First principles study on copper passivated armchair graphene nanoribbon for a supercapacitor electrode material

Abstract

Density functional theory was employed to calculate the electronic properties of three armchair graphene nanoribbon systems (AGNR), namely, hydrogen-passivated (H-AGNR-H), passivated with copper and hydrogen on opposite sides (Cu-AGNR-H), and passivated on both sides with copper (Cu-AGNR-Cu). The calculations were carried out using 1 × 20×1 and 1 × 100×1 k-points for the self consistent field (scf) and non-self consistent field (nscf) calculations, respectively. Based on the formation energies, all three systems were structurally stable when compared to other nanoribbon systems. For the copper-passivated system, Cu–AGNR-H (-0.54 eV) was found to be more stable than Cu-AGNR-Cu (-0.28 eV). Phonon dispersion calculations were also conducted showing that Cu-AGNR-H is more stable dynamically than Cu-AGNR-Cu. The quantum capacitance and the total surface charge were computed to quantify the material's properties as a supercapacitor. Cu-AGNR-Cu showed superior quantum capacitance and surface charge values, while Cu-AGNR-H showed vast improvements when compared to H-AGNR-H. With an ideal structural stability, vibrational stability, quantum capacitance, and surface charge values, the Cu-AGNR-H system was the most viable material for electrodes among the three nanoribbon systems.