Ultrafast water transport within 2D LDH–CNT composite membranes promotes humidity sensing

Abstract

Layered double hydroxides (LDHs), as two-dimensional materials, exhibit multiple active sites for water molecule interaction after exfoliation and reconstruction into nanosheet membranes, presenting significant potential in the field of humidity sensing. This work demonstrates the rapid adsorption and desorption kinetics of water on LDH membranes, highlighting the fast response capability of LDH-based humidity sensors. Furthermore, we doped the LDH nanosheets with single-walled carbon nanotubes (SWCNTs) to modulate the interlayer spacing of LDH membranes and provide additional pathways for water transport, thereby enhancing the sensing performance of the LDH membrane. Our findings indicate that in the LDH–CNT composite membrane, the permeation rate of water molecules is significantly improved, with confined water transitioning from a “restricted” state to a more “relaxed” state, facilitating efficient proton transfer. Experimental results show that the LDH–CNT composite-based humidity sensor exhibits transient response times of 6.99 and 7.07 seconds within a relative humidity range of 30% to 80%. The proposed SWCNT-doping approach not only broadens the application prospects of LDHs in humidity sensing but also paves the way for more diverse applications of LDH materials.