Highly selective sulfonated poly(vinylidene fluoride-cohexafluoropropylene)/poly(ether sulfone) blend proton exchange membranes for direct methanol fuel cells

Proton exchange membranes (PEMs) based on blends of poly(ether sulfone) (PES) and sulfonated poly(vinylidene fluoride- co-hexafluoropropylene) (sPVdF-co-HFP) were prepared successfully. Fabricated blend membranes showed favorable PEM characteristics such as reduced methanol permeability, high selectivity, and improved mechanical integrity. Additionally, these membranes afford comparable proton conductivity, good oxidative stability, moderate ion exchange capacity, and reasonable water uptake. To appraise PEM performance, blend membranes were characterized using techniques such as Fourier transform infrared spectroscopy, AC impedance spectroscopy; atomic force microscopy, and thermogravimetry. Addition of hydrophobic PES confines the swelling of the PEM and increases the ultimate tensile strength of the membrane. Proton conductivities of the blend membranes are about 10(-3) S cm(-1). Methanol permeability of 1.22 3 10(-7) cm(2) s(-1) exhibited by the sPVdF-co-HFP/PES10 blend membrane is much lower than that of Nafion-117. AFM studies divulged that the sPVdF-co-HFP/PES blend membranes have nodule like structure, which confirms the presence of hydrophilic domain. The observed results demonstrated that the sPVdF-co-HFP/PES blend membranes have promise for possible usage as a PEM in direct methanol fuel cells. (C) 2016 Wiley Periodicals, Inc.