Investigation of methanol oxidation electrokinetics on Pt using the asymmetric electrode technique

摘要

The performance of a commercial Pt-black electrocatalyst was investigated in a Direct Methanol Fuel Cell (DMFC). A method for establishing the validity of anode polarization (without the use of a reference electrode) was shown by purging hydrogen and argon gas at the cathode under an asymmetric electrode configuration. It was found that hydrogen crossover to the cathode has a negligible effect on the polarization curve. In order to study methanol oxidation kinetics, the effects of mass transfer and ohmic resistances are eliminated and the correction techniques are discussed. At, approximate to 0.55 V, E-a changes from 60 kJ/mol to 40 kJ/mol (the removal of surface carbon monoxide) which points to the change in the rate determining step of the methanol oxidation reaction. Based on the value of the Tafel slope (138 mV/dec),the rate-determining step on the platinum surface can be the first electron transfer step (first C-H bond breakage of methanol or the activation of water) before 0.55 V.