A photoelectron spectroscopy study on the interfacial chemistry and electronic structure of terephthalic acid adsorption on TiO2(110)- (1×1) surface

The chemical bonding mechanism, electronic structure, and the energy level alignment at the terephthalic acid (TPA)/TiO2 (110)-(1×1) interface were investigated in situ by means of X-ray photoelectron spectroscopy (XPS) and synchrotron radiation photoemission spectroscopy (SRPES). It has been found that the adsorption of TPA on TiO2(110)-(1×1) at room temperature leads to the formation of dicarboxylate species at lower coverage (∼0.2 ML) followed by the formation of monocarboxylate species below 1 ML, indicating a geometry variation from flat-lying to upright adsorption. Further deposition of TPA onto the first monolayer results in a multilayer growth without deprotonation. The energy level alignment at the TPA/TiO2 (110) interface demonstrates a straddling lineup of the organic frontier molecular levels with respect to the oxide bands at the interface. A large energy difference with a value of ∼1.1 eV is present between the lowest unoccupied molecular orbital (LUMO) of TPA and the conduction band (CB) of...