Fundamental Insights into Nanoconfined Devices by Using Electrochemical Impedance Spectroscopy

Despite electrochemical impedance spectroscopy (EIS) being a powerful tool to inspect phenomena that occur at different time scales, its application to nanofluidic devices remains underexplored. In this study, we investigate the electrochemical behavior of glass nanopipettes internally coated with a carbon layer (CNPs, 60 nm radius) using EIS and electrochemical capacitance spectroscopy (ECS) to decouple ion transport from redox reactions. Through systematic measurements under varied conditions, we demonstrate herein that EIS and ECS can facilitate the estimation of key parameters, such as ion and electron transfer resistances, double-layer capacitance, and redox capacitance, by employing equivalent electrical circuits. Complementary methods, i.e., the distribution of relaxation times and differential capacitance, provide consistent values of resistances and capacitances compared to equivalent circuit analysis (