High Ionic Conductivity in 2D Molybdenum Disulfide (MoS2) Membrane

Abstract

Two-dimensional transition metal dichalcogenides (2D TMDs) have a variety of advantages for nanoelectronics, photonics, and opto-electronics due to their unique electrical and optical properties including the band gap modulation with film thickness. 2D TMDs film reveals layered structures with weak van der Waals forces between each neighboring layer and large specific surface area owing to sheet-like structure, which are distinct properties making 2D TMDs highly attractive for capacitive energy storage. Other layered materials, such as graphene oxide and boron nitride, have been well studied as membrane separation for nanofluidic device applications, but the property of ionic transport through 2D molybdenum disulfide (MoS2) has not revealed yet. Here we fabricated few-layer MoS2 nanosheets and measured ionic currents with a variety of hydroxide solutions (LiOH, NaOH, and KOH). The activation energies and ionic conductivities of the solutions are practically calculated, and several orders of magnitude higher ionic conductivity compared to the bulk are measured at low concentration of the solutions. The detail of mechanistic understanding of the ionic conductivity in 2D MoS2 will be discussed.