In this work, the synthesis of a phosphorylated polyvinyl alcohol (p-PVA)/polyoxometalate (tungsto-phosphate) membrane for the BioGenerator, a bio-electrochemical energy storage technology, is reported. It was shown that bonding of lacunary tungsto-phosphate ions to the carbon skeleton of a polymer matrix results in an increase in proton conductivity of up to 2.7 times, compared to previously studied phosphorylated PVA membranes. Testing of the membrane in an actual Fe3+/H2 electrochemical cell showed that it performs significantly better (0.28 W·cm−2 at 0.79 A·cm−2) than the previously used commercial Selemion HSF (Japan) membrane (0.18 W·cm−2 at 0.60 A·cm−2).