Advances in design and development of proton-exchange membranes for high-temperature polymer electrolyte fuel cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) are considered as the potential energy conversion technology owing to the fast reaction kinetics, strong resistance to CO impurities, and better water and thermal management balance. Due to the significant decrease in performance of traditional proton exchange membranes (PEMs) at high temperatures and low humidity, researchers have developed new PEMs or complex modification processes to achieve stable mechanical properties, decent proton conductivity, better thermal stability, and longer service life. This paper reviews the latest developments in two types of high-temperature proton exchange membranes (HT-PEMs): (1) modified perfluorosulfonic acid (PFSA) type HT-PEMs; (2) aromatic polymer-based HT-PEMs, with a focus on polybenzimidazole (PBI) membranes and their composite membranes. It then provides an overview of polymer membranes such as polyaryletherketone (PAEK), polyimide (PI), polyether sulfone (PESs), polysulfone (PSFs), and polyphenylene oxide (PPO). We separately investigated the effects of adding short side chains to the PFSA membrane, incorporating additives, modifying the main chain structure of the aromatic polymer membrane, side chain grafting, crosslinking modification, doping modification, and block copolymerization on the performance. Based on the summary of the preparation method, modification method and core properties of the above-mentioned membrane materials, the proton conduction mechanism was analyzed, and the future research direction and prospect of practical application of HT-PEMs were put forward.