Chemistry, Physics and Technology of Surface

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

n-TiO₂ and n-TiO₂:Ag nanopowders were synthesized by the method of electric explosion of wires (EEW). The doping of nanopowders took place during the explosion of titanium wire, on the surface of which an Ag₂O layer of the appropriate mass was applied. The energy of the explosion was equal to Е = 3.1·Е_s, where E_s is the energy of sublimation of the metal. Based on the synthesized nanopowders, mesoporous n-TiO₂ and n-TiO₂:Ag films were formed. The phase composition of the surface of several series of n-TiO₂ and n-TiO₂:Ag samples under different annealing conditions was studied by X-ray photoelectron spectroscopy. The XPS spectra of the Ti2p- and Ag3d- levels were decomposed by the Gauss-Newton method into interconnected components 2p_3/2/2p_1/2 and 3d_5/2/3d_3/2 with parameters DЕ = 5.76 eV; I₁/I₂ = 0.5 and DЕ = 6.0 eV; I₁/I₂ = 0.66 to take into account the spin-orbit splitting of the pair respectively. The paper presents histograms of the contributions of the components to the Ti2p- and Ag3d- spectra, which vary depending on the degree of doping and annealing conditions for 4 series of samples. According to XPS data, on the surface of EEW nanopowders TiO₂ and TiO₂:Ag titanium is represented by Ti³⁺- and Ti⁴⁺- states, silver by Ag⁰-, Ag¹⁺- and Ag²⁺- states. In all series of samples, the contribution of the Ti³⁺- state simultaneously increases with an increase in the absolute Ag content, which is a consequence of the lattice distortion through the formation of a surface phase with Ti–O–Ag bonds. Annealing at 300 °C in air leads to an increase in the contribution to the spectra of Ti⁴⁺- states of Е_bTi2p_3/2 = 458.3 eV and Ag¹⁺ - states. Pretreatment of the samples with hydrogen peroxide before annealing leads to an increase in the contribution of oxide-hydroxide phases of titanium and Ag⁰- states. Annealing of the samples at 300 °С in argon with pretreatment with hydrogen peroxide leads to an increase in the contribution to the spectra of Ti⁴⁺- states with Е_bTi2p_3/2 = 458.8 eV, oxide-hydroxide phases of titanium and Ag⁰. It has been found that the direction of redox processes on the surface of n-TiO₂ after the action of H₂O₂ and subsequent annealing in air depends on the state of hydration of the original nanopowders.

1. Ranjan P., Nakagawa S., Suematsu H., Sarathi R. Synthesis and photocatalytic activity of anatase/rutile TiO₂ nanoparticles by wire explosion process. INAE Lett. 2018. 3(4): 189. https://doi.org/10.1007/s41403-018-0048-x

2. Zhao Z., Hwang S.H., Jeon S., Hwang B., Jung J.-Yu., Lee J., Park S.-Hu Three-dimensional plasmonic Ag/TiO₂ nanocomposite architectures on flexible substrates for visible-light photocatalytic activity. Sci. Rep. 2017. 7: 8915. https://doi.org/10.1038/s41598-017-09401-z

3. Diesen V., Jonsson M. Formation of H₂O₂ in TiO₂ photocatalysis of oxygenated and deoxygenated aqueous systems: a probe for photocatalytically produced hydroxyl radicals. J. Phys. Chem. C. 2014.118(19): 10083. https://doi.org/10.1021/jp500315u

4. Wu Z., Guo K., Cao S., Yao W., Piao L. Synergetic catalysis enhancement between H₂O₂ and TiO₂ with single-electron-trapped oxygen vacancy. Nano Res. 2020. 13: 551. https://doi.org/10.1007/s12274-020-2650-y

5. Benkoula S., Sublemontier O., Patanen M., Nicolas C., Sirotti F., Naitabdi A., Gaie-Levrel F., Antonsson E., Aureau D., Ouf F.-X., Wada Sh.-I., Etcheberry A., Ueda K., Miron C. Water adsorption on TiO₂ surfaces probed by soft X-ray spectroscopies: bulk materials vs. isolated nanoparticles. Sci. Rep. 2015. 5: 15088. https://doi.org/10.1038/srep15088

6. Gogoi D., Namdeo A., Golder A.K., Peela N.R. Ag-doped TiO₂ photocatalysts with effective charge transfer for highly efficient hydrogen production through water splitting. Int. J. Hydrogen Energy. 2020. 45(4): 2729. https://doi.org/10.1016/j.ijhydene.2019.11.127

7. Shwetharani R., Sakar M., Fernando C.A.N., Binas V., GeethaBalakrishna R. Recent advances and strategies applied to tailor energy levels, active sites and electron mobility in titania and its doped/composite analogues for hydrogen evolution in sunlight. Catal. Sci. Technol. 2019. 9(1): 12. https://doi.org/10.1039/C8CY01395K

8. Cao Y., Tan H., Shi T., Tang T., Li J. Preparation of Ag-doped TiO₂ nanoparticles for photocatalytic degradation of acetamiprid in water. J. Chem. Technol. Biotechnol. 2008. 83(4): 546. https://doi.org/10.1002/jctb.1831

9. Shpak A.P., Korduban A.M., Medvedskij M.M., Kandyba V.O. XPS studies of active elements surface of gas sensors based on WO3−x nanoparticles. J. Electron Spectrosc. Relat. Phenom. 2007. 156-158: 172. https://doi.org/10.1016/j.elspec.2006.12.059

10. Briggs D., Seach M.P. Practical Surface Analysis by Auger and X-ray Photoelectron Spectroscopy. (Chichester - New York: John Wiley & Sons Ltd., 1983).

11. Wagner C.D., Moulder J.F., Davis L.E., Riggs W.M. Handbook of X-ray Photoelectron Spectroscopy. (New York: Perkin-Elmer Corporation, 1979).

12. Nefedov V.I. Roentgenoelectronic Spectroscopy of Chemical Compounds. (Moscow: Khimiya, 1984). [in Russian].

13. Satoh N., Nakashima T., Kamikura K., Yamamoto K. Quantum size effect in TiO₂ nanoparticles prepared by finely controlled metal assembly on dendrimer templates. Nat. Nanotechnol. 2008. 3. 106. https://doi.org/10.1038/nnano.2008.2

14. Sikdar S., Pathak S., Ghorai T.K. Aqueous phase photodegradation of rhodamine B and p-nitrophenol desctruction using titania based nanocomposites. Adv. Mater. Lett. 2015. 6(10): 867. https://doi.org/10.5185/amlett.2015.5858

15. Wint T.H.M., Smith M.F., Chanlek N., Chen F., Oo T.Z., Songsiriritthigul P. Physical origin of diminishing photocatalytic efficiency for recycled TiO₂ nanotubes and Ag-loaded TiO₂ nanotubes in organic aqueous solution. Catalysts. 2020. 10(7): 737. https://doi.org/10.3390/catal10070737

16. Ferraria A.M., Carapeto A.P., Botelho do Rego A.M. X-ray photoelectron spectroscopy: silver salts revisited. Vacuum. 2012. 86(12): 1988. https://doi.org/10.1016/j.vacuum.2012.05.031

17. Thomas S., Durand D., Chassenieux C., Jyotishkumar P. Handbook of Biopolymer-Based Materials: From Blends and Composites to Gels and Complex Networks. (John Wiley & Sons, 2013). P. 61. https://doi.org/10.1002/9783527652457

18. Agirseven O., Rivella D.T.Jr., Haggerty J.E.S., Berry P.O., Diffendaffer K., Patterson A., Kreb J., Mangum J.S., Gorman B.P., Perkins J.D., Chen B.R., Schelhas L.T., Tate J. Crystallization of TiO₂ polymorphs from RF-sputtered, amorphous thin-flm precursors. AIP Adv. 2020. 10(2): 025109. https://doi.org/10.1063/1.5140368

19. Eremenko A., Smirnova N., Gnatiuk I., Linnik O., Vityuk N., Mukha Y., Korduban A. Silver and Gold Nanoparticles on Sol-Gel TiO₂, ZrO₂, SiO₂ Surfaces: Optical Spectra, Photocatalytic Activity, Bactericide Properties. In: Nanocomposites and Polymers with Analytical Methods. Chapter 3: Composite Materials. 2011. P. 51. https://doi.org/10.5772/18252

20. Linnik O., Petrik I., Smirnova N., Kandyba V., Korduban A.M., Eremenko A., Socol G., Stefan N., Ristoscu C., Mihailescu I.N., Sutan C., Viorel M., Djokic V., Janackovic D. TiO₂/ZrO₂ thin films synthesized by PLD in low pressure N-, C- and/or O-containing gases: structural, optical and photocatalytic properties. Digest Journal of Nanomaterials and Biostructures. 2012. 7(3): 1343.