Adsorption and reactions of CH2I2 on Ru(001) surface

SURFACE SCIENCE

卷:460

Article

Kis, A ; Smith, KC ; Kiss, J ; Solymosi, F

关键词: Alkanes;    alkynes;    ruthenium;    single crystal surfaces;    surface photochemistry;    thermal desorption spectroscopy;    X-ray photoelectron spectroscopy;   

DOI  :  10.1016/S0039-6028(00)00532-X

来源: Elsevier

【 摘 要 】

The adsorption and dissociation of CH2I2 were studied at 110 K with the aim of generating CH2 species on the Ru(001) surface. The methods used included X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), temperature programmed desorption (TPD), Auger electron spectroscopy (AES) and work function measurements. Adsorption of CH2I2 is characterized by a work function decrease (0.96 eV at monolayer), indicating that adsorbed CH2I2 has a positive outward dipole moment. Three adsorption states were distinguished: a multilayer (T-p=200 K), a weakly bonded state (T-p=220 K) and an irreversibly adsorbed state. A new feature is the formation of CH3I, which desorbs with T-p=160 K. The adsorption of CH2I2 at 110 K is dissociative at submonolayer, but molecular at higher coverages. Dissociation of the monolayer to CH2 and I proceeded at 198-230 K, as indicated by a shift in the I(3d(5/2)) binding energy from 620.6 eV to 619.9 eV. A fraction of adsorbed CH2 is self-hydrogenated into CH4 (T-p=220 K), and another one is coupled to di-sigma-bonded ethylene, which - instead of desorption - is converted to ethylidyne at 220-300 K. Illumination of the adsorbed CH2I2 initiated the dissociation of CH2I2 monolayer even at 110 K, and affected the reaction pathways of CH2. (C) 2000 Elsevier Science B.V. All rights reserved.

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