Unusual Enhancement of the Adsorption Energies of Sodium and Potassium in Sulfur-Nitrogen and Silicon-Boron Codoped Graphene

Abstract

Herein, we have employed first-principles calculations to investigate the interaction between XY dual-doped graphene (DDG) (X = AL, Si, P, S; Y = B, N, O) and sodium/potassium. The introduction of two dopants alters the adsorption energy (AE) of sodium and potassium with respect to perfect graphene by an average of 0.88 and 0.66 eV, respectively. The systems that display the strongest interactions with the two alkalies assayed are SN and SiB DDG. Although the adsorption energy of sodium on graphene is weaker in comparison to that of potassium, the introduction of these dopants significantly reduces this difference. In effect, in some cases, the AE-K and AE-NA differ by less than 0.05 eV. The protrusion of the 3p dopants out of the graphene plane creates a hole where sodium and potassium can easily be intercalated between two layers of dual-doped graphene. The interlayer distances are reduced by less than 0.4 Å after K intercalation, making the process very favorable. Finally, most importantly, this eminent rise in adsorption energies guarantees exceptional storage capacities at the cost of low doping concentration.