Click chemistry-based azide-substituted polysulfone/alkynyl-substituted sulfonated polyvinyl alcohol/nafion blend membranes for direct methanol fuel cells

At present, commercial Nafion membrane is not suitable for proton exchange membrane used in direct methanol fuel cell (DMFC) due to the severe methanol permeation phenomenon. This work reported the preparation and characterization of azide-substituted polysulfone (PSU-N₃) and alkynyl-substituted sulfonated polyvinyl alcohol (SAPVA) crosslinked in the matrix of Nafion membrane base on click chemistry applied in DMFC. The compatibility between PSU-N₃ and SAPVA is promoted due to the formation of crosslinked network structure. Key properties, including dimensional stability, oxidative stability, mechanical behavior, methanol permeability and proton conductivity, are compared with those of the recast Nafion membrane. The prepared blend membranes exhibit lower methanol permeability due to the crosslinked network and well-dispersed microphase structure of PSU-PVA in the Nafion matrix. The proton selectivity of the Nafion-PSU-PVA-3 membrane is 9.16 × 10⁴ S s/cm³, much higher than that of the recast Nafion membrane (2.82 × 10⁴ S s/cm³). In DMFC single cell tests, the maximum power density of the Nafion-PSU-PVA-3 membrane is 4.6 mW/cm², about 58.6% higher than that of the recast Nafion membrane. All the results indicate that the prepared blend membranes have the potential to be applied in DMFC.