Voltammetry of monovalent cations at the 2D/3D water interface formed by using a slit-like graphene-membrane nanofluidic device.

Herein, we demonstrate that two-dimensional (2D) graphene-nanoconfined water in a slit-like graphene-membrane nanofluidic device can form a 2D/3D water interface with a 3D bulk aqueous phase and a preference for protons over other monovalent cations for transfer across such a novel 2D/3D water interface. This provides a new approach to studying 2D graphene-nanoconfined water.