Nanocomposite Membranes based on Polybenzimidazole and ZrO2 for High-Temperature Proton Exchange Membrane Fuel Cells

Owing to the numerous benefits obtained when operating proton exchange membrane fuel cells at elevated temperature (>100 degrees C), the development of thermally stable proton exchange membranes that demonstrate conductivity under anhydrous conditions remains a significant goal for fuel cell technology. This paper presents composite membranes consisting of poly[2,2-(m-phenylene)-5,5-bibenzimidazole] (PBI4N) impregnated with a ZrO2 nanofiller of varying content (ranging from 0 to 22wt%). The structure-property relationships of the acid-doped and undoped composite membranes have been studied using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, wide-angle X-ray scattering, infrared spectroscopy, and broadband electrical spectroscopy. Results indicate that the level of nanofiller has a significant effect on the membrane properties. From 0 to 8wt%, the acid uptake as well as the thermal and mechanical properties of the membrane increase. As the nanofiller level is increased from 8 to 22wt% the opposite effect is observed. At 185 degrees C, the ionic conductivity of [PBI4N(ZrO2)(0.231)](H3PO4)(13) is found to be 1.04x10(-1)Scm(-1). This renders membranes of this type promising candidates for use in high-temperature proton exchange membrane fuel cells.