In situ detection and surface coverage measurements of CO during CO oxidation on polycrystalline platinum using sum frequency generation

Optical infrared-visible sum-frequency generation (SFG) surface vibrational spectroscopy was used for in situ detection of CO during heterogeneous CO oxidation on a polycrystalline platinum foil. SFG spectra were recorded in the substrate temperature range 300-700 K at a total pressure of 20 mbar. A least-squares fit procedure was employed to determine the temperature depe ndence of the vibrationally nonresonant contribution and the frequency, amp litude and halfwidth of the CO vibrationally resonant contribution from the SFG spectra. Thermal desorption measurements were carried out to investiga te the relationship between the SFG signal and the instantaneous CO surface coverage. After these calibration measurements, it was possible to derive CO surface coverages from the SFG spectra measured under laminar flow condi tions during heterogeneous CO oxidation.