Sulfonated (graphene oxide/poly(ether ketone ether sulfone) (S-GO/S-PEKES) composite proton exchange membrane with high proton conductivity for direct methanol fuel cell

Sulfonated poly(ether ketone ether sulfone) (S-PEKES) was successfully prepared to obtain the currently highest degree of sulfonation of 0.744. Sulfonated graphene oxide (S-GO) was incorporated into the S-PEKES matrix to increase sulfonic groups (SO3H) which significantly improved the proton conductivity, methanol blocking, and mechanical stability. The proton conductivity of the S-GO/S-PEKES composite membrane was enhanced up to 5.93???10(?2)?S.cm(?1), which was 7 times higher than the commercial Nafion 117. S-GO exhibited additional positive effects namely the blocking of methanol passing through the membrane, leading to lower methanol crossover than Nafion 117 by two orders of magnitude and high mechanical stability.