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.