The interaction of 1-butyl iodide with the Mo2C/Mo(100) surface

The adsorption and dissociation of 1-butyl iodide and the reactions of butyl species have been investigated on the Mo-2 C/Mo(100) surface by thermal desorption spectroscopy (TDS), X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS) in the temperature-range of 100-1200 K. 1-Butyl iodide adsorbed molecularly on the clean Mo2C/Mo(100) surface at 100 K. A fraction of the C4H9I(a) desorbed in two peaks at 166 and 280 K, characteristic of condensed and weakly adsorbed layers, respectively. XPS data indicated that the scission of the C-I bond in C4H9I(a) started at as low temperature as 140 K and was completed at 280-300 K. The promotion of rupture of the C-I bond in the adsorbed 1-butyl iodide was achieved by UV irradiation even at 100 K. The dissociation process was not accompanied by any significant changes in the HREEL spectra. Among the reaction products, the thermal desorption of butane was characterized by T-p = 246-290 K and that of butene by T-p = 246 and 322 K, suggesting the disproportionation reaction of butyl groups. The release of both compounds was a reaction-rate limited process, as confirmed by the separate determination of their bonding to the Mo,C/Mo(I 00) surface. A very limited coupling of butyl species was indicated by the desorption of octane with T-p similar to 410 K. Heating the adsorbed layer to 470 K the formation of adsorbed butylidyne group was detected, which decomposed to carbon and hydrogen above 600 K. (C) 2004 Published by Elsevier B.V.