Clay/GO asymmetric bilayer membrane with temperature and concentration dual-responsivity for enhanced ion transport properties

Abstract

The controllable ion transport in the membranes has attracted significant interest for water treatment, molecular sieving, energy storage and harvesting because of the molecular/ion sieving and selectivity of the nanofluidic channels. Here, we selected Li-exchanged montmorillonite (Mt) to prepare montmorillonite/graphene oxide (Mt/GO) bilayer membranes with two-dimensional (2D) nanofluidic channels and studied the ion transport across the nanofluidic membrane under the external stimuli of temperature and concentration. It is interesting that the ion transport is affected by the orientation of Mt./GO bilayer membrane between two electrolyte cells. The bilayer membrane with GO layer facing higher concentration electrolytes shows much higher ionic conductance than that with Mt. layer facing higher concentration electrolytes, also higher than Mt./GO homogenous monolayer membrane. The diffuse current, membrane potential and output power of the bilayer membrane are affected by the external temperature and electrolyte concentration, showing good thermoelectric conversion and abnormal temperature dependence. These asymmetric bilayer membranes with the integration of the cost-effective clay and high ion-selective GO show many advantages such as low cost, facile fabrication and high ion-transport performance. This work provides a new idea for designing clay based nanofluidic membrane for creating smart high-efficient membranes.