Effect of addition of zirconium tungstate, lead tungstate and titanium dioxide on the proton conductivity of polystyrene porous membrane

Proton conducting polymer electrolyte membrane is the most important component of polymer electrolyte membrane fuel cells (PEMFC). The positive effect of addition of oxo-clusters of Ti, Zr, W and hydrophilic additives like SiO2, TiO2 and ZrO2 on the proton conductivity characteristics of Nafion membranes have been reported earlier. Here we report the effect of additives zirconium tungstate, lead tungstate and titanium dioxide on the proton conductivity of pure polystyrene porous membranes in aqueous solution. The enhancement of proton conductivity was observed to be highest for titanium dioxide (by factors of 4.63 for titanium dioxide alone, 1.37 and 16.17 for combinations of titanium dioxide plus zirconium tungstate and titanium dioxide plus lead tungstate) whereas the enhancement factor for zirconium tungstate alone was 0.79 and that for lead tungstate alone was 0.08. This showed that the effect of addition of titanium dioxide on proton conductivity was the highest, while that of zirconium tungstate alone was marginal and that of lead tungstate alone negative. The proton conductivities were calculated from the pH values measured at room temperature using an electrochemical cell and pH meter, on the basis of a proton transport model for porous membranes in aqueous solution, developed by us. The membranes were characterized by FTIR, SEM, TGA/DTA and the observed results are explained in terms of the hydrophilicity of the additives.