Characterization of the Excited State on Methanol/TiO2(110) Interface

The electronic structure of methanol/TiO2(110) interface has been studied by photoeraission spectroscopy. The pronounced resonance which appears at 5.5 eV above the Fermi level in two-photon photoemission spectroscopy (2PPE) is associated with the photocatalyzed dissociation of methanol at fivefold coordinated Ti sites (Ti-5c) on TiO2(110) surface [Chemical Science 1, 575 (2010)]. To check whether this resonance signal arises from initial or intermediate states, photon energy dependent 2PPE and comparison between one-photon photoemission spectroscopy and 2PPE have been performed. Both results consistently suggest the resonance signal originates from the initially unoccupied intermediate states, i.e., excited states. Dispersion measurements suggest the excited state is localized. Time-resolved studies show the lifetime of the excited state is 24 fs. This work presents comprehensive characterization of the excited states on methanol/TiO2(110) interface, and provides elaborate experimental data for the development of theoretical methods in reproducing the excited states on TiO2 surfaces and interfaces