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.