Diffusion coefficient of ions through graphene nanopores

Abstract

In this work, we investigate the transport of ions through graphene nanopores driven by concentration gradients through molecular dynamics simulations. The diffusion coefficients, D, of K+ and Cl− are computed for various pore sizes and porosities. It is found that D is sensitive to the pore size when the pore diameter is smaller than 3 nm. For relatively large pores, D remains largely independent of the pore size. The dependence of D on the porosity shows a near-linear relationship. The effects of pore size and porosity on the diffusion coefficient are caused by the free energy barrier at the pore due to the ion–pore molecular interactions and the dehydration of ions. A general scaling law for the diffusion coefficient is also proposed. The results in this work provide useful information for the design and fabrication of nanoporous structures for ion transport.