Performance evaluation of polymer electrolyte membranes based on hydrogen sulfite ionic liquid for application in direct methanol fuel cell (DMFC)

Abstract

Series of proton conductive membranes were prepared by mixing different weight ratio of 3-hexyl-1-methylimidazolium hydrogensulfite ([C₆C₁Imi][HSO₃]), and N-hexyl-pyridinium hydrogensulfite ([C₆Py][HSO₃]) ionic liquids with poly vinyl alcohol (PVA) polymer. To characterize the PVA-ILs membranes, different methods have been used such as X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and scanning electron microscope (SEM). Moreover, the water uptakes, ion exchange capacity, methanol permeability, and proton conductivity of prepared PVA membranes doped with different weight ratio of ILs have been investigated to find the optimum formulation to use as electrolytes membranes for direct methanol fuel cell. The proton conductivity and the ion exchange capacity were improved as the ILs content increased. At 25 °C, The PVA-60 wt.% of [C₆C₁Imi][HSO₃] membrane had a maximum proton conductivity of 17,47 mS.cm⁻¹, and a methanol permeability of 8.17 10⁻⁷ cm².s ^− 1. Mechanical and thermal data confirmed that addition of ILs improve the membrane flexibility and thermal stability up to 200 °C.