Thermal and Photocatalytic Reactions of Methanol and Acetaldehyde on Pt-Modified Brookite TiO₂ Nanorods

The influence of adding Pt on the catalytic and photocatalytic activity of monodispersed brookite phase TiO₂ (B-TiO₂) nanorods (NRs) was investigated. Pt was deposited on the NRs by photodeposition in solution, and the Pt-modified NRs were characterized using XPS, STEM, and LEIS. The thermal and photocatalytic activity of the Pt-modified NRs were then evaluated using temperature-programmed desorption (TPD) in ultrahigh vacuum (UHV). It was found that while Pt primarily acted as a site blocker for thermal reactions, Pt also acted as a recombination center for photogenerated electrons and holes, resulting in suppressed photocatalytic activity. Upon pretreatment with O₂, however, the Pt-modified NRs exhibited enhanced photoactivity, indicating that adsorbed oxygen prevents electron–hole recombination by reacting with photogenerated conduction band electrons from the B-TiO₂ to produce stable superoxide species on the Pt surface deposits. These results clearly demonstrate how the dynamics of charge carriers at the oxide surface may be altered by metal deposits such as Pt, as well as by the presence of adsorbed species on the metal surface.