▎ 摘　　要

Covalent grafting of polystyrene sulfonic acid (PSSA) on graphene oxide nanoplatelets (GONP) via in situ radical polymerization was conducted. PSSA-g-GONP is used as an additive to form a nanocomposite membrane with sulfonated poly(ether ether ketone) (sPEEK) for its application in direct methanol fuel cells (DMFCs), with better physicochemical properties and reduced methanol crossover compared to that of pristine sPEEK. The optimized sPEEK/PSSA-g-GONP (0.15 wt %) nanocomposite membrane exhibits a DMFC peak power density of 170 mW cm(-2), which is 50 % greater than the 110 mW cm(-2) for pristine sPEEK and one-fold greater than that of 80 mW cm(-2) observed for commercial Nafion (R) 117 due to its high electrochemical selectivity. Furthermore, the nanocomposite membrane shows better durability up to 100 h compared with sPEEK and Nafion (R) 117 electrolyte membranes, demonstrating its potential in diverse membrane applications.