Polybenzimidazole dendrimer containing triazine rings-based high-temperature proton exchange membranes with high performances over a wide humidity range

• Published in: Materials today chemistry Vol. 23; p. 100653
• Main Authors: Sun, Peng, Xia, Zihan, Li, Zhongfang, Fan, Ziwei, He, Fengqi, Liu, Qiang, Yin, Xiaoyan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2022
• Subjects: Degree of branching; Free volume; High-temperature proton exchange membrane; PBI dendrimer containing triazine rings; Proton conductivity; Free volume; Proton conductivity; PBI dendrimer containing triazine rings; Degree of branching; High-temperature proton exchange membrane
• ISSN: 2468-5194; 2468-5194
• DOI: 10.1016/j.mtchem.2021.100653

A high-temperature proton exchange membrane with high proton conductivity over a wide humidity range still remains a challenge. PBI dendrimer containing triazine rings (TPBI) was synthesized to approach this aim considering its high content of hygroscopic terminal groups and of larger free volume. A novel proton conductor previously synthesized (zirconium 3-sulfopropyl phosphonate, ZrSP) was doped due to its good proton conductivity over a wide humidity range. TPBI was post-crosslinked with a tetrafunctional epoxy resin (N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane, TGDDM) to enhance the mechanical stability at low cross-linking degrees, which allowed high doping levels of ZrSP, and thus, high conductivity. The prepared membranes (TPBI-TGDDM/ZrSP) showed good thermal stability, high proton conductivity over wide humidity range, and good dimensional stability. At suitable degrees of branching, TPBI-TGDDM/ZrSP exhibited superior mechanical property, oxidative stability, methanol barrier property, and membrane selectivity than its linear analog (mPBI-TGDDM/ZrSP). As ZrSP instead of PA was applied as the proton conductor, TPBI-TGDDM/ZrSP showed good durability of proton conductivity, especially in comparison with TPBI-TGDDM/PA, which highly retarded decline in conductivity caused by PA leaking. The proton conductivity at 180 °C of TPBI(20)-TGDDM(10)/ZrSP(50) achieved 142, 84.2 and 23.6 mS cm−1 at 100%, 50%, and 0 RH, respectively. [Display omitted] •PBI dendrimer bearing triazine rings was synthesized with tunable branching degree.•A new proton conductor with good conductivity over a wide humidity range was doped.•Low cross-linking degree allowed high doping level and good proton conductivity.•Good and durable proton conductivity over a wide humidity range was achieved.•Suitable branching degree led to superior physicochemical properties.