The microwave irradiation technique was used to prepare platinum and platinum-ruthenium-based electrocatalysts on Vulcan for PEMFCs. The effects of microwave duration, base concentration and surfactant/precursor ratios on the properties of Pt-based catalysts were investigated. The prepared Pt-based catalysts were characterized by XRD and then PEMFC tests were performed. The particle sizes of the catalysts were ranging between 2 and 6 nm. Platinum-ruthenium-based catalysts were prepared to improve the carbon dioxide tolerance of the PEMFCs. The power losses arising from carbon dioxide in hydrogen feed were decreased by using the prepared PtRu-based catalysts when 30% carbon dioxide including hydrogen was sent to the fuel cell. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.