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

Abstract

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.

Catalytic Intermediates of CO2 Hydrogenation on Cu(111) Probed by In Operando Near‐Ambient Pressure Technique

“…2018, 24,16097 -16103 www.chemeurj.org 2018 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim Figure 4s hows the CO 2 pressure-dependente volution of surface species in the gas mixture of CO 2 and H 2 .T he peak areaso fs urface species were normalized by the initial Cu 2p peak areas in each experiment (see the Experimental Section). [13][14][15][16] Our result offers ap romising methodt oc ontrol the formation of carbon speciest hrough tuning the CO 2 partial pressures in the reactants. At the CO 2 partial pressure of 10 À3 mbar,n oa tomico xygen was detected on the Cu(111)s urface (spectrum A, O1s).…”

“…[9,10] However, in this case, "postmortem"c haracterization does not necessarily represent the surfaceo ft he active catalyst, ast he presence of the intermediate is closely related to the partial pressure of the reactants and thep roducts. [13][14][15][16] The formation of graphitic carbon is known to be very detrimental in the reactionp rocess, because it will considerably reduce the reactivity of catalysts owing to its chemicali nertness. [8,12] As ac ommon intermediate in CO 2 conversion, graphitic carbon was widely observed in the catalytic CO 2 hydrogenation reaction.…”

Controlling selectivities in CO2 reduction through mechanistic understanding

“…However, for designing a selective catalyst, it is very important to first have a fundamental understanding of the site requirements, elementary steps and intermediates, which can ultimately lead to the construction of viable mechanisms for both methanation and RWGS. Although intricate interplay between various surface species at different catalyst components that determine product selectivity has been recognized, controversies still exist regarding the detailed mechanism and the roles of surface species 10–15 . Some issues may originate from the different interrogation methods used; for example, some prior conclusions were based on kinetic and spectroscopic information acquired under transient conditions 12 .…”

The Development of Mesoporous Ni‐Based Catalysts and Evaluation of Their Catalytic and Photocatalytic Applications

“…From the aforementioned catalytic systems for hydrogenation and HDO, the systems based on nickel show great potential because of both low cost and high activity of Ni towards hydrogenation. Since the pioneering work by Sabatier, Ni catalysts have been widely studied and utilized as outstanding catalysts for hydrogenation. In the early days, the Ni catalyst was directly prepared by the reduction of Ni oxides .…”