Polypyrrole layered SPEES/TPA proton exchange membrane for direct methanol fuel cells

Hybrid membranes based on sulfonated poly(1,4-phenylene ether ether sulfone) (SPEES)/tungstophosphoric acid (TPA) were prepared. SPEES/TPA membrane surfaces were modified with polypyrrole (Ppy) by in situ polymerization method to reduce the TPA leaching. The morphology and electrochemical property of the surface coated membranes were studied by SEM, AFM, water uptake, ion exchange capacity, proton conductivity, methanol permeability and tensile strength. The water uptake and the swelling ratio of the surface coated membranes decreased with increasing the Ppy layer. The surface roughness of the hybrid membrane was decreased with an increase in Ppy layer on the membrane surface. The methanol permeability of SPEESITPA-Ppy4 hybrid membrane was significantly suppressed and found to be 2.1 x 10(-7) cm(2) s(-1), which is 1.9 times lower than pristine SPEES membrane. The SPEESITPA-Ppy4 membrane exhibits highest relative selectivity (2.86 x 10(4)S cm(-3) s) than the other membrane with low TPA leaching. The tensile strength of hybrid membranes was improved with the introduction of Ppy layer. Combining their lower swelling ratio, high thermal stability and selectivity, SPEESITPA-Ppy4 membranes could be a promising material as PEM for DMFC applications. (C) 2015 Elsevier B.V. All rights reserved.