A carbon supported palladium (Pd/C-NaBH(4)-NH(3)) catalyst was synthesized via modified sodium borohydride reduction method using ammonia as the complexing reagent. The Pd/C catalysts were characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Rotating disk electrode (RIDE), cyclic voltammetry (CV), electrochemical impedance spectra (EIS) and single cell measurements were employed to evaluate the activities of the catalysts. The as-prepared catalysts with face-centered cubic (fcc) structure are uniformly dispersed on the carbon supports. Twinned and polycrystalline structures are observed in the HRTEM image of Pd/C-NaBH(4)-NH(3). The results indicate that the Pd/C-NaBH(4)-NH(3) catalyst shows high activity for the oxygen reduction reaction. Single cell with Pd/C-NaBH(4)-NH(3) as the cathode displays a maximum power density of 508 mW cm(-2). The favorable performance of the Pd/C-NaBH(4)-NH(3) catalyst may be attributed to the uniformly dispersed nanoparticles and more crystalline lattice defects. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.