Proton-conducting hybrid solid electrolytes for intermediate temperature fuel cells

Abstract

A new family of proton-conducting/inorganic hybrid polymer electrolyte membrane was prepared by sol–gel processes. The method involves stabilization of metastable acidic tungsten oxide cluster in the polymer composite membrane. A freestanding, flexible and pale-yellowish transparent membrane was formed from tungsten acidic homogeneous solution by sol–gel condensation with alkoxysilylated polyethylene oxide (PEO). The membrane showed very high protonic conductivity of 10 −2–10 −3 S cm −1 from R.T. to 120 °C, especially, 1.4×10 −2 S cm −1 at 80 °C. The structure of tungsten cluster moieties was neither peroxo complex nor WO 3·2H 2O. It is suggested that nano-size clusters are dispersed homogeneously in polymer matrix without long-range ordering. Tungsten complexes with carboxylate ligands such as malonic acid could form similar homogeneous membrane. Thermal and ionic transport properties could be controlled by this family of organic derivatives.