B/N-doped graphdiyne as superior supercapacitor electrode with record high quantum capacitance

Last decade has witnessed a surge of research in carbonaceous nanostructures as electrode materials for supercapacitors. Herein, we propose a new type of carbon electrode by using two-dimensional (2D) graphdiyne with nonmetal dopants. By first-principles calculations, we systematically investigated the structural, energetic, electronic and capacitance properties of B/N-doped graphdiyne. Results show that B/N doping has low formation energies in graphdiyne, indicating facile experimental synthesis. Interestingly, B/N doping transforms graphdiyne from a direct-band-gap semiconductor to an excellent metal, originating from the shift of Fermi level into the valence/conduction bands. By evaluating the quantum capacitance of graphdiyne with different doping concentrations, we demonstrate that the capacitance of B (N)-doped graphdiyne as anode (cathode) can reach a record high value of 4317 F/g (6150 F/g), significantly outperforming other 2D carbon electrodes. With high specific surface area and tunable electronic properties, we expect graphdiyne and related porous structures to have great potential for supercapacitors and energy storage devices.