Characterization of the surfaces of platinum/tin oxide based catalysts by Fourier Transform Infrared Spectroscopy (FTIR)

A Pt/SnO2 catalyst has been developed at NASA Langley that is effective for the oxidation of CO at room temperature (1). A mechanism has been proposed to explain the effectiveness of this catalyst (2), but most of the species involved in this mechanism have not been observed under actual catalytic conditions. A number of these species are potentially detectable by Fourier Transform Infrared Spectroscopy (FTIR), e.g., HOSnO sub x, HO sub y PtO sub z, Pt-CO, and SnHCO3. Therefore a preliminary investigation was conducted to determine what might be learned about this particular catalyst by transmission FTIR. The main advantage of FTIR for this work is that the catalyst can be examined under conditions similar to the actual catalytic conditions. This can be of critical importance since some surface species may exist only when the reaction gases are present. Another advantage of the infrared approach is that since vibrations are probed, subtle chemical details may be obtained. The main disadvantage of this approach is that FTIR is not nearly as sensitive as the Ultra High Vacuum (UHV) surface analytical techniques such as Auger, Electron Spectroscopy for Chemical Analysis (ESCA), Electron Energy Loss Spectroscopy (EELS), etc. Another problem is that the assignment of the observed infrared bands may be difficult.