Cardo Polybenzimidazole (PBI-O-PhT) Based Membrane Reinforced with m-polybenzimidazole Electrospun Nanofiber Mat for HT-PEM Fuel Cell Applications

Abstract

The further development of high temperature polymer electrolyte membrane (HT-PEM) fuel cells largely depends on the improvement of all components of the membrane-electrode assembly (MEA), especially membranes and electrodes. To improve the membrane characteristics, the cardo-polybenzimidazole (PBI-O-PhT)-based polymer electrolyte complex doped with phosphoric acid is reinforced using an electrospun m-PBI mat. As a result, the PBI-O-PhT/es-m-PBI_net · nH₃PO₄ reinforced membrane is obtained with hydrogen crossover values (~0.2 mA cm^-2 atm^-1), one order of magnitude lower than the one of the initial PBI-O-PhT membrane (~3 mA cm^-2 atm^-1) during HT-PEM fuel cell operation with Celtec^®P1000 electrodes at 180 °C. Just as importantly, the reinforced membrane resistance was very close to the original one (65-75 mΩ cm² compared to ~60 mΩ cm²). A stress test that consisted of 20 start-stops, which included cooling to the room temperature and heating back to 180 °C, was applied to the MEAs with the reinforced membrane. More stable operation for the HT-PEM fuel cell was shown when the Celtec^®P1000 cathode (based on carbon black) was replaced with the carbon nanofiber cathode (based on the pyrolyzed polyacrylonitrile electrospun nanofiber mat). The obtained data confirm the enhanced characteristics of the PBI-O-PhT/es-m-PBI_net · nH₃PO₄ reinforced membrane.

Keywords: HT-PEMFC; PBI-O-PhT; Pt/CNF; carbon nanofiber; electrospinning; fuel cell; hydrogen crossover; polybenzimidazole; polymer–electrolyte complex; reinforced membrane.