Unique ion transport behaviors in two-dimensional (2D) nanochannels have sparked strong interests in exploring 2D nanomaterials for supercapacitor applications, which rely much on the formation of electric double layers (EDLs) at the solid-liquid interface. However, there is still a crucial missing part on understanding how ions with different kinetic properties could affect the formation of EDLs. Here, we examine the real-time ion transport in the formation of EDLs by electrochemical quartz crystal microbalance (EQCM) and observe distinct charge transport behaviors between activated carbon with a tortuous pore structure and graphene films with 2D channel spacing (<2 nm). Using molecular dynamics (MD) simulations, we find that ions with a higher diffusion coefficient predominantly affect the EDLs formation, leading to the anion- or cation-dominated ion exchange process in the sub-2 nm 2D graphene channels. By expanding to different electrolytes, the kinetics-controlled ion transport mechanism is further confirmed by experimental observations and MD simulations. Such findings will bring new insights for improved electrochemical performance of 2D nanomaterials.

二维（2D）纳米通道中独特的离子传输行为引起了人们对探索用于超级电容器应用的2D纳米材料的强烈兴趣，这种材料在很大程度上依赖于在固液界面形成双电层（EDL）。然而，在了解具有不同动力学特性的离子的过程中仍然存在关键的缺失部分可能会影响EDL的形成。在这里，我们检查了电化学石英晶体微天平（EQCM）在EDLs形成中的实时离子迁移，并观察了具有曲折孔结构的活性炭与具有2D通道间距（<2 nm）的石墨烯薄膜之间的明显电荷迁移行为。使用分子动力学（MD）模拟，我们发现具有较高扩散系数的离子主要影响EDL的形成，从而导致亚2 nm 2D石墨烯通道中以阴离子或阳离子为主的离子交换过程。通过扩展到不同的电解质，通过实验观察和MD模拟进一步证实了动力学控制的离子传输机制。这些发现将为改善二维纳米材料的电化学性能带来新的见解。