Alkyl chain modified sulfonated poly(ether sulfone) for fuel cell applications

Abstract

A new alkyl chain modified sulfonated poly(ether sulfone) (mPES) was synthesized and formed into membranes. The MEAs were tested in the PEMFC and evaluated systematically in the DMFC by varying the methanol concentration from 0.5 to 5.0 M at 60 degrees C and 70 degrees C. The synthesized mPES copolymer has been characterized by nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, thermogravimetric analysis, and gel permeation chromatography. The proton conductivity of the resulting membrane is higher than the threshold value of 10(-2) S cm(-1) at room temperature for practical PEM fuel cells. The membrane is insoluble in boiling water, thermally stable until 250 degrees C and shows low methanol permeability. In the H-2/air PEMFC at 70 degrees C, a current density of 600 mA cm(-2) leads to a potential of 637 mV and 658 mV for 50 mu m thick mPES 60 and Nafion NRE 212, respectively. In the DMFC, mPES 60's methanol crossover current density is 4 times lower than that for Nafion NRE 212, leading to higher OCV values and peak power densities. Among all investigated conditions and materials, the highest peak power density of 120 mW cm(-2) was obtained with an mPES 60 based MEA at 70 degrees C and a methanol feed of 2 M. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.