Fabrication and Characterization of Cross-linked Polybenzimidazole Based Membranes for High Temperature PEM Fuel Cells

- A series of phosphoric acid doped cross-linked polybenzimidazole (PBI) membranes were prepared with different cross-linkers.
- The crosslinking in the PBI membrane has positive effect on proton conductivity and acid leaching property.
- The potential of the crosslinked PBI membranes for HT-PEMFC applications was shown.

In this study different types of crosslinked polybenzimidazole (PBI) membranes were compared as high temperature proton exchange membrane fuel cells (HT-PEMFC). Cross-linking of PBI was performed with different cross-linkers including bisphenol A diglycidyl ether (BADGE), ethylene glycol diglycidyl ether (EGDE), α-α'-dibromo-p-xylene (DBpX), and terephthalaldehyde (TPA). The crosslinked membranes have been characterized by thermogravimetric analysis, scanning electron microscopy, acid uptake and impedance analyses. The crosslinking of the PBI polymer matrix helps to improve the acid retention properties. PBI/BADGE presented the highest acid retention properties. Proton conductivities of the membranes were comparable to that of commercial membranes. Conductivity values up to 0.151 S.cm−1 were obtained at 180 °C with PBI/DBpX membranes. Gas diffusion electrodes (GDE) were fabricated by an ultrasonic coating technique with 0.6 mg Pt.cm−2 catalyst loading for both anode and cathode. The crosslinked membranes were tested in a single HT-PEMFC with a 5 cm2 active area at 165 °C without humidification. PBI/BADGE crosslinked membranes demonstrated stability and high performance on single cell HT-PEMFC tests. The maximum power density for PBI/BADGE was determined as 0.123 W.cm−2. As a result, the experimental results suggested that the PBI/BADGE and PBI/DBpX cross-linked membranes are promising electrolyte options for HT-PEMFC.