Non-planar backbone structure polybenzimidazole membranes with excellent solubility, high proton conductivity, and better anti-oxidative for HT-PEMFCs. Issue 93 (23rd September 2016)

• Record Type: Journal Article
• Authors: Sun, Guohua; Han, Kefei; Yu, Jinghua; Zhu, Hong; Wang, Zhongming
• Is Part Of: RSC advances. Volume 6:Issue 93(2016)
• Page Start: 91068
• Page End: 91076
• Publication Date: 2016-09-23
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c6ra18197j
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : This work introduces a bulky stereostructure monomer (BPY) to obtain a series of novel non-planar BPY-PBI- x polymers, which exhibit excellent solubility, high proton conductivity, and better anti-oxidative for HT-PEMFCs. Abstract : As an efficient, inexpensive, readily accessible monomer of the polybenzimidazole (PBI) copolymer, the 4, 4′-[(4, 4′-bipyridine)-2, 6-diyl]dibenzoic acid (BPY) containing bipyridine unit was firstly used to synthesize a series of novel non-planar PBI copolymers (BPY–PBI- x ) by regulating the ratio with 2, 6-pyridinedicarboxylic acid under microwave-assisted conditions. The copolymers exhibit superior solubility in aprotic solvents such as N, N -dimethylacetamide, N, N -dimethylformamide and dimethylsulfoxide than general PBI, and the corresponding BPY–PBI- x serial membranes were prepared by a solution casting method. All the membranes have been characterized by thermal stability, a tension test, scanning electron microscopy, PA-doping ability and swelling ratio, proton conductivity, and a Fenton test. The membranes exhibit excellent comprehensive properties containing high proton conductivity and long lifetime. The conductivity of the doping levels of the BPY–PBI-100% membrane with the highest doping level (342.7%) reaches 78.6 mS cm −1 at 160 °C. The high proton conductivity is attributed to the increase in N atoms of the proton acceptor from the bipyridine monomer and the enhancement of free volume from the existence of a bulky stereostructure BPY unit. The long lifetime is due to the fact that the pyridine unit can quench radicals by the formation of pyridine-N-oxide. The unique anti-oxidation mechanism of the BPY–PBI- x serial membranes, which firstly was pointed out for the application of pyridine heterocyclic rings in HT-PEMs, provides new insights for novel anti-oxidation membrane design. In short, 3-fold objectives, namely, (I) soluble PBI, (II) higher proton conductivity PBI, and (III) anti-oxidative PBI, were achieved in this paper.