Anion exchange membrane fuel cells (AEMFCs) have been a topic of extensive research from academia and industry as an alternative to proton exchange membrane fuel cells (PEMFCs). The AEMFCs offer benefits over PEMFCs such as facile fuel oxidation and enhanced oxygen reduction reaction catalysis¹. However, the chemical stability of anion exchange membrane needs to be improved as most commonly used benzyltrimethyl ammonium cationic group undergoes direct nucleophilic substitution reaction, which results in loss of conductivity and fuel cell performance. One of the approaches to enhance the chemical stability is introducing electron conjugation into cationic functional group. Previous study demonstrated that the conjugated guanidinium possess better stability than non-conjugated guanidinium².

Herein, we report the progress on resonance stabilization of the guanidinium functional group. The extended-resonance stabilized guanidinium functionalized poly(phenylene) (PP-TMG) AEM was synthesized from the Diels-Alder poly(phenylene) by acylation reaction followed by activated fluorophenyl-guanidine reaction³. The alkaline stability of PP-TMG was compared with benzyltrimethyl ammonium-poly(phenylene) (PP-BTMA) and hexamethylenetrimethyl ammonium-poly(phenylene) (PP-HTMA). Spectroscopic analysis with small molecules and cationic group tethered polymers will be also provided to discuss the resonance stabilization effect.

Acknowledgement

This work is supported by the US Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technology Office (Program Manager Dr. David Peterson).

References:

(1) Varcoe, J. R.; Atanassov, P.; Dekel, D. R.; Herring, A. M.; Hickner, M. A.; Kohl, P. A.; Kucernak, A. R.; Mustain, W. E.; Nijmeijer, K.; Scott, K.; Xu, T.; Zhuang, L. Energy Environ. Sci. 2014, 7 (10), 3135–3191.

(2) Kim, D. S.; Fujimoto, C. H.; Hibbs, M. R.; Labouriau, A.; Choe, Y.-K.; Kim, Y. S. Macromolecules 2013, 46 (19), 7826–7833.

(3) Kim, D. S.; Labouriau, A.; Guiver, M. D.; Kim, Y. S. Chem. Mater. 2011, 23 (17), 3795–3797.