Journal
CATALYSIS LETTERS
Volume 147, Issue 8, Pages 1871-1881Publisher
SPRINGER
DOI: 10.1007/s10562-017-2098-1
Keywords
CO2 valorization < processes and reactions; Methanation; Methanol synthesis; CO2 hydrogenation; Nanoparticles < nanotechnology; Titania; Ru; Cu
Categories
Funding
- European Marie Curie Project CATSENSE [607417]
- Italian MIUR through PRIN [2015K7FZLH SMARTNESS]
- Regione Lombardia and Italian CINECA supercomputing centre via the LISA joint initiative
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Using DFT+U calculations with inclusion of van-der-Waals (vdW) forces, we studied CO2 activation and the initial steps of CO2 hydrogenation over Cu-10 and Ru-10 clusters supported on the TiO2 anatase (101) surface. CO2 is readily adsorbed and activated on the Ru cluster where direct CO2 dissociation proceeds with a barrier of 0.8 eV. When H atoms are co-adsorbed on the Ru cluster, H-addition to CO2 becomes preferred, as the best Ru sites for CO2 dissociation are blocked. A H atom is added to the CO2 molecule with formation of a formate [HCOO] species and an activation barrier of 1.2 eV. On Cu-10/TiO2, only weak adsorption modes of the CO2 molecule are found, whereas H-2 readily adsorbs on the Cu cluster. A reduction of the titania support does not significantly change this picture. Therefore, the only viable pathway for the CO2 hydrogenation over Cu-10/TiO2 is the addition of a pre-adsorbed H atom to CO2 coming from the gas phase. This corresponds to an Eley-Rideal mechanism for the H-association to CO2. The work shows the importance to consider the hydrogen coverage on the metal cluster as an important variable in modeling the CO2 hydrogenation reaction.
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