Reducing Methanol Crossover in CH₃OH-Fuel-Cell Membranes

Improved polymer electrolyte membranes for direct methanol fuel cells can be made by impregnating the baseline membrane material with cross-linked polystyrene (a copolymer of styrene and divinylbenzene). The baseline membrane material is a perfluorosulfonic acid-based hydrophilic, proton-conducting ion-exchange polymer sold under the trade name "Nafion". The principal benefit afforded by the impregnation is a reduction in permeability by methanol; this translates to less crossover of methanol in molecular form (denoted "methanol crossover" for short). Methanol crossover is undesired because it wastes fuel and thereby degrades fuel-cell performance.