Reverse Water–Gas Shift or Sabatier Methanation on Ni(110)? Stable Surface Species at Near-Ambient Pressure

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• 作者：Matteo Roiaz ; Enrico Monachino ; Carlo Dri ; Mark Greiner ; Axel Knop-Gericke ; Robert Schlögl ; Giovanni Comelli ; Erik Vesselli
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：March 30, 2016
• 年：2016
• 卷：138
• 期：12
• 页码：4146-4154
• 全文大小：595K
• ISSN：1520-5126

文摘

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 nonequivalent CO species have been distinguished, evidencing the role of coadsorption 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 toward 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.