New anhydrous proton exchange membranes based on polypyrrolone (PPy) for high-temperature polymer electrolyte fuel cells

Polypyrrolone (PPy) possesses excellent heat resistance and mechanical properties, moreover, the N-heterocycle contained in the PPy allows the absorption of phosphoric acid (PA) for proton conduction. In the present work, PPy is synthesized by a two-step method and evaluated for the first time as the polymeric material for high temperature proton exchange membranes (HT-PEMs). The PA-doped PPy membrane reaches a peak power density of 582 mW cm−2 at 160 °C under fully anhydrous conditions, besides, the fuel cell exhibits excellent durability over a period of 300 h with a load voltage decay of only 0.032% per hour and remains 0.647 V after the test. Further, the PPy-impregnated polyimide (PI) nanofiber mat composite membrane ([email protected]) with an optimal thickness is fabricated with enhanced dimensional stability, of which acid swelling ratio noticeably declined by 51% in area and 25% in volume. A higher peak power density (634 mW cm−2) and less cell voltage reduction is also observed in the composite membrane, benefits from the trade–off between proton conductivity and PA retention ability. The results of the present study may contribute to further studies on polypyrrolone-based HT-PEMs and composite membranes.