Chemistry of Methyl and Ethyl Radicals on Pt(111) from the Decomposition of Tri-Alkyl Bismuth Compounds

摘要

The chemistry of trimethyl and triethyl bismuth compounds adsorbed on Pt(111)have been studied using TDS, AES and HREELS. Alkyl radicals and bismuth atoms are delivered to the Pt(111) surface in a 3:1 (alkyl:bismuth) ratio. In the presence of Bi, it is expected that the alkyl radical chemistry is not perturbed substantially. The trialkyl bismuth compounds adsorb molecularly at 110K. Upon heating, the R3Bi compound decomposes and alkyl radicals are introduced to the surface. Below multilayer coverage, the methyl and ethyl radicals, delivered to the surface by thermal decomposition of the parent, show similar trends. There is some fraction of parent (BiR3) desorption at approximately 158K. The remaining methyl or ethyl radicals follow two reaction pathways. The first is hydrogenation which leads to CH4 or CH3CH3 formation, respectively. This pathway leads to reaction rate limited desorption of CH4 or CH3CH3 which occurs at -285K. The second reaction pathway is dehydrogenation of the methyl or ethyl radical leading to an on-top methylidyne or ethylidyne species, respectively, remaining on the surface. Platinum, alkyl fragments, vibrational spectroscopy.