Dispersion of Defects in TiO2 Semiconductor: Oxygen Vacancies in the Bulk and Surface of Rutile and Anatase

Abstract

Oxygen deficiency (O-vacancy) contributes to the photoefficiency of TiO2 semiconductors by generating electron rich active sites. In this paper, the dispersion of O-vacancies in both bulk and surface of anatase and rutile phases was computationally investigated. The results showed that the O-vacancies dispersed in single- and double-cluster forms in the anatase and rutile phases, respectively, in both bulk and surface. The distribution of the O-vacancies was (roughly) homogeneous in anatase, and heterogenous in rutile bulk. The O-vacancy formation energy, width of defect band, and charge distribution indicated the overlap of the defect states in the rutile phase and thus eased the formation of clusters. Removal of the first and the second oxygen atoms from the rutile surface took less energy than the anatase one, which resulted in a higher deficiency concentration on the rutile surface. However, these deficiencies formed one active site per unit cell of rutile. On the other hand, the first O-vacancy formed on the surface and the second one formed in the subsurface of anatase (per unit cell). Supported by previous studies, we argue that this distribution of O-vacancies in anatase (surface and subsurface) could potentially create more active sites on its surface.

Oxygen vacancies induced photoluminescence in $$\hbox {SrZnO}_2$$ nanophosphors probed by theoretical and experimental analysis

“…We found that for 3.125% O vacancy concentration, = 4.1 eV, while for 12.5% O vacancy concentration, = 4.7 eV. These trends in formation energies and the relative stabilities of different O vacancy concentrations were comparable to what reported in other oxide system 33 . Note that in many semiconductors, charged O vacancy is known to be thermodynamically stable and thus energetically feasible, more so in n -type conductive systems.…”

“…In order to understand the relative formation of different O vacancy concentrations, we calculated formation energies ( ) corresponding to two different O vacancy concentrations in our study. In this definition, , correspond to formation energy, supercell energy with single O vacancy, and the pristine supercell energy, respectively, while refers to the chemical potential of O which is half of the total energy of an isolated oxygen molecule 33 . We found that for 3.125% O vacancy concentration, = 4.1 eV, while for 12.5% O vacancy concentration, = 4.7 eV.…”

Synthesis and Characterization of Titanium Dioxide Hollow Nanofiber for Photocatalytic Degradation of Methylene Blue Dye

“…As the Ti-Ti distance in rutile is shorter than in anatase, the rutile TiO 2 is 9% denser. Therefore, this has caused more pronounced orbital localization of the Ti 3 d and O 2 p and resulted in a narrower bandgap [ 31 ]. In accordance with the XRD patterns in Figure 7 , the bandgap narrowing was attributed to the higher crystallinity of THNF600, in which the majority of the fraction was rutile (75.8%).…”

Insight into the influence of defect sites in mixed phase of mesoporous titania nanoparticles toward photocatalytic degradation of 2‐chlorophenol: Effect of light source

“…The formation of site defects on the surface of rutile was higher than anatase because the energy needed for production of site defect on rutile was lower than anatase. [ 58 ] The BET, FESEM, and TEM data also confirmed the formation of mesopores with high surface area in MTN particles. [ 59 ] These properties have proved a great potential of MTN to be utilized as a photocatalyst.…”