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 the occurrence of undesired water electrolysis on the electrode–electrolyte interface pose significant challenges to the practical deployment of aqueous supercapacitors. Interestingly, biological ion channels exhibit remarkable abilities to facilitate the de-solvation and low-energy transport of hydrated ions, and these are achieved through their size-limited confinement effects and electrostatic interactions. Inspired by such transit mechanisms of ion channels, we propose an interesting strategy to facilitate the rapid desolvation of electrode surface ions with low-energy transport. This strategy utilizes the aperture confinement effect and charge effect of biological ion channels to construct porous carbon electrodes. Concretely, we systematically reveal 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 sequentially incorporated into the carbon-based electrode, and it was determined that the –COOH group exhibited the optimal effect for 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, thereby enabling the establishment of a low-resistance ion transport pathway. Concurrently, it achieved a fourfold enhancement in potassium ion permeation while significantly inhibiting the HER. This bio-inspired approach provides a new paradigm for designing high-performance aqueous energy storage systems through rational control of ion transport behavior on a molecular scale.