Carbon-onion-supported platinum nanoparticles were synthesized using a simplified arc-discharge-in-solution method. Pt nanoparticles with diameters of 5 nm were found to form during reduction of chloroplatinic acid and were simultaneously supported on carbon onions formed in the arc discharge process. X-ray powder diffraction, scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy were used to study the structural and morphological properties of the samples. The formation mechanism of the Pt/carbon onion hybrids was briefly discussed. (C) 2008 Elsevier B.V. All rights reserved.