Platinum nanoparticles have been synthesized by the water-in-oil (w/o) microemulsion technique and deposited onto boron-doped diamond (BDD) electrodes. Transmission electron microscopy (TEM) has shown that Pt particles size is limited to 2-5 nm range with narrow distribution. Anodic treatment at high overpotentials activates Pt deposit that is mechanically stabilized by a Nafion (R) layer. Such activation results in enhancement of activity towards methanol electrooxidation, due to additional cleaning of the particles by oxidation of the residual surfactant by electrogenerated hydroxyl radicals. (c) 2004 Elsevier Ltd. All rights reserved.