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Modification of TiO2 with Metal Chalcogenide Nanoclusters for Hydrogen Evolution

preprint
submitted on 02.11.2020, 12:54 and posted on 03.11.2020, 11:32 by Stephen Rhatigan, Lorenzo Niemitz, Michael Nolan
Using density functional theory, corrected for on-site Coulomb interactions (DFT+U), we have investigated surface modification of TiO2 with metal chalcogenide nanoclusters for hydrogen evolution. The nanoclusters have composition M4X4 (M = Sn, Zn; X = S, Se) and are adsorbed at the rutile (110) surface. The nanoclusters adsorb exothermically, with adsorption energies in the range -3.00 eV to -2.70 eV. Computed density of states (DOS) plots show that cluster-derived states extend into the band-gap of the rutile support, which indicates that modification produces a redshift in light absorption. After modification, photoexcited electrons and holes are separated onto surface and cluster sites, respectively. The free energy of H adsorption is used to assess the performance of metal chalcogenide modified TiO2 as a catalyst for HER. Adsorption of H at nanocluster (S, Se) and surface (O) sites is considered, together with the effect of H coverage. Adsorption free energies at cluster sites in the range (-0.15 eV, 0.15 eV) are considered to be favourable for HER. The results of this analysis indicate that the sulphide modifiers are more active towards HER than the selenide modifiers and exhibit hydrogen adsorption free energies in the active range, for most coverages. Conversely, the adsorption free energies at the selenide nanoclusters are only in the active range at low H coverages. Our results indicate that surface modification with small, dispersed nanoclusters of appropriately selected materials can enhance the photocatalytic activity of TiO2 for HER applications.

Funding

Science Foundation Ireland 14/US/E2915

Science Foundation Ireland 16/M-ERA/3418

H2020 ERA.Net for Materials Research and Innovation (M-ERA.Net 2), grant agreement number 685451

History

Email Address of Submitting Author

michael.nolan@tyndall.ie

Institution

Tyndall National Institute

Country

Ireland

ORCID For Submitting Author

0000-0002-5224-8580

Declaration of Conflict of Interest

No conflict of interest

Version Notes

Submitted version

Exports