scholarly journals Synthesis and Properties of Phosphoric-Acid-Doped Polybenzimidazole with Hyperbranched Cross-Linkers Decorated with Imidazolium Groups as High-Temperature Proton Exchange Membranes

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 515 ◽  
Author(s):  
Chunmei Gao ◽  
Meishao Hu ◽  
Li Wang ◽  
Lei Wang

Highly phosphoric-acid (PA)-doped polybenzimidazole (PBI) membranes exhibit good proton conductivity at high temperatures; however, they suffer from reduced mechanical properties and loss of PA molecules due to the plasticity of PA and the weak interactions between PA and benzimidazoles, especially with the absorption of water. In this work, a series of PBIs with hyperbranched cross-linkers decorated with imidazolium groups (ImOPBI-x, where x is the weight ratio of the hyperbranched cross-linker) as high-temperature proton exchange membranes are designed and synthesized for the first time. We observe how the hyperbranched cross-linkers can endow the membranes with improved oxidative stability and acceptable mechanical performance, and imidazolium groups with strong basicity can stabilize the PA molecules by delocalization and hydrogen bond formation to endow the membranes with an enhanced proton conductivity and a decreased loss of PA molecules. We measured a high proton conductivity of the ImOPBI-x membranes, ranging from 0.058 to 0.089 S cm−1 at 160 °C. In addition, all the ImOPBI-x membranes displayed good mechanical and oxidative properties. At 160 °C, a fuel cell based on the ImOPBI-5 membrane showed a power density of 638 mW cm−2 and good durability under a hydrogen/oxygen atmosphere, indicating its promising use in anhydrous proton exchange membrane applications.

Author(s):  
Hsiu-Li Lin ◽  
Chih-Ren Hu ◽  
Po-Hao Su ◽  
Yu-Cheng Chou ◽  
Che-Yu Lin

Phosphoric acid doped poly(benzimidazole) (PBI) is one of excellent candidates of proton exchange membranes for high temperature (150–180°C) proton exchange membrane fuel cells (PEMFCs). However, the strong inter-polymer hydrogen bonds cause low elongation and brittleness of PBI membranes. In this work, we synthesize poly(benzimidazole) (PBI) and butylsulfonated poly(benzimidazole) (PBI-BS), in which around 22 mole% of imidazole –NH groups of PBI are grafted with sulfonated butyl groups. We show the elongation, phosphoric acid doping level, and proton conductivity of PBI can be improved by blending ∼ 20 wt% of PBI-BS in the PBI membrane, and the membrane electrode assembly prepared from PBI/PBI-BS (8/2 by wt) blend membrane has a better PEMFC performance at 140°C ∼ 180°C than that prepared from PBI membrane. It is believed that the crosslink interactions of imidazole -NH and -N=C-groups with side chain –C4H8−SO3H groups of PBI-BS reduces the inter-PBI hydrogen bonds and increases the free volume of polymers, which leads to the enhancements of the membrane toughness and phosphoric acid doping level and the PEMFC performance.


Author(s):  
Peng Wang ◽  
Jinwu Peng ◽  
Bibo Yin ◽  
Xian-Zhu Fu ◽  
Lei Wang ◽  
...  

Porous polybenzimidazole (PBI) membranes with high ability to store phosphoric acid (PA) and transfer protons are promising materials as high-temperature proton exchange membranes (HT-PEMs) for fuel cell applications. However, porous...


RSC Advances ◽  
2015 ◽  
Vol 5 (66) ◽  
pp. 53870-53873 ◽  
Author(s):  
Xiaobai Li ◽  
Hongwei Ma ◽  
Hailong Wang ◽  
Shitong Zhang ◽  
Zhenhua Jiang ◽  
...  

This work outlines polybenzimidazole-based high temperature proton exchange membranes with a high phosphoric acid-doping level, high proton conductivity and high stability.


2014 ◽  
Vol 5 (17) ◽  
pp. 4939-4947 ◽  
Author(s):  
Na Zhang ◽  
Chengji Zhao ◽  
Wenjia Ma ◽  
Shuang Wang ◽  
Baolong Wang ◽  
...  

The phosphoric acid doped quaternary ammonium poly(ether ether ketone) membranes cross-linked with PBI showed improved performance.


RSC Advances ◽  
2016 ◽  
Vol 6 (66) ◽  
pp. 61029-61036 ◽  
Author(s):  
Jingshuai Yang ◽  
Chao Liu ◽  
Liping Gao ◽  
Jin Wang ◽  
Yixin Xu ◽  
...  

Phosphoric acid doped novel high temperature proton exchange membranes based on the imidazolium functionalized poly(epichlorohydrin) and porous polyetrafluoroethylene were fabricated and investigated.


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