Modeling catalytic reactions on metal surfaces

CO2 activation and hydrogenation on Ni surfaces for organic synthesis
(Maria Peressi, Michele Rizzi, Xunlei Ding and Alfonso Baldereschi)

Copper is one of the most widely used catalysts for the formation of methanol from carbon dioxide and hydrogen, but recent experiments have shown that Cu/Ni alloys can be up to 40 times more reactive. Our study aims at providing new fundamental insight into the catalytic properties of Ni surfaces, by characterizing the stable intermediates of the hydrogen-assisted transformation of CO2 and by identifying the relevant reaction paths. Remarkably, we demonstrate that CO2 chemisorbs on Ni(110) in a “V” configuration with a relevant (0.9 e-) charge transfer from the metal surface, at variance with most low-index transition metals surfaces where it is physisorbed. 

 Most of the predicted adsorption geometries are consistent with the experimental STM images obtained for the first time, and the adsorption energy values predicted using GGA with DFT-D corrections for the Van der Waals contribution are in good agreement with TPD data.

Atomic level description of the carbon dioxide hydrogenation mechanisms on Ni is achieved on a model system, by comparing density functional theory simulations with experimental findings for CO2 adsorbed on single crystal Ni(110) surface in UHV followed by exposure to molecular or atomic hydrogen beam. Upon hydrogenation, HCOO can be always easily formed via a Langmuir-Hinshelwood process - but is just a “dead-end” spectator, whereas the reaction proceeds via parallel Eley-Rideal channels with low barriers for the hydrogen-assisted C-O bond cleavage in CO2 yielding CO.

C. Dri, A. Peronio, E. Vesselli, C. Africh, M. Rizzi, A. Baldereschi, M. Peressi, and G. Comelli
Imaging and characterization of activated CO2 species on Ni(110)
Phys. Rev. B 82, 165403 (1-6) (2010)

E. Vesselli, M. Rizzi, L. De Rogatis, X. Ding, A. Baraldi, G. Comelli, L. Savio, L. Vattuone, M. Rocca, P. Fornasiero, A. Baldereschi and M. Peressi
Hydrogen-assisted transformation of CO2 on nickel: the role of formate and carbon monoxide
J. Phys. Chem. Lett. 1, 402-406 (2010)

X. Ding, L. De Rogatis, E. Vesselli, A. Baraldi, G. Comelli, R. Rosei, L. Savio, L. Vattuone, M. Rocca, P. Fornasiero, F. Ancilotto, A. Baldereschi, M. Peressi
Interaction of carbon dioxide with Ni(110): a combined experimental and theoretical study
Frontiers of Fundamental and Computational Physics: 9th International Symposium", AIP Conference Proceedings 1018, Issue 1, 197 (2008)

E. Vesselli, L. De Rogatis, X. Ding, A. Baraldi, L. Savio, L. Vattuone, M. Rocca, P. Fornasiero, M. Peressi, A. Baldereschi, R. Rosei and G. Comelli
Carbon Dioxide hydrogenation on Ni(110)
J. Am. Chem. Soc. 130, 11417 (2008)

X. Ding, V. Pagan, M. Peressi, and F. Ancilotto
Modeling adsorption of CO2 on Ni(110) surface
Mat. Sci. Eng. C 27, 1355-1359 (2007)

X. Ding, L. De Rogatis, E. Vesselli, A. Baraldi, G. Comelli, R. Rosei, L. Savio, L. Vattuone, M. Rocca, P. Fornasiero, F. Ancilotto, A. Baldereschi, and M. Peressi
Interaction of carbon dioxide with Ni(110): a combined experimental and theoretical study
Phys. Rev. B 76, 195425-(1-12) (2007)

In collaboration with:

  • ELETTRA - SuperESCA beamline (A. Baraldi)
  • INFM-CNR TASC National Laboratory (E. Vesselli, G. Comelli, R. Rosei)

Adsorption of ethylene (C2H4) on silver surfaces
(Paola Gava, Tone Kokalj, Stefano de Gironcoli, and Stefano Baroni)

The epoxidation of ethylene, catalyzed by silver, is one of the most important selective oxidation processes based on heterogeneous metallic catalysis. This reaction produces ethylene epoxide (oxirane), which is an important intermediate in the fabrication of glycols and polyols. The emphasis of this study is to study the influence of surface imperfections (defects) on the adsorption of ethylene. We have found that less coordinated surface atoms located near defects are more reactive, and are therefore the active reaction sites. The role of adsorbed oxygen in the adsorption of the ethylene is also investigated. We have found that atomic oxygen adsorbed on the surface influences the adsorption properties of the surface only slightly, while subsurface atomic oxygen influences the reactivity of the surface to a much larger extent. In the foregoing future we will investigate the role of surface imperfections and oxygen adsorbed subsurface on the partial oxidation of ethylene by calculating associated reactions barriers.

Anton Kokalj, Paola Gava, Stefano de Gironcoli and Stefano Baroni
What determines the catalyst's selectivity in the ethylene epoxidation reaction
J. Catal. 254, 304 (2008)

Anton Kokalj, Paola Gava, Stefano de Gironcoli and Stefano Baroni
Activated Adsorption of Ethylene on Atomic-Oxygen-Covered Ag(100) and Ag(210): Formation of an Oxametallacycle
J. Phys. Chem. C 112, 1019 (2008)

Dehydrogenation of methane (CH4) on transition metal surfaces
(Tone Kokalj, Stefano de Gironcoli, and Stefano Baroni)

The elementary steps of the dehydrogenation reaction of methane (CH4) catalyzed by transition metal surfaces are investigated by density functional theory calculations. Tuning the relative rates of different reaction steps would allow for an optimal design of novel catalysts for the direct conversion of methane to methanol. We have revealed and understood the dependency of the reaction barriers of the initial stages of methane dehydrogenation on the local atomic structure and chemical composition of the reaction surface sites.

Anton Kokalj, Nicola Bonini, Stefano de Gironcoli, Carlo Sbraccia, Guido Fratesi, and Stefano Baroni
Methane Dehydrogenation on Rh@Cu(111): A First-Principles Study of a Model Catalyst
J. Am. Chem. Soc. 128, 12448 (2006)