Synthesis and Characterization of a Composite Membrane for Polymer Electrolyte Fuel Cell

Abstract

A new proton exchange membrane (PEM) has been fabricated using a novel patented polymer structure modification technology. It has been shown that the new membrane has a higher proton transfer rate and lower resistance as compared to Nafion® . This paper discusses issues related to membrane fabrication and testing procedures. (i) A brief fabrication procedure of PEM is outlined. The fabrication technique used here separates the proton exchange and structural requirements of the PEM allowing greater flexibility in membrane design. The proton exchange material developed herein is a terpolymer composed of various ratios of acrylic acid, styrene, and vinylsulfonic acid. Following a patented polymer structure modification technology, these materials were bound to an ethylene-tetrafluoroethylene copolymer mesh that had been rendered adhesive by hydroxylation in a two-step water-borne process. (ii) A previously developed theoretical model is used to calculate the relative resistance and proton transfer rate. According to the model, a simple second order differential equation describes the entire process and established a relationship between the membrane resistance and the total time taken for a specific amount of protons to pass through it. Finally, (iii) a simple two-cell experimental procedure is developed to calculate the relative membrane resistance and proton transfer capacity. The results show that theoretical predictions are in excellent agreement with the experimental observations. The new membrane could transfer protons approximately 80% faster than Nafion® per unit area under the test conditions utilized. Membrane resistance is also 71% lower compared to Nafion® . These results suggest that there is now a new route of fabricating cost effective proton exchange membranes for fuel cell applications wherein one may focus more on the proton exchange capacity of the membrane allowing the structural properties of the membrane to be considered separately.