Facile preparation of triazole-functionalized poly(arylene perfluorophenyl) high temperature proton exchange membranes via para-fluoro-thiol click reaction with high radical resistance

Abstract

For the development of high temperature proton exchange membranes (HT-PEMs), several challenges still need to be overcome, including high proton conductivity, low swelling, and superior oxidation stability. In this work, we reported a facile and efficient strategy to developing a novel class of phosphoric acid (PA) doped HT-PEMs based on triazole-functionalized poly(arylene perfluorophenyl)s. Arylene ether-free all-carbon backbone aromatic polymers were synthesized via a superacid-catalyzed reaction, and the grafting of sulfide-linked triazole groups was completed by a quantitative and selective para-fluoro-thiol click reaction. 1H and 19F NMR spectra confirmed their chemical structures and the grafting degrees of 100%. The series of triazole-functionalized polymers exhibited high thermal decomposition temperatures (Td5% above 200 °C) and tensile strengths. At 180 °C, the obtained HT-PEMs showed a proton conductivity up to 109.8 mS cm-1 while maintaining volume swellings below 152% and thickness swellings below 52%. In a single fuel cell at 160 °C, the high proton conductivity of the membrane resulted in a peak power density of 760 mW cm-2 without external humidification and backpressure. Owing to the existence of sulfide group in the side chain, HT-PEMs remained intact and retained high residual weight after 72 hours treatment with Fenton's reagent, enabling them to have good durability in fuel cell. The results demonstrate that the prepared HT-PEMs with high radical resistance and superior performance have promising potential for application in high temperature proton exchange membrane fuel cells.