Sulfonated poly(vinyl alcohol)/triazole blends as anhydrous proton conducting membranes for polymer electrolyte membrane fuel cells

Abstract

A new type of cross-linked poly(vinyl alcohol) (PVA)-sulfosuccinic acid (SSA) polymers were synthesized by varying the amount of SSA and then blending with 3-amino-1,2,4-triazole (ATri) and 1H-1,2,4-triazole (Tri) at different stoichiometric ratios to obtain proton conductive membranes in anhydrous state. The proton conductivities of membranes were investigated as a function of azole composition, SSA composition, and operating temperature. The final structures of the copolymers were confirmed by Fourier transform infrared spectra. The resultant hybrid membranes are transparent, flexible, and showed good thermal stability up to approximately 200 degrees C. Differential scanning calorimetry results illustrated the homogeneity of the materials. The cross-linking of the structure was confirmed by the alteration of solubility of the membranes. Methanol permeability measurements showed that the composite membranes have lower methanol permeability compared to Nafion 112. The proton conductivity of the membranes continuously increased with increasing SO3H content and 3-amino-1,2,4-triazole (ATri) content. A maximum proton conductivity of 7.26 x 10(-3) S/cm was achieved for ATri-3 at 140 degrees C under anhydrous conditions. Incorporation of ATri unit (according to Tri unit) significantly increased the proton conductivity of the membranes, probably due to the ion transport channel or network structures formed in the membranes.