High-Performance Proton Exchange Membrane with Vertically Aligned Montmorillonite Nanochannels

The traditional perfluorosulfonic acid proton exchange membrane is crucial for proton exchange membrane fuel cells, but its high cost has impeded broader commercialization. In this study, a novel concept of a cost-effective and stable vertically aligned polydopamine-intercalated montmorillonite membrane (VAPMM) is introduced. 2D nanochannels formed within the lamellar structure of polydopamine-coated montmorillonite nanosheets provide a significant stable in-plane proton conductivity of 0.58 S cm^-1. The stacked lamellar structure is embedded in epoxy resin to maintain its orientation. Subsequently, precise slicing along the vertical direction of the 2D nanochannels yields a thin film ≈150 µm thick, featuring vertically aligned proton conductive transmembrane nanochannels. When assembled into a membrane electrode assembly with commercial gas diffusion electrodes, the VAPMM exhibits a maximum areal peak power density of up to 534.00 mW cm^-2 at 75 °C with 100% RH, surpassing by more than four times that of a commercial Nafion membrane of similar thickness (N117, 183 µm, 116.17 mW cm^-2). This study outlines a pathway for developing next-generation proton exchange membranes that are both cost-effective and highly stable. Additionally, it introduces a straightforward method to create fully vertically aligned transmembrane nanochannels while preserving the interlayer structure, which is crucial for advancements in nanofluidics.