Porous nanofibrous composite membrane for unparalleled proton conduction

Nanostructured porous nanofiber membranes hold a great promise for ultrafast transport of ion and molecule but it remains a technologic challenge to fabricate them with stable nanochannels. We report the use of a new soft template of ionic liquid which has excellent fluidity and molecular-level size to produce porous nanofibers comprising interconnected ~ 4 nm pores/channels. In addition, the topology of the nanopores/channels can be facilely tailored by the types and loading amount of ionic liquids. After incorporating polymer matrix, an unique type of porous nanofibrous composite membranes (PNFCMs) was fabricated accordingly. In the PNFCMs, the nanochannels can well function as transfer shortcuts and uptake abundant water/moisture while releasing conducting groups, eventually permitting unparalleled proton conduction. The conductivity of PNFCM can be as high as 1.03 S cm−1 in hydrated condition and 0.22 S cm−1 in anhydrous condition, which is around 10 times higher than that of the state-of-the-art Nafion. As a further demonstration, the PNFCMs is used for hydrogen fuel cells, exhibiting excellent performance in anhydrous condition, making it great potential for practical application. This soft template approach is also expected to be used for fabrication of other nanostructured porous nanofiber membranes with well-defined porosity and nanostructures.