In the case of functionalized channels, the water molecules rearrange during the relaxation period by getting attracted to the intercalated cations. However, no observable trend in water affinities with different cations is found (Figure ). Interestingly, in the case of graphitic channels the water molecules show a higher density around the Ca 2+ than the monovalent cations of K + and Na + (Error! Reference source not found.C-E). The higher density around the Ca 2+ suggests that cations with larger hydration shells attract water more tightly in the confined environment of graphene nanocapillaries. Despite allowing a larger number of water molecules to intercalate into the capillaries and expanding the space for the water to travel, the flux declines and slip length decreases, as shown in our experimental results. From the simulation results, we may conclude that this decline is based on the increased interaction between water molecules and intercalated cations. As the differences in water affinities of cations in the simulations was prominent in the case of cation-π interaction and not observable in cation intercalation with functionalized areas, it suggests that the cation-π interaction on the graphitic areas of GO is the more dominant case for governing the slip length. A similar increase in friction was predicted with AIMD simulations of water transport with impurities in the graphitic nanochannel walls . In this case, the friction was correlated with the hydrogen bond ability of impurities. This increase in interaction between cations and water molecules may affect the slip length in two different ways. The slip length can be interpreted as a description of the friction of water with the nanochannel walls. Increased attraction of water molecules via the absorbed cation would cause increased friction and explains the trend of decreasing slip length with increasing hydrated diameter. The large slip length in graphene-based nanochannels may also be explained by a depletion layer with reduced viscosity close to the channel walls . Increased interaction between the channel walls and the intercalated cations may also reduce the depletion layer and increase the viscosity close to the channel walls, explaining the increase in slip length with increasing hydration diameter.