Anion exchange composite membrane based on ionic liquid-grafted covalent organic framework for fuel cells

Guanidinium/Hydroxyl-Functionalized Polybenzimidazole for High-Temperature Proton Exchange Membrane Fuel Cell Applications

“…The chemical structures of [BrBuTMG]­Br, OH-PBI-10, and TMG/PBI-10 were investigated by 1 H nuclear magnetic resonance (NMR) spectroscopy (Figures and S1). In the 1 H NMR spectrum of [BrBuTMG]Br (Figure S1), the chemical shift at 7.91 ppm is attributed to the −NH– proton; chemical shifts within 2.92–2.96 ppm are attributed to the protons of methyl groups; those within 3.34–3.40 ppm and at 1.94 ppm are attributed to methylene groups. , In the spectrum of OH-PBI-10, the chemical shifts within 7.37–8.35 ppm and at 13.07 ppm are attributed to the protons on the benzene ring of PBI and the −NH– moiety of the imidazole ring, respectively; the chemical shift corresponding to the phenolic hydroxyl groups appeared at 10.77 ppm . In the spectrum of TMG/PBI-10, no chemical shift was observed at ∼13.07 ppm (which was observed in the spectrum of OH-PBI-10); instead, new chemical shifts were observed within 1.93–3.41 ppm corresponding to the protons of [BrBuTMG]­Br, confirming the reaction of [BrBuTMG]Br with PBI-10 …”

“…Additionally, OH-PBI- X membranes show a lower oxidative stability than pure PBI membranes, with 73.56% of PBI retention after 200 h. OH-PBI-10 and OH-PBI-20 membranes exhibit 73.39 and 70.14% of PBI retention, respectively. Therefore, the introduction of hydroxyl groups reduces the chemical stability of PBI membranes by increasing their susceptibility to free-radical attack . Notably, TMG/PBI- X membranes exhibit higher chemical stability than pure PBI membranes; TMG/PBI-10 and TMG/PBI-20 membranes show weight retentions of 81.62 and 76.92%, respectively.…”

“…[BrBuTMG]Br was synthesized according to the previous paper . TMG was dissolved in acetonitrile and 1,4-dibromobutane was added slowly dropwise into the solution under ice bath.…”

“…Therefore, the introduction of hydroxyl groups reduces the chemical stability of PBI membranes by increasing their susceptibility to free-radical attack. 39 Notably, TMG/PBI-X membranes exhibit higher chemical stability than pure PBI membranes; TMG/PBI-10 and TMG/PBI-20 membranes show weight retentions of 81.62 and 76.92%, respectively. Guanidinium ions exhibit excellent thermal and chemical stability owing to the highly stable delocalization of the positive charge in guanidinium ions over the central C atom and three N atoms through conjugated bonds.…”

“…[BrBuTMG]Br was synthesized according to the previous paper. 39 TMG was dissolved in acetonitrile and 1,4dibromobutane was added slowly dropwise into the solution under ice bath. The reaction was carried out at room temperature under a nitrogen atmosphere for 24 h. Then, the product was dried via rotary evaporation and washed with ethyl acetate 3 times.…”