Development of Polarization-Dependent Infrared Spectroscopy for Studies of Catalytic Reactions on Pt(111)

The development of polarization-dependent infrared spectroscopy (PD-RAIRS) to study ambient pressure catalytic reactions on Pt(111) and other transition metal surfaces is described in detail in this thesis. The technique is similar to a polarization modulated - RAIRS technique, but utilizes a single polarizer so the surface and gas phase species present during a catalytic reaction on a metal, such as Pt(111), can be simultaneously monitored. PD-RAIRS also provides a high S/N ratio, so peaks assigned to surface species with a weak dipole moment normal to the surface can be seen in the spectra. Three different studies on Pt(111) are discussed showcasing the technique. First, spectra showing peaks that describe a new mechanism for low temperature CO oxidation are shown. The data show that the installation of the polarizer increases the S/N ratio of the spectra allowing for better determination of species adsorbed on the surface. Next, PD-RAIRS is used to monitor the ambient pressure hydrogenation of acetylene to ethane with a pressure and temperature range from 1.0×10-2 to 4.0 Torr and 120 and 370 K. This study shows the capabilities of the PD-RAIRS setup. The last study is on the reactivity of the carbidic layer present during acetylene hydrogenation to ambient pressure of H2. The data show the carbidic layer is composed of C2 species that can be easily hydrogenated to ethane at 400 K and 10 Torr of H2.