KINETICS OF METHANOL OXIDATION ON CARBON-SUPPORTED PT AND PT+RU CATALYSTS

The kinetics of methanol electro-oxidation on carbon-supported particu late Pt and Pt + Ru catalysts is studied on PTFE-bonded electrodes mad e of these materials, The electrochemical characterization is carried out both galvanostatically and potentiostatically in sulphuric acid, a nd special attention is paid to the effects of low methanol concentrat ions in the range from 5.0 mM to 2.0 M, Furthermore, the effects of re action temperature, catalyst loading and electrolyte concentration are discussed. A steady-state adsorption model which explains the observe d polarization behaviour is presented. The model highlights the subtle balance between the initial methanol adsorption-dehydrogenation and t he subsequent oxidative removal steps as well as the important roles o f water and surface intermediates in the oxidation reaction. Rough est imates are given for the rate constants and activation energies of the individual reaction steps.