Proton-conducting blend membranes of Nafion/poly(vinylphosphonic acid) for proton exchange membrane fuel cells

Abstract

Nafion/poly(vinylphosphonic acid) blends were synthesized and characterized in this work. Poly(vinylphosphonic acid), PVPA, was synthesized by the free-radical polymerization of vinylphosphonic acid. Then Nafion/PVPA blend membranes were prepared by means of film casting from Nafion/PVPA solutions with several molar ratios of PVPA repeat unit to – SO3H. Homogeneous Nafion/PVPA films were produced. Nafion–PVPA interactions were studied by Fourier transform infrared (FT-IR) spectroscopy. Thermal properties were investigated via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The TGA results illustrated that all of these Nafion/PVPA electrolytes are thermally stable up to 400 °C. The membrane properties were further characterized by studying their morphologies using scanning electron microscopy (SEM). The proton conductivity of the Nafion/P(VPA)3 blend membrane was 1.1×10−5 S/cm in an anhydrous state at 130 °C. The conductivities of the blends increased by at least three orders of magnitude upon hydration, exceeding 10−2 S/cm with RH=50 % at ambient temperature