Ion Adsorption at the Graphene/Electrolyte Interface

The segregation of ions (Na+, OH-, H3O+, and Cl-) at the graphene/water interface, as well as at the graphene oxide/water interface, is investigated by classical molecular dynamics simulations employing polarizable force fields. Hydronium and hydroxide ions show a strong affinity for the hydrophobic graphene/water interface. This behavior is rationalized by consideration of both the amphiphilic nature of the two ions and the favorable interactions between the surface-induced electrical potential gradient and the permanent and induced dipoles of the ions. Ionizable groups on the graphene oxide surface are able to interact strongly with sodium ions that are repelled from the pristine graphene surface.