In situ IR study of surface hydroxyl species of dehydrated TiO2: towards understanding pivotal surface processes of TiO2 photocatalytic oxidation of toluene

The surface species on P25–TiO2 were characterized by FTIR after evacuation at 50–550 °C. The functions of OH groups on P25–TiO2 catalysts have been tested by the adsorption and photooxidation of toluene in an in situ IR cell. FTIR studies show that the hydroxyl species on P25–TiO2 are clearly temperature-dependent and P25–TiO2 has six isolated hydroxyls with bands at 3734, 3715, 3688, 3671, 3658 and 3640 cm−1. The OH groups on P25 play different roles in the photo-oxidation process: surface hydroxyls with bands at 3688, 3671, 3658 and 3640 cm−1 act as adsorption sites while surface hydroxyls with bands at 3734 and 3715 cm−1 act as sources of the ˙OH radical.