High temperature proton-exchange and fuel processing membranes for fuel cells and other applications

Proton-exchange membrane fuel cells (PEMFCs) have become a very active research area for both mobile and stationary applications, particularly for fuel cell vehicles. Compared to inner combustion engines, PEMFCs can decrease pollution and increase the energy efficiency. New proton-exchange membrane (PEM) materials and new technologies for fuel processing are the most important and challenging parts in this research field.;Dupont's NafionRTM and other perfluorinated sulfonic acid membranes are still the only commercial PEM materials so far. However, their high cost and low performance at high temperatures significantly limit their applications. In this research, new five-member ring and six-member ring soft segment-containing sulfonated polyimide (SPI)- based membranes and new sulfonated polybenzimidazole (SPBI)-based membranes were successfully synthesized. The resulting membranes could outperform NafionRTM at various conditions, particularly at high temperatures and low relative humidities (RHs). Moreover, the new membrane materials should be much more cost-effective since the starting materials are more than two orders of magnitude less expensive than those for NafionRTM membranes.;In the research on fuel processing, amine carriers were successfully incorporated into the SPBI copolymer or the crosslinked poly(vinyl alcohol) (PVA) matrix, which could react reversibly with acid gases, such as CO2. Thus, the resulting membranes have shown very promising CO2 selectivity vs. the other gas molecules, such as H2 and CH4, by the facilitated transport mechanism. These newly synthesized membranes have many applications in the field of gas separations, including the low pressure synthesis gas purification for fuel cell applications, the high pressure synthesis gas purification for refinery industrial applications, and the high pressure natural gas purification to obtain high purity CH4.