Kinetics of methanol oxidation on carbon-supported Pt and Pt+Ru catalysts

The kinetics of methanol electro-oxidation on carbon-supported particulate Pt and Pt + Ru catalysts is studied on PTFE-bonded electrodes made of these materials, The electrochemical characterization is carried out both galvanostatically and potentiostatically in sulphuric acid, and special attention is paid to the effects of low methanol concentrations in the range from 5.0 mM to 2.0 M, Furthermore, the effects of reaction temperature, catalyst loading and electrolyte concentration are discussed. A steady-state adsorption model which explains the observed polarization behaviour is presented. The model highlights the subtle balance between the initial methanol adsorption-dehydrogenation and the subsequent oxidative removal steps as well as the important roles of water and surface intermediates in the oxidation reaction. Rough estimates are given for the rate constants and activation energies of the individual reaction steps.