Oxidation of carbon monoxide at a platinum film electrode studied by Fourier transform infrared spectroscopy with attenuated total reflection technique

Fourier transform infrared reflection absorption spectroscopy with the attenuated total reflection technique (ATR-FTIR), coupled with cyclic voltammetry (CV) measurement, is used to observe the oxidation process df adsorbed CO at Pt film sputtered on a silicon prism. The interesting bipolar shape of the linearly bonded CO band is observed at high coverage of CO, although no CO band is included in the reference spectrum. This asymmetric shape is ascribed to Fano resonance. In addition to a linear CO and a bridged CO, a new absorption band, presumably assigned to a carboxyl radical, was detected. This band may be formed by a heterogeneous reaction between adsorbed CO and H2O on the Pt surface in the hydrogen adsorption potential region. The adsorbed carboxyl radical was oxidized at a less positive potential than the adsorbed CO, which can be ascribed to a presumable origin for the pre-peak that appeared in a CV reading prior to the oxidation of such a linear or bridged CO. This oxidation led to the rearrangement of CO ad-layers, especially at the high coverage of CO. In the case of the low coverage of CO, the conversion from the bridged CO to the linear CO is ascribed to the potential induced electronic effects of the electrode surface on the adsorption states. A consumption of adsorbed H2O and a production of CO2 were also clearly indicated by the spectroscopy when COOH or CO disappeared from the surface.