A superhydrophobic bromomethylated poly(phenylene oxide) as a multifunctional polymer filler in SPEEK membrane towards neat methanol operation of direct methanol fuel cells

Development of novel proton exchange membrane (PEM) with the aim toward neat methanol operation of direct methanol fuel cell (DMFC) has attracted increasing attention. Proton exchange membrane technology with remarkably low methanol permeability has been considered as one of the most facile ways to approach this target. Here, sulfonated poly(ether ether ketone) (SPEEK) membrane was modified by blending with superhydrophobic bromomethylated poly(phenylene oxide) (BPPO). The fabricated SPEEK/BPPO membranes possess obviously low methanol permeability, which is attributed to the formed interrupted methanol transport channels arising from the combined properties of the hydrophobic BPPO polymeric backbone, the formed spherical BPPO obstacles and the cross-linking networks derived from the Friedel-Craft reaction between bromobenzyl groups and nucleophilic phenyl rings. Therefore, the SPEEK/BPPO membrane DMFC demonstrates a much higher cell performance both at low methanol concentration and high methanol concentration than the Nafion 117 DMFC. In particular, the actual value of the maximum power density at high methanol concentration of 20 M suggests that the SPEEK/BPPO membranes can be considered as a desirable candidate for potential application in high methanol concentration DMFCs.