New proton conducting membranes based on PVAL/H3PO2/H2O

Solid polymer proton conductors were prepared by chemical doping of poly (v inyl alcohol) (PVAL) with hypophosphorous acid (H3PO2) Transparent, strong and dry to the touch membranes were obtained if the air relative humidity w as smaller than 50%. A stable solid phase was exhibited in the 8-70 degrees C temperature region for a wide doping range. The ionic conductivity of th e 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 incre ased. While the raw membranes showed an Arrhenius-type behavior in their co nductivities, with an activation energy between 0.37 and 0.12 eV as the aci d concentration was increased, the thermally treated ones were better model ed 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 tha t the water content and temperature of the samples have consequences on the proton conductivity and fuel cell performances of these samples. (C) 1999 Elsevier Science Ltd. All rights reserved.