Sulfonated Polybenzimidazoles for High Temperature PEM Fuel Cells

High molecular weight, highly PA-doped s-PBI membranes have been developed with robust mechanical properties and excellent proton conductivities (>0.1 S cm(-1)) at elevated temperatures (> 100 degrees C). These membranes show high PA loadings of 30-35 mol PA/PBI, and average tensile stress and strain of 0.804 MPa and 69.64%, respectively. Proton conductivities were dependent on the acid doping level and measured between 0.1 and 0.25 S cm(-1) at 180 degrees C, a pronounced increase over most phosphoric acid-doped sulfonated PBI membranes to date. Preliminary fuel cell testing with hydrogen fuel and air or oxygen oxidants was performed at temperatures greater than 100 degrees C without external feed gas humidification and show excellent performance (0.62-0.68 Vat 0.2 A cm(-2) and 160 degrees C, hydrogen/air; 0.69-0.76 V at 0.2 A cm(-2) and 160 degrees C, hydrogen/oxygen). Initial performance stability studies were conducted for similar to 3000 h and indicate great promise as high temperature membranes, with a degradation rate of 30 mu V h(-1).