Polyelectrolyte-assisted fabrication of large-area 2D polymer nanosheet membranes with ultrafast proton conduction

Ionic two-dimensional polymer (2DP) nanosheets with unique merits are attractive candidates for next-generation proton exchange membranes (PEMs), but the fabrication of large-area 2DP nanosheet-based PEMs is still awaiting success. Here, we report a flexible and intrinsically proton-conductive polyelectrolyte (Poly(sodium 4-styrenesulfonate), PSS) assisted assembling method to fabricate large-area PEMs (∼400 cm 2 ) using sulfonated 2DP nanosheets as building blocks. Specifically, the optimized membrane achieves a superior proton conductivity of 802 mS cm −1 (70 °C, 95 % relative humidity), owing to the construction of low-energy barrier proton conduction pathways consisted of high density of sulfonic acid groups provided by PSS and sulfonated 2DP nanosheets. Moreover, PEMs with enhanced properties can also be accomplished by introducing different polyelectrolyte, indicating the good versatility of this powerful platform method. This work opens opportunities in large-scale fabrication of 2DP nanosheet membranes and paves a way for fabricating other 2D material-based membranes for diverse applications.