Poly(ionic liquid)/OPBI Composite Membrane with Excellent Chemical Stability for High-Temperature Proton Exchange Membrane

Despite the outstanding proton conductivity of phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes as high-temperature proton exchange membranes (HT-PEMs), chemical stability is a critical issue for the operation life of PEM fuel cells (PEMFCs). Herein, we introduced polymerized [HVIM]H2PO4 ionic liquids (PIL) into an OPBI membrane to accelerate proton transfer and enhance the chemical stability of the membrane. Based on the regulation of the intrinsic viscosity of PIL, the entanglement between PIL chains and OPBI chains is enhanced to prevent the loss of PIL and the oxidative degradation of membrane materials. The PIL/OPBI membrane with the intrinsic viscosity of 2.34 dL & BULL;g(-1) (2.34-PIL/OPBI) exhibited the highest proton conductivity of 113.9 mS & BULL;cm(-1) at 180 & DEG;C, which is 3.5 times that of the original OPBI membrane. The 2.34-PIL/OPBI membrane exhibited the highest remaining weight of 92.1% under harsh conditions (3 wt% H2O2; 4 ppm Fe2+ at 80 & DEG;C) for 96 h, and a much lower attenuation amplitude than the OPBI did in mechanical strength and proton conductivity performance. Our present work demonstrates a simple and effective method for blending PIL with OPBI to enhance the chemical durability of the PA-PBI membranes as HT-PEMs.

Automated summary

In this study, polymerized [HVIM]H2PO4 ionic liquids (PIL) were introduced into an OPBI membrane to improve proton transfer and enhance chemical stability. By regulating the intrinsic viscosity of PIL, entanglement between PIL chains and OPBI chains was enhanced to prevent PIL loss and oxidative degradation of membrane materials. The 2.34-PIL/OPBI membrane exhibited the highest proton conductivity of 113.9 mS•cm(-1) at 180°C, which is 3.5 times higher than the original OPBI membrane. It also showed a high remaining weight of 92.1% and lower degradation in mechanical strength and proton conductivity under harsh conditions. This study presents a simple and effective method to enhance the chemical durability of PA-PBI membranes as HT-PEMs by blending PIL with OPBI.