Investigation of Diamine Cross-Linker on Semi-IPNs of BPPO/SPEEK Membranes for Direct Methanol Fuel Cell

Low methanol permeability is one of the most critical factors for proton exchange membranes utilized in direct methanol fuel cells (DMFCs). Here, sulfonated poly(ether ether ketone) (SPEEK) polymer chains are interpenetrated into the semi-interpenetrating polymer networks (semi-IPNs) constructed by the alkylation reaction between bromobenzyl groups of bromomethylated poly(phenylene oxide) and amine groups of 2,2′-(ethylenedioxy)bis(ethylamine) cross-linker. The influences of crosslinking network contents on the key properties of SPEEK membranes are systematically investigated. Dimensional stability and methanol-permeability resistance are enhanced as the increase of the crosslinking network contents. The relative selectivity is significantly improved due to the largely reduced methanol permeability. The DMFC assembled by the membrane with 20 wt.% crosslinking networks demonstrates four times higher power output than the Nafion 117 DMFC in 5 M methanol solution.