The synthesis and characterization of anhydrous proton conducting membranes based on sulfonated poly(vinyl alcohol) and imidazole

Abstract

Membranes with high anhydrous proton conducting properties have attracted remarkable interest as polymer electrolyte membrane fuel cell (PEMFC) at intermediate temperature (100–200 °C). In this study, a new anhydrous proton conducting membrane based on poly(vinyl alcohol) (PVA), sulfosuccinic acid (SSA), and imidazole (Im) at various stoichiometric ratios was prepared. Sulfosuccinic acid was used as sulfonating agent to form a crosslinked structure and as proton source. Im was intercalated into the crosslinked PVA–SSA matrix and used as a proton transfer agent in the absence of humidity. The proton conductivities of membranes were investigated as a function of blend composition, SSA composition, and operating temperature. For characterizations, the synthesized membranes were analyzed by means of FT-IR, TGA, DSC, mechanical analysis, methanol permeability and impedance measurements for proton conductivity. The thermal decomposition of the PVA–SSA–Im hybrid membranes occurred at about 200 °C. Differential scanning calorimetry (DSC) results illustrated the homogeneity of the blends. The conductivities of PVA–SSA–Im hybrid membranes increased with the increasing temperature, SSA content and Im content. In the absence of humidity, the proton conductivity of PVA–SSA–Im (S1) was 1.4 × 10 −3 at 140 °C and the conductivity of PVA–SSA–Im (M1) was 1.7 × 10 −4 at 140 °C. Mechanical analysis showed that the storage modulus increases with increasing the crosslink density.