Quaternary ammonium-biphosphate ion-pair based copolymers with continuous H+ transport channels for high-temperature proton exchange membrane

• Published in: Journal of membrane science Vol. 660; p. 120878
• Main Authors: Jiang, Junqiao, Li, Zhen, Xiao, Min, Wang, Shuanjin, Miyatake, Kenji, Meng, Yuezhong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2022
• Subjects: ammonium; composite polymers; durability; electric potential difference; HT-PEMFC; Low PA doping Level; Micro-phase separation; PA retention; phosphoric acid; quaternary ammonium compounds; Quaternized polymer; PA retention; Low PA doping Level; Micro-phase separation; HT-PEMFC; Quaternized polymer
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2022.120878

Phosphoric acid (PA)-doped polymer electrolyte membranes are the most promising materials for high-temperature proton exchange membranes (HT-PEMs). However, their development is subject to the compromise between proton conductivity and phosphoric acid (PA) doping level. Here, an ether-free QPAF-4 membrane (a copolymer containing perfluoroalkylene and fluorenyl groups with pendant ammonium groups) is directly doped with phosphoric acid and studied as HT-PEMs. Due to the intrinsic micro-phase separation structure of QPAF-4 matrix and strong interaction of quaternary ammonium (QA)-PA, the PA-doped membranes possess high proton conductivity and eminent PA retention at comparatively low PA doping level, respectively. The QPAF-4 membrane with 150% PA uptake (QPAF-4-150%PA) offers a proton conductivity of 52 mS cm−1 at 160 °C. As expected, the single cell with QPAF-4-150%PA membrane shows the maximum peak power density of 683 mW cm−2 at 160 °C under anhydrous condition. Meanwhile, the single cell exhibits excellent durability over a period of 60 h with only a slight reduction in voltage of 3.1%. These results indicate that the as-prepared PA-doped quaternized polymer with micro-phase separation structure seems to offer a promising way to develop performing and long-life HT-PEMs with low PA doping levels. [Display omitted] •The PA-doped QPAF-4 membrane has continuous H+ transport channels.•The QPAF-4 membrane achieves high proton conductivity at low PA doping level.•The PA-doped QPAF-4 membrane owns eminent PA retention.•Single cell possesses high peak power density and excellent durability.