Impact of surface hydroxylation in MgO-/SnO-nanocluster modified TiO_2 anatase(101) composites on visible light absorption, charge separation and reducibility

摘要

Surface 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 Mg_4O_4 and Sn_4O_4 nanoclusters modifying the(101) surface of anatase TiO_2 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 TiO_2 surface and metal oxide nanocluster respectively. Comparisons with bare TiO_2 and other TiO_2-based photocatalyst materials are presented throughout.