Fig. 1

Interaction between alkali-metal cations with graphene. a Potential energy surface of the cation adsorption on the graphene surface with a total excess charge of \({q}_{{\rm{grp}}}=-0.5\ e\) in 1 M LiCl, NaCl, KCl, and CsCl aqueous electrolytes. Inset represents the cation–graphene system, where the green-yellow circles represent a hydrated alkali cation. b Ionic charge of the cations at different \({q}_{{\rm{grp}}}\) and adsorption locations. Inset: interfacial charge transfer between Cs\({}^{+}\) and the graphene electrode as an example, where the cyan and yellow isosurfaces indicate charge depletion and accumulation regions, respectively. c Schematic description of the charge transfer (CT) effect on the potential response of charged graphene electrode. d The overall charge transfer obtained by integrating the charge transfer per ion, shown in b, and local cation density (inset). The isosurface is set to be \({10}^{-4}\) and \(1.6\times{10}^{-4}\) a.u. for the oxygen density in the ion solvation shell (in a) and electronic density difference (in b), respectively