Pt-Se/C catalyst for oxygen reduction reaction (ORR) was prepared by a modified organic colloid method with sodium citrate and triphenyl phosphine as complexing agents. The active components were highly dispersed on the carbon black support. The addition of Se improved the dispersion of platinum significantly and reduced the particle size to be less than 1.8 nm. The catalyst showed similar activity compared to Pt/C catalyst, and had a higher tolerance to methanol than Pt/C catalyst. The catalyst was characterized with X-ray diffraction (XRD) and transmission electron microscope (TEM). Electrochemical measurements showed that the synthesized Pt-Se/C catalyst had a four-electron transfer mechanism for oxygen reduction. (C) 2007 Elsevier B.V. All rights reserved.