Temperature-Controlled CO Adsorption Configurations on (2 x 1)Ni-O/Ni(110) Surfaces

摘要

CO adsorptions and configuration evolutions with temperatures on (2 X 1)Ni-O row structures on Ni(110) surfaces were studied by using ultrahigh vacuum-Fourier transform infrared spectroscopy, thermal desorption spectroscopy, and density functional theory calculations. Two kinds of adsorption configurations were identified. In the top configuration at low temperature (90 K), the carbon atom of one CO binds to one Ni atom in the Ni-O rows with a tilt angle of about 53 degrees, and the vibration frequency of CO is 2100-2119 cm(-1) depending on CO coverage. In the bridge configuration near room temperature (280 K), the carbon atom of one CO binds to two Ni atoms from the neighboring Ni-O rows, and the vibration frequency is 2030-2039 cm(-1). By annealing the sample prepared at 90 to 280 K, the top adsorption configuration gradually evolves into the ordered bridge adsorption configuration via a disordered state. In the disordered state, the top and bridge configurations are distributed in disorder, induce strong transverse distortion of the Ni-O rows along [1 (1) over bar0] direction, and thus lead to the significant CO frequency shifts. The distortion disappears after the complete desorption of CO above 300 K. The high stability of Ni-O rows may be the key factor to prevent CO oxidation on such surfaces.