In-situ crosslinked SPBI/SPEEK blend membranes with enhanced proton conductivity and suppressed methanol crossover for DMFCs

Developing novel proton exchange membranes that combine superior proton conductivity and low methanol permeation for direct methanol fuel cells is of great significance. Herein, an in-situ ionically crosslinked membrane was prepared by blending sulfonated polybenzimidazole (SPBI, DS = 200%) and sulfonated poly(ether ether ketone) (SPEEK, DS = 80%) utilizing ionic interactions between protonated imidazole rings and -SO 3 H. The ionic crosslinking suppresses the water solubility of the highly sulfonated SPEEK while enhancing the water uptake of the blend membrane, promoting the formation of continuous hydrophilic channels within the membrane. Meanwhile, due to the restriction of segmental motion by ionic crosslinking, the mechanical properties and methanol barrier performance of the blended membranes were notably enhanced. As a result, the assembled DMFC single cell with SPBI/SPEEK-H + -20% blended membrane exhibits a power density of 117.24 mW cm −2 and low methanol crossover current density of 254.18 mA cm −2 under 80°C with a 2 M methanol concentration.