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(647f) Polyelectrolyte Multilayers for Direct-Methanol Fuel Cells

Authors: 
Argun, A. A., Massachusetts Institute of Technology
Ashcraft, J. N., Massachusetts Institute of Technology
Hammond, P. T., Massachusetts Institute of Technology

The global need for clean and sustainable energy is ever increasing and electrochemical devices such as fuel cells, batteries, and solar cells show great potential. A major component of these devices is an ion-conducting electrolyte which enables fast charge transport between electrodes. The alternating adsorption of oppositely charged molecular species, known as the electrostatic layer-by-layer (LBL) technique, is a simple and elegant method of constructing highly tailored polymer electrolytes and organic-inorganic composites. We have utilized this method to develop proton-exchange membranes for direct-methanol fuel cells (DMFCs). This approach presents strong advantages as it allows the incorporation of many different functional materials within a single film at a full range of compositions with exceptional homogeneity. By pairing a sulfonated poly(2,6-dimethyl 1,4-phenylene oxide) (sPPO) with various amine-based polymers, we obtain ionic conductivity values of up to 35 mS/cm at fully humidified conditions.(1) Furthermore, these multilayer systems exhibit low liquid methanol permeability and have high chemical and mechanical stability due to the use of aromatic polymers. Coating a traditional fuel cell membrane with these highly conductive LBL films reduces the methanol crossover and improves the power output of DMFCs by up to 50%.

(1) Argun, A.A.; Ashcraft, J.N.; Hammond, P.T., ?Highly Conductive, Methanol Resistant Polyelectrolyte Multilayers.? Adv. Mater. 2008, 20, 1539-1543.