Issue 9, 2019

Cross-linked sulfonated poly(ether ether ketone) electrolytes bearing pendent imidazole groups for high temperature proton exchange membrane fuel cells

Abstract

An ionically cross-linked sulfonated poly(ether ether ketone) (SPEEK) bearing imidazole groups (SPEEK-Im) has been synthesized via the 1,1′-carbonyldiimidazole (CDI) activating reaction. By regulating the molar ratio of p-xylene dibromide to the imidazole groups of SPEEK-Im, a series of ionic-covalently cross-linked membranes (C-SPEEK-Im-x) can be achieved. Phosphoric acid (PA) doped membranes (PA-SPEEK-Im and PA-C-SPEEK-Im-x) were further prepared by a simple impregnation method for application in high temperature (>100 °C) fuel cells. The ionic interactions between the imidazole and sulfonic acid groups in SPEEK-Im improve the thermal and oxidative stability of the corresponding membrane while offering an elongation at break of 400%. After the ionic-covalent cross-linking process, the mechanical properties, and oxidative and dimensional stability of Im-C-SPEEK-x membranes have been greatly enhanced due to their more compact chemical structure. More importantly, the PA-Im-C-SPEEK-x membranes display high proton conductivity with a low PA doping level at high temperature. Notably, the proton conductivity of PA-Im-C-SPEEK-10 reaches 0.067 S cm−1 at 150 °C and 30% relative humidity. The proton exchange membrane fuel cell using PA-Im-C-SPEEK-20 exhibits a peak power density of 209 mW cm−2 at 130 °C in H2/O2 under anhydrous conditions. The results indicate that ionic-covalently cross-linked membranes with a relatively low PA doping level are suitable for use in high temperature fuel cells.

Graphical abstract: Cross-linked sulfonated poly(ether ether ketone) electrolytes bearing pendent imidazole groups for high temperature proton exchange membrane fuel cells

Supplementary files

Article information

Article type
Paper
Submitted
23 May 2019
Accepted
09 Jul 2019
First published
09 Jul 2019

Sustainable Energy Fuels, 2019,3, 2426-2434

Cross-linked sulfonated poly(ether ether ketone) electrolytes bearing pendent imidazole groups for high temperature proton exchange membrane fuel cells

J. Jiang, X. Zhu, H. Qian, J. Xu, Z. Yue, Z. Zou and H. Yang, Sustainable Energy Fuels, 2019, 3, 2426 DOI: 10.1039/C9SE00318E

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