A new pyridine-based porous organic polymer composited high-temperature proton exchange membrane

Abstract

As promising high-temperature proton exchange membranes, phosphoric acid (PA) doped polybenzimidazole (PBI) membranes still face challenges, including excessive PA leaching and limited long-term stability. The preparation of mixed matrix membranes (MMMs) has emerged as a viable strategy to address these limitations, which can combine the excellent mechanical properties of polymers with the structural advantages of porous fillers. Among various filler materials, nitrogen-containing porous organic polymers (POPs) have shown particular promise because of their excellent compatibility with polymers. Therefore, in this work, a new pyridine-based POP called Py-POP was synthesized. Py-POP was mixed with commercial poly[2,2′-(p-oxidiphenylene)-5,5′-benzimidazole] (OPBI) to prepare MMMs. Theoretical calculations indicate that the pyridine groups exhibit strong interactions with PA, significantly enhancing both PA retention and proton conduction efficiency. Remarkably, the PA retention rate of the composite membrane doped with 10 wt% Py-POP is 77.2% at 80 °C/40% RH, which is much higher than that of the OPBI (62.7%). Furthermore, the membrane achieves an outstanding proton conductivity of 0.173 S cm⁻¹ at 180 °C, which is 4.2 times higher than that of the OPBI membrane. The peak power density of the composite membrane can achieve 915.1 mW cm⁻² and remains at 891.5 mW cm⁻² after 80 cycles of testing at 180 °C.