Sulfonated poly(ether ether ketone)/amino-acid functionalized titania hybrid proton conductive membranes

Inspired by the proton conducting mechanism in organisms where the amino acid groups play a crucial and multiple role, a novel kind of amino acid-functionalized titania submicrospheres was prepared and incorporated into sulfonated poly(ether ether ketone) (SPEEK) to fabricate the hybrid membranes for potential application in direct methanol fuel cells (DMFCs). The pristine titania submicrospheres (TiO2) with a uniform particle size of similar to 220 nm were synthesized via a sol-gel process and modified with amino acid groups through a facile chelation method. Meanwhile, amino groups, carboxylic groups and phenyl groups were introduced in the same way for comparison purpose. Compared with the control SPEEK membrane, the methanol crossover was reduced and the membrane mechanical strength was enhanced by incorporation of the functionalized titania submicrospheres. Due to the different proton acceptor/donor capability of the different functional groups, the hybrid membrane embedded with amino-functionalized titania exhibited lower proton conductivity at 20 degrees C but higher values at elevated temperature of 60 degrees C compared with carboxylic-functionalized titania: the hybrid membrane embedded with amino acid-functionalized titania displayed a superior proton-conducting ability with the highest proton conductivity of 0.258 S cm(-1) at 60 degrees C. (C) 2012 Elsevier B.V. All rights reserved.