N-H group-rich dendrimer doped polybenzimidazole composite membrane with consecutive proton transportation channels for HT-PEMFCs

It's of significant importance for the development of proton exchange membranes with low phosphoric acid (PA) uptake, high proton conductivity, better proton conduction stability and low production-costs for high temperature proton exchange membrane fuel cells (HT-PEMFCs). Featured with variable structure and diversified functionality, porous organic networks are newly emerged filler materials for polyelectrolytes in energy conversion field. In this work, a typical Schiff-base type porous polymeric network (SNW-1) with abundant N–H sites was synthesized and blended with ether-type polybenzimidazole (PBI) for the first time. The thermal and chemical stability of the as-prepared composite membranes completely satisfy the practical requirements of HT-PEMFCs. The constructed consecutive proton conduction channels endow the composite membranes higher proton conductivity with low PA uptake. When the doping content of SNW-1 reached 30%, the PBI/30%-SNW-1 membrane showed much higher proton conductivity with lower PA uptake (114.0 mS cm−1, 175.0%) comparing with those of the pristine PBI (67.3 mS cm−1, 270.0%) at 160 °C. The PBI/x%-SNW-1 membranes also exhibited better proton conduction stability. After 30 h of long-time evaluation at 140 °C, PBI/30%-SNW-1 composite membrane gives only an 8.47% decay of proton conductivity, which is lower than that of the pristine PBI (12.84%). The preparation procedure of PBI/x%-SNW-1 composite membranes is simple, which provides a potential pathway for the development of high-performance proton exchange membrane for HT-PEMFCs.