Microsecond kinetics of photocatalytic oxidation on Pt/TiO2 traced by vibrational spectroscopy

2-Propanol oxidation to acetone was examined by time-resolved infrared spectroscopy on a Pt/TiO2 photocatalyst in an aqueous solution. Holes generated by the band-gap excitation were found to attach to the adsorbed reactant within the first 0.5 μs. Subsequent rearrangement of atoms in the hole-attached reactant was observed on a series of time-resolved vibrational spectra. The CO stretching band of a reaction intermediate to be converted to acetone appeared at time delays of 0–20 μs. The observed wavenumber of the intermediate, 1640 cm−1, was compared with theoretically predicted CO stretching frequencies of possible species. An acceptable agreement was obtained with the anion radical of acetone adsorbed on the catalyst.