Fourier transform infrared spectroscopy has been employed to investigate the N(CH3)3 adsorption, thermal stability, and photochemical reactions on powdered TiO2. N(CH3) 3 molecules are adsorbed on TiO2 without dissociation at 35 °C and are completely desorbed from the surface at 300 °C in a vacuum. The CH3 rocking frequencies of N(CH3)3 on TiO2 are affected via the interaction between N(CH 3)3 and TiO2 surface OH groups. In the presence of O2, adsorbed N(CH3)3 decomposes thermally at 230 °C and photochemically under UV irradiation. In the latter case with comparative 16O2 and 18O2 studies, CO2(g), NCO(a), HCOO(a), and surface species containing C=N or NHx functional groups are identified to be the photoreaction products or intermediates. In the presence of 18O 2, the main formate species formed is HC16O 18O(a). As H2O is added to the photoreaction system, a larger percentage of adsorbed N(CH3)3 is consumed. However, in the presence of 18O2 and H 2O, the amount of HC16O18O(a) becomes relatively small, compared to HC16O16O (a). A mechanism is invoked to explain these results. Furthermore, based on the comparison of isotopic oxygens in the formate products obtained from CH3O(a) photooxidation in 16O2 and 18O2, it is concluded that the N(CH3) 3 photooxidation does not generate CH3O(a) in which the oxygen belongs to TiO2.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry