Bioinspired Tunable Subnanochannels in Two-Dimensional Montmorillonite Membranes for Fast and Stable Proton Transport

Nanoconfined interlayer channels analogous to biological proton channels are promising to develop state-of-the-art proton exchange membranes (PEMs), while prevailing large channel sizes (typically >6 Å) fail to maximize proton conduction potential. In this work, we fabricated intrinsic proton-conductive membranes with well-defined subnanochannels of 3.5 Å using montmorillonite (MMT) nanosheets. Numerous hydroxyl groups and atomically small capillaries of nanosheets endow the resulting membranes with bioinspired proton channel structures for fast and robust proton transport. Following this, an “internal regulation” strategy based on the layer charge density (LCD) property of nanosheets was developed. Characterization and simulations revealed the tunable spatial orientation, proton concentration, and electrostatic effect of MMT subnanochannels controlled by LCDs, which played critical roles in proton conduction. Consequently, the optimal MMT membrane realized excellent proton conductivity (79.11 mS cm^–1) in the absence of external proton carriers, outperforming most reported PEMs. Our work provides a novel perspective on the design of high-performance PEMs.