Guanidimidazole-quanternized and cross-linked alkaline polymer electrolyte membrane for fuel cell application

•Guanidimidazole designed and synthesized.•It could quaternize and cross-link polymer simultaneously for AEM fabrication.•The AEM showed better alkali stability than imidazole-quaternized one due to enhanced resonance.•The beneficial effect was confirmed by DFT study.

A modified imidazole, namely guanidimidazole (GIm) was designed and synthesized as a novel quaternizing- and cross-linking agent for alkaline polymer electrolyte membrane fabrication. The resulting membrane was more alkali tolerant and swelling resistant than that quaternized purely by 1-methylimidazole owing to the enhanced resonance and cross-linking ability of GIm, the former confirmed by a LUMO (lowest unoccupied molecular orbital) energy calculation. The membrane also showed good ionic conductivity, mechanical strength and thermal stability. A H2/O2 fuel cell using the synthesized membrane showed a peak power density of 39 mW cm−2 at 50 °C. This work preliminarily demonstrates the beneficial effect of imidazole modification by both experimental and computational investigation; it provides a new cation design strategy that may potentially achieve simultaneous improvement of alkali stability and swelling resistance of alkaline electrolyte membranes.

Graphical abstractEnhanced resonance and bi-functionality of guanidimidazolium cation help to make the alkaline electrolyte membrane more robust.Figure optionsDownload full-size imageDownload high-quality image (230 K)Download as PowerPoint slide