Physicochemical properties of proton conducting membranes based on ionic liquid impregnated polymer for fuel cells†
Abstract
Polymer electrolyte membranes containing a room temperature ionic liquid, 2,3-dimethyl-1-octylimidazolium triflate (DMOImTf) in polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP), show conductivity of 0.96 × 10−3 S cm−1 at 80 °C. The addition of triflic acid (HCF3SO3) increases the conductivity of the polymer electrolytes by providing free H+ ions, which is important for their potential use in proton exchange membrane fuel cells (PEMFCs) and other electrochemical devices. Line narrowing observed in the variation of 1H and 19F NMR line width with temperature shows that both protons and anions are mobile in these electrolytes. The membranes have been found to be thermally stable up to 200–300 °C. Polymer electrolyte membranes containing the ionic liquid have also been tested in a single cell fuel cell under non-humid conditions and found to be electroactive for hydrogen oxidation and oxygen reduction at platinum electrodes.