Synthesis and characterization of new sulfonated polytriazole proton exchange membrane by click reaction for direct methanol fuel cells (DMFCs)

Sulfonated polytriazole (SPTA) in which the acidic sulfonic acid and basic triazole groups act as physical crosslinking sites within a polymer backbone has been successfully prepared, for use as a proton exchange membrane, using the click reaction. The acid-base interactions of the SPTA membranes leads to the formation of well-dispersed ionic clusters and the random distribution of ion channels with good connectivity resulting in lower methanol permeabilities at ambient temperatures and similar or higher proton conductivities than Nafion 117 at 80 °C in conditions of near zero relative humidity. Proton conductivities (σ) of 0.149 S cm−1 at 80 °C and 9 × 10−5 S cm−1 in anhydrous conditions together with low methanol permeability (P) at 0.1 × 10−6 cm2 s−1 that are comparable or superior to Nafion 117 (σT=80 : 0.151 S cm−1; σRH=0 : 3 × 10−5 S cm−1; PT=30: 1.31 × 10−6 cm2 s−1) were achieved. Additionally, the selectivity of SPTA is approximately four times higher than that of Nafion 117, thus it may have potential for use in direct methanol fuel cells (DMFCs).