Chalcogenide (S, Se, and Te)-modified ruthenium catalysts prepared by a wet impregnation method demonstrated the electrocatalytic activities in the order of Ru-Te > Ru-Se > Ru-S for the oxygen reduction reaction (ORR) in acidic media. The ORR activity of Ru-Te supported on carbon black (Ru-Te/C) significantly depends on the initial Te/Ru atomic ratio. The catalyst obtained at a Te/Ru = 2 produced the maximum value current density, the reaction was confirmed to form a RuTe2 intermetallic compound, based on the XRD. The TEM image of RuTe2/C shows that the loaded RuTe2 particles consist of well-crystallized plate-like particles with diameters of about 10 nm. Rotating ring disk electrode (RRDE) measurements indicated that RuTe2/C generates about 4% H2O2 during the ORR, preferentially proceeding via the four-electron charge transfer pathway to form H2O center dot RuTe2/C showed a comparable activity with regard to the cathodic current to that of the conventional Pt/C catalyst at the same metal loading, Unfortunately, the onset electrode potential for oxygen reduction by RuTe2/C was more negative than that catalyzed by the commercial Pt/C by about 0.2 V. (C) 2008 Elsevier B.V. All rights reserved.