Cerium sulfophenyl phosphate (CeSPP), a novel proton conductor, is prepared starting from mixtures of m-sulfophenyl phosphonic acid (msPPA) and ammonium ceric nitrate. The CeSPP samples are combined with poly (2, 5-benzimidazole) (ABPBI) to prepare ABPBI/CeSPP composite membranes by polyphosphoric acid (PPA) hot-pressed method. The ABPBI/CeSPP composite membranes are characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR). Thermogravimetric analysis (TGA) indicates thermal stability of the composite membranes below 200 degrees C. Scanning electron microscopy (SEM) indicates that CeSPP particles are homogenously dispersed into the composite membranes. Ce, P and S atoms are well illustrated and uniformly distributed in composite membranes via energy-dispersive X-ray spectroscopy (EDX) analysis. The proton conductivity of membrane doped in 38 wt.% CeSPP reaches 0.14 Scm(-1) at 180 degrees C under 100% relative humidity. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.