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-TiO 2 were characterized by FTIR after evacuation at 50-550 °C. The functions of OH groups on P25-TiO 2 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-TiO 2 are clearly temperature-dependent and P25-TiO 2 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 &z.rad;OH radical. The isolated hydroxyls on the P25-TiO 2 surface are selective to the adsorption of toluene. The 3688, 3671 and 3640 cm −1 bands were preferentially removed than the 3735 and 3715 cm −1 bands during the initial adsorption of toluene.