To explain the change in surface tension with ionic concentrations and surface charge, we calculate the difference between the cohesive energy, , (calculated as the sum of waterwater, water-ion, ion-ion van der Waals and Coulomb energy contributions) and the adhesive energy, , (calculated as the sum of water-graphene and ion-graphene van der Waals and Coulomb energy contributions). Both are calculated with a cut-off of 1.4 nm, which is the maximum permissible cut-off for our system size. The results, presented in Figure , show that this difference decreases with the increase in ionic concentration while remaining negative, confirming that the presence of the ionic species makes the surface more hydrophilic.