Effect of addition of zirconium tungstate, lead tungstate and titanium dioxide on the proton conductivity of polystyrene porous membrane Krishna Gandhi*, Brajesh Kumar Dixit, Deepesh Kumar Dixit Department of Physics, Bipin Behari P.G. College, Outside Sainyer Gate, Jhansi-284001, India article info Article history: Received 27 February 2011 Received in revised form 24 April 2011 Accepted 26 April 2011 Available online 11 June 2011 Keywords: Fuel cell Proton conducting membrane Zirconium tungstate Lead tungstate Titanium dioxide Hydrophilicity abstract 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 SiO 2 , TiO 2 and ZrO 2 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, devel- oped 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. Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Hetero-poly-acids (HPA) like phospho-tungstic acid (H 3 PW 12 O 40 .nH 2 O), silicotungstic acid (H 4 SiW 12 O 40 .nH 2 O) and phospho-molybdic acid (H 3 PMo 12 O 40 .nH 2 O) have been used as additives to Nafion and other polymer proton conducting membranes to improve proton conductivity[1e4]. These membranes showed a strong performance enhancement that increased with increasing temperature. However, upon heating HPA dehydrate and the conductivity drops sharply. HPA is highly water soluble and eventually leeches out from the polymer electrolyte membrane. Other drawbacks are their high cost and the adverse effects on the mechanical strength of the membrane. The positive effects of addition of oxo-clusters of Ti, Zr, W on the proton conductivity characteristics have been reported earlier, where it was postulated that these oxo-clusters act as cross-linkers between the sulphonyl groups of Nafion membranes [5]. This motivated us to find out whether tungtate salts of heavy ions like Zr and Pb will be helpful in improving the proton conductivity of polystyrene based membranes. A lot of work has been done in Nafion membranes doped with hydrophilic inorganic additives like SiO 2 , TiO 2 and ZrO 2 * Corresponding author. Tel.: þ91 9415057538. E-mail address: krishnagandhikr@gmail.com (K. Gandhi). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 3922 e3930 0360-3199/$ e see front matter Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2011.04.209