Hydroxylation of the Rutile TiO₂(110) Surface Enhancing Its Reducing Power for Photocatalysis

Abstract

Hydroxylation of the rutile TiO2(110) surface has attracted much attention as the excess unpaired electrons introduced by hydroxyls play a critical role in surface chemistry and photocatalysis process of this material. In this work, based on density functional theory calculations with the Hubbard U correction, the electronic structures of the hydroxylated TiO2(110) surfaces have been studied. One interesting effect is found that the hydroxylation can elevate band edges of TiO2, and thus can enhance its reducing power for photocatalysis. The underlying physical mechanism for such shifts of the band edges are associated with the electric dipoles arising from the hydroxyl groups on the surface.

Iron oxide surfaces

“…For example, it is known that OH groups donate electrons to the oxide lattice in much the same way as V O s [595], and that this affects the binding strength of coadsorbed atoms and molecules, and can have a direct impact on surface chemistry [596]. Moreover, it has been shown that the nucleation of Au clusters occurs homogeneously on the terraces on a TiO 2 (110) surface with V O s, but preferentially occurs at step edges in the presence of OH [597].…”

Improving the photocatalytic activity of TiO2 through reduction

“…According to our previous study, 26 such embedded polarons are only weakly contribute to the total dipole moment comparing with the exposed hydroxyl, as well as the exposed O-vac here.…”

“…26 The stoichiometric rutile TiO2 (110) surface 11 itself is non-polar and has a neglectable dipole moment of only~0.15 Debye given by our DFT+U calculation. However, when the surface is reduced, the dipoles are created.…”

Deeply Repairing Surface States with Wet Chemistry Methods: Enhanced Performance in TiO2 Nanowire Arrays‐Based Optoelectronic Device

“…The optimized lattice constant of rutile TiO 2 is in good agreement with experimental ones, where the differences between DFT result and experimental values are only 0.043% for the a/b‐axes and 0.23% for the c‐axis. Unlike the prefect TiO 2 (110) surface (Figure A), the density of states (DOS) with oxygen vacancy (Figure B) shows two excess electrons donated by the two specific Ti atoms, implying that the adjacent Ti atoms changed from Ti 4+ to Ti 3+ . According to the ligand field for octahedral coordinated metal oxide, the excess electron would occupy one of Ti's 3d t 2g orbitals, which can lead to the local Jahn‐Teller distortion due to the electron‐lattice coupling .…”

“…To further explore this interpretation, we performed calculations based on density functional theory (DFT) . Four kinds of models are built as following: (1) the perfect TiO 2 (110) interface (TiO 2 , Figure A top image); (2) the TiO 2 (110) interface with oxygen vacancy (TiO 2 ‐O 2c , Figure A bottom image); (3) single PbS molecule adsorbed on the TiO 2 (110) interface with O 2c site (PbS@TiO 2 ‐O 2c , Figure B); (4) single CdS molecule adsorbed on the O 2c site of the TiO 2 (110) interface (CdS@TiO 2 ‐O 2c , Figure C).…”