Acid–base blend membranes consisting of sulfonated poly(ether ether ketone) and 5-amino-benzotriazole tethered polysulfone for DMFC

Low cost, acid–base blend membranes have been synthesized by blending sulfonated poly(ether ether ketone) (SPEEK) (an acid polymer) and various amounts of polysulfone tethered with 5-amino-benzotriazole (a basic polymer). The blend membranes have been characterized by ion-exchange capacity (IEC), liquid uptake, proton conductivity, methanol crossover, and fuel cell performance measurements. The blend membranes exhibit superior performance in direct methanol fuel cells (DMFC) compared to plain SPEEK and Nafion 115 membranes due to enhanced proton conductivity and much suppressed methanol crossover while preserving good swelling stability. The maximum power density of the blend membrane is two times higher than that of Nafion 115 membrane at 80 °C with 1 M methanol feed. Additionally, the effects of the size, pKa, and the number of nitrogen atoms of the tethered heterocycle groups on the properties of the blend membranes have also been investigated by comparing the properties of the blend membranes consisting of SPEEK and different basic polymers.

Research highlights▶ A novel polysulfone tethered amino-benzotriazole (PSf-BTraz) polymer has been synthesized and characterized. ▶ Membranes obtained by blending the sulfonated poly (ether ether ketone) (SPEEK) polymer with the PSf-BTraz polymer show better performance in direct methanol fuel cells (DMFC) than plain SPEEK or Nafion 115 membranes. ▶ The better performance in DMFC of the SPEEK/PSf-BTraz blend membranes is due to acid-base interactions between SPEEK and PSf-BTraz and much reduced methanol crossover compared to that in plain SPEEK or Nafion 115 membranes. ▶ The size, pKa, and number of nitrogen atoms of the heterocycles are found to tune the properties of the acid-base blend membranes.