Synthesis and characterization of polyantimonic acid membranes

Membranes consisting of polyantimonic acid and an organic binder have been manufactured by a film-casting technique. Polyvinylidene fluoride and polysulfone have been used as the organic binder material. The thickness of these film-casted membranes was 0.1-0.3 mm. Several membrane characteristics such as ionic conductance, membrane potential and Hittorf transference numbers have been measured in different experimental set-ups. The temperature dependence of the membrane conductance exhibits an exponential decay when working in an alkaline solution (1N KOH). Activation energies on the order of 0.17-0.18 eV have been calculated for this ionic conduction process. The cation transference numbers E₊, as determined from permselectivity measurements in different aquous KOH solutions, show a gradual decrease from about 0.8 towards 0.5 for a tenfold increase in concentration (0.1→1 N). The actual performance of the polyantimonic acid membranes under water-electrolysis conditions has been measured, and cell voltages of about 2 Volts at high current densities (8-10 kAm^-2) and at temperatures below 100 °C could be obtained.