Novel proton exchange membrane nanocomposites based on sulfonated tungsten trioxide for application in direct methanol fuel cells

Abstract

Novel sulfonated poly (phthalazinone ether ketone) (SPPEK)/sulfonated poly (vinylidene fluoride-co-hexafluoropropylene) (SPVdF-co-HFP)/sulfonated tungsten trioxide (SWO3) nanocomposite blend membranes were fabricated as alternative proton exchange membranes (PEM) for application in direct methanol fuel cell (DMFC). PPEK and PVdF-co-HFP were sulfonated using sulfuric acid and chlorosulfonic acid, respectively. The degree of sulfonation (DS) of produced SPPEK and SPVdF-co-HFP were determined by titration method and found to be 68% and 30%, respectively. The dominant characteristics of the prepared membranes, such as water uptake, membrane swelling, proton conductivity, methanol permeability, selectivity and DMFC performance were investigated. The membranes containing SWO3 nanoparticles indicated higher proton conductivity and lower methanol permeability compared with pristine SPPEK and blend membranes. This improvement is attributed to presence of the sulfonated groups of nanoparticles that increases proton conductivity with Grotthus and vehicle mechanisms. The catalytic properties of SWO3 nanoparticles increase kinetic of reaction in interface surface of membrane and electrode and improve performance of DMFCs. Well optimized nanocomposite blend membrane (MSSW5) showed proton conductivity of 0.071 S cm−1, methanol permeability of 9.5 × 10−8 cm2 S−1 and power density of 63.60 mW cm−2 at room temperature, thus it can be a suitable candidate for DMFC application.