Proton exchange membranes for high temperature proton exchange membrane fuel cells: Challenges and perspectives

Proton exchange membranes (PEMs) have received immense attentions for their core roles in high temperature proton exchange membrane fuel cells (HT-PEMFCs). For a high-performance polymer electrolyte, stable mechanical property and high proton conductivity on the order of 10−2 S cm−1 at low humidity (or anhydrous conditions) and high temperature are ultimately necessary. With emphasis on this practical principle, phosphoric acid doped polybenzimidazoles (PBIs) have become one of the hottest materials in the field of proton conducting membrane that exhibit high proton conductivity with values closing to 10−2 S cm−1. In addition to PBI, non-PBI based proton conducting polymers that exhibit satisfactory conductivity and intrinsic mechanical stability are also exciting research in HT-PEMs. This review summarizes the recent progresses in the HT-PEMs, and addresses the challenges and promising directions for further development of HT-PEMs.