Polybenzimidazole-Based Semi-Interpenetrating Proton Exchange Membrane with Enhanced Stability and Excellent Performance for High-Temperature Proton Exchange Membrane Fuel Cells

It is of great significance to explore an approach for developing high-strength and enhanced stability materials for high-temperature proton exchange membranes (HT-PEMs) due to their high temperature and strong acid working environment. In this work, proton exchange membranes with semi-interpenetrating (semi-IPN) network structure are constructed by a simple in situ cross-linking method, from linear poly(4,4′-(diphenyl ether)-5,5′-bibenzimidazole) (OPBI) and a cross-linkable poly(arylene ether ketone) with a grafted carboxyl group (c-PAEK), using amino-terminated polybenzimidazole (PBI-4NH2) as a cross-linker. The chemical reaction between the diamine functional group of PBI-4NH2 and the carboxyl group of c-PAEK results in the double anchoring of the molecules. The semi-IPN-1.0/0.7OPBI membrane shows the maximum proton conductivity of 59.6 mS cm–1 at 160 °C under anhydrous conditions. Remarkably, the title membranes (semi-IPN-x/yOPBI) with semi-IPN structure exhibit both excellent chemical stability and highly mechanical properties compared to pristine OPBI. Single cells with semi-IPN-x/yOPBI are successfully operated with dry hydrogen and oxygen at 160 °C, where one using the semi-IPN-1.0/0.7OPBI membrane achieves the maximum power density of 608 mW cm–2, which is 30% higher compared with the OPBI membrane (469 mW cm–2).