1120 - 1200 Xuemin Yang
Photocatalyzed Dissociation of Methanol on TiO2(110) Surface
We report direct evidence of methanol photodissociation on TiO2(110) detected by time-resolved two-photon photoemission (2PP) spectroscopy. The rise of an excited resonance in the 2PP spectra on the CH3OH/TiO2(110) surface as a function of laser illumination time strongly suggests that the observed excited resonance is photoinduced by the 400 nm laser. The appearance rate of the excited resonance is strongly dependent on the laser power. A large isotope effect on the appearance rate of the excited resonance has also been observed. Based on these experimental results along with results of previous experimental and theoretical studies, the excited resonance observed in the 2PP spectra is attributed to methanol photodissociation on the TiO2(110) surface in which the hydroxyl hydrogen on methanol is transferred from the methanol oxygen atom, which is bonded to the Ti4+; sites, to the nearby bridge bonded oxygen (BBO) site. This picture is supported by recent STM studies on the same surface. The rate constant of the photocatalyzed dissociation of methanol appears to time dependent, suggesting that this process is heterogeneous.
