New Proton Exchange Membranes with Low Methanol Permeability for Direct Methanol Fuel Cells

The purpose of the proposed BMDO Phase I program is to develop and commercialize ion-conducting thermally stable polymers for use as high temperature proton exchange membrane/membrane electrode assembly (PEM/MEA) materials with low methanol permeability ascomponents of direct methanol fuel cells (DMFC). Polymer electrolyte/proton exchange membrane (PEM) fuel cell systems are an environmentally friendly power source for a wide range of applications that include transportation (cars and buses), stationary(home power generation), and consumer electronics (computers and phones).1-6 Sulfonated ion-conducting sites will be introduced via direct polymerization, allowing control of both their location and concentration. Preliminary work has indicated that thePI and his colleagues are capable of synthesizing such materials exceeding the conductivity and methanol permeability performance of perfluorinated sulfonic acid Nafion materials at, or above, room temperature These new sulfonated copolymers generate twicethe conductivity of the current state-of-the-art Nafion material (~0.1 S/cm) for a period of 4 days at 120 ¿C, in continuous operation, at 70 psi water pressure. Additionally, cast films of the novel copolymers demonstrated a marked (nearly four-fold)decrease in methanol permeability (fuel cross-over), which could greatly limit flooding, and the decreased efficiency associated with this phenomenon. These new materials also are much less costly than fluoropolymers and they can be synthesized fromcommercially available starting materials.Power needs for small electronic devices often limit the lifetime of current battery technologies. Direct methanol fuel cells (DMFCs) have the advantage of a liquid phase fuel source, unlike related pressurizedhydrogen fuel cells, which minimizes the size of the overall DMFC system. With power output lifetimes that are several orders of magnitude greater than current battery systems, DMFC technology is an excellent candidate as a next generation of power sourcefor electronics and other items where a portable power source is needed.