Unveiling hygroresponsive ion conduction performances of layered double hydroxide nanosheets

Abstract

Layered double hydroxide (LDH) nanostructures have attracted significant attention as versatile two-dimensional building blocks with exceptional properties, including specific surface area, selective growth, variable anion exchange, catalytic reactivity, and intrinsic hydroxide ion conductivity. Due to the rare intrinsic hydroxide ion conduction arising from the abundant hydroxyl groups, LDHs have been applied in various fields, including supercapacitors, batteries, electrocatalysts, photocatalysts, and proton exchange membranes. However, the correlation between temperature, humidity, and structural properties of LDH as an ion conductive channel device has not yet been investigated. In this study, we verified the ion-conducting mechanism of LDH by utilizing closely packed two-dimensional scroll nanosheets with variations in temperature and humidity. The ion flux in the LDH nanosheets operates through surface-to-surface hopping influenced by water activity and the desorption/adsorption state of water. Moreover, the LDH nanosheets demonstrate an exceptional ability for self-recovery, absorbing moisture from the surrounding environment and diffusing it to internal structures. This water absorption property significantly contributes to the surface water-induced ion conduction observed in LDH nanosheets.