Polybenzimidazole dendrimer containing triazine rings-based high-temperature proton exchange membranes with high performances over a wide humidity range. (March 2022)

• Record Type: Journal Article
• Authors: Sun, Peng; Xia, Zihan; Li, Zhongfang; Fan, Ziwei; He, Fengqi; Liu, Qiang; Yin, Xiaoyan
• Is Part Of: Materials today chemistry. Volume 23(2022)
• Publication Date: 2022-03
• Subjects: High-temperature proton exchange membrane -- PBI dendrimer containing triazine rings -- Degree of branching -- Free volume -- Proton conductivity; Chemistry -- Periodicals; Materials -- Research -- Periodicals; Materials science -- Periodicals; Chemistry; Materials -- Research; Electronic journals; Periodicals; 660.282
• DOI: 10.1016/j.mtchem.2021.100653
• Languages: English
• ISSNs: 2468-5194

Abstract

Abstract: 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. Graphical abstract: Image 1 Highlights: 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.