Pt nanoparticles supported on Vulcan XC-72 carbon and carbon nanotubes (CNTs) were prepared by a microwave-assisted polyol process. The catalysts were characterized by TEM, XRD and XPS. The Pt nanoparticles, which were uniformly dispersed on carbon, were 2-6 nm in diameter. The Pt/C catalysts prepared as such displayed the characteristic diffraction peaks of a Pt fcc structure. XPS analysis revealed that the catalysts contained mostly Pt(0), with traces of Pt(II) and Pt(IV). The electroreduction of oxygen was studied by cyclic voltammetry. It was found both Pt/C catalysts had high electrocatalytic activity in the oxygen reduction reaction. Test runs on a single stack proton exchange membrane (PEM) fuel cell showed that these electrocatalysts are very promising for fuel cell applications. (C) 2004 Elsevier B.V. All rights reserved.