Improving Ionic Current Rectification in Misaligned Janus Bilayer Nanoporous Graphene through Tuning Electric Field Direction

Abstract In recent years, nanoporous graphene has shown great potential in nanofluidic devices and ion separation applications. However, in multilayer architectures, pore misalignment significantly suppresses ion transport efficiency, and its underlying mechanism remains insufficiently understood. To address this issue, this study employs molecular dynamics simulations to systematically examine the effect of pore alignment and electric field direction on ionic current rectification (ICR) in Janus bilayer nanoporous graphene (NPG). The results show that, with increasing pore offset, ions become strongly enriched in the NPG interlayer region, forming a localized high-concentration environment that hinders ion migration and induces an ICR inversion. Further analysis reveals that, under a fixed pore offset, tuning the angle between the electric field and the membrane normal can effectively reconstruct the ionic distribution in the NPG, thereby enhancing transport asymmetry between forward and reverse directions. As a result, the rectification inversion caused by pore misalignment can be recovered, yielding a maximum ICR ratio of approximately 30 in the fixed-functional-group model. Notably, this enhancement in ICR is accompanied by a monotonic decrease in electropumping efficiency, suggesting that ionic rectification and directional water transport are not directly correlated. These findings demonstrate that both pore offset and electric field orientation serve as key tunable parameters governing ICR performance in NPGs, providing a new strategy for the design of high-performance and controllable ICR devices.