A series of Pt/C catalysts with controlled Pt particle sizes is synthesized using a surfactant-free process with ethylene glycol as the weak reducing agent. The Pt particle size can be regulated by controlling the pH of the Pt (IV) complex via the addition of different amounts of urea. The results of X-ray diffraction and transmission electron microscopy confirm that the Pt nanoparticles on the carbon exhibit good size controllability and dispersion. The electroactive surface area (ESA), the electron transfer coefficient, and the electrocatalytic activity to dimethyl ether electrooxidation are dependent on the Pt particle size, and a comparison of the electrochemical properties of the samples reveals that the relationships are parabolic. The results are important for understanding the mechanism of and designing an effective catalyst for dimethyl ether (DME) electrooxidation and providing a size-controlled synthetic method for Pt-based catalysts. (C) 2012 Elsevier B.V. All rights reserved.