Fe3O4 nanoparticles supported on graphene (Fe3O4/graphene) and Printex carbon (Fe3O4/Printex) are reported as promising catalysts for oxygen reduction reaction (ORR) to H2O2 in alkaline medium. The catalysts were synthesized by a simple precipitation method using NaBH4 as reducing agent to favor the formation of the magnetite phase. The structure and morphology of the catalysts was evaluated by x-ray diffraction, transmission electron microscopy and small angle electron diffraction. The electrocatalytic activity towards ORR was investigated by means of cyclic and linear voltammetries in 1 mol L (-1) KOH. The linear polarization curves highlighted the synergetic effect between the oxide and the carbon supports. Analysis of the polarization curves showed that electro-catalytic activity of the materials towards oxygen reduction expressed by the current density at -0.3 V vs SCE increases from Printex (0.29 mA cm (-2)) < Fe3O4/Printex (0.38 mA cm (-2)) < graphene (0.85 mA cm (-2)) < Fe3O4/graphene (1.12 mA cm (-2)). The number of exchanged electrons was close to 2.7 for both catalysts, and the % H2O2 electro-generated above 60% in the -0.2 to -0.7 V (vs SCE) potential range. Furthermore, both Fe3O4/graphene and Fe3O4/ Printex catalysts show excellent durability. (C) 2015 Elsevier Ltd. All rights reserved.