A facile hydrothermal method has been proposed to prepare reduced graphene oxide (RGO) and enhance its reducing ability. For the first time, the spontaneous redox reaction between PtCl42- and RGO has been reported and no additional reductants or surfactants were needed. X-ray photoelectron spectroscopy and transmission electron microscope images were used to characterize the synthesized Pt nanoparticles supported on RGO sheet (PtNPs/RGO) composites. The reaction mechanism has been investigated by changing the medium pH of the reaction. We further proved that the electro-catalytic property of PtNPs/RGO could be tuned and, because of the clean, well-dispersed PtNPs and the synergistic effect between the PtNPs and RGO, the PtNPs/RGO expressed higher electro-catalytic activity and better tolerance for methanol oxidization than a commercial Pt/C catalyst. (c) 2013 Elsevier Ltd. All rights reserved.