Tuning Na adsorption on the edge of a graphitic nanopore by incorporating a functionalized-ligand and single-heteroatom dopant

Abstract

The formation of functionalized nanopores on graphene has been shown to improve the Na adsorption strength significantly. However, the fundamental design structure that improves nanopore performance with regard to Na adsorption is still unclear. By considering that both armchair and zigzag edges most likely will be present simultaneously in the graphitic nanopore structure, we propose that the enhancement of the graphene-based anode capacity can be achieved by modifying the edge structures of the graphitic nanopore with either B or P dopants combined with the HOOC functional group. Herein, by means of comprehensive first-principles density functional theory (DFT) calculations, we study the effect of incorporating several functional groups (viz., hydrogen (H), oxygen (carbonyl (O), hydroxyl (HO⁻) and carboxyl (HOOC⁻)) and single heteroatom dopants (viz., B, N, S and P) at the armchair and zigzag edge of the graphitic structure on the thermodynamics of Na adsorption. Our findings indicate that the incorporation of several functional groups and the presence of single heteroatom dopants always result in a low formation energy with an appropriate Na adsorption energy for both edges. Besides, the addition of a substitutional heteroatom dopant near the functionalized ligand further strengthens the Na adsorption, which is strongly correlated to the enhancement of the Na capacity that can be stored by the nanopore-incorporated graphene.