Molecule stratification in 2D heterostructured nanochannels towards enhanced selective permeation

Abstract

Here, lamellar membranes with hydrophilic/hydrophobic heterostructured nanochannels are constructed by alternately stacking graphene oxide (GO) and reduced graphene oxide (RGO) nanosheets via dual-needle electrostatic atomization. This technology exhibits facile controllability over membrane nanostructure, where the dual-needle device can compel active reactants to contact in confined space. Through subtly designing spraying parameters, GO and RGO nanosheets can be alternately deposited on the substrate to construct heterostructured nanochannels. And we demonstrate that the asymmetric channel wall-molecule interactions can induce molecule stratification for acetonitrile/water mixture, where hydrophilic GO layer exerts strong attraction to acetonitrile, whereas water molecules are pushed to hydrophobic RGO layer. Then, the strong attraction further induces acetonitrile molecules to form orderly aligned aggregates and transfer quickly, while water molecules are randomly distributed and transfer slowly. The pre-determined different transfer rates afford a high acetonitrile permeance of 38.9 L m–2h−1 bar−1 and separation factor of acetonitrile/water up to 4.8, surpassing that of homostructured lamellar membranes. Furthermore, this stratification and hence separation performance can be enhanced by channel length, acetonitrile amount in feed, operation temperature and pressure. The first discovery of molecule stratification in heterostructured nanochannels facilitates the sustainable development of advanced separation membranes.