Frequency-Resolved Dual-Regime Ion Transport in Stacked Graphene Nanopores

Nanofluidic ion transport arises from a competition between bulk conduction and interfacial electrostatics, yet conventional DC measurements collapse these contributions into a single averaged response, obscuring the underlying transport physics. Here, we experimentally isolate and control two distinct ion-transport regimes in stacked graphene nanopores by using frequency-resolved electrochemical impedance spectroscopy (EIS). The Nyquist spectra reveal two discrete time constants─geometric pore resistance at high frequency and electric-double-layer (EDL) relaxation at low frequency─allowing quantitative decoupling of bulk transport from interfacial ion dynamics through constant-phase-element (CPE) circuit modeling. This dual-regime behavior, amplified in stacked membranes and tunable through Debye screening and ion identity, constitutes direct evidence of frequency-governed ionic dynamics in atomically thin nanopores. These results reveal transport physics that remain hidden in DC nanofluidics and position frequency-domain interrogation as a required tool─not a characterization convenience─for decoding ion motion in electrostatically modulated nanofluidic devices.