Abstract:

TiO₂ nanostructures with strong interfacial adhesion and diverse morphologies have been in-situ grown on Ti foil substrate through a multiple-step method based on conventional plasma electrolytic oxidation (PEO) technology, hydrothermal reaction and ion exchange process. The PEO process is critical to the formation of TiO₂ seeding layer for the nucleation of Na₂Ti₃O₇ and H₂Ti₃O₇ mediates that are strongly attached to the Ti foil. An ion exchange reaction can finally lead to the formation of H₂Ti₃O₇ nanostructures with diverse morphologies and the calcination process can turn the H₂Ti₃O₇ nanostructures into TiO₂ nanostructures with enhanced crystallinity. The morphology of the TiO₂ nanostructures including nanoparticles (NP), nanowhiskers (NWK), nanowires (NW) and nanosheets (NS) can be easily tailored by controlling the NaOH concentration and reaction time during hydrothermal process. The morphology, composition and optical properties of TiO₂ photocatalysts were analyzed using scanning electron microscope (SEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy and UV-vis absorption spectrum. Photocatalytic tests indicate that the TiO₂ nanosheets calcined at 500 °C show good crystallization and the best capability of decomposing organic pollutants. The decoration of Ag cocatalyst can further improve the photocatalytic performance of the TiO₂ nanosheets as a result of the enhanced charger separation efficiency. Cyclic photocatalytic test using TiO₂ nanostructures grown on Ti foil substrate demonstrates the superior stability in the photodegradation of organic pollutant, suggesting the promising potential of in-situ growth technology for industrial application.

Key words: Plasma electrolytic oxidation, In-situ growth, TiO₂, Photocatalysis, Ag co-catalyst