Assembly of two-dimensional nanofluidic channel with high proton conductivity using single-layer MnO2 nanosheets

Abstract

Two-dimensional (2D) single-layer δ-MnO2 (SLMO) with cations intercalated in the interlayers demonstrates specific structural characteristics, possessing superiority in the fields such as energy storage, catalysis, and sensor. However, the synthesis technology of large-lateral-size SLMO nanosheets with high uniformity is rare, which hinders their correlated research. Herein, we report an intercalation-assisted exfoliation approach to produce large-sized SLMO nanosheets with high dispersity in aqueous solution. Few-layer K+-intercalated δ-MnO2 (KMnO) nanosheets were used as a precursor to ensure complete exfoliation. On account of high dispersion and ultrathin 2D morphology, SLMO nanosheets self-assembled into a flexible and free-standing film to construct ordered nanochannels. A high surface charge density of 1.71 mC m−2 and proton mobility of 2.59 × 10−3 cm2 V−1 s−1 were achieved in the free-standing SLMO film. With the extraordinary properties and easily scaled fabrication of the 2D SLMO film, this approach will pave the way for the study of confined ion transportation and enable the easy construction of nanofluidic devices.