Effect of Oxygen Vacancies on Adsorption of Small Molecules on Anatase and Rutile TiO₂ Surfaces: A Frontier Orbital Approach

Abstract

Adsorption is a critical step in the initial stage of a catalytic reaction. Oxygen vacancies often become a central topic of discussion with respect to the reaction mechanism on metal oxide surfaces because oxygen vacancies change the surface electronic properties and affect the adsorption process. In this study, we use first-principles calculations and regression analyses to investigate the effect of oxygen vacancies on a metal oxide surface on the adsorption of small molecules. We adopt the anatase (101) and rutile (110) TiO2 surfaces as research targets. The calculation results show that the removal of an oxygen atom causes a large difference in the electronic structure due to the presence of two unpaired electrons. Our previous study showed that the adsorption energy of a defect-free surface is linearly correlated with the energy of the highest occupied molecular orbital for small adsorbed molecules. In the case of a defective anatase surface, we found that the energy of the lowest unoccupied molecular orbital also plays an important role in enhancing the adsorption of small molecules, especially those with an unpaired electron. Notably, our results demonstrate that hardness is a prime descriptor to explain the adsorption of various molecules by TiO2 surfaces.

Investigation of a high-entropy oxide photocatalyst for hydrogen generation by first-principles calculations coupled with experiments: Significance of electronegativity

“…Here, a comparison of water adsorption energy on HEO with that on TiO2 polymorphs as the most active photocatalysts for water splitting is beneficial. The adsorption energy calculated in this study for the anatase (101) atomic plane is -0.93 eV, while some other reported data in the literature for different TiO2 polymorphs are given in Table 4 [35][36][37][38][39][40][41]. The comparison demonstrates that the adsorption energy of water over the titanium cation of the HEO is somehow smaller than in the TiO2 anatase (101) plane.…”

Temperature-Dependent Ferroelectric Properties and Aging Behavior of Freeze-Cast Bismuth Ferrite–Barium Titanate Ceramics

“…An increase in the peak area of the O–H, O–C/O–C=O, and O–H 2 O peaks was observed in the porous BF-BT. In some works 37 , 38 the O 1s peaks at ∼531 eV have been correlated to the presence of oxygen vacancy in the ceramics lattice since the vacancy can promote the adsorption of small molecules, e.g., OH and CO 2 , 39 leading to an increase in the peak intensity at ∼531 eV. Therefore, an analysis of the peak area ratios of O–H to O–M and O–C to O–M was performed in Figure 4 c. These two ratios were both higher for the porous sample than for the dense one, indicating that more oxygen vacancies were present in the porous BF-BT.…”

Oxygen deficient α-MoO3 with enhanced adsorption and state-quenching of H2O for gas sensing: a DFT study

“…The charge transfer from this localized state induced by V O to the H 2 O molecule is more likely to occur. 45 Therefore, the presence of V O could alter the energetics and charge state of adsorbed H 2 O. The presence of H 2 O and V O may significantly affect the properties such as carrier density and mobility which is appealing for sensing of moisture.…”