In situ Fourier transform infrared reflection absorption spectroscopic studies of the effects of tin on the electrochemical oxidation of carbon monoxid

The modifications in the mode of bonding of CO on polycrystalline Pt in perchloric acid electrolytes induced by the presence of tin have been examined using in situ Fourier Transform Infrared Reflection Absorption Spectroscopy. It has been concluded, based on the results obtained, that tin adsorbs on a CO-saturated Pt surface displacing up to half of the original CO, and brings about a sizable reduction in the overpotential for CO electrooxidation. In addition, the integrated intensity of the CO peak normalized by the integrated intensity of the CO₂ peak obtained after full CO oxidation appears to be much higher than the corresponding value observed on a tin-free Pt surface. This effect is especially marked for moderate tin coverages at potentials negative to the onset of CO oxidation and has been tentatively associated with the presence of CO on special sites on the tin-free polycrystalline Pt surface for which the IR cross sections are very small.