Poly(phenylene oxide) cross-linked with polybenzimidazole for the applications of high-temperature proton-exchange membrane fuel cells

A series of imidazolium-functionalized poly(phenylene oxide) (QPPO) cross-linked with polybenzimidazole (PBI) (cQPPOx-PBI) membranes were prepared. Compared to the pure PBI membrane without a cross-linked structure nor imidazolium groups, the cQPPOx-PBI membranes showed enhanced toughness, phosphoric acid (PA) retention, and chemical stability. The cQPPOx-PBI membranes showed a enhanced PA uptake than that of PBI membranes, and the cQPPO35-PBI membrane achieves a high conductivity of 139 mS cm-1 at 160 degrees C, which is much higher than that of PBI membrane under the same conditions (26 mS cm-1). The performance of the single fuel cell assembled with the obtained membranes showed a similar trend as their conductivity, and the cell with cQPPO35-PBI showed a maximum power density of 344 mW cm-2 at 140 degrees C, while the value for PBI membrane was only 175 mW cm-2 under the same conditions. Herein, a straightforward method was developed for introducing imidazolium groups and cross-linked structures, which can be employed to prepare PEMs with enhanced performance for HT-PEMFCs application.