Preparation and Characterisation of Proton Exchange Membranes Based on Crosslinked Polybenzimidazole and Phosphoric Acid

Abstract

Crosslinked polybenzimidazole (PBI) was synthesised via free radical polymerisation between N‐vinylimidazole and vinylbenzyl substituted PBI. The degree of crosslinking increases with increasing content of the crosslinker. The phosphoric acid doping behaviour, mechanical properties, proton conductivity and acid migration stability of crosslinked PBI and linear PBI are discussed. The results show that the acid doping ability decreases with increasing degree of crosslinking of PBI. The introduction of N‐vinylimidazole in PBI is beneficial to its oxidation stability. The mechanical stability of crosslinked PBI/H3PO4 membrane is better than that of linear PBI/H3PO4 membrane. The proton conductivity of the acid doped membranes can reach ∼10–4 S cm–1 for crosslinked PBI/H3PO4 composite membranes at 150 °C. The temperature dependence of proton conductivity of the acid doped membranes can be modelled by an Arrhenius relation. The proton conductivity of crosslinked PBI/H3PO4 composite membranes is a little lower than that of linear PBI/H3PO4 membranes with the same acid content. However, the migration stability of H3PO4 in crosslinked PBI/H3PO4 membranes is improved compared with that of linear PBI/H3PO4 membranes.

Polybenzimidazole-crosslinked poly(vinylbenzyl chloride) with quaternary 1,4-diazabicyclo (2.2.2) octane groups as high-performance anion exchange membrane for fuel cells

“…S1) and Fourier transform infrared (FT-IR) absorption spectrum ( Fig. S2) was in good agreement with those shown in literature [31]. 1, 4-diazabicyclo (2.2.2) octane (DABCO) and poly(vinylbenzyl chloride) (PVBC, 60/40 mixture of 3-and 4-isomers average M n~5 5,000, average M w~1 00,000 by GPC/ MALLS, powder) were procured from SigmaeAldrich.…”

“…As shown in Fig. 4a, PBI is thermal stable up to~600 C [31]; PVBC starts to degrade from~350 C, which comes from the degradation of eCH 2 Cl groups, and then the decomposition of main chain occurs above 450 C. As for PBI-c-PVBC, the weight loss before 150 C may result from the release of residual solvent, which is followed by a new weight loss step, probably due to the degradation of conductive crosslinking point (benzimidazolium) formed between PBI and eCH 2 Cl groups, and thereafter the weight loss may come from the decomposition of the non-conductive crosslinking points and remaining eCH 2 Cl groups in PVBC. Therefore, it can be seen that the TG curve of PBI-c-PVBC is totally different from that of PBI and PVBC, i.e., PBI-c-PVBC was not the simple physical mixture of PBI Fig.…”

Proton Conducting Membranes Based on Poly(2,2′‐imidazole‐5,5′‐bibenzimidazole)

“…Really, pure PBI with low molecular weight seems useless. However, our recent work involves to prepare reinforced PEM, for example, semi-IPN PEM or crosslinked PBI PEMs [5,8]. These will make such kind of PBI-imi useful in the future.…”

“…At the same acid concentration, PBI-imi shows a little better acid doping ability than PBI-ph. The factors that affect the acid doping ability of PBI-ph/H 3 PO 4 membranes have been studied before [5,16]. The concentration of the acid solution and doping time are the two main methods to adjust the acid doping level.…”

“…Polymer electrolyte membrane fuel cells (PEMFCs) have attracted a lot of attention these years due to their eco-friendliness and high efficiency of energy conversion [1][2][3][4][5]. The widely used proton exchange membranes (PEMs) for PEMFCs are perfluorosulfonic acid polymers, such as Nafion ® and Flemion ® [6][7][8][9][10].…”