STUDIES OF THE ROLE OF WATER IN THE ELECTROCATALYSIS OF METHANOL OXIDATION

The oxidation of methanol has been carried out on electrodes prepared by evaporating Pt directly onto a Nafion membrane and then introducing the methanol either in the gas-fed mode or directly from the electrol yte in the electrolyte-fed mode. It was found that the oxidation carri ed out using a gas-fed electrode was shifted 100-150 mV more cathodic than the electrolyte-fed electrode. A similar set of experiments was c arried out using hydrophobic gas-diffusion electrodes and similar resu lts were obtained. These results suggest that the mechanism of the met hanol oxidation reaction depends on the nature of the surroundings and the orientation of the methanol with respect to the electrode surface . In the electrolyte-fed configuration the methanol will be in a hydro gen-bonded water cluster allowing the carbon end of the molecule to mo re readily approach the catalyst surface. While in the gas-fed configu ration the methanol will interact with the water or oxidic surface thr ough the hydroxyl end of the molecule. Clearly, these two possible mec hanisms will lead to different products and one may enhance the rate o f the direct oxidation of methanol as observed in this work.