In situ ATR-FTIR study of H2O and D2O adsorption on TiO2 under UV irradiation

Abstract

The adsorption of water and deuterium oxide on TiO₂ surfaces was investigated in the dark as well as under UV(A) irradiation using in situ ATR-FTIR spectroscopy under oxygen and oxygen free conditions. Adsorption of H₂O–D₂O mixtures revealed an isotopic exchange reaction occurring onto the surface of TiO₂ in the dark. Under UV(A) irradiation, the amount of both OH and OD groups was found to be increased by the presence of molecular oxygen. Furthermore, the photocatalytic formation of hydroperoxide under oxygenated condition has been recorded utilizing Attenuated Total Reflection Fourier Transformed Infrared (ATR-FTIR) spectroscopy which appeared as new band at 3483 cm⁻¹. Different possible mechanisms are discussed in terms of the source of hydroxyl groups formed and/or hydration water on the TiO₂ surface for the photocatalytic reaction and photoinduced hydrophilicity.