In situ etching strategy for the preparation of high-temperature proton-exchange membranes with continuous porous proton-transport channels

Phosphoric acid (PA)-doped polybenzimidazole (PBI) is widely used in high-temperature (HT) proton-exchange membrane fuel cells (PEMFCs). The efficiency of proton conduction is intricately linked to the performance of cell. Thus, constructing a continuous proton-transport channel in the PBI matrix is an effective approach to enhance the performance of PA-doped PBI. In this study, for the first time, a segmented block copolyamide with a microphase-separated structure was used as a template to fabricate a range of HT-proton-exchange membranes (PEMs) with continuous porous proton-transport channels using an in situ etching strategy, which used poly-amide as a sacrificial template hydrolyzed under high-temperature PA conditions. The HT-PEMs with continuous porous proton-transport channels exhibit excellent cell performances. The membranes with 30% segmented block copolyamides possess an ultra-high PA doping of 420.7% and high in-plane conductivity of 117 mS cm-1 at 160 degrees C without humidification. Therefore, the resulting membrane has an excellent cell performance at 160 degrees C in H2/O2 (680.02 mW cm-2), which is considerably higher than that of the OPBI membranes under the same conditions. The results indicate that continuous porous proton-transport channels can comprehensively improve the performance of membranes. This efficient, simple, and environment-friendly in situ etching strategy is ex-pected to become a routine method for preparing PA-doped HT-PEMs.

Automated summary

For the first time, a segmented block copolyamide with a microphase-separated structure was used as a template to fabricate high-temperature proton exchange membranes (PEMs) with continuous porous proton-transport channels. The resulting membranes showed excellent cell performances, with an ultra-high PA doping and high in-plane conductivity. The efficient and simple in situ etching strategy is expected to become a routine method for preparing PA-doped HT-PEMs.