Fig. 3: Ion entry process into graphene nanoslits.

a Molecular dynamics (MD) simulation model (left) and snapshoot (right) for HCO3- ions entering the graphene nanoslits decorated with -COOH edge and -OH/-C-O-C- interior. The red and white spheres indicate O and H atoms, respectively. The grey balls indicate C atoms in graphene nanoslits. The purple and blue balls indicate C and O atoms in HCO3- ions. b The potential of mean force (PMF) curves of HCO3- ions when entering the graphene nanoslits. The position of x = 0 is defined as the position of the C atom on the edge. The error bars in b represent the standard deviation of the mean. c The number (N) of HCO3- ions coordinated with the oxygen groups of graphene nanoslits as the modeling time increases.