The adsorption of CO on Au/TiO2 catalysts was examined at room temperature using FTIR transmission spectroscopy. Adsorption was observed as (i) a sharp peak at ∼2100 cm-1 due to CO molecular vibration (the Au-CO peak), and (ii) a broad-band infrared (BB-IR) signal. The Au-CO peak and BB-IR signal are correlated and quantitatively related to the amount of CO adsorbed on the Au nanoparticles. For comparison purposes, we also examined CO adsorption on Au/Al2O3 catalysts. When supported on this nonreducible support, CO adsorption on Au showed only the Au-CO peak; the BB-IR signal was absent. This allowed us to determine that the BB-IR signal observed for CO adsorption on the Au/TiO2 catalyst is associated with the reducibility of the support. Comparison of the two catalysts also enabled us to determine that the BB-IR signal is due to a decrease in transmission through the powdered catalysts when CO adsorbs on Au/TiO2. Consistent with previously published studies, we propose that this BB-IR signal is related to the reversible, partial reduction of the TiO2 at the Au-TiO2 interface. This reduction leads to an increase in surface disorder or roughening of TiO2 particles that produces a decrease in IR transmission through the catalyst (i.e. an increase in IR scattering). These results suggest an efficient CO-Au-TiO2 adsorbate-induced electronic metal-support interaction (EMSI) that may play an important role in understanding CO reactions on Au/TiO2 catalysts.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films