Direct Methanol Fuel Cell Performance of Disulfonated Poly(arylene ether benzonitrile) Copolymers

Abstract

This paper reports the performance of direct methanol fuel cells (DMFCs) using novel disulfonated poly(arylene ether benzonitrile) copolymers derived from hexafluoro-isopropylidene diphenol (6F), 2,6-dichlorobenzonitrile, and 3,3'-disulfonated -dichloro diphenyl sulfone (SDCDPS). The membrane electrode assembly (MEA) which employed the sulfonated copolymer with 35 mol % of disulfonated comonomer as the proton exchange membrane had approximately 2-fold lower methanol crossover and slightly higher (about 10%) cell resistance than the MEA using the perfluorosulfonic acid Nafion membrane, resulting in an approximately 50% improvement in selectivity, regardless of membrane thickness. Accordingly, this MEA outperformed the Nafion MEA control in a DMFC single-cell test. For example, 200 mA/cm2 was obtained (compared with 150 mA/cm2 for the Nafion MEA) at 0.5 V at a temperature of 80°C and ambient air pressure. Similar experiments performed with nonfluorine-containing biphenol-based sulfonated poly(arylene ether sulfone) copolymers (BPSH) indicated that the compatibility of the polymer electrolyte with the electrodes likely has a critical role in initial DMFC performance. © 2004 The Electrochemical Society. All rights reserved.