Ion transport behavior in a vertically-oriented asymmetric Ti3C2Tx nanochannel membrane

Exceptional ion release and storage ability of biological ion channels are regarded as a prerequisite for various life activities. Constructing biomimetic nanochannels to modulate selective ion transport has received enormous attention. Herein, a study on ion transport behavior in a vertically-oriented three-sectional Ti3C2Tx membrane with asymmetric charge distribution was presented. The surface charge polarity of Ti3C2Tx nanosheet was changed from negativity to positivity by successfully grafting the silane molecules onto the surface. The heterogenous Ti3C2Tx nanochannel membrane consisting of three different charged sections was prepared to build up the nanofluidic device. The diode-like ion transport property was observed for the heterogenous membrane, and the maximum ion current rectification ratio reached approximately 32. The numerical simulation based on the Poisson-Nernst-Planck (PNP) equations indicated that the directional ion diffusion was attributed to the accumulation and depletion of ions in the nanochannels under different potential biases. Moreover, the application potential of desalination and ion storage of the heterogenous membrane was assessed. Our work paves the way for the design of heterogenous nanochannels for controllable ion transport and introduces a new perspective for ion sieving, energy conversion, and sensing applications.