The hydrated GO systems were built using the PACKMOL program. The shortest possible distance between the water molecules and the GO surfaces has been imposed to be at least 2 Å to avoid steric overload because of the functional groups on the surface of GO. The distance between the two GO sheets has been determined based on the number of water layers. We assumed a thickness of the water layer of ≈ 3 Å. Therefore, the interlayer distance (i.e., the distance between the centers of mass of the two GO sheets in the z direction) in the models with 1-3 water layers has been set to be 8-14 Å. The models will be labeled OGOn and RGOn with n = 1, 2, 3.