Enhancing proton conduction and methanol barrier performance of sulfonated poly(ether ether ketone) membrane by incorporated polymer carboxylic acid spheres

▶ The composite membranes were fabricated by blending SPEEK and PCASs. ▶ The PCASs optimized the free volume characteristics of the composite membranes. ▶ Enhanced proton conduction and methanol barrier performance, stability have achieved.