Adsorption of Propylene Carbonate Molecules on a TiO2(110) Surface

Abstract

Adsorption of propylene carbonate (PC) molecules on a rutile titanium dioxide (TiO2) (110)-(1 × 1) surface was examined at room temperature by a scanning tunneling microscope (STM) and a Kelvin probe method. The work function of the (1 × 1) surface decreased with the coverage of the PC admolecules, which indicated that the PC molecules adsorbed through the negatively charged carbonate group induced surface dipole moments pointing toward the vacuum. The STM observation revealed that the PC molecules were adsorbed on the Ti atom rows and at the bridging O vacancies. The PC admolecules at the bridging O vacancies were immobile, while the admolecules on the Ti atom rows migrated. The PC molecule was presumably stabilized when the carbonyl O atom was coordinated to two Ti atoms exposed at the vacancy. The coverage of the stable PC admolecules increased on the vacancy-rich surface prepared by electron beam irradiation.