Photochemistry of methanol and methoxy groups adsorbed on powdered TiO2

The photochemistry of CH3OH(a) and CH3O(a) adsorbed on TiO2 and the effect uf O-2 have been studied by infrared spectroscopy and mass spectrometry. In the absence of O-2, CH3OH(a) desorbs molecularly, while CH3O(a) decomposes to form CH2O(g) under UV irradiation. The rate of CH3O(a) decomposition re aches maximum in the initial stage of UV irradiation and then decreases sig nificantly. On the other hand, for the reaction in O-2, the behavior of CH3 O(a) depletion upon UV irradiation is very different, giving rise to adsorb ed HCOO(a) and H2O(a). A radical mechanism is proposed to explain the varia tion of CH3O(a) depletion upon UV irradiation, the role of O-2, and the for mation of the reaction products.