the quantum capacitance of pristene graphene. Our results clearly shows that the number of adatom containing groups and the location of adatom region largely influence the electronic properties of graphene and thus the quantum capacitance, when compared to pristine graphene. Our work highlights the importance of the quantum capacitance in the overall performance of graphene - based super capacitors. Quantum capacitance calculations confirmed the greater advantage of some chemically modified graphene compared with those pristine graphene. This work suggests the possibility to enhance quantum capacitance of the graphene based electrodes using the effect of chemical modification and suggests that 2D graphene is a promising electrode material for supercapacitor applications. (author)