Abstract
The valence-band structure and the vibrational modes of CO adsorbed on nickel-promoted TiO 2(110) surfaces as a function of CO exposure have been studied by means of ultraviolet photoelectron spectroscopy (UPS) and high-resolution electron energy-loss spectroscopy (HREELS). It is found that CO exists in molecular form at room temperature on the nickel-promoted TiO 2(110) surfaces and most likely binds to the Ni atoms or nickel-affected sites rather than to the substrate atoms. At saturation coverage, CO molecules adsorb simultaneously on the 2-fold bridge sites and terminal sites on the (111)-oriented Ni islands deposited upon TiO 2(110). The occupation of the edge sites of Ni islands gives rise to an anomalously low frequency of the CO stretching vibration. This frequency, indicative of a weakened CO bond, suggests existence of a precursor to the dissociated state.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have