Synthesis of TiO2 nanotube coatings, nanoporous coatings, and nanofibres by using titanium anodizing, microplasma electrolytic oxidation, and microwave-assisted hydrothermal synthesis in different regimes was studied. Optimal conditions for each of the methods for obtaining nanostructures were determined. The obtained TiO2 nanofibres and nanotube and nanoporous coatings were modified with Au, Ag, Pt, Pd, S, WO3, and Eu2O3, nanoparticles to improve photocatalytic activity under ultraviolet and visible light irradiation. Photocatalytic properties of photocatalysts were tested by the degradation of methylene blue solution under the influence of ultraviolet and visible light irradiation. The obtained modified photocatalysts exhibited higher photocatalytic activity than pure TiO2 nanostructured photocatalysts. Properties of modified photocatalysts obtained with different methods are compared.
1. Dolez, P. I. Nanomaterials definitions, classifications, and applications. In Nanoengineering. Elsevier, 2015, 3–40.
https://doi.org/10.1016/B978-0-444-62747-6.00001-4
2. Fujishima, A. and Honda, K. Electrochemical photolysis of water at a semiconductor electrode. Nature, 1972, 238, 37–38.
https://doi.org/10.1038/238037a0
3. Fujishima, A., Rao, T. N., and Tryk, D. A. Titanium dioxide photocatalysis. J. Photochem. Photobiol. C Photochem. Rev., 2000, 1, 1–21.
https://doi.org/10.1016/S1389-5567(00)00002-2
4. Cao, Z., Zhu, S., Qu, H., Qi, D., Ziener, U., Yang, L., et al. Preparation of visible-light nano-photocatalysts through decoration of TiO2 by silver nanoparticles in inverse miniemulsions. J. Colloid Interface Sci., 2014, 435, 51–58.
https://doi.org/10.1016/j.jcis.2014.08.021
5. Xiao, J., Tao, R., Costa, B. F. O., and Paixão, J. A. Nanostructured titania photoanodes for dye solar cells. Mater. Today Proc., 2015, 2, 141–146.
https://doi.org/10.1016/j.matpr.2015.04.041
6. Grätzel, M. The artificial leaf, molecular photovoltaics achieve efficient generation of electricity from sunlight. Coord. Chem. Rev., 1991, 111, 167–174.
https://doi.org/10.1016/0010-8545(91)84022-W
7. Song, H., Shang, J., and Suo, C. Fabrication of TiO2 nanotube arrays by rectified alternating current anodization. J. Mater. Sci. Technol., 2015, 31, 23–29.
https://doi.org/10.1016/j.jmst.2014.07.005
8. Bayati, M. R., Moshfegh, A. Z., and Golestani-Fard, F. On the photocatalytic activity of the sulfur doped titania nano-porous films derived via micro-arc oxidation. Appl. Catal. Gen., 2010, 389, 60–67.
https://doi.org/10.1016/j.apcata.2010.09.003
9. Liu, Y., Yu, H., Lv, Z., Zhan, S., Yang, J., Peng, X., et al. Simulated-sunlight-activated photocatalysis of Methylene Blue using cerium-doped SiO2/TiO2 nanostructured fibers. J. Environ. Sci., 2012, 24, 1867–1875.
https://doi.org/10.1016/S1001-0742(11)61008-5
10. Espino-Estévez, M. R., Fernández-Rodríguez, C., González-Díaz, O. M., Araña, J., Espinós, J. P., Ortega-Méndez, J. A., and Doña-Rodríguez, J. M. Effect of TiO2–Pd and TiO2–Ag on the photocatalytic oxidation of diclofenac, isoproturon and phenol. Chem. Eng. J., 2016, 298, 82–95.
https://doi.org/10.1016/j.cej.2016.04.016
11. Shahri, Z., Allahkaram, S. R., Soltani, R., and Jafari, H. Optimization of plasma electrolyte oxidation process parameters for corrosion resistance of Mg alloy. J. Magnes. Alloys. In press, corrected proof available online 12 December 2018.
https://doi.org/10.1016/j.jma.2018.10.001
12. Lin, G-W., Chen, J-S., Tseng, W., and Lu, F-H. Formation of anatase TiO2 coatings by plasma electrolytic oxidation for photocatalytic applications. Surf. Coat. Technol., 2019, 357, 28–35.
https://doi.org/10.1016/j.surfcoat.2018.10.010
13. Tarkhanova, I. G., Bryzhin, A. A., Gantman, M. G, Yarovaya, T. P., Lukiyanchuk, I. V., Nedozorov, P. M., and Rudnev, V. S. Ce-, Zr-containing oxide layers formed by plasma electrolytic oxidation on titanium as catalysts for oxidative desulfurization. Surf. Coat. Technol., 2019, 362, 132–140.
https://doi.org/10.1016/j.surfcoat.2019.01.101
14. Arrabal, R., Mohedano, M., Matykina, E., Pardo, A., Mingo, B., and Merino, M. C. Characterization and wear behaviour of PEO coatings on 6082-T6 aluminium alloy with incorporated α-Al2O3 particles. Surf. Coat. Technol., 2015, 269, 64–73.
https://doi.org/10.1016/j.surfcoat.2014.10.048
15. Drunka, R., Grabis, J., Jankovica, D., Krumina, A., and Rasmane, D. Microwave-assisted synthesis and photocatalytic properties of sulphur and platinum modified TiO2 nanofibers. IOP Conf. Ser. Mater. Sci. Eng., 2015, 77, 012010.
https://doi.org/10.1088/1757-899X/77/1/012010
16. Park, T-E., Choe, H-C., and Brantley, W. A. Bioactivity evaluation of porous TiO2 surface formed on titanium in mixed electrolyte by spark anodization. Surf. Coat. Technol., 2013, 235, 706–713.
https://doi.org/10.1016/j.surfcoat.2013.08.051
17. Tang, Y., Fu, S., Zhao, K., Xie, G., and Teng, L. Synthesis of TiO2 nanofibers with adjustable anatase/ rutile ratio from Ti sol and rutile nanoparticles for the degradation of pollutants in wastewater. Ceram. Int., 2015, 41, 13285–13293.
https://doi.org/10.1016/j.ceramint.2015.07.111
18. Cheng, X., Deng, X., Wang, P., and Liu, H. Coupling TiO2 nanotubes photoelectrode with Pd nano-particles and reduced graphene oxide for enhanced photocatalytic decomposition of diclofenac and mechanism insights. Sep. Purif. Technol., 2015, 154, 51–59.
https://doi.org/10.1016/j.seppur.2015.09.032
19. K., Alamelu, B. M., and Jaffar, A. TiO2-Pt composite photocatalyst for photodegradation and chemical reduction of recalcitrant organic pollutants. J. Environ. Chem. Eng., 2018, 6, 5720–5731.
https://doi.org/10.1016/j.jece.2018.08.042
20. Ramacharyulu, P. V. R. K., Praveen Kumar, J., Prasad, G. K., and Sreedhar, B. Sulphur doped nano TiO2: synthesis, characterization and photocatalytic degradation of a toxic chemical in presence of sunlight. Mater. Chem. Phys., 2014, 148, 692–698.
https://doi.org/10.1016/j.matchemphys.2014.08.036
21. Sanzone, G., Zimbone, M., Cacciato, G., Ruffino, F., Carles, R., Privitera, V., and Grimaldi, M. G. Ag/TiO2 nanocomposite for visible light-driven photocatalysis. Superlattices Microstruct., 2018, 123, 394–402.
https://doi.org/10.1016/j.spmi.2018.09.028
22. Wang, Y., Jiang, X., and Pan, C. “In situ” preparation of a TiO2/Eu2O3 composite film upon Ti alloy substrate by micro-arc oxidation and its photo-catalytic property. J. Alloys Compd., 2012, 538, 16–20.
https://doi.org/10.1016/j.jallcom.2012.05.083
23. Yang, J. and Mou, C-Y. Ordered mesoporous Au/TiO2 nanospheres for solvent-free visible-light-driven plasmonic oxidative coupling reactions of amines. Appl. Catal. B Environ., 2018, 231, 283–291.
https://doi.org/10.1016/j.apcatb.2018.02.054
24. Yang, J., Zhang, X., Liu, H., Wang, C., Liu, S., Sun, P., et al. Heterostructured TiO2/WO3 porous microspheres: preparation, characterization and photocatalytic properties. Catal. Today, 2013, 201, 195–202.
https://doi.org/10.1016/j.cattod.2012.03.008
25. Drunka, R. Synthesis and Properties of Modified TiO2 Photocatalysts. Summary of doctoral thesis. University of Latvia, 2018.