Vinyl-based in-situ crosslinked polybenzimidazoles for anion exchange membranes water electrolysis

In the present work, a series of crosslinked polybenzimidazole (PBI) anion exchange membranes (AEMs) were prepared via the vinyl-based in-situ crosslinking method. The crosslinked AEMs (PcPBI-x-C) had simultaneously improved dimensional stability, mechanical properties and chemical stability compared to the pre-crosslinked AEM (PcPBI). The effect of different crosslinker structures including rigid benzene ring, flexible alkanes and flexible alkanes containing hydrophilic imidazolium on the performance of AEMs was systematically investigated. As results, the swelling ratio of the PcPBI-Vbc-C membrane containing rigid benzene ring crosslinked structure was reduced by 49.8% (from 22.1% to 11.1%), the tensile strength of PcPBI-Im-C membrane containing flexible hydrophilic imidazolium crosslinked structure increased by 33.5% (from 48.1 MPa to 64.2 MPa) and the elongation at break by 115.2% (from 28.9% to 62.2%). PcPBI-x-C crosslinked AEMs had conductivities of 87.6-98.7 mS/cm at 80 °C, their conductivity retentions were 72.5-82.4% after immersion in 2 M KOH solution for 2400 h. Furthermore, the anion exchange membrane water electrolysis (AEMWE) with PcPBI-Im-C as AEM could be stably operated for 100 h at the current density of 200 mA/cm2, indicating that PBI AEMs containing flexible hydrophilic imidazolium crosslinked structure possess great potential for application in AEMWE.