Rational Fabrication of MXene/Graphene Oxide Membrane and Its Voltage-Gated Ion Transport Behavior

The hybrid MXene/graphene oxide membrane (MGOm) exhibits excellent conductivity and chemical stability, achieving an outstanding voltage-gated ion transport behavior. When a positive potential (+0.6 V) is applied to MGOm under only osmotic pressure, the electrostatic repulsion between charged MGOm sheets and cations (Li+, Mg2+, or Al3+) is enhanced, which promotes ion permeation. On the contrary, the application of a negative potential (−0.6 V) boosts the electrostatic attraction, resulting in a decrease in ion permeation. Furthermore, the influence of the cation−π interaction between a cation (K+) and graphene oxide sheet on the voltage-gated ion transport is also investigated. Regardless of whether a positive or negative potential is applied, KCl-treated MGOm shows low Li+, Mg2+, and Al3+ permeation rates (<2 mmol m–2 h–1). This demonstrates that the electrostatic repulsion induced by a positive potential is not enough to counteract the cation−π interaction. In summary, conductive membranes with voltage-gated nanochannels are promising alternative for ion transport.