Pt nanoparticles were synthesized by the H2O-in-oil (w/o) microemulsion technique and deposited onto B-doped diamond (BDD) electrodes. TEM showed that Pt particles size is limited to 2-5 nm range with narrow distribution. Anodic treatment at high overpotentials activates Pt deposit that is mech. stabilized by a Nafion layer. Such activation results in enhancement of activity towards MeOH electrooxidn., due to addnl. cleaning of the particles by oxidn. of the residual surfactant by electrogenerated hydroxyl radicals. [on SciFinder (R)]