Nafion/zirconium sulphophenyl phosphate (ZrSPP) composite membranes were prepared to maintain proton conductivity at elevated temperatures. ZrSPP was precipitated by the reaction of Zr4+ ion and m-sulphophenyl phosphonic (SPP) acid with a stoichiometric ratio P/Zr = 2. The synthesis of ZrSPP was confirmed by phosphonate (P-O) stretching band, assigned at 900-1300 cm(-1) in FTIR spectra. The sharp diffraction pattern at 2theta=5degrees indicated crystalline a-layered structure of ZrSPP. The proton conductivity of Nafion/ZrSPP (12.5 wt.%) composite membrane reached ca. 0.07 Skin at 140degreesC without extra humidification. (C) 2004 Published by Elsevier Ltd.