Photochemistry of Methanol and Methoxy Groups Adsorbed on Powdered TiO2

The photochemistry of CH 3 OH (a) and CH 3 O (a) adsorbed on TiO 2 and the effect of O 2 have been studied by infrared spectroscopy and mass spectrometry. In the absence of O 2, CH 3 OH (a) desorbs molecularly, while CH 3 O (a) decomposes to form CH 2 O (g) under UV irradiation. The rate of CH 3 O (a) decomposition reaches maximum in the initial stage of UV irradiation and then decreases significantly. On the other hand, for the reaction in O 2, the behavior of CH 3 O (a) depletion upon UV irradiation is very different, giving rise to adsorbed HCOO (a) and H 2 O (a) . A radical mechanism is proposed to explain the variation of CH 3 O (a) depletion upon UV irradiation, the role of O 2, and the formation of the reaction products.