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submitted on 27.09.2017 and posted on 12.10.2017by Michael Nolan, Stephen Rhatigan
modification with metal oxide nanoclusters has emerged as a candidate for the
enhancement of the photocatalytic activity of titanium dioxide. An increase in
visible light absorption and the suppression of charge carrier recombination
are necessary to improve the efficiency. We have studied Mg4O4
and Sn4O4 nanoclusters modifying the (101) surface of
anatase TiO2 using density functional theory corrected for on-site
Coulomb interactions (DFT + U). Such studies typically focus on the pristine
surface, free of the point defects and surface hydroxyls present in real
surfaces. We have also examined the impact of partial hydroxylation of the anatase
surface on a variety of outcomes such as nanocluster adsorption, light absorption,
charge separation and reducibility. Our results indicate that the modifiers
adsorb strongly at the surface, irrespective of the presence of hydroxyl
groups, and that modification extends light absorption into the visible range
while enhancing UV activity. Our model for the excited state of the
heterostructures demonstrates that photoexcited electrons and holes are
separated onto the TiO2 surface and metal oxide nanocluster
respectively. Comparisons with bare TiO2 and other TiO2-based
photocatalyst materials are presented throughout.