Hydrous Proton Transfer through Graphene Interlayer: An Extraordinary Mechanism under Magnifier

Abstract

AbstractBalancing ionic selectivity against permeability in filters made from graphene remains a challenge today. Interlayer distance, as the most important factor, dominates nearly all aspects of the flow inside the channel, from the formation of water molecules to the hydration shell of the ions. Unraveling the effects of the interlayer distance on the proton diffusion process helps lay a foundation for the cutting‐edge proton conduction technology. Here, the reactive molecular dynamics simulations are used to probe the proton flow through a series of hydrated graphene channels with different interlayer distance values. The results show that the proton‐selectivity experiences a sharp increase when the channel height is reduced to values under 8 Å, which is near the end of the hydration radii range of the monovalent and divalent cations. Reducing the interlayer distance also decreases the number of confined water molecules, consequently reducing the proton diffusion rate as the hopping platform fades. This way, spatial hindrance combined with the proton‐selective Grotthuss mechanism provide a proton‐exclusive membrane. The outputs of this work can be used for the optimization of proton‐exclusive nanochannels and to serve affordable proton‐exchange membranes (PEMs) for technological advancement in diverse fields from PEM fuel cells to storing liquid hydrogen.