Reactions of ''hot'' methyl groups with surface hydrogen during CH3-I bond scission on Ni(111)

We have studied the reactions between submonolayer coverage amounts of methyl iodide and adsorbed hydrogen on Ni(111) using high-resolution electron energy loss spectroscopy (HEELS), temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and low-energy ion scattering (LEIS). Methane is the only hydrocarbon product during TPD to 500 K and consists of original methyl groups plus one coadsorbed hydrogen atom. Methane desorbs in a sharp peak at about 150 K and in broader peaks at 230 and 260 K. The 150 K process does not occur for coadsorbed CH3 and H but rather involves abstractions of surface hydrogen atoms by nascent, unaccommodated methyl groups formed during CH3-I bond scission. The higher temperature bond formation processes involve accommodated methyl groups.