Abstract: Pt catalysts supported on Vulcan XC-72 carbon were prepared by the NaBH₄ reduction of H₂PtCl₆ in the presence of a carbon support. One of the catalysts was deliberately treated with H₂O₂ after chemical reduction to alter the oxidation state of Pt and to promote methanol oxidation through more efficient water dissociation on the Pt sites. X-ray photoelectron spectroscopy confirmed that H₂O₂ treatment resulted in a more oxidized Pt catalyst. The electrooxidation of methanol over treated and untreated Pt catalysts in acidic solutions at room temperature was investigated by cyclic voltammetry and chronoamperometry. Despite their design, the more oxidized Pt catalysts could not supply active oxygen capable of removing the reaction-inhibiting CO-like reaction intermediates. As a result the catalytic activity was still largely dependent on the Pt oxidation state with the more “metallic” catalyst showing higher methanol oxidation activity and more CO tolerance.

Key words: platinum, catalytic activity, oxidation state, methanol oxidation