Next, for each ion and water molecule, we slice the full simulation trajectory whenever the species moves across the cutoff distance, thus generating short trajectories in which the species is either only at the interface or only in the center of the slit. Both the diffusion coefficients in Fig. and the ion-water residence times presented in Fig. are computed from these split trajectories. We only consider trajectory slices that are at least 5 ps long to ensure that we can adequately probe the diffusive regime. Furthermore, we omit the first ps from each sliced trajectory from the analysis to remove edge effects.