Photochemistry of Methanol and Methoxy Groups Adsorbed on Powdered TiO₂

Abstract

The photochemistry of CH3OH(a) and CH3O(a) adsorbed on TiO2 and the effect of O2 have been studied by infrared spectroscopy and mass spectrometry. In the absence of O2, CH3OH(a) desorbs molecularly, while CH3O(a) decomposes to form CH2O(g) under UV irradiation. The rate of CH3O(a) decomposition reaches maximum in the initial stage of UV irradiation and then decreases significantly. On the other hand, for the reaction in O2, the behavior of CH3O(a) depletion upon UV irradiation is very different, giving rise to adsorbed HCOO(a) and H2O(a). A radical mechanism is proposed to explain the variation of CH3O(a) depletion upon UV irradiation, the role of O2, and the formation of the reaction products.