Adjusting structure-activity relationship to obtain hybrid proton exchange membrane with enhanced transport efficiency by introducing functionalized nano-coated MOFs

Abstract

Designing proton exchange membranes (PEMs) with high H+ conductivity and good dimensional stability has been a challenge. The porous structure of ZIF-8 could load ionic liquids (IL) (ZIF-8@IL). The ZIF-8@IL was coated by sulfonated polydopamine (SPDA), then ZIF-8@IL-SPDA as proton conductors was fabricated. ZIF-8@IL-SPDA would not lose in water environment like small molecule proton conductors (such as sulfuric acid, phosphoric acid, imidazole, etc.). The different loadings of ZIF-8@IL-SPDA were introduced into sulfonated poly (aryl ether ketone sulfone) containing fluorene groups (F-SPAEKS). The novel composite PEMs was investigated. The prepared hybrid matrix membrane with optimum ZIF-8@IL-SPDA doping content (1.5 wt%) showed the highest H+ conductivity of 149.87 mS cm−1 at 80 °C. In addition, a maximum peak power density of 818 mW cm−2 was achieved in a single-cell performance test of this membrane. The good dispersion of ZIF-8@IL-SPDA nanoparticles in the F-SPAEKS matrix reduced the fuel cross-over flux to 2.15 mA cm−2. Therefore, the newly prepared hybrid matrix membranes were expected to be applied in proton exchange membrane fuel cells.