Electrocatalytic oxidation of methanol at tantalum oxide-modified Pt electrodes

Abstract

The current study addresses the electrocatalytic activity of tantalum oxide (TaOx)-modified Pt electrode as a novel catalyst for methanol oxidation in acidic media. The modified Pt electrode is shown to support a larger oxidation current of methanol compared to that obtained at the unmodified Pt electrode concurrently with a favorable significant shift of the onset potential of methanol oxidation. Tafel plots, with a slope close to 0.118 V decade−1, were obtained for methanol oxidation at the unmodified and TaOx-modified Pt electrodes, reflecting that the methanol oxidation proceeds with the first electron transfer as the rate-determining step. The observed enhancement was attributed to a favorable d–d metal–metal oxide interaction which changes the electronic property of Pt and hence enhances the oxidation of the adsorbed reaction intermediates (e.g., COads). Moreover, a possible contribution of the OH spillover via a so-called “bifunctional mechanism” is proposed. The influence of the temperature on the oxidation current of methanol at the TaOx-modified Pt electrode is investigated and apparent activation energy, Ea, for methanol oxidation is calculated as 39 kJ mol−1 at a specific potential. The proposed catalyst showed a good enhancement for methanol oxidation for a prolonged time of continuous potentiostatic electrolysis.