Methanol oxidation reaction (MOR) has been investigated at sputtered Pt−Ru, Ru, and Pt electrodes by using in-situ FTIR spectroscopy with the attenuated total reflection technique (ATR), which can identify species adsorbed on the electrode surface. Linear CO, bridged CO, and COO- were detected as the intermediates in the MOR. The electro-oxidation of preadsorbed CO was also studied to clarify the mechanism of the MOR at these electrodes. Water molecules coadsorbed with CO were clearly detected at Pt−Ru and Ru electrodes at less positive potential region below the onset potential of ca. 400 mV vs RHE for the electro-oxidation of both methanol and preadsorbed CO. The IR-band intensities of both the adsorbed CO and water commenced to decrease simultaneously at ca. 400 mV on Pt−Ru alloy, demonstrating that the adsorbed CO is oxidized by consuming the adsorbed water. The pure Ru electrode exhibited a high activity for the oxidation of preadsorbed CO, but showed a low activity for the MOR due to the slow dehydrogenation adsorption of the methanol. It is clarified that Pt sites on the alloy surface dehydrogenate methanol and form CO dominantly while Ru sites adsorb water molecules preferentially as oxygen-species needed for the CO oxidation, presumably involved as Ru−OH formed by discharging the adsorbed water. These results support the “bifunctional mechanism” at Pt−Ru alloy for the oxidation of methanol and CO.

Methanol oxidation has been investigated at a sputtered Pt film electrode by using in situ Fourier transform infrared spectroscopy with the attenuated total reflection technique, which can identify directly adsorbed species on the electrode surface. Linear CO, bridged CO, formyl species, and formic acid-related species have been clearly identified during the electro-oxidation of methanol in the intact cyclic voltammogram between 0.05 and 1.0 V, where the initial potential is applied at 0.05 or 1.0 V. The formyl species, linear CO, and bridged CO adsorb on the Pt surface at a low potential, for example, 0.05 V. A potential-induced conversion between the linear CO, the bridged CO, and the formic acid-related species is observed during the methanol oxidation. It was clear that an oxidation via formic acid, at least up to formic acid, is the predominant route for the methanol oxidation in a potential range from 0.2 V to ca. 0.6 V and the oxidation is prohibited by the high coverage of Pt sites with CO. In a higher potential region than that, the CO and HCOOH parallel routes are opened for the complete methanol oxidation. The correlation between the methanol oxidation and the oxides formed on Pt surface is also discussed, which affects the reactivity of the electrode and the reaction mechanism.

Adsorbed water molecules which promote the methanol oxidation reaction (MOR) at Pt-Ru alloy electrode are clearly detected by in-situ FTIR spectroscopy with the attenuated total reflection configuration, which directly supports the "bi-functional mechanism" for the MOR.