Chemistry, Physics and Technology of Surface

ISSN 2518-1238 (Online), ISSN 2079-1704 (Print)

Theoretical studies of the interactions of an oxygen molecule with the surface of a solid phase are of great importance for understanding the mechanisms of reactions involving oxygen on a solid surface. In this work, the spatial and electronic structure of oxygen defects and nitrogen impurity centers of the anatase surface and their manifestation in water adsorption are investigated. The anatase surface was simulated for by clusters of the composition Ti₁₄H₂₂O₃₉ (defect-free face (001)), Ti₁₄H₂₂O₃₈ (surface with oxygen vacancy), and Ti₁₄H₂₂N₂O₃₆ (surface with both oxygen vacancy and incorporated nitrogen), terminated with boundary hydrogen atoms.

Calculations on the total energy of the optimized geometric structures of the model TiO₂ clusters and on the corresponding theoretical XPS spectra were performed using the density functional theory (DFT) method and the B3LYP hybrid functional with an extended valence-split basis set 6-31G (d, p).

In the XPS spectra of O1s, each peak can be attributed to a specific type of oxygen atoms in the initial structure, dependent on their coordination environment. The substitution of nitrogen atoms for oxygen ones leads to a complication of the spectrum. Simultaneous replacement of nitrogen atoms for oxygen ones and presence of an oxygen vacancy leads to further complication of the XPS spectrum.

The different structure of the adsorption complexes of water molecules on the anatase surface formed due to the HOH∙∙∙O hydrogen bond (this displaces by 0.05 eV all the peaks in the XPS spectrum) or the coordination bond Ti∙∙∙OH₂ has been also considered.

Based on the analysis of theoretical results, the role of various forms of defects in the adsorption of water on the anatase surface is considered.

The results of quantum chemical studies of molecular models simulated for the bulk and surface of titanium dioxide are compared with the literature data available.

1. Trushina A.P., Goldort V.G., Kochubei S.A., Baklanov A.V. UV-photoexcitation of encounter complexes of oxygen O₂ -O₂ as a source of singlet oxygen O₂ (¹Δg) in gas phase. Chem. Phys. Lett. 2010. 485(1-3): 11. https://doi.org/10.1016/j.cplett.2009.11.058

2. Mo S., Ching W. Electronic and optical properties of three phases of titanium dioxide: Rutile, anatase and brookite. Phys. Rev. B. 1995. 51(19): 13023. https://doi.org/10.1103/PhysRevB.51.13023

3. Anpo M., Shima T., Kodama S., Kubokawa Y. Photocatalytic hydrogenation of propyne with water on small-particle titania: size quantization effects and reaction. J. Phys. Chem. 1987. 91(16): 4305. https://doi.org/10.1021/j100300a021

4. Smirnova O., Grebenyuk A., Linnik O., Lobanov V. Quantum chemical study of water molecule adsorption on the nitrogen-doped titania thin films. Nanophysics, Nanomaterials, Interface Studies, and Applications: Selected Proc. 4th Int. Conf. Nanotechnology and Nanomaterials (NANO2016, Aug. 24-27, 2016, Lviv, Ukraine. Springer, 2017): 603. https://doi.org/10.1007/978-3-319-56422-7_45

5. Sauer J. Molecular models in ab initio studies of solids and surfaces: from ionic crystals and semiconductors to catalysts. Chem. Rev. 1989. 89(1): 199. https://doi.org/10.1021/cr00091a006

6. Becke A. Density-functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 1993. 98(7): 5648. https://doi.org/10.1063/1.464913

7. Cohen A.J., Mori-Sanchez P, Yang W. Challenges for density functional theory. Chem. Rev. 2012. 112(1): 289. https://doi.org/10.1021/cr200107z

8. Schmidt M., Baldridge K., Boatz J., Elbert S., Gordon M., Jensen J., Koseki S., Matsunaga N., Nguyen K., Su S., Windus T., Dupuis M., Montgomery J. General atomic and molecular electronic structure system. J. Comput. Chem. 1993. 14(11): 1347. https://doi.org/10.1002/jcc.540141112

9. Besogonov E.V., http://g-tools.narod.ru

10. Chobal A.I., Rizak I.M., Grebenyuk A.G., Rizak V.M. Electronic and spatial structure of nanoclusters of Sn2P2S6 ferroelectric crystals. Phys. Solid State. 2010. 52(7): 1468. https://doi.org/10.1134/S1063783410070231