Enhancement of Mass Transport in Catalyst Layers of HT‐PEMFC with Tetrafluorophenyl Phosphonic Acid Binder

Abstract The design and development of new and efficient catalyst binder materials are important for improving cell performance in high‐temperature proton‐exchange membrane fuel cells (HT‐PEMFCs). In this study, a series of tetrafluorophenyl phosphonic acid−based binder materials (PF‐y‐P, y=1, 0.83, and 0.67) with rigid structures and controllable degrees of phosphonation were prepared and used in HT‐PEMFCs using the ultra‐strong acid‐catalyzed Friedel−Crafts reaction and the combined Michaelis−Arbuzov reaction. The samples exhibited high stability, low water uptake, superior proton conductivity, and cell performance. In addition, the oxygen mass transport properties of the PF‐1‐P binder were investigated using high‐temperature microelectrode electrochemical testing techniques. Compared with the phosphoric acid‐doped polybenzimidazole (PBI) binder, the O 2 solubility of PF‐1‐P binder material increased by 30 % (5.36×10 −6 mol cm −3 ) and the PF‐1‐P binder material exhibited better cell stability in HT‐PEMFCs. After 10.5 h of discharge at a constant current of 0.12 A cm −2 , the MEA voltage decreased by 7.1 % and 20.8 % in case of the PF‐1‐P and PBI binders, respectively.