Enhanced proton conductivity of sulfonated poly(arylene ether ketone sulfone) for fuel cells by grafting triazole groups onto polymer chains

• SPT membranes with both triazole and sulfonic acid were prepared.
• Triazole enhanced proton conductivity at high temperatures and low humidity.
• The membranes showed excellent dimensional stability and thermal property.
• SPT membranes have good prospective usages in PEMFC.

A series of triazole-grafted sulfonated poly(arylene ether ketone sulfone)s (SPTs) were fabricated via an amide coupling reaction between 3-amino-1,2,4-triazole and carboxylic acid group. The degree of sulfonation (DS) was set to 80% for preventing excessive swelling. The chemical structures of synthesized polymers were characterized by Fourier transform infrared spectroscopy (FT-IR) and 1H NMR spectroscopy. The triazole group affected the properties of membranes dramatically. Increasing the triazole group content was conductive to promoting the thermal property and oxidative stability. And all SPT membranes retained above 92% of their weight after the test in Fenton's reagent at 80 °C for 1 h. The swelling ratio of SPT-3 membrane was only 12.66% and it was lower than that of C-SPAEKS-3 membrane at 100 °C. It was also found that the proton conductivity was distinctly improved by introducing triazole groups and the SPT-4 membrane exhibited a proton conductivity of 0.166 S cm−1 at 120 °C, which was larger than that of Nafion 117. In addition, all SPT membranes showed higher proton conductivity when compared with C-SPAEKS-3 membranes over the range of relative humidity from 20% to 90% at 80 °C.