Facile Fabrication of Subnanopores in Graphene under Ion Irradiation: Molecular Dynamics Simulations

Two-dimensional (2D) nanoporous membranes have attracted great interest in water desalination, energy conversion, electrode, and gas separation. The performances of these membranes are mainly determined by the nanopores, and only with satisfactory subnanometer pores can applications such as high-precision ion separation be realized. Therefore, to efficiently create subnanopores in 2D materials is of great importance. Here, using molecular dynamics simulations, we demonstrate that the direct irradiation of energetic ion is capable of introducing subnanopores in monolayer graphene. By changing the energy of the incident Au ion, the averaged pore diameter can be adjusted from 4.2 to 5.6 Å, and pore diameter distributions are narrow. In the formation processes of the subnanopores, the cascade collisions caused by the primary knock-on atom (PKA) predominates, and pores can only be created in ion impact positions close to the PKA, especially for the incident ion with high energy. Our results show the promise of ion irradiation as a facile method to fabricate subnanopores in 2D materials. As hydrated ions, gases, and small organic molecules have diameters of several angstroms, close to the pore sizes, the created nanoporous membranes can be used to separate those matter, which is conducive to accelerating related applications.