Sulfonated PVdF-HFP/shuttle-like SrBaWO4 nanocomposite membranes for the evolution of high performance and durable DMFCs

Abstract

Sulfonated poly (vinylidene fluoride-co-hexafluoropropylene) (sPVdF-HFP) nanocomposite membranes with shuttle-like sulfonated barium tungstate (sBaWO4) and strontium barium tungstate (sSrBaWO4) nanofillers are formulated as solid state electrolytes for direct methanol fuel cells (DMFCs). Morphological features of shuttle-like fillers are intact even after their blending with sPVdF-HFP in the form of nanocomposite membranes, which exemplifies their structural and physical integrities, conscripting the high oxidative and thermal stabilities of sPVdF-HFP/sBaWO4/sSrBaWO4 nanocomposite membranes. Owing to the prevalence of oxygen vacancies and the consequent surface reactivities, sBaWO4 and sSrBaWO4 nanofillers augment the water adsorption properties of sPVdF-HFP based nanocomposite membranes, whilst their substantial ion exchange capacities are corroborated with the ionizable functionalities. The elevated oxygen and cation vacancies and hydrogen bonding exerted amid the neighborhood oxygen lattices of SrBaWO4 nanostructures enunciate the swift ionic mobility for sPVdF-HFP/sSrBaWO4 nanocomposite membrane. Hydrogen bonding stimulated between the sulfonic acid moieties of both the filler and host polymer/hydroxyl functionalities of filler with free water molecules and hydrophobic polymeric backbone narrow down the molecular transportation networks, confining the methanol permeation of as-formulated nanocomposite membranes. Thus, the discerning channels implanted for H+ ions and methanol in sPVdF-HFP/sSrBaWO4 nanocomposite membrane enumerate the maximal ionic conductivity/methanol permeation selectivity ratio that enacts the maximum power density of 127 mW cm−2 with uplifted durability over the Nafion 117 membrane, convening it's propriety as a dynamic solid electrolyte in high performance and durable DMFCs.