The PdNi nanoparticles dispersed on Nafion solution was used as an ink-type electrode for oxygen reduction reaction (ORR), in acid media. This bimetallic catalyst was synthesized via the metallic reductive precipitations of the chloride precursors with NaBH4 in tetrahydrofuran (THF) at 25 degrees C. The characterization of the electrocatalyst using X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed bimetallic nanoparticles having a narrow size ranged 8-10 nm with face-centered cubic (fcc) hexagonal structure. Cyclic voltammograms and polarization curves from rotating-disk electrode measurements showed significantly higher activity on PdNi than observed on Pd catalyst, with a mechanism involving four electrons transfer to water formation. The incorporation of Ni, a less electronegative metal to Pd shifts the onset potential for the ORR approximately 110 mV more positive, and at 0.5mA cm(-2) the cathode overpotential is reduced by 260mV in relation to that obtained on Pd,in a 0.5 M H2SO4 solution at 25 degrees C. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.