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Activation of CO2 at Chromia-Nanocluster-Modified Rutile and Anatase TiO2

preprint
submitted on 25.03.2018 and posted on 26.03.2018 by Michael Nolan, Marco Fronzi
Converting CO2 to fuels is required to enable the production of sustainable fuels and to contribute to alleviating CO2 emissions. In considering conversion of CO2, the initial step of adsorption and activation by the catalyst is crucial. In addressing this difficult problem, we have examined how nanoclusters of reducible metal oxides supported on TiO2 can promote CO2 activation. In this paper we present density functional theory (DFT) simulations of CO2 activation on heterostructures composed of extended rutile and anatase TiO2 surfaces modified with chromia nanoclusters. The heterostructures show non-bulk Cr and O sites in the nanoclusters and an upshifted valence band edge that is dominated by Cr 3d- O 2p interactions. We show that the supported chromia nanoclusters can adsorb and activate CO2 and that activation of CO2 is promoted whether the TiO2 support is oxidised or hydroxylated. Reduced heterostructures, formed by removal of oxygen from the chromia nanocluster, also promote CO2 activation. In the strong CO2 adsorption modes, the molecule bends giving O-C-O angles of 127 - 132o and elongation of C-O distances up to 1.30 Å; no carbonates are formed. The electronic properties show a strong CO2-Cr-O interaction that drives the interaction of CO2 with the nanocluster and induces the structural distortions. These results highlight that a metal oxide support modified with reducible metal oxide nanoclusters can activate CO2, thus helping to overcome difficulties associated with the difficult first step in CO2 conversion.

Funding

Science Foundation Ireland through the US-Ireland R&D Partnership Program Project SusChem SFI 14/US/E2915 and the M-ERA.net co-fund program, grant number SFI 16/M-ERA/2918, H2020 Grant Agreement 685451

History

Email Address of Submitting Author

michael.nolan@tyndall.ie

Institution

Tyndall National Institute, University College Cork

Country

Ireland

ORCID For Submitting Author

0000-0002-5224-8580

Declaration of Conflict of Interest

No conflict of interest

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