New proton conducting membranes based on PVAL/H 3PO 2/H 2O

Abstract

Solid polymer proton conductors were prepared by chemical doping of poly (vinyl alcohol) (PVAL) with hypophosphorous acid (H 3PO 2). Transparent, strong and dry to the touch membranes were obtained if the air relative humidity was smaller than 50%. A stable solid phase was exhibited in the 8–70°C temperature region for a wide doping range. The ionic conductivity of the samples at room temperature showed a sensitive variation with the doping rate, between 10 −6 and 10 −1 Scm −1 as the acid concentration was increased. While the raw membranes showed an Arrhenius-type behavior in their conductivities, with an activation energy between 0.37 and 0.12 eV as the acid concentration was increased, the thermally treated ones were better modeled by a VTF equation. The open circuit voltage of a hydrogen concentration cell using the membranes as electrolytic separator was of the order of 100 mV for high acid dopings. The results are discussed taking into account that the water content and temperature of the samples have consequences on the proton conductivity and fuel cell performances of these samples.