Slip-enhanced convective ion transport through sub-1nm graphene oxide channels

Fast transport of water inside carbon nanotubes and graphene-based nanomaterials due to the surface slippage has been addressed in the past years. It is expected to enhance nanofluidic ion flow, such as electrical current and streaming current. In this work, ion transport in sub-1nm nanochannels constructed by graphene oxide was investigated via electrical measurements. The experimental results showed that the electrical conductance at high salt concentration is significantly higher than the bulk conductance. According to the electrokinetic theory, the electrical conductance contributed from the slip-enhanced electroosmosis (EO) has a scaling law of bσ², where b and σ are slip length and surface charge density, respectively. It implies that slip-enhanced electrical conductance becomes considerable at the condition of high surface charge density, e.g. high pH value and salt concentration. As a result, we inferred that the convective ionic current is greatly enhanced by slip EO at high salt concentration. Based on the charge regulation model, the slip length of 10~20 nm was estimated, which is consistent with the value reported in the literature.