Chemical Potential-Driven Ion Transport through Interlayer Ti₃C₂T_x MXene Channels

Considering that a solid in contact with a liquid bears surface charges, an impact of charged interfaces is of increased importance in understanding fluidic behaviors inside nanoconfined channels since they have a high surface-to-volume ratio. Here, we exploit 2D interlayer nanochannels with surface charges, formed between randomly stacked neighboring metal carbide and nitride (MXene) sheets, to investigate confined ionic motions under chemical potential gradients. Plenty of surface terminal groups, arising from etching and exfoliation processes during MXene synthesis, endow the planar sheets with negative surface charges and help create the interlayer spacing at the sub-nanometer scale. The MXene confined channels harness the chemical potential differences by salinity gradients via charge-selective ion transportation. Furthermore, coupled with the inherent photothermal conversion performance of MXene materials, the MXene capillaries convert thermochemical potential driven by local photothermal heating to an active ion flux from colder to hotter sides. The MXene-based ion conductor may be an important nanofluidic platform possibly for biomimetic sensory systems.