A Pt-Nafion/C catalyst is synthesized through a modified ion-exchange method, in which [Pt(NH3)(2)](2+) cations exchange with H+ ions of Nafion/C composites and are reduced by H-2. Based on the results from transmission electron microscopy and inductively coupled plasma atomic emission spectrometry, it is found that the average size of Pt particles is around 2.3 nm and the Pt loading is about 1.8 wt% in the Pt-Nafion/C catalyst. Although the Pt mass activities (MAs) toward oxygen reduction reaction tested in half cells are similar, when used as cathode catalyst for a direct methanol fuel cell, the Pt MA as high as 4.36 A mg(Pt)(-1) are achieved for the Pt-Nafion/C catalyst at 825 mV, which is 6 times higher than that of the Pt/C catalyst. The enhanced Pt utilization could be attributed to the defined location of Pt nanoparticles in the triple phase zones in electrode. Crown Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.