アイテム詳細

要旨

The interaction of CO, CO₂, CO+H₂, CO₂+H₂, and CO+CO₂+H₂ with the nickel (110) single crystal termination has been investigated at 10^-1 mbar in situ as a function of the surface temperature in the 300-525 K range by means of Infrared-Visible Sum Frequency Generation (IR-Vis SFG) vibrational spectroscopy and by Near-Ambient Pressure X-Ray Photoelectron Spectroscopy (NAP-XPS). Several stable surface species have been observed and identified. Besides atomic carbon and precursors for graphenic C phases, five non-equivalent CO species have been distinguished, evidencing the role of co-adsorption effects with H and C atoms, of H-induced activation of CO, and of surface reconstruction. At low temperature, carbonate species produced by the interaction of CO₂ with atomic oxygen, which stems from the dissociation of CO₂ into CO+O, are found on the surface. A metastable activated CO₂^- species is also detected, being at the same time a precursor state towards dissociation into CO and O in the reverse water-gas shift mechanism and a reactive species that undergoes direct conversion in the Sabatier methanation process. Finally, the stability of ethylidyne is deduced on the basis of our spectroscopic observations.