CO adsorption and oxidation studies on nanofabricated model catalysts using multilayer enhanced IRAS technique

CO adsorption and oxidation studies have been performed on model Pt catalysts using multilayer enhanced infrared reflection absorption spectroscopy (MEIRAS) technique demonstrated in our laboratory. The multilayer model catalysts prepared for this study consist of semitransparent thin Pt films or Pt nanowires over SiO2 or TiO2 dielectric films of varying thicknesses with reflecting gold films underneath. CO adsorption results show that different types of oxidation and reduction pretreatments on Pt/SiO2/Au thin film catalysts lead to changes in the CO stretch region of the spectra and in morphology of Pt films. Ignition behavior of CO oxidation reaction was studied on these catalysts and a change in the baseline of the spectra was observed as an indication of change in surface oxygen coverage with change in reaction conditions. CO adsorption studies on Pt/TiO2/Au nanowires catalysts show a shift in the peak position towards lower wavenumbers with a decrease nanowire width. The results indicate that these spectral changes might be related to the boundary adsorption sites near the edges of Pt particles and nanowires. Further, experiments involving modification of boundary sites at Pt/TiO2 junctions by applying external voltage to a catalytic nanodiode with Pt nanowires on TiO2 are in progress.

Multilayer enhanced FTIR study on Pt/SiO2/Au thin film structures show changes in the spectra of CO adsorbed after different types of sample pretreatment: O2 followed by H2 (run 1), H2 (run 2), O2–CO–H2 (run 3), and H2 (run 4). A pretreatment in CO (run 3) also caused significant morphological changes in the Pt film.Figure optionsDownload high-quality image (54 K)Download as PowerPoint slideResearch highlights▶ Novel FTIR enhancement technique suitable for multilayer model catalysts. ▶ Reduction treatment causes red-shift in spectra of adsorbed CO. ▶ Spectral changes sensitive to Pt particle size and nanowire width. ▶ Baseline changes indicate surface oxygen coverage.