Bio-Inspired Ion Channels for Suppressing Interfacial Parasitic Reactions and Enabling Low-Energy Ion Desolvation in Aqueous Supercapacitors

Abstract

The sluggish de-solvation reaction kinetics of hydrated ions and undesired water electrolysis on the electrode/electrolyte interface are the main challenges that hinder the application prospect of aqueous supercapacitor. Interestingly, biological ion channels exhibit remarkable capabilities in facilitating the de-solvation and low-energy transport of hydrated ions, achieved through their size-limited confinement effects and electrostatic interactions. Inspired by such transit mechanism of ion channel, we propose an interesting strategy to facilitate rapid desolvation of electrode surface ions with low-energy transport, which utilized the aperture confinement effect and charge effect of biological ion channels to construct porous carbon electrodes. Concretely, we systematically revealed the relationship between the aperture size of the carbon electrode and ion migration rate, thereby obtaining the optimal channel radius (10 Å). To verify the modulation mechanism of the charge effect, four functional groups were decorated on the carbon-based electrode in sequence and determined that the -COOH group possessed the optimal effect on accelerating the ion migration kinetics and restricting parasitic reactions. This modification destabilized the hydration shell of potassium ions, decreasing their average coordination number (ACN) from 6.0 to 2.1 and enabling the establishment of a low-resistance ion transport pathway. Concurrently, it achieved a fourfold enhancement in potassium ion permeation while significantly inhibiting HER. This bioinspired approach provides a new paradigm for designing high-performance aqueous energy storage systems through rational control of ion transport behavior at molecular scales.