Effects of potassium on the reaction pathways of CH2 fragment over Mo2C/Mo( 100)

• Published in: Surface science 2007-09, Vol.601 (18), p.3736-3739
• Main Authors: FARKAS, A. P, BUGYI, L, KOOS, A, SOLYMOSI, F
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Physics
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2007.04.064

The adsorption and surface reactions of CH2beta on the K-dosed Mo2C/Mo(100) have been studied by high resolution electron energy loss spectroscopy, X-ray photoelectron spectroscopy and thermal desorption spectroscopy. Potassium is an effective promoter for the rupture of C-I bond in the adsorbed CH2beta. A partial dissociation of this compound occurred even at 100K and was completed at 190K at monolayer K coverage. The dissociation was further promoted by the illumination of coadsorbed layer at 100K. As revealed by HREELS and XPS measurements the primary products of the dissociation are CH2 and I. Methylene was converted to pi-bonded ethylene characterized by Tp=160K, and di-sigma-ethylene with Tp=350K. Other products of the surface reaction are hydrogen and methane. The coupling reaction of CH2 species was clearly facilitated by potassium. The effect of potassium was explained by the extended electron donation to adsorbed alkyl iodide in one hand, and by the direct interaction between potassium and I on the other hand.